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Network Working Group                                           J. KempfRequest for Comments: 3082                                J. GoldschmidtCategory: Experimental                                  Sun Microsystems                                                              March 2001Notification and Subscription for SLPStatus 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 (2001).  All Rights Reserved.Abstract   The Service Location Protocol (SLP) provides mechanisms whereby   service agent clients can advertise and user agent clients can query   for services.  The design is very much demand-driven, so that user   agents only obtain service information when they specifically ask for   it.  There exists another class of user agent applications, however,   that requires notification when a new service appears or disappears.   In theRFC 2608 design, these applications are forced to poll the   network to catch changes.  In this document, we describe a protocol   for allowing such clients to be notified when a change occurs,   removing the need for polling.1. Introduction   The Service Location Protocol (SLP) [1] provides a mechanism for   service agent (SA) clients to advertise network services and for user   agent (UA) clients to find them.  The mechanism is demand-driven.   UAs obtain service information by actively querying for it, and do   not obtain any information unless they do so.  While this design   satisfies the requirements for most applications, there are some   applications that require more timely information about the   appearance or disappearance in the services of interest.   Ideally, these applications would like to be notified when a new   service comes up or when a service disappears.  In order to obtain   this information with SLP as described inRFC 2608, such applications   must poll the network to periodically refresh their local cache of   available service advertisements.Kempf & Goldschmidt           Experimental                      [Page 1]

RFC 3082         Notification and Subscription for SLP        March 2001   An example of such a client is a desktop GUI that wants to display   network service icons as soon as they appear to provide users with an   accurate picture of all services available to them.   Because polling is inefficient and wasteful of network and processor   resources, we would like to provide these applications a mechanism   whereby they can be explicitly notified of changes.  In this   document, we describe a scalable mechanism allowing UAs to be   notified of changes in service availability.2. Notation Conventions   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 [2].3. Terminology   In this section, we present some additional terminology beyond that   in [1] and [3].   Notification - A message sent to an interested agent informing that                  agent that a service has appeared or disappeared.   Subscription - A request to be informed about changes in service                  availability for a particular service type and scopes.4. Design Considerations   The primary design consideration in a notification protocol for SLP   is that we would like it to exhibit the same high degree of   scalability and robustness that the base SLP protocol exhibits.   Notification should work in small networks with only a few SAs, as   well as large enterprise networks with thousands of SAs and hundreds   of DAs.  Small networks should not be required to deploy DAs in order   to receive the benefits of notification.  We also want to assure that   notification in large networks does not cause heavy processing loads   to fall on any one particular SLP agent.  This requires that the task   of notification be distributed rather than centralized, to avoid   loading down one agent with doing all the notification work.   Finally, we would like the notification scheme to be robust in the   face of DA failures, just as the base SLP design is.   An important consideration is that the UA clients obtain   notifications of SA events in a timely fashion.  If a UA has   subscribed to notification for a particular service type, the UA   should receive such notification regardless of the state of   intervening DAs.  SLP is transparent with respect to DAs supporting aKempf & Goldschmidt           Experimental                      [Page 2]

RFC 3082         Notification and Subscription for SLP        March 2001   particular scope; that is, a UA can use any DA with a particular   scope and expect to get the same service advertisements.   Notifications should exhibit the same property.  Whether or not a UA   receives a notification should not depend on the DA to which they   happen to connect. This preserves the DAs' identity as a pure cache.   Another goal is that the notification messages contain enough   information about the triggering event that the UA can determine   whether or not it is of interest in the large majority of cases   without having to issue another SLP request a priori.  The UA may, of   course, issue an SLP request for related reasons, but it should not   have to issue a request to obtain more information on the event that   triggered the notification in most cases.  This reduces the amount of   network traffic related to the event.   In order to simplify implementation, we would like to use similar   mechanisms for notification in large and small networks.  The   mechanisms are not identical, obviously, but we want to avoid having   radically different mechanisms that require completely separate   implementations.  Having similar mechanisms reduces the amount of   code in UA and SA clients.   A minor goal is to make use of existing SLP message types and   mechanisms wherever possible.  This reduces the amount of code   necessary to implement the notification mechanism, because much code   can be reused between the base SLP and the notification mechanism.   In particular, we expect to make use of the SLP extension mechanism   in certain cases to support subscription.5. Notification Design Description   In order to support scalability, we split the design into two parts.   A small network design is used when no DAs are present in the   network.  A large network design is used in networks with DAs.  The   following subsections describe the two designs.5.1 Small Network Design   In networks without DAs, UAs are notified by an SA when the SA   initially appears, and when the SA disappears.  This allows UAs to   know about the list of service types the SA supports.  In small   networks, there is no centralized agent available to administer   subscriptions for newly appearing SAs.  This rules out any kind of   subscription design in which a UA subscribes to notifications for a   particular service type in particular scopes of interest, because a   newly appearing SA can't tell whether or not there are any   subscriptions without a centralizing agent to tell it.Kempf & Goldschmidt           Experimental                      [Page 3]

