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Network Working Group                                      P. RadoslavovRequest for Comments: 2909                                     D. EstrinCategory: Experimental                                       R. Govindan                                                                 USC/ISI                                                              M. Handley                                                                   ACIRI                                                                S. Kumar                                                                 USC/ISI                                                               D. Thaler                                                               Microsoft                                                          September 2000The Multicast Address-Set Claim (MASC) ProtocolStatus of this Memo   This memo defines an Experimental Protocol for the Internet   community.  It does not specify an Internet standard of any kind.   Discussion and suggestions for improvement are requested.   Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2000).  All Rights Reserved.Abstract   This document describes the Multicast Address-Set Claim (MASC)   protocol which can be used for inter-domain multicast address set   allocation.  MASC is used by a node (typically a router) to claim and   allocate one or more address prefixes to that node's domain.  While a   domain does not necessarily need to allocate an address set for hosts   in that domain to be able to allocate group addresses, allocating an   address set to the domain does ensure that inter-domain group-   specific distribution trees will be locally-rooted, and that traffic   will be sent outside the domain only when and where external   receivers exist.Radoslavov, et al.            Experimental                      [Page 1]

RFC 2909                   The MASC Protocol              September 2000Table of Contents1 Introduction ..................................................41.1 Terminology .................................................41.2 Definitions .................................................42 Requirements for Inter-Domain Address Allocation ..............53 Overall Architecture ..........................................53.1 Claim-Collide vs. Query-Response Rationale ..................64 MASC Topology .................................................64.1 Managed vs Locally-Allocated Space ..........................84.2 Prefix Lifetime .............................................84.3 Active vs. Deprecated Prefixes ..............................94.4 Multi-Parent Sibling-to-Sibling and Internal Peering ........94.5 Administratively-Scoped Address Allocation ..................95 Protocol Details ..............................................105.1 Claiming Space ..............................................105.1.1 Claim Comparison Function .................................125.2 Renewing an Existing Claim ..................................125.3 Expanding an Existing Prefix ................................125.4 Releasing Allocated Space ...................................136 Constants .....................................................137 Message Formats ...............................................147.1 Message Header Format .......................................147.2 OPEN Message Format .........................................157.3 UPDATE Message Format .......................................177.4 KEEPALIVE Message Format ....................................217.5 NOTIFICATION Message Format .................................218 MASC Error Handling ...........................................248.1 Message Header Error Handling ...............................248.2 OPEN Message Error Handling .................................258.3 UPDATE Message Error Handling ...............................268.4 Hold Timer Expired Error Handling ...........................288.5 Finite State Machine Error Handling .........................288.6 NOTIFICATION Message Error Handling .........................288.7 Cease .......................................................298.8 Connection Collision Detection ..............................299 MASC Version Negotiation ......................................3010 MASC Finite State Machine ....................................3010.1 Open/Close MASC Connection FSM .............................3111 UPDATE Message Processing ....................................3511.1 Accept/Reject an UPDATE ....................................3611.2 PREFIX_IN_USE Message Processing ...........................3811.2.1 PREFIX_IN_USE by PARENT ..................................3811.2.2 PREFIX_IN_USE by SIBLING .................................3811.2.3 PREFIX_IN_USE by CHILD ...................................3811.2.4 PREFIX_IN_USE by INTERNAL_PEER ...........................3811.3 CLAIM_DENIED Message Processing ............................3911.3.1 CLAIM_DENIED by CHILD or SIBLING .........................39Radoslavov, et al.            Experimental                      [Page 2]

RFC 2909                   The MASC Protocol              September 200011.3.2 CLAIM_DENIED by INTERNAL_PEER ............................3911.3.3 CLAIM_DENIED by PARENT ...................................3911.4 CLAIM_TO_EXPAND Message Processing .........................3911.4.1 CLAIM_TO_EXPAND by PARENT ................................3911.4.2 CLAIM_TO_EXPAND by SIBLING ...............................4011.4.3 CLAIM_TO_EXPAND by CHILD .................................4011.4.4 CLAIM_TO_EXPAND by INTERNAL_PEER .........................4011.5 NEW_CLAIM Message Processing ...............................41   11.6 PREFIX_MANAGED Message Processing.  ........................4111.6.1 PREFIX_MANAGED by PARENT .................................4111.6.2 PREFIX_MANAGED by CHILD or SIBLING .......................4111.6.3 PREFIX_MANAGED by INTERNAL_PEER ..........................4111.7 WITHDRAW Message Processing ................................4211.7.1 WITHDRAW by CHILD ........................................4211.7.2 WITHDRAW by SIBLING ......................................4211.7.3 WITHDRAW by INTERNAL .....................................4211.7.4 WITHDRAW by PARENT .......................................4311.8 UPDATE Message Ordering ....................................4311.8.1 Parent to Child ..........................................4311.8.2 Child to Parent ..........................................4411.8.3 Sibling to Sibling .......................................4411.8.4 Internal to Internal .....................................4412 Operational Considerations ...................................4512.1 Bootup Operations ..........................................4512.2 Leaf and Non-leaf MASC Domain Operation ....................4512.3 Clock Skew Workaround ......................................4512.4 Clash Resolving Mechanism ..................................4612.5 Changing Network Providers .................................4712.6 Debugging ..................................................4712.6.1 Prefix-to-Domain Lookup ..................................4712.6.2 Domain-to-Prefix Lookup ..................................4713 MASC Storage .................................................4714 Security Considerations ......................................4815 IANA Considerations ..........................................4816 Acknowledgments ..............................................4817 APPENDIX A: Sample Algorithms ................................4917.1 Claim Size and Prefix Selection Algorithm ..................4917.1.1 Prefix Expansion .........................................4917.1.2 Reducing Allocation Latency ..............................5017.1.3 Address Space Utilization ................................5017.1.4 Prefix Selection After Increase of Demand ................5017.1.5 Prefix Selection After Decrease of Demand ................5117.1.6 Lifetime Extension Algorithm .............................5118 APPENDIX B: Strawman Deployment ..............................5119 Authors' Addresses ...........................................5220 References ...................................................5421 Full Copyright Statement .....................................56Radoslavov, et al.            Experimental                      [Page 3]

RFC 2909                   The MASC Protocol              September 20001.  Introduction   This document describes MASC, a protocol for inter-domain multicast   address set allocation.  The MASC protocol (a Layer-3 protocol in the   multicast address allocation architecture [MALLOC]) is used by a node   (typically a router) to claim and allocate one or more address   prefixes to that node's domain.  Each prefix has an associated   lifetime, and is chosen out of a larger prefix with a lifetime at   least as long, in a manner such that prefixes are aggregatable.  At   any time, each MASC node (a Prefix Coordinator in [MALLOC]) will   typically advertise several prefixes with different lifetimes and   scopes, allowing Multicast Address Allocation Servers (MAAS's) in   that domain or child MASC domains to choose appropriate addresses for   their clients.   The set of prefixes ("address set") associated with a domain is   injected into an inter-domain routing protocol (e.g., BGP4+ [MBGP]),   where it can be used by an inter-domain multicast tree construction   protocol (e.g., BGMP [BGMP]) to construct inter-domain group-shared   trees.   Note that a domain does not need to allocate an address set for the   hosts in that domain to be able to allocate group addresses, nor does   allocating necessarily guarantee that hosts in other domains will not   use an address in the set (since, for example, hosts are not forced   to contact a MAAS before using a group address).  Allocating an   address set to a domain does, however, ensure that inter-domain   group-specific multicast distribution trees for any group in the   address set will be locally-rooted, and that traffic will be sent   outside the given domain only when and where external receivers   exist.1.1.  Terminology   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described inRFC 2119 [RFC2119].   Constants used by this protocol are shown as [NAME_OF_CONSTANT], and   summarized inSection 6.1.2.  Definitions   This specification uses a number of terms that may not be familiar to   the reader. This section defines some of these and refers to other   documents for definitions of others.Radoslavov, et al.            Experimental                      [Page 4]

RFC 2909                   The MASC Protocol              September 2000   MAAS (Multicast Address Allocation Server)      A host providing multicast address allocation services to end      users (e.g. via MADCAP [MADCAP]).   MASC server      A node running MASC.   Peer      Other MASC speakers a node directly communicates with.   Multicast      IP Multicast, as defined for IPv4 in [RFC1112] and for IPv6 in      [RFC2460].   Multicast Address      An IP multicast address or group address, as defined in [RFC1112]      and [RFC2373].  An identifier for a group of nodes.2.  Requirements for Inter-Domain Address Allocation   The key design requirements for the inter-domain address allocation   mechanism are:   o  Efficient address space utilization when space is scare, which      naturally implies that address allocations be based on the actual      address usage patterns, and therefore that it be dynamic.   o  Address aggregation, that implies that the address allocation      mechanism be hierarchical.   o  Minimize flux in the allocated address sets (e.g. the address sets      should be reused when possible).   o  Robustness, by using decentralized mechanisms.   The timeliness in obtaining an address set is not a major design   constraint as this is taken care of at a lower level [MALLOC].3.  Overall Architecture   The Multicast Address Set Claim (MASC) protocol is used by MASC   domains to claim and allocate address sets for use by Multicast   Address Allocation Servers (MAASs) within each domain.  Typically one   or more border routers of each domain that requires multicast address   space of its own would run MASC.  Throughout this document, the term   "MASC domain" refers to a domain that has at least one node running   MASC; typically these domains will be Autonomous Systems (AS's).  A   MASC node (on behalf of its domain) chooses an address set to claim,Radoslavov, et al.            Experimental                      [Page 5]

RFC 2909                   The MASC Protocol              September 2000   sends a claim to other MASC domains in the network, and waits while   listening for any colliding claims. If there is a collision, the   losing claimer gives up the colliding claim and claims a different   address set.   After a sufficiently long collision-free waiting period, the address   set chosen by a MASC node is considered allocated to that node's   domain.  Three things may then happen:   a) The allocated prefix can then be injected as a "multicast route"      into the inter-domain routing protocol  (e.g., BGP4+ [MBGP]) as      "G-RIB" Network Layer Reachability Information (NLRI), where it      may be used by an inter-domain multicast routing protocol (e.g.,      BGMP [BGMP]) to construct group-shared trees.  To reduce the size      and slow the growth of the G-RIB, MASC nodes may perform CIDR-like      aggregation [CIDR] of the multicast NLRI information.  This      motivates the need for an algorithm to select prefixes for domains      in such a way as to ensure good aggregation in addition to      achieving good address space utilization.   b) The node's domain may assign to itself a sub-prefix which can be      used by MAASs within the domain.   c) Sub-prefixes may be allocated to child domains, if any.3.1.  Claim-Collide vs. Query-Response Rationale   We choose a claim-collide mechanism instead of a query-response   mechanism for the following reasons.  In a query-response mechanism,   replicas of the MASC node would be needed in parent MASC domains in   order to make their responses be robust to failures.  This brings   about the associated problem of synchronization of the replicas and   possibly additional fragmentation of the address space.  In addition,   even in this mechanism, address collisions would still need to be   handled.  We believe the proposed claim-collide mechanism is simpler   and more robust than a query-response mechanism.4.  MASC Topology   The domain hierarchy used by MASC is congruent to the somewhat   hierarchical structure of the inter-domain topology, e.g., backbones   connected to regionals, regionals connected to metropolitan   providers, etc.  As in BGP, MASC connections are locally configured.   A MASC domain that is a customer of other MASC domains will have one   or more of those provider domains as its parent.  For example, a MASC   domain that is a regional provider will choose one (or more) of its   backbone provider domains as its parent(s).  Children are configured   with their parent MASC domain, and parents are configured with theirRadoslavov, et al.            Experimental                      [Page 6]

