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Internet Engineering Task Force (IETF)                      S. PerreaultRequest for Comments: 7648                           Jive CommunicationsCategory: Standards Track                                   M. BoucadairISSN: 2070-1721                                           France Telecom                                                                R. Penno                                                                 D. Wing                                                                   Cisco                                                             S. Cheshire                                                                   Apple                                                          September 2015Port Control Protocol (PCP) Proxy FunctionAbstract   This document specifies a new Port Control Protocol (PCP) functional   element: the PCP proxy.  The PCP proxy relays PCP requests received   from PCP clients to upstream PCP server(s).  A typical deployment   usage of this function is to help establish successful PCP   communications for PCP clients that cannot be configured with the   address of a PCP server located more than one hop away.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7648.Perreault, et al.            Standards Track                    [Page 1]

RFC 7648                        PCP Proxy                 September 2015Copyright Notice   Copyright (c) 2015 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .31.1.  Use Case: The NAT Cascade . . . . . . . . . . . . . . . .41.2.  Use Case: The PCP Relay . . . . . . . . . . . . . . . . .52.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .53.  Operation of the PCP Proxy  . . . . . . . . . . . . . . . . .63.1.  Optimized Hairpin Routing . . . . . . . . . . . . . . . .83.2.  Termination of Recursion  . . . . . . . . . . . . . . . .93.3.  Source Address for PCP Requests Sent Upstream . . . . . .103.4.  Unknown Opcodes and Options . . . . . . . . . . . . . . .103.4.1.  No NAT Is Co-located with the PCP Proxy . . . . . . .103.4.2.  PCP Proxy Co-located with a NAT Function  . . . . . .103.5.  Mapping Repair  . . . . . . . . . . . . . . . . . . . . .113.6.  Multiple PCP Servers  . . . . . . . . . . . . . . . . . .114.  Security Considerations . . . . . . . . . . . . . . . . . . .125.  References  . . . . . . . . . . . . . . . . . . . . . . . . .125.1.  Normative References  . . . . . . . . . . . . . . . . . .125.2.  Informative References  . . . . . . . . . . . . . . . . .13   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .13   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .14Perreault, et al.            Standards Track                    [Page 2]

RFC 7648                        PCP Proxy                 September 20151.  Introduction   This document defines a new Port Control Protocol (PCP) [RFC6887]   functional element: the PCP proxy.  As shown in Figure 1, the   PCP proxy is logically equivalent to a PCP client back-to-back with a   PCP server.  The "glue" between the two is what is specified in this   document.  Other than that "glue", the server and the client behave   exactly like their regular counterparts.   The PCP proxy is responsible for relaying PCP messages received from   PCP clients to upstream PCP servers and vice versa.   Whether or not the PCP proxy is co-located with a flow-aware function   (e.g., NAT, firewall) is deployment specific.                              .................              +------+       : +------+------+ :    +------+              |Client|-------:-|Server|Client|-:----|Server|              +------+       : +------+------+ :    +------+                             :      Proxy      :                              .................                     Figure 1: Reference Architecture   This document assumes a hop-by-hop PCP authentication scheme.  That   is, referring to Figure 1, the leftmost PCP client authenticates with   the PCP proxy, while the PCP proxy authenticates with the upstream   server.  Note that in some deployments, PCP authentication may only   be enabled between the PCP proxy and an upstream PCP server (e.g., a   customer premises host may not authenticate with the PCP proxy, but   the PCP proxy may authenticate with the PCP server).  The hop-by-hop   authentication scheme is more suitable from a deployment standpoint.   Furthermore, it allows implementations to easily support a PCP proxy   that alters PCP messages (e.g., strips a PCP option, modifies a   PCP field).Perreault, et al.            Standards Track                    [Page 3]