RFC 3082         Notification and Subscription for SLP        March 2001   As a result, SAs perform notification when they come on line and   prior to shutting down regardless of their scope or service type, if   they are capable of performing notification.  This means that a UA   receives notification of all types of changes for all scopes and   service types, and consequently must be prepared to filter out those   changes in which it is not interested (other scopes, other service   types).   The design requires SAs to perform notification by IP multicasting   (or broadcasting in IPv4 if multicast is not available) SLP SrvReg or   SrvDereg messages using the multicast transmit algorithm described inSection 9.0.  The port number for notifications is not the default   SLP port, because that port is only accessible to privileged users on   some operating systems, but rather the port 1847, as assigned by   IANA.   In IPv4, the SA performs multicast on the SLP multicast address   (239.255.255.253, default TTL 255) and is administratively scoped in   the same manner as SLP [4].  IPv4 UAs interested in notification join   the multicast group 239.255.255.253 and listen on port 1847.  In   IPv6, the multicast is performed to the scoped IPv6 addresses for the   service type advertised, as described in [8].  The SA advertises on   all addresses up to and including the largest multicast scope that it   supports.  IPv6 UAs interested in notification join the multicast   groups corresponding to the multicast scopes and service type in   which they are interested and listen on port 1847.  For example, an   IPv6 UA that has access to site local scope and is interested in a   service type whose hash is 42, calculated according to the algorithm   in [8], joins the groups FF01:0:0:0:0:0:10042 through   FF05:0:0:0:0:0:10042.5.2 Large Network Design   In networks with DAs, a DA supporting a particular scope can act as   an intermediary for administering UA subscriptions.  A subscription   consists of a service type and a collection of scopes.  A UA   interested in being notified about changes in a particular service   type attaches the Subscribe extension to a SrvRqst message sent to   the DA.  The DA obtains multicast group addresses for notification   based on the algorithm described inSection 8.0 and puts them into a   NotifyAt extension which it attaches to the SrvRply.  The UA listens   on the group addresses in the reply for notifications.   When a new subscription comes in, existing SAs are informed about the   subscription using the following procedure.  The DA compares the   service type and scopes in the new subscription against a list of   existing subscriptions.  If no previous subscription has the same   service type and scopes, the DA MUST multicast a DAAdvert, using theKempf & Goldschmidt           Experimental                      [Page 4]