RFC 2909                   The MASC Protocol              September 2000   children domains.  At the top, a  number of Top-Level Domains are   connected in a (sparse) mesh and share the global multicast address   space.  To improve the robustness, a pair of children of the same   parent domain MAY be configured as siblings with regard to that   parent.   Figure 1 illustrates a sample topology.  Double-line links denote   intra-domain TCP peering sessions, and single-line links denote   inter-domain TCP connections. T1 and T2 are Top-Level Domains (e.g.,   backbone providers), containing MASC speakers T1a and T2a,   respectively.  P3 and P4 are regional domains, containing (P3a, P3b),   and (P4a, P4b) respectively.  P3 has a single customer (or "child"),   C5, containing (C5a, C5b, C5c).  P4 has three children, C5, C6, C7,   containing (C5a, C5b, C5c), (C6a, C6b), and (C7a) respectively.                         T1a-----------T2a                          |             |                          |             |                          |             |                  P3a====P3b           P4a====P4b                   |      |           / |    / | \                   |      |   _______/  |   /  |  \                   |      |  /          |  /   |   \______                   |      | /           | /    |          \                  C5a====C5b           C6a====C6b----------C7a                    \\  //                     \\//                     C5c                  Figure 1: Example MASC Topology   All MASC communications use TCP. Each MASC node is connected to and   communicates directly with other MASC nodes.  The local node acts in   exactly one of the following four roles with respect to each remote   note:   INTERNAL_PEER      The local and remote nodes are both in the same MASC domain.  For      example, P4b is an INTERNAL_PEER of P4a.   CHILD      A customer relationship exists whereby the local node may obtain      address space from the remote node.  For example, C6a is a CHILD      in its session with P4a.Radoslavov, et al.            Experimental                      [Page 7]

RFC 2909                   The MASC Protocol              September 2000   PARENT      A provider relationship exists whereby the remote node may obtain      address space from the local node.  For example, T2a is a PARENT      in its session with P4a.  Whether space is actually requested is      up to the implementation and local policy configuration.   SIBLING      No customer-provider relationship exists.  For example, T2a is a      SIBLING in its session with T1a (Top-Level Domain SIBLING      peering).  Also, C6b is a SIBLING in its session with C7a with      regard to their common parent P4.   A node's message will be propagated to its parent, all siblings with   the same parent, and its children.  Since a domain need not have a   direct peering session with every sibling, a MASC domain must   propagate messages from a child domain to other children, can   propagate messages from a parent domain to other siblings, and, if a   Top-Level Domain, it must propagate messages from a sibling to other   siblings, otherwise may propagate messages from a sibling domain to   its parent and other siblings.4.1.  Managed vs Locally-Allocated Space   Each domain has a "Managed" Address Set, and a "Locally-Allocated"   Address Set.  The "managed" space includes all address space which a   domain has successfully claimed via MASC.  The "locally-allocated"   space, on the other hand, includes all address space which MAASs   inside the domain may use.  Thus, the locally-allocated space is a   subset of the managed space, and refers to the portion which a domain   allocates for its own use.   For leaf domains (ones with no children), these two sets are   identical, since all claimed space is allocated for local use.  A   parent domain, on the other hand, "manages" all address space which   it has claimed via MASC, while sub-prefixes can be allocated to   itself and to its children.4.2.  Prefix Lifetime   Each prefix has an associated lifetime.  If a domain wants to use a   prefix longer than its lifetime, that domain must "renew" the prefix   BEFORE its lifetime expires (seeSection 5.2).  If the lifetime   cannot be extended, then the domain should either retry later to   extend, or should choose and claim another prefix.Radoslavov, et al.            Experimental                      [Page 8]

RFC 2909                   The MASC Protocol              September 2000   After a prefix's lifetime expires, MASC nodes in the domain that own   that prefix must stop using that prefix.  The corresponding entry   from the G-RIB database must be removed, and all information   associated with the expired prefix may be deleted from the MASC   node's local memory.4.3.  Active vs. Deprecated Prefixes   Each prefix advertised by a parent to its children can be either   "active" or "deprecated".  A "deprecated" prefix is a prefix that the   parent wishes to discontinue to use after its lifetime expires.  The   "active" prefixes only are candidates for size expansion or lifetime   extension.  Usually, this information will be used by a child as a   hint to know which of the parent's prefixes might have their lifetime   extended.4.4.  Multi-Parent Sibling-to-Sibling and Internal Peering   Two sibling nodes that have more than one common parent will create   and use between them a number of transport-level connections, one per   each common parent.  The information associated with a parent will be   sent over the connection that corresponds to the same parent.   Internal peers do not need to open multiple connections between them;   a single connection is used for all information.4.5.  Administratively-Scoped Address Allocation   MASC can also be used for sub-allocating prefixes of addresses within   an administrative scope zone [SCOPE], but only if the scope is   "divisible" (as described in [MALLOC] and [MZAP]).  A MASC node can   learn what scopes it resides within by listening to MZAP [MZAP]   messages.   A "Zone TLD" is a domain which has no parent domain within the scope   zone.  Zone TLDs act as TLDs for the prefix associated with the   scope.  Figure 2 gives an example, where a scope boundary around   domains P3 and C5 has been added to Figure 1.  Domain P3 is a Zone   TLD, since its only parent (T1) is outside the boundary.  Hence, P3   can claim space directly out of the prefix associated with the scope   itself.  Domain C5, on the other hand, has a parent within the scope   (namely, P3), and hence is not a Zone TLD.Radoslavov, et al.            Experimental                      [Page 9]

RFC 2909                   The MASC Protocol              September 2000                                 T1a-----------T2a                                  |             |                      ............|.......      |                      .           |      .      |                      .   P3a====P3b     .     P4a                      .    |      |      .    /                      .    |      |   _______/                      .    |      |  /   .                      .    |      | /    .                      .   C5a====C5b     .                      .     \\  //       .                      .      \\//        .                      .      C5c         .                      .                  .                      . Admin Scope Zone .                      ....................                 Figure 2: Scope Zone Example   It is assumed that the role of a node (as discussed inSection 4)   with respect to a given peering session is the same for every scope   in which both ends are contained.  A peering session that crosses a   scope boundary (such as the session between C5b and P4a in Figure 2)   is ignored when propagating messages that pertain to the given scope.   That is, such messages are not sent across such sessions.5.  Protocol Details5.1.  Claiming Space   When a MASC node, on behalf of a MASC domain, needs more address   space, it decides locally the size and the value of the address   prefix(es) it will claim from one of its parents.  For example, the   decision might be based on the knowledge this node has about its   parent's address set, its siblings' claims and allocations, its own   address set, the claim messages from its siblings, and/or the demand   pattern of its children and the local domain.  A sample algorithm is   given inAppendix A.   A MASC node which is not in a top-level domain can initiate a claim   toward a parent MASC domain if and only if it currently has an   established connection with at least one node in that parent domain.   After the prefix address and size are decided, the claim proceeds as   follows:Radoslavov, et al.            Experimental                     [Page 10]

RFC 2909                   The MASC Protocol              September 2000   a) The claim is scheduled to be sent after a random delay in the      interval (0, [INITIATE_CLAIM_DELAY]).  If a claim originated by a      node from the same MASC domain is received, and that claim      eliminates the need for the local claim, the local claim is      canceled and no further action is taken.   b) The claim is sent to one of the parents (if the domain is not a      top-level domain), all known siblings with the same parent, and      all internal peers.  A Claim-Timer is then started at      [WAITING_PERIOD], and the MASC node starts listening for colliding      claims.   c) If a colliding claim is received while the Claim-Timer is running,      that claim is compared with the locally initiated claim using the      function described inSection 5.1.1.  If the local claim is the      loser, a new prefix must be chosen to claim, and the loser claim's      Claim-Timer must be canceled.  The loser claim can be either      explicitly withdrawn, or can be left to expire without taking      further actions.  If the winning claim was originated by a node      from the same MASC domain, no new claim will be initiated.  If the      local claim is the winner, no actions need to be taken.   d) If the Claim-Timer expires, the claimed prefix becomes associated      with the claimer's domain, i.e. it is considered allocated to that      domain and the following actions can be performed:      o  Advertise the prefix to its parent, and to all siblings with         the same parent, by sending a PREFIX_IN_USE claim to them.      o  Inject the prefix into the G-RIB of the inter-domain routing         protocol.      o  Send a PREFIX_MANAGED message to all children and internal         peers, informing them that they may issue claims within the         managed space.  A sub-prefix may then be claimed for local         usage (seeSection 12.2).   Each MASC node receives all claims from its siblings and children.  A   received claim must be evaluated against all claims saved in the   local cache using the function described inSection 5.1.1.  The   output of the function will define the further processing of that   claim (seeSection 11).Radoslavov, et al.            Experimental                     [Page 11]

RFC 2909                   The MASC Protocol              September 20005.1.1.  Claim Comparison Function   Each claim message includes:   o  a "type", being one of: PREFIX_IN_USE, CLAIM_DENIED,      CLAIM_TO_EXPAND, or NEW_CLAIM  (PREFIX_MANAGED and WITHDRAW are      not considered as claims that have to be compared)   o  timestamp when the claim was initiated   o  the claimed prefix and lifetime   o  MASC Identifier of the node that originated the claim   When two claims are compared, first the type is compared based on the   following precedence:   PREFIX_IN_USE > CLAIM_DENIED > CLAIM_TO_EXPAND > NEW_CLAIM   If the type is the same, then the timestamps are used to compare the   claims.  In practice, two claims will have the same type if the type   is either NEW_CLAIM (ordinary collision) or PREFIX_IN_USE (signal for   a clash).  When the timestamps are compared, the claim with the   smallest, i.e. earliest timestamp wins.  If the timestamps are the   same, then the claim with the smallest Origin Node Identifier wins.5.2.  Renewing an Existing Claim   The procedure for extending the lifetime of prefixes already in use   is the same as claiming new space (seeSection 5.1), except that the   claim type must be CLAIM_TO_EXPAND, while the Address and the Mask of   the claim (seeSection 7.3) must be the same as the already allocated   prefix.  If the Claim-Timer expires and there is no collision, the   desired lifetime is assumed.5.3.  Expanding an Existing Prefix   The procedure for extending the lifetime of prefixes already in use   is the same as claiming new space (seeSection 5.1), except that the   claim type must be CLAIM_TO_EXPAND, while the Address and the Mask of   the claim (seeSection 7.3) must be set to the desired values.  If   the Claim-Timer expires and there is no collision, the desired larger   prefix is associated with the local domain.Radoslavov, et al.            Experimental                     [Page 12]

RFC 2909                   The MASC Protocol              September 20005.4.  Releasing Allocated Space   If the lifetime of a prefix allocated to the local domain expires and   the domain does not need to reuse it, all resources associated with   this prefix are deleted and no further actions are taken.  If the   lifetime of the prefix has not expired, and if no subranges of that   prefix have being allocated for local usage or by some of the   children domains, the space may be released by sending a withdraw   message to the parent domain, all known siblings with the same   parent, and all internal peers.6.  Constants   MASC uses the following constants:   [PORT_NUMBER]      2587.  The TCP port number used to listen for incoming MASC      connections, as assigned by IANA.   [WAITING_PERIOD]      The amount of time (in seconds) that must pass between a NEW_CLAIM      (or CLAIM_TO_EXPAND), and a PREFIX_IN_USE for the same prefix.      This must be long enough to reasonably span any single inter-      domain network partition.  Default: 172800 seconds (i.e. 48      hours).   [INITIATE_CLAIM_DELAY]      The amount of time (in seconds) a MASC node must wait before      initiating a new claim or a claim for space expansion. This must      be a random value in the interval (0, [INITIATE_CLAIM_DELAY]).      Default value for [INITIATE_CLAIM_DELAY]: 600 seconds (i.e. 10      minutes).   [TLD_ID]      The Parent Domain Identifier used by a Top-Level Domain (which has      no parent). Must be 0.   [HOLDTIME]      The amount of time (in seconds) that must pass without any      messages received from a remote node before considering the      connection is down.  Default: 240 seconds (i.e. 4 minutes).Radoslavov, et al.            Experimental                     [Page 13]

RFC 2909                   The MASC Protocol              September 20007.  Message Formats   This section describes message formats used by MASC.   Messages are sent over a reliable transport protocol connection.  A   message is processed only after it is entirely received.  The maximum   message size is 4096 octets.  All implementations are required to   support this maximum message size.7.1.  Message Header Format   Each message has a fixed-size (4-octets) header.  There may or may   not be a data portion following the header, depending on the message   type.  The layout of these fields is shown below:    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |          Length               |      Type     |   Reserved    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Length:      This 2-octet unsigned integer indicates the total length of the      message, including the header, in octets.  Thus, e.g., it allows      one to locate in the transport-level stream the start of the next      message.  The value of the Length field must always be at least 4      and no greater than 4096, and may be further constrained,      depending on the message type.  No "padding" of extra data after      the message is allowed, so the Length field must have the smallest      value required given the rest of the message.   Type:      This 1-octet unsigned integer indicates the type code of the      message.  The following type codes are defined:            1 - OPEN            2 - UPDATE            3 - NOTIFICATION            4 - KEEPALIVE   Reserved:      This 1-octet field is reserved.  MUST be set to zero by the sender,      and MUST be ignored by the receiver.Radoslavov, et al.            Experimental                     [Page 14]