RFC 3082         Notification and Subscription for SLP        March 2001   multicast transmit algorithm described inSection 9.0, and MUST   include the NotifyAt extension with the multicast group addresses for   notification.  If an existing subscription covers the same service   type and scopes as the new subscription, the DA MUST NOT multicast a   DAAdvert.   A DA MUST keep track of subscriptions it has arranged as well as   subscriptions arranged by other DAs in any scopes with which the DA   is configured.  To avoid multiple multicast NotifyAt messages, a DA   MUST wait a random amount of time, uniformly distributed between 0   and 3 seconds before sending the multicast DAAdvert with NotifyAt.   During this period, the DA MUST listen for NotifyAt messages that   match the one from the new subscription.  If a matching NotifyAt is   detected, the DA MUST not multicast.   When a new SA registers with a DA that has existing subscriptions,   the new SA is informed of notifications it should perform using the   following procedure.  If the service type and scopes in the new SA's   SrvReg messages match an existing subscription, a NotifyAt containing   the multicast addresses for notification MUST be included in the   SrvAck.  If the SA doesn't support notification, it simply ignores   the extension.  If the service type and scopes in the new SA's SrvReg   do not match any existing subscriptions, the DA MUST NOT include a   NotifyAt.   The DA itself MUST also perform notification, according to the   multicast transmit algorithm, when a service advertisement times out.   Time-out of a service advertisement results in the DA multicasting a   SrvDereg for the deregistered URL.  This allows interested UAs to be   informed of the service advertisement's demise even if the SA has   disappeared without deregistering.  A DA MUST NOT perform   notification when it receives a SrvReg from an SA, however, that is   the job of the SA.   As in small networks, notification is performed primarily by SAs.  If   an SA receives a DAAdvert or SrvAck with a NotifyAt extension and the   following conditions are met:           1. The SA supports notification.           2. The SA's service type matches the service type in the              NotifyAt extension.           3. The SA's scopes match one of the scopes of the NotifyAt              extension.Kempf & Goldschmidt           Experimental                      [Page 5]

RFC 3082         Notification and Subscription for SLP        March 2001   then the SA saves the multicast addresses that correspond to the   scopes and service types it supports.  The SA MUST perform   notification immediately after the SA has performed the SrvReg or   SrvDereg with the DA.  An SA that has detected a DA in its scopes   MUST NOT multicast any notifications unless it receives a NotifyAt   extension in a SrvAck with service type and scopes matching the SA's   service type and scopes.6. Subscribe Extension   The Subscribe extension has the following format:     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    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |    Extension Type = 0x0004    |        Extension Length       |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    | Ex. Len. (ct) | Abs. Type Fl. |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   The scope list and service type of the extension are taken from the   accompanying SrvRqst.  The abstract type flag indicates whether the   UA is interested in hearing from all SAs advertising concrete   instances of an abstract type [3], and is only of interest if the   service type in the SrvRqst is a concrete type.  If the flag is 1,   the UA is interested in hearing from all SAs advertising concrete   types having the same abstract type as the type of the SrvRqst.  If   the flag is 0, the UA is only interested in hearing from SAs   supporting the particular concrete type in the SrvRqst.  If the   service type in the accompanying SrvRqst is not a concrete type, the   flag is ignored.7. NotifyAt Extension     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    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |    Extension Type = 0x0005    |        Extension Length       |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    | Ext. Len (ct) |  Subscription Lifetime        |SGL List Len.  \    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |SGL L. Len (ct)|       Scope/Group List                        \    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |  Length of Service Type Name  |        Service Type Name      \    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Kempf & Goldschmidt           Experimental                      [Page 6]

RFC 3082         Notification and Subscription for SLP        March 2001   The service type name is in the same format as in the SrvRqst.  The   scope/group list is a list of scope names and multicast group   addresses.  The following ABNF [5] syntax describes the list:        sglist          = sgitem / sgitem "," sglist        sgitem          = scope-name ":" ip-addr        ip-addr         = ipv4-number | ipv6-number        scope-name      =  ; SeeRFC 2608 for the format of scope names.        ipv4-number     =  1*3DIGIT 3("." 1*3DIGIT)        ipv6-number     = ;SeeRFC 2373 [9]Section 2.2   An example of a scope/group list for IPv4 is:        eng:239.255.255.42,corp:239.255.255.43   An example of a scope/group listfor IPv6 is:        eng:FF02:0:0:0:0:0:1:1042,corp:FF03:0:0:0:0:0:1:1042   The scope/group list gives the multicast addresses to use for   notifications involving the service type for the given scopes.   The service type name can be a simple type name, an abstract type   name, or a concrete type name.  If the name is an abstract type name,   all SAs advertising the abstract type MUST notify.  If the name is a   concrete or simple type name, ONLY those SAs advertising the simple   or concrete type MUST notify, others MUST NOT notify.  A DA that   receives a subscription for a concrete type with the abstract type   flag set, MUST include the abstract type name in all the NotifyAt   messages it sends.  If the DA receives a subscription for a concrete   type with the abstract type flag not set, the DA MUST NOT include the   abstract type, but rather MUST include the concrete type name.   There are three cases in which an agent may receive a NotifyAt   extension: in a SrvRply returned to a UA, in a multicast DAAdvert,   and in a SrvAck returned to an SA.  The three subsections below   describe the response in each of these cases.7.1 NotifyAt received with SrvRply   When a UA sends a SrvRqst with a Subscribe extension, the DA responds   with a SrvRply including a NotifyAt.  The DA MUST NOT unicast a   NotifyAt to a UA with any other message and MUST NOT send a NotifyAt   unless a SrvRqst with a Subscribe extension was received.   The UA responds by setting up a multicast listener to the group   addresses included in the extension on the SLP notification port   1847.  The UA MAY also want to note the expiration lifetime of theKempf & Goldschmidt           Experimental                      [Page 7]