RFC 2909                   The MASC Protocol              September 20007.2.  OPEN Message Format   After a transport protocol connection is established, the first   message sent by each side is an OPEN message.  If the OPEN message is   acceptable, a KEEPALIVE message confirming the OPEN is sent back.   Once the OPEN is confirmed, UPDATE, KEEPALIVE, and NOTIFICATION   messages may be exchanged.   The minimum length of the OPEN message is 20 octets (including   message header).  In addition to the fixed-size MASC header, the OPEN   message contains the following fields:    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |    Version    |R| AddrFam |Rol|           Hold Time           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |         Sender Domain Identifier    (variable length)         |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |         Sender MASC Node Identifier (variable length)         |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |         Parent's Domain Identifier  (variable length)         |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                                                               |   +                     (Optional Parameters)                     |   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Version:      This 1-octet unsigned integer indicates the protocol version      number of the message.  The current MASC version number is 1.   R bit:      This 1-bit field is reserved.  MUST be set to zero by the sender,      and MUST be ignored by the receiver.   AddrFam:      This 5-bit field is the IANA-assigned address family number of the      encoded prefix [IANA].  These include (among others):      Number    Description      ------    -----------         1      IP (IP version 4)         2      IPv6 (IP version 6)Radoslavov, et al.            Experimental                     [Page 15]

RFC 2909                   The MASC Protocol              September 2000   My Role (Rol):      This 2-bit field indicates the proposed relationship of the      sending system to the receiving system:         00 = INTERNAL_PEER (sent from one internal peer to another)         01 = CHILD (sent from a child to its parent)         10 = SIBLING (sent from one sibling to another)         11 = PARENT (sent from a parent to its child)   Hold Time:      This 2-octet unsigned integer indicates the number of seconds that      the sender proposes for the value of the Hold Timer.  Upon receipt      of an OPEN message, a MASC speaker MUST calculate the value of the      Hold Timer by using the smaller of its configured Hold Time for      that peer and the Hold Time received in the OPEN message.  The      Hold Time MUST be either zero or at least three seconds.  An      implementation may reject connections on the basis of the Hold      Time.  The calculated value indicates the maximum number of      seconds that may elapse between the receipt of successive      KEEPALIVE and/or UPDATE messages by the sender.  RECOMMENDED value      is [HOLDTIME] seconds.   Sender Domain Identifier:      A globally unique identifier.  Its length is determined based on      the Address Family, and should be treated as an unsigned integer      (e.g. a 4-octet integer for IPv4, or a 16-octet integer for IPv6),      but must be at least 4 octets long.  It should be set to the      Autonomous System number of the sender, but the network unicast      prefix address is also acceptable.   Sender MASC Node Identifier:      This field's length and format are same as the Sender Domain      Identifier field, and indicates the MASC Node Identifier of the      sender.  A given MASC speaker sets the value of its MASC Node      Identifier to a globally-unique value assigned to that MASC      speaker (e.g., an IPv4 or IPv6 address).  The value of the MASC      Node Identifier is determined on startup and is the same for every      MASC session opened.   Parent's Domain Identifier:      This field's length and format are same as the Sender Domain      Identifier field, and is set to the Domain Identifier of the      sender's parent (e.g. the parent's Autonomous System number, or      network prefix address), or is set to [TLD_ID] if the sender is a      TLD.  Used only when Rol is INTERNAL_PEER or SIBLING, otherwise is      ignored.  This field is used to determine the common parents      between siblings, to associate each sibling-to-sibling connection      with a particular parent, and to discover TLD-relatedRadoslavov, et al.            Experimental                     [Page 16]

RFC 2909                   The MASC Protocol              September 2000      configuration problems among internal peers.  If a non-TLD node      does not know yet the Domain ID of any of its parents, it can use      its own Domain ID in the OPEN messages to its internal peers.   Optional Parameters:      This field may contain a list of optional parameters, where each      parameter is encoded as a <Parameter Length, Parameter Type,      Parameter Value> triplet.  The combined length of all optional      parameters can be derived from the Length field in the message      header.       0                   1       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...      |  Parm. Length |  Parm. Type   |  Parameter Value (variable)      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...      Parameter Length is a one octet field that contains the length of      the Parameter Value field in octets.  Parameter Type is a one      octet field that unambiguously identifies individual parameters.      Parameter Value is a variable length field that is interpreted      according to the value of the Parameter Type field.  Unrecognized      optional parameters MUST be silently ignored.      This document does not define any optional parameters.7.3.  UPDATE Message Format   UPDATE messages are used to transfer Claim/Collision/PrefixManaged   information between MASC speakers.  The UPDATE message always   includes the fixed-size MASC header, and one or more attributes as   described below.  The minimum length of the UPDATE message is 40   octets (including the message header).   Each attribute is of the form:    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |              Length           |     Type      |   Reserved    |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |    Data ...                                                   |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   All attributes are 4-octets aligned.Radoslavov, et al.            Experimental                     [Page 17]

RFC 2909                   The MASC Protocol              September 2000   Length:      The Length is the length of the entire attribute, including the      length, type, and data fields.  If other attributes are nested      within the data field, the length includes the size of all such      nested attributes.   Type:      This 1-octet unsigned integer indicates the type code of the      attribute.  The following type codes are defined:         0 = PREFIX_IN_USE (prefix is being used by the origin)         1 = CLAIM_DENIED (the claim is refused (probably by the             origin's parent domain))         2 = CLAIM_TO_EXPAND (origin is trying to expand the size of             an existing prefix)         3 = NEW_CLAIM (origin is trying to claim a new prefix)         4 = PREFIX_MANAGED (parent is informing child of space             available)         5 = WITHDRAW (origin is withdrawing a previous claim)      Types 128-255 are reserved for "optional" attributes.  If a      required attribute is unrecognized, a NOTIFICATION with UPDATE      Error Code and Unrecognized Required Attribute subcode will be      sent.  Unrecognized optional attributes are simply ignored.   Reserved:      This 1-octet field is reserved.  MUST be set to zero by the      sender, and MUST be ignored by the receiver.   Types 0-3 are collectively called "CLAIMs".  The message format below   describes the encoding of a CLAIM, PREFIX_MANAGED and WITHDRAW.Radoslavov, et al.            Experimental                     [Page 18]

RFC 2909                   The MASC Protocol              September 2000    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   Reserved1   |D| AddrFam |Rol|           Reserved2           |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    Claim Timestamp                            |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    Claim Lifetime                             |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    Claim Holdtime                             |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    Origin Domain Identifier (variable length) |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    Origin Node Identifier   (variable length) |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    Address (variable length)                  |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                    Mask    (variable length)                  |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                                                               |   +                     (Optional Parameters)                     |   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Reserved1:      This 1-octet field is reserved.  MUST be set to zero by the      sender, and MUST be ignored by the receiver.   D-bit:      DEPRECATED_PREFIX bit. If set, indicates that the advertised      address prefix is Deprecated, otherwise the prefix is Active (seeSection 4.3).   AddrFam:      This 5-bit field is the IANA-assigned address family number of the      encoded prefix [IANA].   Rol:      This 2-bit field indicates the relationship/role of the Origin of      the message to the node sending that message:         00 = INTERNAL (originated by the sender's domain)         01 = CHILD (originated by a child of the sender's domain)         10 = SIBLING (originated by a sibling of the sender's domain)         11 = PARENT (originated by a parent of the sender's domain)   Reserved2:      This 2-octet field is reserved.  MUST be set to zero by the      sender, and MUST be ignored by the receiver.Radoslavov, et al.            Experimental                     [Page 19]

RFC 2909                   The MASC Protocol              September 2000   Claim Timestamp:      The timestamp of the claim when it was originated. The timestamp      is expressed in number of seconds since midnight (0 hour), January      1, 1970, Greenwich.   Claim Lifetime:      The time in seconds between the Claim Timestamp, and the time at      which the prefix will become free.   Claim Holdtime:      The time in seconds between the Claim Timestamp, and the time at      which the claim should be deleted from the local cache. For      PREFIX_IN_USE and PREFIX_MANAGED claims it should be equal to      Claim Lifetime; for CLAIM_TO_EXPAND, NEW_CLAIM, and CLAIM_DENIED      it should be equal to [WAITING_PERIOD].   Origin Domain Identifier:      The domain identifier of the claim originator.  Its length and      format definition are same as the Sender Domain Identifier (seeSection 7.2).   Origin Node Identifier:      The MASC Node ID of the claim originator.  Its length and format      definition are same as the Sender MASC Node Identifier (seeSection 7.2).   Address:      The address associated with the given prefix to be encoded.  The      length is determined based on the Address Family (e.g. 4 octets      for IPv4, 16 for IPv6)   Mask:      The mask associated with the given prefix.  The length is the same      as the Address field and is determined based on the Address      Family. The field contains the full bitmask.   Optional Parameters:      This field may contain a list of optional parameters, where each      parameter is encoded using same format as the optional parameters      of an OPEN message (seeSection 7.2).  Unrecognized optional      parameters MUST be silently ignored.  This document does not      define any optional parameters.Radoslavov, et al.            Experimental                     [Page 20]

RFC 2909                   The MASC Protocol              September 20007.4.  KEEPALIVE Message Format   MASC does not use any transport protocol-based keep-alive mechanism   to determine if peers are reachable.  Instead, KEEPALIVE messages are   exchanged between peers often enough as not to cause the Hold Timer   to expire.  A reasonable maximum time between the last KEEPALIVE or   UPDATE message sent, and the time at which a KEEPALIVE message is   sent, would be one third of the Hold Time interval.  KEEPALIVE   messages MUST NOT be sent more frequently than one per second.  An   implementation MAY adjust the rate at which it sends KEEPALIVE   messages as a function of the Hold Time interval.   If the negotiated Hold Time interval is zero, then periodic KEEPALIVE   messages MUST NOT be sent.   A KEEPALIVE message consists of only a message header, and has a   length of 4 octets.7.5.  NOTIFICATION Message Format   A NOTIFICATION message is sent when an error condition is detected.   Depending on the error condition, the MASC connection might or must   be closed immediately after sending the message.  If the sender of   the NOTIFICATION decides that the connection is to be closed, it will   indicate this by zeroing the O-bit in the NOTIFICATION message (see   below).   In addition to the fixed-size MASC header, the NOTIFICATION message   contains the following fields:    0                   1                   2                   3    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |O| Error code  | Error subcode |           Data                |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +   |                                                               |   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   O-bit:      Open-bit.  If zero, it indicates that the sender will close the      connection.  If '1', it indicates that the sender has chosen to      keep the connection open.   Error Code:      This 7-bit unsigned integer indicates the type of NOTIFICATION.      The following Error Codes have been defined:Radoslavov, et al.            Experimental                     [Page 21]

RFC 2909                   The MASC Protocol              September 2000         Error Code       Symbolic Name               Reference           1         Message Header ErrorSection 8.1           2         OPEN Message ErrorSection 8.2           3         UPDATE Message ErrorSection 8.3           4         Hold Timer ExpiredSection 8.4           5         Finite State Machine ErrorSection 8.5           6         NOTIFICATION Message ErrorSection 8.6           7         CeaseSection 8.7   Error subcode:      This 1-octet unsigned integer provides more specific information      about the nature of the reported error.  Each Error Code may have      one or more Error Subcodes associated with it.  If no appropriate      Error Subcode is defined, then a zero (Unspecific) value is used      for the Error Subcode field, and the O-bit must be zero (i.e. the      connection will be closed).  The notation used in the error      description below is: MC = Must Close connection = O-bit is zero;      CC = Can Close connection = O-bit might be zero.               Message Header Error subcodes:                        0 - Unspecific                        (MC)                        1 - Bad Message Length                (MC)                        2 - Bad Message Type                  (CC)               OPEN Message Error subcodes:                        0 - Unspecific                        (MC)                        1 - Unsupported Version Number        (MC)                        2 - Bad Peer Domain ID                (MC)                        3 - Bad Peer MASC Node ID             (MC)                        6 - Unacceptable Hold Time            (MC)                        7 - Invalid Parent Configuration      (MC)                        8 - Inconsistent Role                 (MC)                        9 - Bad Parent Domain ID              (MC)                       10 - No Common Parent                  (MC)                       13 - Unrecognized Address Family       (MC)Radoslavov, et al.            Experimental                     [Page 22]