RFC 3082         Notification and Subscription for SLP        March 2001   subscription assigned by the DA, and reissue a  subscription before   the lifetime expires.7.2 NotifyAt received with Multicast DAAdvert   The DA multicasts a NotifyAt with a DAAdvert using the multicast   transmit algorithm when a UA has requested notification and the   scopes and service type in the subscription were not previously seen.   This message informs existing SAs having the service type and scopes   in the announcement that they should multicast notifications when   they shut down.   A receiving SA participating in notification responds by noting the   multicast address if the service type and scopes match.  When the SA   is about to go down, the SA MUST first unicast a SrvDereg without   attribute tag list to its DAs (as per standard SLP), then it MUST   multicast the same SrvDereg message according to the multicast   transmit algorithm.  The SA MUST cease performing notification when   the subscription lifetime expires, unless a subsequent NotifyAt is   received prolonging the subscription.   A UA that is performing passive DA detection will naturally also   receive the extension, but the UA SHOULD ignore the extension.7.3 NotifyAt received with SrvAck   An SA can receive a NotifyAt with a SrvAck when it first comes up and   registers itself with a DA.  If the DA has any subscriptions from UAs   for the service type and scopes represented by the SA, it MUST return   a NotifyAt with the SrvAck.   The SA upon receiving the NotifyAt immediately multicasts the same   SrvReg it sent to the DA, according to the multicast transmit   algorithm.  The SA MUST only perform the multicast algorithm once,   even if it registers with more than one DA and receives the NotifyAt   in reply from more than one.  Prior to its demise and after   deregistering with a DA, the SA MUST notify with the same SrvDereg,   as described inSection 7.2.8. Multicast Address Allocation   Enterprise networks that allow SLP notification SHOULD deploy the   Multicast Address Allocation Architecture (MAAA) including   administratively scoped multicast and Multicast Address Dynamic   Client Allocation Protocol (MADCAP) [6].   If it is not possible to obtain a multicast address for use in SLP   notifications, the SLP multicast address is used.Kempf & Goldschmidt           Experimental                      [Page 8]

RFC 3082         Notification and Subscription for SLP        March 2001   If the MAAA infrastructure is deployed, DAs and SAs obtain their   scope configuration from MADCAP, because the SLP scopes are the same   as the MADCAP scopes.  Each SLP scope MUST correspond to a multicast   scope name, in the sense of [6].  In such a case, a DA allocates,   using MADCAP, a new multicast group address for each new service   type/scope pair to which a UA subscribes.  The allocation is made by   MADCAP from the multicast address range for the scope.  In this way,   only those UAs interested in the service type and scopes in the   subscription receive the multicast notification.  The DA sets up the   lease on the multicast address to correspond with the duration of the   subscription.  If the MADCAP server runs out of addresses, the SLP   multicast group is used as a last resort.   For example, if the multicast scope has an address range of 239.1.0.0   through 239.1.255.255, the notification group address for service   type X in scope A could be 239.1.0.42 and for service type Y in scope   B could be 239.1.42.42.9. Multicast Transmit Algorithm   The DA and SAs use a multicast transmit algorithm similar to that   used for discovering services in SLP, described inRFC 2608 [1],   except the agent performing the notification doesn't wait for   replies.  The agent performing the notification transmits a   notification message repeatedly over a period of 15 seconds, backing   off exponentially on the duration of the time interval between the   multicasts.  The rationale for this algorithm is to limit the   duration and scope of the multicast announcement while still   repeating the announcement enough times to increase the probability   that one message gets through.   For an SA, a notification message is either a SrvReg or a SrvDereg   message, depending on whether the SA is registering a new service or   deregistering a service.  When a new service is registered, the   SrvReg message MUST have the fresh bit set in the SLP header.  The   entire list of attributes for the service SHOULD be included.  The   SrvDereg message MUST NOT include an attribute tag list.   Notifications MUST NOT be transmitted at any other time, to minimize   multicast traffic.   Since a SrvReg could contain attribute lists of arbitrary length, the   message could potentially overflow the packet MTU for UDP.  If an   attribute list causes a packet MTU overflow, the SA MUST set the   overflow bit in the SLP header.  The attribute list in the   notification message MUST be formatted so that a UA can use the   attributes even if an overflow occurs.  If a UA needs more attributes   than are transmitted in the notification message, it can contact the   SA (if no DA is present) or the DA for the attributes it needs.Kempf & Goldschmidt           Experimental                      [Page 9]

RFC 3082         Notification and Subscription for SLP        March 2001   A DA multicasts a DAAdvert when a subscription comes in containing a   service type and scopes that do not match any on the DA's list of   known subscriptions.  The same algorithm MUST be used.  If the   combination of the DA attributes and the NotifyAt message cause the   DAAdvert to overflow a UDP packet, DA attributes MUST be truncated to   allow the NotifyAt to fit and the overflow bit MUST be set in the   header.  An SA knows that the purpose of the message is to inform it   of a new subscription rather than for passive advertisement, because   of the extension, and it can therefore ignore the DA attribute list   field if the overflow bit is set in the header.  A DA also transmits   a SrvDereg message when a service advertisement is deregistered due   to timeout, following the same rules as for an SA.10.0 DA Disappearance   Robustness to DA failure is an important goal of the design.  When a   DA disappears due to unforeseen circumstances, subscription   information from UAs is lost.  UAs continue to get notifications from   existing SAs.  However, new SAs will not be informed of the   subscription unless other DAs also have the subscription information.   Because a UA may not discover a new DA until it tries to perform an   active request, the UA could potentially miss the appearance of new   services.  For this reason, UAs that are concerned about receiving   notification of absolutely every service that appears SHOULD issue   subscriptions to every newly discovered DA that supports the scopes   it supports.  Similarly, if a DA disappears through controlled   shutdown, a UA performing passive discovery can detect the shutdown   and reissue the subscription to an alternate DA.   On the SA side, when a DA goes down, existing SAs continue to notify   until the subscription expires.  Before ceasing to notify, an SA MUST   determine whether the DA is still active and, if not, verify with   another DA whether the subscription has been extended.  If no other   DA is available, the SA MUST ignore the subscription expiration time   and continue notifying until a new DA is discovered.  When a new DA   is discovered the SA must send a new SrvReg to the DA, according toRFC 2608 [1].  The replying SrvAck contains a NotifyAt extension if   the UA has renewed its subscription with the DA.  If the SrvAck does   not contain a NotifyAt message the SA MUST continue to notify until   the subscription expires.  If a UA is interested in continuing the   notification, it renews the subscription with the new DA prior to the   expiration  of the old one, and so the SA is informed to continue   notifying.Kempf & Goldschmidt           Experimental                     [Page 10]