RFC 2909                   The MASC Protocol              September 2000               UPDATE Message Error subcodes:                        0 - Unspecific                        (MC)                        1 - Malformed Attribute List          (MC)                        2 - Unrecognized Required Attribute   (CC)                        5 - Attribute Length Error            (MC)                       10 - Invalid Address field             (CC)                       11 - Invalid Mask field                (CC)                       12 - Non-Contiguous Mask               (CC)                       13 - Unrecognized Address Family       (MC)                       14 - Claim Type Error                  (CC)                       15 - Origin Domain ID Error            (CC)                       16 - Origin Node ID Error              (CC)                       17 - Claim Lifetime Too Short          (CC)                       18 - Claim Lifetime Too Long           (CC)                       19 - Claim Timestamp Too Old           (CC)                       20 - Claim Timestamp Too New           (CC)                       21 - Claim Prefix Size Too Small       (CC)                       22 - Claim Prefix Size Too Large       (CC)                       23 - Illegal Origin Role Error         (CC)                       24 - No Appropriate Parent Prefix      (CC)                       25 - No Appropriate Child Prefix       (CC)                       26 - No Appropriate Internal Prefix    (CC)                       27 - No Appropriate Sibling Prefix     (CC)                       28 - Claim Holdtime Too Short          (CC)                       29 - Claim Holdtime Too Long           (CC)         Hold Timer Expired subcodes (the O-bit is always zero):                        0 - Unspecific                        (MC)               Finite State Machine Error subcodes:                        0 - Unspecific                        (MC)                        1 - Open/Close MASC Connection FSM Error (MC)                        2 - Unexpected Message Type FSM Error (MC)               Cease subcodes (the O-bit is always zero):                        0 - Unspecific                        (MC)               NOTIFICATION subcodes (the O-bit is always zero):                        0 - Unspecific                        (MC)   Data:      This variable-length field is used to diagnose the reason for the      NOTIFICATION.  The contents of the Data field depend upon the      Error Code and Error Subcode.  SeeSection 8 for more details.Radoslavov, et al.            Experimental                     [Page 23]

RFC 2909                   The MASC Protocol              September 2000      Note that the length of the Data field can be determined from the      message Length field by the formula:         Message Length = 6 + Data Length      The minimum length of the NOTIFICATION message is 6 octets      (including message header).8.  MASC Error Handling   This section describes actions to be taken when errors are detected   while processing MASC messages.  MASC Error Handling is similar to   that of BGP [BGP].   When any of the conditions described here are detected, a   NOTIFICATION message with the indicated Error Code, Error Subcode,   and Data fields is sent.  In addition, the MASC connection might be   closed.  If no Error Subcode is specified, then a zero (Unspecific)   must be used.   The phrase "the MASC connection is closed" means that the transport   protocol connection has been closed and that all resources for that   MASC connection have been deallocated.   Unless specified explicitly, the Data field of the NOTIFICATION   message is empty.8.1.  Message Header Error Handling   All errors detected while processing the Message Header are indicated   by sending the NOTIFICATION message with Error Code Message Header   Error.  The Error Subcode elaborates on the specific nature of the   error.  The Data field contains the erroneous Message (including the   message header).   If the Length field of the message header is less than 4 or greater   than 4096, or if the length of an OPEN message is less  than the   minimum length of the OPEN message, or if the length of an UPDATE   message is less than the minimum length of the UPDATE message, or if   the length of a KEEPALIVE message is not equal to 4, then the Error   Subcode is set to Bad Message Length.   If the Type field of the message header is not recognized, then the   Error Subcode is set to Bad Message Type.Radoslavov, et al.            Experimental                     [Page 24]

RFC 2909                   The MASC Protocol              September 20008.2.  OPEN Message Error Handling   All errors detected while processing the OPEN message are indicated   by sending the NOTIFICATION message with Error Code OPEN Message   Error.  The Error Subcode elaborates on the specific nature of the   error.  The Data field contains the erroneous OPEN Message (excluding   the Message Header), unless stated otherwise.   If the version number contained in the Version field of the received   OPEN message is not supported, then the Error Subcode is set to   Unsupported Version Number.  The Data field is a 1-octet unsigned   integer, which indicates the largest locally supported version number   less than the version the remote MASC node bid (as indicated in the   received OPEN message).   If the Sender Domain Identifier field of the OPEN message is   unacceptable, then the Error Subcode is set to Bad Peer Domain ID.   The determination of acceptable Domain IDs is outside the scope of   this protocol.   If the Sender MASC Node Identifier field of the OPEN message is   unacceptable, then the Error Subcode is set to Bad Peer MASC Node ID.   The determination of acceptable Node IDs is outside the scope of this   protocol.   If the Hold Time field of the OPEN message is unacceptable, then the   Error Subcode MUST be set to Unacceptable Hold Time.  An   implementation MUST reject Hold Time values of one or two seconds.   An implementation MAY reject any proposed Hold Time.  An   implementation which accepts a Hold Time MUST use the negotiated   value for the Hold Time.   If the remote system's proposed Role is INTERNAL_PEER, and either   (but not both) the local system or the remote system's Parent Domain   ID is [TLD_ID], then the Error Subcode is set to Invalid Parent   Configuration.  The Data field must be filled with all the local   system's Parent Domain IDs.   If the remote system's proposed Role conflicts with its expected role   (based on the local system's configured Role), then the Error Subcode   is set to Inconsistent Role.  The Data field is 1-octet long, and   contains the local system's configured Role.   If the remote system's Parent Domain ID is unacceptable, then the   Error Subcode is set to Bad Parent Domain ID, and the Data field is   filled with the erroneous Parent Domain ID.  The determination of   acceptable Parent Domain ID is outside the scope of this protocol.Radoslavov, et al.            Experimental                     [Page 25]

RFC 2909                   The MASC Protocol              September 2000   If the remote system is supposed to be a sibling, but it does not   have a common parent with the local system (based on the Parent   Domain ID information in the OPEN message), the Error Subcode is set   to No Common Parent, and the Data field is filled with all Parent   Domain IDs of the local MASC domain.   If the Address Family is unrecognized, then the Error Subcode is set   to Unrecognized Address Family.8.3.  UPDATE Message Error Handling   All errors detected while processing the UPDATE message are indicated   by sending the NOTIFICATION message with Error Code UPDATE Message   Error.  The error subcode elaborates on the specific nature of the   error.  The Data field contains the erroneous UPDATE Message   (including the attribute header, but excluding the Message Header),   unless stated otherwise.   If any recognized attribute has an Attribute Length that conflicts   with the expected length (based on the attribute type code), then the   Error Subcode is set to Attribute Length Error.   If any of the mandatory well-known attributes are not recognized,   then the Error Subcode is set to Unrecognized Required Attribute.   If the Address field includes an invalid address (except 0), then the   Error Subcode is set to Invalid Address.   If the Mask field includes an invalid mask (for example, starting   with 0), then the Error Subcode is set to Invalid Mask.   If the Mask field includes a non-contiguous bitmask, and that MASC   server does not support, or is not configured to use non-contiguous   masks, then the Error Subcode is set to Non-Contiguous Mask.   If the Address Family is unrecognized, then the Error Subcode is set   to Unrecognized Address Family.   If the Origin Role/Claim Type combination is not one of the   following, then the Error Subcode is set to Claim Type Error.Radoslavov, et al.            Experimental                     [Page 26]

RFC 2909                   The MASC Protocol              September 2000      Origin  Claim      Role    Type      ICS     PREFIX_IN_USE   (0)      I  P    CLAIM_DENIED    (1)      ICS     CLAIM_TO_EXPAND (2)      ICS     NEW_CLAIM       (3)      I  P    PREFIX_MANAGED  (4)      ICSP    WITHDRAW        (5)   If there is a reason to believe that the Origin Domain ID is invalid,   then the Error Subcode is set to Origin Domain ID Error.  The same   applies for Origin Node ID (the corresponding error is Origin Node ID   Error).   If a node (usually a parent receiving a claim from a child) decides   that the Claim Lifetime is too short (for example, less than 172800,   i.e. 48 hours), it MAY send an UPDATE Message Error with subcode   Claim Lifetime Too Short.   If a node (usually a parent receiving a claim from a child) decides   that the Claim Lifetime is too long (for example, more than   15,768,000, i.e. half year), then it MAY send an UPDATE Message Error   with subcode Claim Lifetime Too Long.  Note that usually a parent   MASC node should send first CLAIM_DENIED collision messages with   Claim Lifetime field filled with the longest acceptable lifetime.  If   the child refuses to claim with shorter lifetime, then Claim Lifetime   Too Long should be sent.   If a node (usually a parent receiving a claim from a child) decides   that the Claim Timestamp is too small, i.e. too old (for example, if   a node is self-confident that its clock is quite accurate), then it   MUST send an UPDATE Message Error with subcode Claim Timestamp Too   Old.  Claim Timestamp Too New is defined similarly.   If a node (usually a parent receiving a claim from a child) decides   that the prefix size implied by the Mask field is too small (for   example, smaller than 16 addresses), then it MAY send an UPDATE   Message Error with subcode Claim Prefix Size Too Small.   If a node (usually a parent receiving a claim from a child) decides   that the prefix size implied by the Mask field is too large, then it   MAY send an UPDATE Message Error with subcode Claim Prefix Size Too   Large.  Note that usually a parent MASC node should send first   CLAIM_DENIED collision messages for some subrange of the child's   large claimed address range.  If the child refuses to shrink the   claim size, then Claim Prefix Size Too Large should be sent.Radoslavov, et al.            Experimental                     [Page 27]

RFC 2909                   The MASC Protocol              September 2000   If the received UPDATE message's computed Updated Origin Role is   illegal (see Table 1 inSection 11.1), then the Error Subcode is set   to Illegal Origin Role Error.   If the received UPDATE message needs to be associated with a parent's   prefix, but the association is not successful, then the Error Subcode   is set to No Appropriate Parent Prefix.  The No Appropriate Child   Prefix, No Appropriate Internal Prefix, and No Appropriate Sibling   Prefix Error Subcodes are defined similarly.   If a node decides that the Claim Holdtime is too short (for example,   just few seconds), it MAY send an UPDATE Message Error with subcode   Claim Holdtime Too Short.   If a node decides that the Claim Holdtime is too long (for example,   more than 15,768,000, i.e. half year), then it SHOULD send an UPDATE   Message Error with subcode Claim Holdtime Too Long.   If any other error is encountered when processing attributes, then   the Error Subcode is set to Malformed Attribute List, and the erratic   attribute is included in the data field.8.4.  Hold Timer Expired Error Handling   If a system does not receive successive KEEPALIVE and/or UPDATE   and/or NOTIFICATION messages within the period specified in the Hold   Time field of the OPEN message, then the NOTIFICATION message with   Hold Timer Expired Error Code must be sent and the MASC connection   closed.8.5.  Finite State Machine Error Handling   Any error detected by the MASC Finite State Machine (e.g., receipt of   an unexpected event) is indicated by sending the NOTIFICATION message   with Error Code Finite State Machine Error.  The Error Subcode   elaborates on the specific nature of the error.8.6.  NOTIFICATION Message Error Handling   If a node sends a NOTIFICATION message, and there is an error in that   message, and the O-bit of that message is not zero, a NOTIFICATION   with O-bit zeroed, Error Code of NOTIFICATION Error, and subcode   Unspecific must be sent.  In addition, the Data field must include   the erratic NOTIFICATION message.  However, if the erratic   NOTIFICATION message had the O-bit zeroed, then any error, such as an   unrecognized Error Code or Error Subcode, should be noticed, loggedRadoslavov, et al.            Experimental                     [Page 28]

RFC 2909                   The MASC Protocol              September 2000   locally, and brought to the attention of the administrator of the   remote node.  The means to do this, however, lies outside the scope   of this document.8.7.  Cease   In absence of any fatal errors (that are indicated in this section),   a MASC node may choose at any given time to close its MASC connection   by sending the NOTIFICATION message with Error Code Cease.  However,   the Cease NOTIFICATION message must not be used when a fatal error   indicated by this section does exist.8.8.  Connection Collision Detection   If a pair of MASC speakers try simultaneously to establish a TCP   connection to each other, then two parallel connections between this   pair of speakers might well be formed.  We refer to this situation as   connection collision.  Clearly, one of these connections must be   closed.  Note that if the nodes were siblings, and each of those   connections was associated with a different parent, then we do not   consider this situation as collision (seeSection 4.4).   Based on the value of the MASC Node Identifier a convention is   established for detecting which MASC connection is to be preserved   when a connection collision does occur.  The convention is to compare   the MASC Node Identifiers of the remote nodes involved in the   collision and to retain only the connection initiated by the MASC   speaker with the higher-valued MASC Node Identifier.   Upon receipt of an OPEN message, the local system must examine all of   its connections that are in the OpenConfirm state.  A MASC speaker   may also examine connections in an OpenSent state if it knows the   MASC Node Identifier of the remote node by means outside of the   protocol.  If among these connections there is a connection to a   remote MASC speaker whose MASC Node Identifier equals the one in the   OPEN message, and, in case of a sibling-to-sibling connection, the   Parent Domain ID of that connection equals the one in the OPEN   message, then the local system performs the following connection   collision resolution procedure:   1. The MASC Node Identifier of the local system is compared to the      MASC Node Identifier of the remote system (as specified in the      OPEN message).  Comparing MASC Node Identifiers is done by      treating them as unsigned integers (e.g. 4-octets long for IPv4      and 16-octets long for IPv6).Radoslavov, et al.            Experimental                     [Page 29]

RFC 2909                   The MASC Protocol              September 2000   2. If the value of the local MASC Node Identifier is less than the      remote one, the local system closes MASC connection that already      exists (the one that is already in the OpenConfirm state), and      accepts the MASC connection initiated by the remote system.   3. Otherwise, the local system closes the newly created MASC      connection (the one associated with the newly received OPEN      message), and continues to use the existing one (the one that is      already in the OpenConfirm state).   A connection collision with an existing MASC connection that is in   the Established state causes unconditional closing of the newly   created connection.  Note that a connection collision cannot be   detected with connections that are in Idle, or Connect, or Active   states (seeSection 10).   Closing the MASC connection (that results from the collision   resolution procedure) is accomplished by sending the NOTIFICATION   message with the Error Code Cease.9.  MASC Version Negotiation   MASC speakers may negotiate the version of the protocol by making   multiple attempts to open a MASC connection, starting with the   highest version number each supports.  If an open attempt fails with   an Error Code OPEN Message Error, and an Error Subcode Unsupported   Version Number, then the MASC speaker has available the version   number it tried, the version number the remote node tried, the   version number passed by the remote node in the NOTIFICATION message,   and the version numbers that it supports.  If the two MASC speakers   do support one or more common versions, then this will allow them to   rapidly determine the highest common version. In order to support   MASC version negotiation, future versions of MASC must retain the   format of the OPEN and NOTIFICATION messages.10.  MASC Finite State Machine   This section specifies MASC operation in terms of a Finite State   Machine (FSM).  The FSM and the operations are peer peering session.   Following is a brief summary and overview of MASC operations by state   as determined by this FSM.   Initially the peering session is in the Idle state.Radoslavov, et al.            Experimental                     [Page 30]

RFC 2909                   The MASC Protocol              September 200010.1.  Open/Close MASC Connection FSM   Idle state:      In this state MASC refuses all incoming MASC connections from the      peer.  No resources are allocated to the remote node.  In response      to the Start event (initiated by either system or operator) the      local system initializes all MASC resources, starts the      ConnectRetry timer, initiates a transport connection to the remote      node, while listening for a connection that may be initiated by      the remote MASC node, and changes its state to Connect.  The exact      value of the ConnectRetry timer is a local matter, but should be      sufficiently large to allow TCP initialization.      If a MASC speaker detects an error, it shuts down the connection      and changes its state to Idle. Getting out of the Idle state      requires generation of the Start event.  If such an event is      generated automatically, then persistent MASC errors may result in      persistent flapping of the speaker.  To avoid such a condition it      is recommended that Start events should not be generated      immediately for a node that was previously transitioned to Idle      due to an error. For a node that was previously transitioned to      Idle due to an error, the time between consecutive generation of      Start events, if such events are generated automatically, shall      exponentially increase. The value of the initial timer shall be 60      seconds. The time shall be doubled for each consecutive retry, but      shall not be longer than 24 hours.      Any other event received in the Idle state is ignored.   Connect state:      In this state MASC is waiting for the transport protocol      connection to be completed.      If the transport protocol connection succeeds, the local system      clears the ConnectRetry timer, completes initialization, sends an      OPEN message to the remote node, and changes its state to      OpenSent. If the transport protocol connect fails (e.g.,      retransmission timeout), the local system restarts the      ConnectRetry timer, continues to listen for a connection that may      be initiated by the remote MASC node, and changes its state to      Active state.Radoslavov, et al.            Experimental                     [Page 31]

RFC 2909                   The MASC Protocol              September 2000      In response to the ConnectRetry timer expired event, the local      system restarts the ConnectRetry timer, initiates a transport      connection to the other MASC node, continues to listen for a      connection that may be initiated by the remote MASC node, and      stays in the Connect state.      The Start event is ignored in the Connect state.      In response to any other event (initiated by either system or      operator), the local system releases all MASC resources associated      with this connection and changes its state to Idle.   Active state:      In this state MASC is trying to acquire a remote node by listening      for a transport protocol connection initiated by the remote node.      If the transport protocol connection succeeds, the local system      clears the ConnectRetry timer, completes initialization, sends an      OPEN message to the remote node, sets its Hold Timer to a large      value, and changes its state to OpenSent.  A Hold Timer value of      [HOLDTIME] seconds is suggested.      In response to the ConnectRetry timer expired event, the local      system restarts the ConnectRetry timer, initiates a transport      connection to other MASC node, continues to listen for a      connection that may be initiated by the remote MASC node, and      changes its state to Connect.      If the local system detects that a remote node is trying to      establish a MASC connection to it, and the IP address of the      remote node is not an expected one, the local system restarts the      ConnectRetry timer, rejects the attempted connection, continues to      listen for a connection that may be initiated by the remote MASC      node, and stays in the Active state.      The Start event is ignored in the Active state.      In response to any other event (initiated by either system or      operator), the local system releases all MASC resources associated      with this connection and changes its state to Idle.   OpenSent state:      In this state MASC waits for an OPEN message from the remote node.      When an OPEN message is received, all fields are checked for      correctness.  If the MASC message header checking or OPEN message      checking detects an error (seeSection 8.2), or a connectionRadoslavov, et al.            Experimental                     [Page 32]

RFC 2909                   The MASC Protocol              September 2000      collision (seeSection 8.8) the local system sends a NOTIFICATION      message and, if the connection is to be closed, it changes its      state to Idle.      If the locally configured role is SIBLING and there is no parent      domain with Domain ID equal to the Parent Domain ID in the OPEN      message, the local system sends a NOTIFICATION Open Message  Error      with Error Subcode set to No Common Parent, the connection must be      closed, and the state of the local system must be changed to Idle.      If there are no errors in the OPEN message, MASC sends a KEEPALIVE      message and sets a KeepAlive timer.  The Hold Timer, which was      originally set to a large value (see above), is replaced with the      negotiated Hold Time value (seeSection 7.2).  If the negotiated      Hold Time value is zero, then the Hold Time timer and KeepAlive      timers are not started.  If the value of the MASC Domain ID field      is the same as the local MASC Domain ID, and if the Role field of      the OPEN message is set to INTERNAL_PEER, then the connection is      an "internal" connection; otherwise, it is "external".  Finally,      the state is changed to OpenConfirm.      If a disconnect notification is received from the underlying      transport protocol, the local system closes the MASC connection,      restarts the ConnectRetry timer, while continue listening for      connection that may be initiated by the remote MASC node, and goes      into the Active state.      If the Hold Timer expires, the local system sends a NOTIFICATION      message with error code Hold Timer Expired and changes its state      to Idle.      In response to the Stop event (initiated by either system or      operator) the local system sends a NOTIFICATION message with Error      Code Cease and changes its state to Idle.      The Start event is ignored in the OpenSent state.      In response to any other event the local system sends a      NOTIFICATION message with Error Code Finite State Machine Error      and Error Subcode Open/Close MASC Connection FSM Error, and      changes its state to Idle.      Whenever MASC changes its state from OpenSent to Idle, it closes      the MASC (and transport-level) connection and releases all      resources associated with that connection.Radoslavov, et al.            Experimental                     [Page 33]

RFC 2909                   The MASC Protocol              September 2000   OpenConfirm state:      In this state MASC waits for a KEEPALIVE or NOTIFICATION message.      If the local system receives a KEEPALIVE message, it changes its      state to Established.      If the Hold Timer expires before a KEEPALIVE message is received,      the local system sends a NOTIFICATION message with error code Hold      Timer Expired and changes its state to Idle.      If the local system receives a NOTIFICATION message with the O-bit      zeroed, it changes its state to Idle.      If the KeepAlive timer expires, the local system sends a KEEPALIVE      message and restarts its KeepAlive timer.      If a disconnect notification is received from the underlying      transport protocol, the local system changes its state to Idle.      In response to the Stop event (initiated by either system or      operator) the local system sends a NOTIFICATION message with Error      Code Cease and changes its state to Idle.      The Start event is ignored in the OpenConfirm state.      In response to any other event the local system sends a      NOTIFICATION message with Error Code Finite State Machine Error      and Error Subcode Unspecific, and changes its state to Idle.      Whenever MASC changes its state from OpenConfirm to Idle, it      closes the MASC (and transport-level) connection and releases all      resources associated with that connection.   Established state:      In the Established state MASC can exchange UPDATE, NOTIFICATION,      and KEEPALIVE messages with the remote node.      If the local system receives an UPDATE, or KEEPALIVE message, or      NOTIFICATION message with O-bit set, it restarts its Hold Timer,      if the negotiated Hold Time value is non-zero.      If the local system receives a NOTIFICATION message, with the O-      bit zeroed, it changes its state to Idle.Radoslavov, et al.            Experimental                     [Page 34]

RFC 2909                   The MASC Protocol              September 2000      If the local system receives an UPDATE message and the UPDATE      message error handling procedure (seeSection 8.3) detects an      error, the local system sends a NOTIFICATION message and, if the      O-bit was zeroed, changes its state to Idle.      If a disconnect notification is received from the underlying      transport protocol, the local system changes its state to Idle.      If the Hold Timer expires, the local system sends a NOTIFICATION      message with Error Code Hold Timer Expired and changes its state      to Idle.      If the KeepAlive timer expires, the local system sends a KEEPALIVE      message and restarts its KeepAlive timer.      Each time the local system sends a KEEPALIVE or UPDATE message, it      restarts its KeepAlive timer, unless the negotiated Hold Time      value is zero.      In response to the Stop event (initiated by either system or      operator), the local system sends a NOTIFICATION message with      Error Code Cease and changes its state to Idle.      The Start event is ignored in the Established state.      After entering the Established state, if the local system has      UPDATE messages that are to be sent to the remote node, they must      be sent immediately (seeSection 11.8).      In response to any other event, the local system sends a      NOTIFICATION message with Error Code Finite State Machine Error      with the O-bit zeroed and Error Subcode Unspecific, and changes      its state to Idle.      Whenever MASC changes its state from Established to Idle, it      closes the MASC (and transport-level) connection, releases all      resources associated with that connection, and deletes all state      derived from that connection.11.  UPDATE Message Processing   The UPDATE message are accepted only when the system is in the   Established state.   In the text below, a MASC domain is considered a child of itself with   regard to the claims that are related to the address space with local   usage purpose (i.e. to be used by the MAASs within that domain).  ForRadoslavov, et al.            Experimental                     [Page 35]

RFC 2909                   The MASC Protocol              September 2000   example, a NEW_CLAIM initiated by a MASC node to obtain more space   for local usage from a prefix managed by that domain will have field   Role = CHILD.   If an UPDATE is to be propagated further, it should not be sent back   to the node that UPDATE was received from, unless there is an   indication that the connection to that node was down and then   restored.   If the local system receives an UPDATE message, and there is no   indication for error, it checks whether to accept or reject the   message, and if it is not rejected, the UPDATE is processed based on   its type.   If an UPDATE message must be associated with a parent domain, then   there must be a PREFIX_MANAGED by some parent domain for a prefix   that covers the prefix of the particular UPDATE.11.1.  Accept/Reject an UPDATE   The Origin Role field is first compared against the local system's   configured Role, according to Table 1, to determine the relationship   of the origin to the local system, where Locally-Configured Role is   the local configuration with regard to the peer-forwarder of the   message.  A result of "---" means that receiving such an UPDATE is   illegal and should generate a NOTIFICATION.  Any other result is the   value to use as the "Updated" Origin Role when propagating the UPDATE   to others.  This is analogous to updating a metric upon receiving a   route, based on the metric of the link.                       Locally-Configured Role   Origin   Role     || INTERNAL_PEER | CHILD   | SIBLING | PARENT   =========++===============+=========+=========+=========   INTERNAL || INTERNAL_PEER | PARENT  | SIBLING | CHILD   CHILD    || CHILD         | SIBLING | ---     | ---   SIBLING  || SIBLING       | ---     | SIBLING | CHILD   PARENT   || PARENT        | ---     | PARENT  | ---                Table 1: Updated Origin Role Computation   After the Origin Role is updated, the following additional processing   needs to be applied:   o  If the output from the Updated Origin Role Computation is SIBLING,      but the Origin Domain ID is the same as the local MASC domain, the      Updated Origin Role is changed to INTERNAL.  This is necessary in      case a MASC node receives from a parent or sibling its own UPDATEsRadoslavov, et al.            Experimental                     [Page 36]