RFC 3082         Notification and Subscription for SLP        March 2001   Note that this procedure still does not inform SAs that come up   between the time a newly booted DA comes up and the time the UA has   renewed its subscription with the newly booted DA.  If this situation   is of concern, multiple DAs can be used to assure that all   subscriptions are covered when a DA goes down.11.  Network Administration Considerations   In SLP networks with DAs as described inRFC 2608, the only multicast   is the SrvRqst for DAAdverts performed during active DA discovery,   and unsolicited DAAdverts sent periodically by the DA for passive   discovery.  There is no multicast involved in UA queries or SA   registrations.  This allows network administrators to set up DAs for   a particular collection of IP subnets and confine all service   discovery traffic to unicast between the SA and UA clients and the   DA.  Administratively scoped multicast can additionally be used to   limit the extent of active DA discovery and passive DA advertising.   The amount of multicast involved is not high and DHCP DA and scope   configuration can be used to limit which DAs a particular UA or SA   client sees, or to inhibit multicast entirely so that UAs and SAs   only use configured DAs.   With notification, however, multicast traffic involving events in SAs   becomes available.  Because DAs request multicast addresses based on   scope and service type, the multicast associated with particular   events should only propagate to those subnets in which UAs and SAs of   the same scope are interacting.  Routers should be configured with   administrative multicast scoping to limit multicast.  If DAs are not   deployed (or the MAAA is not deployed), however, the amount of   multicast on the SLP multicast address when notifications are being   used could quickly become very large.  Therefore, it is crucial that   DAs supporting notification be deployed in large networks where UA   clients are interested in notification.12. Security Considerations   The SrvReg and SrvDereg messages contain authentication blocks for   all SLP SPIs supported by the DAs with which the SA registers.  Since   these SPIs are necessarily the same as those that UAs can verify, a   UA receiving a multicast notification is in a position to verify the   notification.  It does so by selecting the authentication block or   blocks that it can verify.  If authentication fails, either due to   lack of an authentication block, or lack of the proper SPI, the UA   simply discards the notification.  In a network without DAs, the SPIs   of the UA and SA must also match.Kempf & Goldschmidt           Experimental                     [Page 11]

RFC 3082         Notification and Subscription for SLP        March 200113. IANA Considerations   The SLP Notification services use the IANA-assigned port number of   1847.  The SLP extension identifiers assigned by IANA are 0x0004 for   Subscribe and 0x0005 for NotifyAt.14. Acknowledgements   The authors would like to thank Charles Perkins, of Nokia, and Erik   Guttman and Jonathan Wood, of Sun Microsystems, for their stimulating   discussion and suggestions during the initial phases of the   subscription/notification design.  We would also like to thank Erik   for his intense scrutiny of the specification during the later   phases.  His comments were instrumental in refining the design.   Shivaun Albright, of HP, motivated simplification of the protocol to   focus on initial registration and deregistration only.  Vaishali   Mithbaokar implemented the simplified protocol.15. References   [1] Guttman, E., Perkins, C., Veizades, J. and M. Day, "Service       Location Protocol",RFC 2608, July 1999.   [2] Bradner, S., "Key Words for Use in RFCs to Indicate Requirement       Levels",BCP 14,RFC 2119, March 1997.   [3] Guttman, E., Perkins, C. and J. Kempf, "Service Templates and       service: Schemes",RFC 2609, July 1999.   [4] Meyer, D., "Administratively Scoped IP Multicast",RFC 2365, July       1998.   [5] Crocker, D. and P. Overell, "Augmented BNF for Syntax       Specifications: ABNF",RFC 2234, November 1997.   [6] Hanna, S., Patel,B. and M. Shah, "Multicast Address Dynamic       Client Allocation Protocol (MADCAP)",RFC 2730, December 1999.   [7]http://www.isi.edu/in-notes/iana/assignments/multicast-addresses   [8] Guttman, E.,"Service Location Protocol Modifications for IPv6",       Work in Progress.   [9] Hinden, R. and S. Deering, "IP Version 6 Addressing       Architecture",RFC 2375, July 1997.Kempf & Goldschmidt           Experimental                     [Page 12]

RFC 3082         Notification and Subscription for SLP        March 200116. Author's Addresses   James Kempf   Sun Microsystems   UMPK15-214   901 San Antonio Rd.   Palo Alto, CA 94040   USA   Phone:    +1 650 786 5890   EMail:    james.kempf@sun.com   Jason Goldschmidt   Sun Microsystems   UMPK17-202   901 San Antonio Rd.   Palo Alto, CA 94040   USA   Phone: +1 650 786 3502   EMail: jason.goldschmidt@sun.comKempf & Goldschmidt           Experimental                     [Page 13]

RFC 3082         Notification and Subscription for SLP        March 2001Full Copyright Statement   Copyright (C) The Internet Society (2001).  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.Kempf & Goldschmidt           Experimental                     [Page 14]