RFC 2909                   The MASC Protocol              September 2000      after reboot, or if because of internal partitioning, the      INTERNAL_PEERs are exchanging UPDATEs via other MASC domains      (either parent or sibling(s)).   o  If both Locally-Configured Role, and Origin Role are equal to      PARENT, and the Origin Domain ID is the same as the local MASC      domain, the Updated Origin Role is changed to INTERNAL.  This is      necessary to allow a parent to receive its own UPDATEs through its      own children, although the parent might drop those UPDATEs if it      has a reason not to believe its children.   o  If both Locally-Configured Role, and Origin Role are equal to      PARENT, and the Origin Domain ID is the same as the remote MASC      domain, and the UPDATE type is CLAIM_DENIED, the Updated Origin      Role is changed to INTERNAL.  This is necessary to allow a parent      to receive the CLAIM_DENIED it has originated through the child      whose claim was denied.  If the Origin Domain ID is not same as      the remote MASC domain, but is same as some of the other MASC      children domains, the Updated Origin Role still should be changed      to INTERNAL, although the parent might drop this UPDATE if it has      a reason not to believe a third party child.   If the Updated Origin Role is INTERNAL, but the Origin Domain ID   differs from the local Domain ID, a NOTIFICATION of <UPDATE Message   Error, Illegal Origin Role> must be sent back, and the claim is   rejected.   If Claim Timestamp and Claim Holdtime indicate that the claim has   expired (e.g. Timestamp + Claim Holdtime <= CurrentTime), the UPDATE   is silently dropped and no further actions are taken.   Each new arrival UPDATE is compared with all claims in the local   cache.  The following fields are compared, and if all of them are the   same, the message is silently rejected and no further actions are   taken:   o  Role, D-bit, Type   o  AddrFam   o  Claim Timestamp   o  Claim Lifetime   o  Claim Holdtime   o  Origin Domain IdentifierRadoslavov, et al.            Experimental                     [Page 37]

RFC 2909                   The MASC Protocol              September 2000   o  Origin Node Identifier   o  Address   o  Mask   Further processing of an UPDATE is based on its type and the Updated   Origin Role.11.2.  PREFIX_IN_USE Message Processing11.2.1.  PREFIX_IN_USE by PARENT   The claim is rejected, and a NOTIFICATION of <UPDATE Message Error,   Illegal Origin Role> should be sent back.11.2.2.  PREFIX_IN_USE by SIBLING   If the claim cannot be associated with any parent's PREFIX_MANAGED,   the claim is dropped, a NOTIFICATION of <UPDATE Message Error, No   Appropriate Parent Prefix> must be sent back and no further actions   should be taken.   If the claim collides with some of the local domain's pending claims,   the local claims must not be considered further, and the Claim-Timer   of each of them must be canceled. If the received PREFIX_IN_USE claim   clashes with and wins over some of the local domain's allocated   prefixes, resolve the clash according toSection 12.4. Finally, the   claim must be propagated further to all INTERNAL_PEERs, all MASC   nodes from the corresponding parent MASC domain and all known   siblings with the same parent domain.11.2.3.  PREFIX_IN_USE by CHILD   If the claim's prefix is not a subrange of any of the local domain's   PREFIX_MANAGED, the claim is dropped, a NOTIFICATION of <UPDATE   Message Error, No Appropriate Parent Prefix> must be sent back and no   further actions should be taken.  Otherwise, the claim must be   propagated further to all INTERNAL_PEERs and all MASC children   domains.11.2.4.  PREFIX_IN_USE by INTERNAL_PEER   If the MASC node decides that the local domain does not need that   prefix any more, it may be withdrawn, otherwise, the claim is   processed as PREFIX_MANAGED.Radoslavov, et al.            Experimental                     [Page 38]

RFC 2909                   The MASC Protocol              September 200011.3.  CLAIM_DENIED Message Processing11.3.1.  CLAIM_DENIED by CHILD or SIBLING   The message is rejected, and a NOTIFICATION of <UPDATE Message Error,   Illegal Origin Role> should be sent back.11.3.2.  CLAIM_DENIED by INTERNAL_PEER   Propagate to all INTERNAL_PEERs and all MASC children nodes.11.3.3.  CLAIM_DENIED by PARENT   If the Origin Domain ID is not same as the local domain ID, and the   UPDATE cannot be associated with any parent domain, the message is   dropped, a NOTIFICATION of <UPDATE Message Error, No Appropriate   Parent Prefix> must be sent back and no further actions should be   taken.   If the Origin Domain ID is not same as the local domain ID, and the   UPDATE can be associated with a parent domain, the message is   propagated to all nodes from that parent domain, all INTERNAL_PEERs,   and all known SIBLINGs with regard to that parent.   If the Origin Domain ID is same as the local domain ID, and there is   no corresponding pending claim originated by the local MASC domain   (i.e. a NEW_CLAIM or CLAIM_TO_EXPAND with same AddrFam, Origin Domain   ID, Claim Timestamp, Address and Mask), a NOTIFICATION of <UPDATE   Message Error, No Appropriate Internal Prefix> must be sent back and   no further actions should be taken. Otherwise, the matching NEW_CLAIM   or CLAIM_TO_EXPAND's Claim-Timer must be canceled and the claim must   not be considered further. Finally, the received CLAIM_DENIED must be   propagated to all INTERNAL_PEERs, all MASC nodes from the   corresponding parent MASC domain, and all known SIBLINGs with regard   to that parent.11.4.  CLAIM_TO_EXPAND Message Processing11.4.1.  CLAIM_TO_EXPAND by PARENT   The claim is rejected, and a NOTIFICATION of <UPDATE Message Error,   Illegal Origin Role> should be sent back.Radoslavov, et al.            Experimental                     [Page 39]

RFC 2909                   The MASC Protocol              September 200011.4.2.  CLAIM_TO_EXPAND by SIBLING   If the claim cannot be associated with any parent's PREFIX_MANAGED,   the claim is dropped, a NOTIFICATION of <UPDATE Message Error, No   Appropriate Parent Prefix> must be sent back and no further actions   should be taken.   If there is no overlapping PREFIX_IN_USE by the same MASC domain, the   claim is dropped, a NOTIFICATION of <UPDATE Message Error, No   Appropriate Sibling Prefix> must be sent back and no further actions   should be taken.   If the claim collides with and wins over some of the local domain's   pending claims, the loser claims must not be considered further, and   the Claim-Timer of the each of them must be canceled.  Also, the   received claim must be propagated further to all INTERNAL_PEERs, all   MASC nodes from the corresponding parent MASC domain and all known   siblings with the same parent domain.11.4.3.  CLAIM_TO_EXPAND by CHILD   If the claim cannot be associated with any of the local domain's   PREFIX_MANAGED, the claim is dropped, a NOTIFICATION of <UPDATE   Message Error, No Appropriate Parent Prefix> must be sent back and no   further actions should be taken.   If there is no overlapping PREFIX_IN_USE by the same MASC domain, the   claim is dropped, a NOTIFICATION of <UPDATE Message Error, No   Appropriate Child Prefix> must be sent back and no further actions   should be taken.   Otherwise, the claim has to be propagated to all INTERNAL_PEERs.  If   the lifetime of the claim is longer than the lifetime of the   corresponding prefix managed by the local domain, or if there is an   administratively configured reason to prevent the child from   succeeding allocating the claimed prefix, a CLAIM_DENIED must be sent   to all MASC children nodes that have same Domain ID as Origin Domain   ID in the received message.  The CLAIM_DENIED must be the same as the   received claim, except Rol=INTERNAL, and Claim Lifetime should be set   to the maximum allowed lifetime.  Otherwise, propagate the claim to   all children as well.11.4.4.  CLAIM_TO_EXPAND by INTERNAL_PEER   If the claim cannot be associated with any parent's PREFIX_MANAGED,   the claim is dropped, a NOTIFICATION of <UPDATE Message Error, No   Appropriate Parent Prefix> must be sent back and no further action   should be taken.Radoslavov, et al.            Experimental                     [Page 40]

RFC 2909                   The MASC Protocol              September 2000   If there is no overlapping PREFIX_IN_USE by the local MASC domain,   the claim is dropped, a NOTIFICATION of <UPDATE Message Error, No   Appropriate Internal Prefix> must be sent back and no further actions   should be taken.   If the MASC node decides that the local domain does not need that   pending claim any more, it MAY be withdrawn. Otherwise, the claim   must be propagated to all INTERNAL_PEERs and all MASC nodes from the   corresponding parent MASC domain.11.5.  NEW_CLAIM Message Processing   If the claim's Address field is 0 (i.e. a hint by a child to a parent   to obtain more space), the claim should be propagated only among the   nodes that belong to the child Origin Domain and the parent domain.   Otherwise, process like CLAIM_TO_EXPAND, except that no check for   overlapping PREFIX_IN_USE needs to be performed.11.6.  PREFIX_MANAGED Message Processing.11.6.1.  PREFIX_MANAGED by PARENT   If the Origin Domain ID matches one of the parents' domain ID's, the   prefix is recorded, and can be used by the address allocation   algorithm for allocating subranges.  Also, the message is propagated   to all MASC nodes of the corresponding parent domain, all   INTERNAL_PEERs, and SIBLINGs with same parent.11.6.2.  PREFIX_MANAGED by CHILD or SIBLING   The message is rejected, and a NOTIFICATION of <UPDATE Message Error,   Illegal Origin Role> should be sent back.11.6.3.  PREFIX_MANAGED by INTERNAL_PEER   The prefix is recorded as allocated to the local domain, propagated   to all INTERNAL_PEERs, and can be used for (all items apply):   a) address ranges/prefixes advertisements to all MASC children and      local domain's MAASs;   b) injection into G-RIB;   c) further expansion by the address allocation algorithm (seeAppendix A);Radoslavov, et al.            Experimental                     [Page 41]

RFC 2909                   The MASC Protocol              September 200011.7.  WITHDRAW Message Processing11.7.1.  WITHDRAW by CHILD   If the WITHDRAW cannot be associated with any of the child domain's   PREFIX_IN_USE (i.e. no child's PREFIX_IN_USE covers WITHDRAW's   range), or if the WITHDRAW does not match any of the child domain's   NEW_CLAIM or CLAIM_TO_EXPAND (i.e. there is no child's claim with   same Address, Mask and Timestamp), the message is dropped, a   NOTIFICATION of <UPDATE Message Error, No Appropriate Child Prefix>   must be sent back and no further actions should be taken. Otherwise,   propagate to all INTERNAL_PEERs and children.11.7.2.  WITHDRAW by SIBLING   If the WITHDRAW cannot be associated with any of the siblings'   PREFIX_IN_USE (i.e. no sibling's PREFIX_IN_USE covers WITHDRAW's   range), or if the WITHDRAW does not match any of the sibling domain's   NEW_CLAIM or CLAIM_TO_EXPAND (i.e. there is no sibling's claim with   same Address, Mask and Timestamp), the message is dropped, a   NOTIFICATION of <UPDATE Message Error, No Appropriate Sibling Prefix>   must be sent back and no further actions should be taken. Otherwise,   propagate to all INTERNAL_PEERs, all MASC nodes from the same parent   MASC domain and all known siblings with the same parent domain.11.7.3.  WITHDRAW by INTERNAL   If the WITHDRAW cannot be associated with any of the local domain's   PREFIX_IN_USE or PREFIX_MANAGED (i.e. no local domain's prefix covers   WITHDRAW's range), or if the WITHDRAW does not match any of the local   domain's NEW_CLAIM or CLAIM_TO_EXPAND (i.e. there is no local   domain's claim with same Address, Mask and Timestamp) the message is   dropped, a NOTIFICATION of <UPDATE Message Error, No Appropriate   Internal Prefix> must be sent back and no further actions should be   taken.   Otherwise, propagate to all INTERNAL_PEERs, all MASC nodes of the   corresponding parent domain of that prefix, all known siblings with   that parent domain, and all children.  If the WITHDRAW can be   associated with some of local domain's PREFIX_IN_USE or   PREFIX_MANAGED, stop advertising the WITHDRAW range to the MAASs and   withdraw that range from the G-RIB database.  In the special case   when there is an indication that the WITHDRAW has been originated by   the local domain because of a clash, and the range specified in   WITHDRAW is a subrange of the local PREFIX_MANAGED, and the Claim   Holdtime of WITHDRAW is shorter than the Claim Holdtime ofRadoslavov, et al.            Experimental                     [Page 42]

RFC 2909                   The MASC Protocol              September 2000   PREFIX_MANAGED, the WITHDRAW's range should not be withdrawn from the   G-RIB.  If the WITHDRAW matches a local domain's NEW_CLAIM or   CLAIM_TO_EXPAND, cancel the matching claim's Claim-Timer.11.7.4.  WITHDRAW by PARENT   If the WITHDRAW cannot be associated with any parent domain, a   NOTIFICATION of <UPDATE Message Error, No Appropriate Parent Prefix>   must be sent back and no further actions should be taken.   Otherwise, propagate to all INTERNAL_PEERs and all known siblings   with the same parent domain. Also, originate a WITHDRAW message for   each intersection of a locally owned PREFIX_MANAGED/PREFIX_IN_USE and   the received WITHDRAW.  The locally originated WITHDRAW message's   Claim Holdtime should be at least equal to the Claim Holdtime in the   WITHDRAW message received from the parent; the Origin Node ID should   be the same as the particular PREFIX_MANAGED/PREFIX_IN_USE.11.8.  UPDATE Message Ordering   To simplify consistency and sanity check implementations, if there is   more than one UPDATE message that needs to be send to a peer (for   example, after a connection (re)establishment), some of the UPDATEs   must be sent before others.   The rules that always apply are:   o  PREFIX_IN_USE must always be sent BEFORE CLAIM_TO_EXPAND,      NEW_CLAIM, and WITHDRAW by the same MASC domain   o  WITHDRAW must always be sent AFTER PREFIX_IN_USE, CLAIM_TO_EXPAND,      NEW_CLAIM, and PREFIX_MANAGED by the same MASC domain   Any further ordering is defined below by the roles of the sender and   the receiver.11.8.1.  Parent to Child   Messages are sent in the following order:   1) Parent's PREFIX_MANAGED and WITHDRAWs.   2) All children's PREFIX_IN_USE, CLAIM_TO_EXPAND, and NEW_CLAIMs.      CLAIMs from third party children that are hints for more space      (i.e. address = 0) should not be propagated; if propagated, the      child should drop them.Radoslavov, et al.            Experimental                     [Page 43]

RFC 2909                   The MASC Protocol              September 2000   3) Parent initiated CLAIM_DENIED and children initiated WITHDRAWs.      CLAIM_DENIED regarding third party children's claims/hints with      address = 0 should not be propagated; if propagated, the child      should drop them.11.8.2.  Child to Parent   Messages are sent in the following order:   1) Parent's PREFIX_MANAGED and WITHDRAWs.   2) All PREFIX_IN_USE, CLAIM_TO_EXPAND, and NEW_CLAIMSs from that      parent's space, initiated by that child and all its siblings.   3) Parent's initiated CLAIM_DENIED, and all WITHDRAWSs that can be      associated with that parent's space and are initiated by the local      domain or all known siblings with that parent.11.8.3.  Sibling to Sibling   Messages are sent in the following order:   1) All common parent's PREFIX_MANAGED and WITHDRAWs.   2) PREFIX_IN_USE, CLAIM_TO_EXPAND, and NEW_CLAIMs, initiated by      siblings.   3) CLAIM_DENIEDs initiated by common parent, and WITHDRAWs initiated      by local domain and all known siblings with that parent.11.8.4.  Internal to Internal   Messages are sent in the following order:   1) All parents' PREFIX_MANAGED and WITHDRAWs.   2) Local domain's and all siblings' PREFIX_IN_USE, CLAIM_TO_EXPAND,      and NEW_CLAIMs.  CLAIMs from siblings that are hints for more      space (i.e. address = 0) should not be propagated; if propagated,      the recipient should drop them.   3) CLAIM_DENIEDs initiated by all parents, and WITHDRAWs initiated by      local domain and all known siblings.   4) All children's PREFIX_IN_USE, CLAIM_TO_EXPAND, and NEW_CLAIMs.   5) All local domain initiated CLAIM_DENIED regarding children claims      and all children initiated WITHDRAWs.Radoslavov, et al.            Experimental                     [Page 44]

RFC 2909                   The MASC Protocol              September 200012.  Operational Considerations12.1.  Bootup Operations   To learn about its parent domains' IDs and prefixes, a MASC node   SHOULD try to establish connections to its PARENT nodes before   initiating a connection to a SIBLING node.  To avoid learning about   its own PREFIX_MANAGED from its children or siblings, a MASC node   SHOULD try to establish connections to its PARENT nodes and   INTERNAL_PEER nodes before initiating a connection to a CHILD or   SIBLING node.12.2.  Leaf and Non-leaf MASC Domain Operation   A non-leaf MASC domain (i.e. a domain that has children domains)   should advertise its PREFIX_MANAGED addresses to its children, and   should claim from that space the sub-ranges that would be advertised   to the internal MAASs (the claim wait time SHOULD be equal to   [WAITING_PERIOD]).  A MASC node that belongs to a non-leaf MASC   domain should perform dual functions by being a child of itself with   regard to the claiming and management of the sub-ranges for local   usage.  A leaf MASC domain should advertise all PREFIX_MANAGED   addresses to its MAASs without explicitly claiming them for internal   usage.  A MASC node can assume that it belongs to a leaf domain if it   simply does not have any UPDATEs by children domains.  If an UPDATE   by a child is received, the domain MUST switch from "leaf" to "non-   leaf" mode, and if it needs more addresses for internal usage, it   MUST claim them from that domain's PREFIX_MANAGED.  After the last   UPDATE originated by a child expires, the domain can switch back to   "leaf" mode.12.3.  Clock Skew Workaround   Each UPDATE has "Claim Timestamp" field that is set to the absolute   time of the MASC node that originated that UPDATE. The timestamp is   used for two purposes: to resolve collisions, and to define how long   an UPDATE should be kept in the local cache of other MASC nodes. A   skew in the clock could result in unfair collision decision such that   the claims originated by nodes that have their clock behind the real   time will always win; however, because collisions are presumably   rare, this will not be an issue.  Skew in the clock however might   result in expiring an UPDATE earlier than it really should be   expired, and a node might assume too early that the expired   UPDATE/prefix is free for allocation. To compensate for the clock   skew, an UPDATE message should be kept longer than the amount of time   specified in the Claim Holdtime. For example, keeping UPDATEs for an   additional 24 hours will compensate for clock skew for up to 24   hours.Radoslavov, et al.            Experimental                     [Page 45]

RFC 2909                   The MASC Protocol              September 200012.4.  Clash Resolving Mechanism   If a MASC node receives a PREFIX_IN_USE claim originated by a sibling   and the claim overlaps with some of the local prefixes, the clash   must be resolved.  Two MASC domains should not manage overlapping   address ranges, unless the domains have an ancestor-descendant (e.g.   parent-child) relationship in the MASC hierarchy.  Also, two MASC   domains should not have locally-allocated overlapping address ranges.   The clashed address ranges should not be advertised to the MAASs and   allocated to multicast applications/sessions.  If a clashed address   has being allocated to an application, the application should be   informed to stop using that address and switch to a new one.   The G-RIB database must be consistent, such that it does not have   ambiguous entries.  "Ambiguous G-RIB entries" are those entries that   might cause the multicast routing protocol to loop or lose   connectivity.  In MASC the WITHDRAW message is used to solve this   problem.  When a clashing PREFIX_IN_USE is received, it is compared   (using the function describe inSection 5.1.1) against all prefixes   allocated to the local domain.  If the local PREFIX_IN_USE is the   winner, no further actions are taken.  If the local PREFIX_IN_USE is   the loser, the clashing address range must be withdrawn by initiating   a WITHDRAW message. The message must have Role = INTERNAL, Origin   Node ID and Origin Domain ID must be the same as the corresponding   local PREFIX_IN_USE message, while Claim Timestamp, Claim Lifetime,   Claim Holdtime, Address and Mask must be the same as the received   winning PREFIX_IN_USE.  The initiated WITHDRAW message must be   processed as described inSection 11.7.   If a cached WITHDRAW times out and the local MASC domain owns an   overlapping PREFIX_MANAGED or PREFIX_IN_USE, the overlapping prefix   ranges can be injected back into the G-RIB database.  Similarly, the   address ranges that were not advertised to the local domain's MAASs   due to the WITHDRAW, can now be advertised again.   In addition to the automatic resolving of clashes, a MASC   implementation should support manual resolving of clashes.  For   example, after a clash is detected, the network administrator should   be informed that a clash has occurred.  The specific manual   mechanisms are outside the scope of this protocol.   A MASC node must be configured to operate using either manual or   automatic clash resolution mechanisms.Radoslavov, et al.            Experimental                     [Page 46]

RFC 2909                   The MASC Protocol              September 200012.5.  Changing Network Providers   If a MASC domain changes a network provider, such that the old   provider cannot be used to provide connectivity, any traffic for   sessions that are in progress and use that MASC domain as the root of   multicast distribution trees will not be able to reach that domain.   If the new network provider is willing to carry the traffic for the   old sessions rooted at the customer domain, then it must propagate   the customer's old prefixes through the G-RIB.  However, at least one   MASC node in the customer domain must maintain a TCP connection to   one of the old network provider's MASC nodes.  Thus, it can continue   to "defend" the customer's prefixes, and should continue until the   old prefixes' lifetimes expire.   If the new network provider is not willing to propagate the old   prefixes, then the customer should remove its prefixes from the G-   RIB.  If BGMP is in use, the old network provider's domain will   automatically become the Root Domain for the customer's old groups   due to the lack of a more specific group route.  MASC nodes in the   customer domain MAY still connect with the old provider's MASC nodes   to defend their allocation.12.6.  Debugging12.6.1.  Prefix-to-Domain Lookup   Use mtrace [MTRACE] to find the BGMP/MASC root domain for a group   address chosen from that prefix.12.6.2.  Domain-to-Prefix Lookup   We can find the address space allocated to a particular MASC domain   by directly querying one of the MASC servers within that domain, by   observing the state in parents, siblings, or children MASC domains,   or by observing the G-RIB information originated by that domain.   From those three methods, the first method can provide the most   detailed information. Finding the address of one of the MASC nodes   within a particular domain is outside the scope of MASC.13.  MASC Storage   In general, MASC will be run by a border routers, which, in general   do not have stable storage.  In this case, MASC must use the Layer 2   protocol/mechanism (e.g., ([AAP]) as described in [MALLOC] to store   the important information (the prefixes allocated by the local   domain) in the domain's MAASs who should have stable storage.  If theRadoslavov, et al.            Experimental                     [Page 47]

RFC 2909                   The MASC Protocol              September 2000   MASC speaker has local storage, it should use it instead of the Layer   2 protocol/mechanism.  Claims that are in progress do not have to be   saved by using the Layer 2 protocol/mechanism.14.  Security Considerations   IPsec [IPSEC] can be used to address security concerns between two   MASC peering nodes.  However, because of the store-and-forward nature   of the UPDATE messages, it is possible that if a non-trustworthy MASC   node can connect to some point of the MASC topology, then this node   can undetectably inject malicious UPDATEs that may disturb the normal   operation of other MASC nodes.  To address this problem, each MASC   node should allow peering only with trustworthy nodes.   After a reboot, a MASC node/domain can restore its state from its   neighbors (internal peers, parents, siblings, children). Typically,   the state received from a parent or internal peer will be   trustworthy, but a node may choose to drop its own UPDATEs that were   received through a sibling or a child.   A misbehaving node may attempt a Denial of Service attack by sending   a large number of colliding messages that would prevent any of its   siblings from allocating more addresses.  A single mis-behaving node   can easily be identified by all of its siblings, and all of its   UPDATEs can be ignored.  A Denial of Service attack that uses   multiple origin addresses can be prevented if a third-party UPDATE   (e.g. by a non-directly connected sibling) is accepted only if it is   sent via the common parent domain, and the MASC nodes in the parent   domain accept children UPDATEs only if they come via an internal   peer, or come directly from a child node that is same as the Origin   Node ID.15.  IANA Considerations   This document defines several number spaces (MASC message types, MASC   OPEN message optional parameters types, MASC UPDATE message attribute   types, MASC UPDATE message optional parameters types, and MASC   NOTIFICATION message error codes and subcodes).  For all of these   number spaces, certain values are defined in this specification.  New   values may only be defined by IETF Consensus, as described in [IANA-   CONSIDERATIONS].  Basically, this means that they are defined by RFCs   approved by the IESG.16.  Acknowledgments   The authors would like to thank the participants of the IETF for   their assistance with this protocol.Radoslavov, et al.            Experimental                     [Page 48]

RFC 2909                   The MASC Protocol              September 200017.  APPENDIX A: Sample Algorithms   DISCLAIMER: This section describes some preliminary suggestions by   various people for algorithms which could be used with MASC.17.1.  Claim Size and Prefix Selection Algorithm   This section covers the algorithms used by a MASC node (on behalf of   a MASC domain) to satisfy the demand for multicast addresses.  The   allocated addresses should be aggregatable, the address utilization   should be reasonably high, and the allocation latency to the MAASs   should be shorter than [WAITING_PERIOD] whenever possible.17.1.1.  Prefix Expansion   For ease of implementation and troubleshooting, MASC should use   contiguous masks to specify the address ranges, i.e. prefixes.   (Research indicates that sufficiently good results can be achieved   using contiguous masks only.)  The chosen prefixes should be as   expandable as possible.  The method used to choose the children sub-   prefixes from the parent's prefix is the so called Reverse Bit   Ordering (idea by Dave Thaler; inspired by Kampai [KAMPAI]).  For   example, if the parent's prefix width is four bits, the addresses of   the sub-prefixes are chosen in the following order:   Parent:       xxxx   Child A:      0000   Child B:      1000   Child C:      0100   Child D:      1100   If some of the children need to expand their sub-prefix, they try to   double the corresponding sub-prefix starting from the right:   Child A:      000x   Child A:      00xx   Child D:      110x   Child D:      11xx   and so on.   However, because the address ordering is very strict, to reduce the   probability for collision, when a new sub-prefix has to be chosen,   the choice should be random among all candidates with the same   potential for expandability.  For example, if the free sub-prefixes   are 01xx, 10xx, 110x, then the new prefix to claim should be chosen   with probability of 50% for 01xx and 50% for 10xx for example.Radoslavov, et al.            Experimental                     [Page 49]

RFC 2909                   The MASC Protocol              September 200017.1.2.  Reducing Allocation Latency   To reduce the allocation latency, a MASC node uses pre-allocation.   It constantly monitors the demand for addresses from its children (or   MAASs), and predicts what would be the address usage after   [WAITING_PERIOD].  Only if the available addresses will be used up   within [WAITING_PERIOD], a MASC node claims more addresses in   advance.17.1.3.  Address Space Utilization   Because every prefix size is a power of two, if a node tries to   allocate just a single prefix, the utilization at that node (i.e. at   that node's domain) can be as low as 50%.  To improve the   utilization, a MASC node can have more than one prefix allocated at a   time (typically, each of them with different size).  By using a pre-   allocation and allocating several prefixes of different size (see   below), a MASC node should try to keep its address utilization in the   range 70-90%.17.1.4.  Prefix Selection After Increase of Demand   To additionally reduce the allocation latency by reducing the   probability for collision, and to improve the aggregability of the   allocated addresses, a MASC node carefully chooses the prefixes to   claim. The first prefix is chosen at random among all reasonably   expandable candidates.  If a node chooses to allocate another,   smaller prefix, then, instead of doubling the size of the first one   which might reduce significantly the address utilization, a second   "neighbor" prefix is chosen.  For example, if prefix 224.0/16 was   already allocated, and the MASC domain needs 256 more addresses, the   second prefix to claim will be 224.1.0/24. If the domain needs more   addresses, the second prefix will eventually grow to 224.1/16, and   then both prefixes can be automatically aggregated into 224.0/15.   Only if 224.0.1/24 could not be allocated, a MASC node will choose   another prefix (eventually random among the unused prefixes).   If the number of allocated prefixes increases above some threshold,   and none of them can be extended when more addresses are needed,   then, to reduce the amount of state, a MASC node should claim a new   larger prefix and should stop re-claiming the older non-expandable   prefixes.  Research results show that up to three prefixes per MASC   domain is a reasonable threshold, such that the address utilization   can be in the range 70-90%, and at the same time the prefix flux will   be reasonably low.Radoslavov, et al.            Experimental                     [Page 50]

RFC 2909                   The MASC Protocol              September 200017.1.5.  Prefix Selection After Decrease of Demand   If the demand for addresses decreases, such that its address space is   under-utilized, a MASC node implicitly returns the unused prefixes   after their lifetimes expire, or re-claims some smaller sub-prefixes.   For example, if prefix 224.0/15 is 50% used by the MAASs and/or   children MASC domains, and the overall utilization is such that   approximately 2^16 (64K) addresses should be returned, a MASC node   should stop reclaiming 224.0/15 and should start reclaiming either   224.0/16 or 224.1/16 (whichever sub-prefix utilization is higher).17.1.6.  Lifetime Extension Algorithm   If the demand for addresses did not decrease, then a MASC node re-   claims the prefixes it has allocated before their lifetime expires.   Each prefix (or sub-prefix if the demand has decreased) should be   re-claimed every 48 hours.18.  APPENDIX B: Strawman Deployment   At the moment of writing, 225.0.0.0-225.255.255.255 is temporarily   allocated to MALLOC.  Presumably this block of addresses will be used   for experimental deployment and testing.   If MASC were widely deployed on the Internet, we might expect numbers   similar to the following:   o  Initially will have approximately 128 Top-Level Domains   o  Assume initially approximately 8192 level-2 MASC domains; on      average, a TLD will have approximately 64 children domains.   o  MASC managed global addresses:      The following (large) ranges are not allocated yet (2^N represents      the size of the contiguous mask prefixes):       225.0.0.0 - 231.255.255.255 = 2^26 + 2^25 + 2^24       234.0.0.0 - 238.255.255.255 = 2^25 + 2^25 + 2^24       ---------------------------       Total:   12*2^24 addresses      Initially, the range 228.0.0.0 - 231.255.255.255 (4*2^24 = 2^26 =      64M) could be used by MASC as the global addresses pool. The rest      (8*2^24) should be reserved.  Part of it could be added later to      MASC, or can be used to enlarge the pool of administratively      scoped addresses (currently 239.X.X.X), or the pool for static      allocation (233.X.X.X).Radoslavov, et al.            Experimental                     [Page 51]

RFC 2909                   The MASC Protocol              September 2000   o  If the multicast addresses are evenly distributed, each TLD would      have a maximum of 2^19 (512K) addresses, while each level-2 MASC      domain would have 8192 addresses.   o  Initial claim size: 256 addresses/MASC domain   o  Could use soft and hard thresholds to specify the maximum amount      of claimed+allocated addresses per domain.  For example, trigger a      warning message if claimed+allocated addresses by a domain is >=      1.0*average_assumed_per_domain (a strawman default soft      threshold):         * if a TLD claim+allocation >= 512K         * if a second level MASC domain claim+allocation >= 8K      The hard threshold (for example, 2.0*average_assumed_per_domain)      can be enforced by sending an explicit DENIED message.      The TLDs thresholds (with regard to the claims by the second level      MASC domains) is a private matter and is a part of the particular      TLD policy: the thresholds could be per customer, and the warnings      to the administrators could be a signal that it is time to change      the policy.   o  Initial claim lifetime is of the order of 30 days.  Prefix      lifetime is periodically (every 48 hours) reclaimed/extended,      unless the prefix is under-utilized (see APPENDIX A).  Because the      allocation is demand-driven, the allocated prefix lifetime will be      automatically extended if the MAASs need longer prefix lifetime      (e.g. 3-6 months).   o  A level-2 MASC domain could have children (i.e. level-3) MASC      domains.   o  If a level-2 or level-3 MASC domain uses less than 128 addresses,      a Layer 2 protocol/mechanism (e.g. AAP) should be run among that      domain and its parent MASC domain.19.  Authors' Addresses   Pavlin Radoslavov   Computer Science Department   University of Southern California/ISI   Los Angeles, CA 90089   USA   EMail: pavlin@catarina.usc.eduRadoslavov, et al.            Experimental                     [Page 52]

RFC 2909                   The MASC Protocol              September 2000   Deborah Estrin   Computer Science Department   University of Southern California/ISI   Los Angeles, CA 90089   USA   EMail: estrin@isi.edu   Ramesh Govindan   University of Southern California/ISI   4676 Admiralty Way   Marina Del Rey, CA 90292   USA   EMail: govindan@isi.edu   Mark Handley   AT&T Center for Internet Research at ISCI (ACIRI)   1947 Center St., Suite 600   Berkeley, CA 94704   USA   EMail: mjh@aciri.org   Satish Kumar   Computer Science Department   University of Southern California/ISI   Los Angeles, CA 90089   USA   EMail: kkumar@usc.edu   David Thaler   Microsoft   One Microsoft Way   Redmond, WA 98052   USA   EMail: dthaler@microsoft.comRadoslavov, et al.            Experimental                     [Page 53]

RFC 2909                   The MASC Protocol              September 200020.  References   [AAP]                 Handley, M. and S. Hanna, "Multicast Address                         Allocation Protocol (AAP)", Work in Progress.   [API]                 Finlayson, R., "An Abstract API for Multicast                         Address Allocation",RFC 2771, February 2000.   [BGMP]                Thaler, D., Estrin, D. and D. Meyer, "Border                         Gateway Multicast Protocol (BGMP): Protocol                         Specification", Work in Progress.   [BGP]                 Rekhter, Y. and T. Li, "A Border Gateway                         Protocol 4 (BGP-4)",RFC 1771, March 1995.   [CIDR]                Rekhter, Y. and C. Topolcic, "Exchanging                         Routing Information Across Provider Boundaries                         in the CIDR Environment",RFC 1520, September                         1993.   [IANA]                Reynolds, J. and J. Postel, "Assigned Numbers",                         STD 2,RFC 1700, October 1994.   [IANA-CONSIDERATIONS] Alvestrand, H. and T. Narten, "Guidelines for                         Writing an IANA Considerations Section in                         RFCs",BCP 26,RFC 2434, October 1998.   [IPSEC]               Kent, S. and R. Atkinson, "Security                         Architecture for the Internet Protocol",RFC2401, November 1998.   [KAMPAI]              Tsuchiya, P., "Efficient and Flexible                         Hierarchical Address Assignment", INET92, June                         1992, pp. 441--450.   [MADCAP]              Hanna, S., Patel, B. and M. Shah, "Multicast                         Address Dynamic Client Allocation Protocol                         (MADCAP)",RFC 2730, December 1999.   [MALLOC]              Thaler, D., Handley, M. and D. Estrin, "The                         Internet Multicast Address Allocation                         Architecture",RFC 2908, September 2000.   [MBGP]                Bates, T., Chandra, R., Katz, D. and Y.                         Rekhter, "Multiprotocol Extensions for BGP-4",RFC 2283, September 1997.Radoslavov, et al.            Experimental                     [Page 54]

RFC 2909                   The MASC Protocol              September 2000   [MTRACE]              Fenner, W., and S. Casner, "A `traceroute'                         facility for IP Multicast", Work in Progress.   [MZAP]                Handley, M, Thaler, D. and R. Kermode                         "Multicast-Scope Zone Announcement Protocol                         (MZAP)",RFC 2776, February 2000.   [RFC1112]             Deering, S., "Host Extensions for IP                         Multicasting", STD 5,RFC 1112, August 1989.   [RFC2119]             Bradner, S., "Key words for use in RFCs to                         Indicate Requirement Levels",BCP 14,RFC 2119,                         March 1997.   [RFC2373]             Hinden, R. and S. Deering, "IP Version 6                         Addressing Architecture",RFC 2373, July 1998.   [RFC2460]             Deering, S. and R. Hinden, "Internet Protocol,                         Version 6 (IPv6) Specification",RFC 2460,                         December 1998.   [SCOPE]               Meyer, D., "Administratively Scoped IP                         Multicast",RFC 2365, July 1998.Radoslavov, et al.            Experimental                     [Page 55]

RFC 2909                   The MASC Protocol              September 200021.  Full Copyright Statement   Copyright (C) The Internet Society (2000).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Radoslavov, et al.            Experimental                     [Page 56]