RFC 7648                        PCP Proxy                 September 20151.1.  Use Case: The NAT Cascade   In today's world, with public routable IPv4 addresses becoming less   readily available, it is increasingly common for customers to receive   a private address from their Internet Service Provider (ISP), and the   ISP uses a NAT gateway of its own to translate those packets before   sending them out onto the public Internet.  This means that there is   likely to be more than one NAT on the path between client machines   and the public Internet:   o  If a residential customer receives a translated address from their      ISP and then installs their own residential NAT gateway to share      that address between multiple client devices in their home, then      there are at least two NAT gateways on the path between client      devices and the public Internet.   o  If a mobile phone customer receives a translated address from      their mobile phone carrier and uses "Personal Hotspot" or      "Internet Sharing" software on their mobile phone to make Wireless      LAN (WLAN) Internet access available to other client devices, then      there are at least two NAT gateways on the path between those      client devices and the public Internet.   o  If a hotel guest connects a portable WLAN gateway to their hotel      room's Ethernet port to share their room's Internet connection      between their phone and their laptop computer, then packets from      the client devices may traverse the hotel guest's portable NAT,      the hotel network's NAT, and the ISP's NAT before reaching the      public Internet.   While it is possible, in theory, that client devices could somehow   discover all the NATs on the path and communicate with each one   separately using PCP [RFC6887], in practice it is not clear how   client devices would reliably learn this information.  Since the NAT   gateways are installed and operated by different individuals and   organizations, no single entity has knowledge of all the NATs on the   path.  Also, even if a client device could somehow know all the NATs   on the path, requiring a client device to communicate separately with   all of them imposes unreasonable complexity on PCP clients, many of   which are expected to be simple low-cost devices.   In addition, this goes against the spirit of NAT gateways.  The main   purpose of a NAT gateway is to make multiple downstream client   devices appear, from the point of view of everything upstream of the   NAT gateway, to be a single client device.  In the same spirit, it   makes sense for a PCP-capable NAT gateway to make multiple downstreamPerreault, et al.            Standards Track                    [Page 4]

RFC 7648                        PCP Proxy                 September 2015   client devices requesting port mappings appear, from the point of   view of everything upstream of the NAT gateway, to be a single client   device requesting port mappings.1.2.  Use Case: The PCP Relay   Another envisioned use case of the PCP proxy is to help establish   successful PCP communications for PCP clients that cannot be   configured with the address of a PCP server located more than one hop   away.  A PCP proxy can, for instance, be embedded in a CPE (Customer   Premises Equipment) while the PCP server is located in a network   operated by an ISP.  This is illustrated in Figure 2.                 |       +------+  |       |Client|--+       +------+  |  +-----+                               +------+                 +--|Proxy|--------<ISP network>----------|Server|       +------+  |  +-----+                               +------+       |Client|--+    CPE       +------+  |                 |                LAN                       Figure 2: PCP Relay Use Case   This works because the proxy's server side is listening on the   address used as a default gateway by the clients.  The clients use   that address as a fallback when discovering the PCP server's address.   The proxy picks up the requests and forwards them upstream to the   ISP's PCP server, with whose address it has been provisioned through   regular PCP client provisioning means.   This particular use case assumes that provisioning the server's   address on the CPE is feasible while doing it on the clients in the   LAN is not, which is what makes the PCP proxy valuable.   An alternative way to contact an upstream PCP server that may be   several hops away is to use a well-known anycast address   [PCP-ANYCAST], but that technique can be problematic when multiple   PCP servers are to be contacted [PCP-DEPLOY].2.  Terminology   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and   "OPTIONAL" in this document are to be interpreted as described in   "Key words for use in RFCs to Indicate Requirement Levels" [RFC2119].Perreault, et al.            Standards Track                    [Page 5]

RFC 7648                        PCP Proxy                 September 2015   Where this document uses the terms "upstream" and "downstream", the   term "upstream" refers to the direction outbound packets travel   towards the public Internet, and the term "downstream" refers to the   direction inbound packets travel from the public Internet towards   client systems.  Typically, when a home user views a web site, their   computer sends an outbound TCP SYN packet upstream towards the public   Internet, and an inbound downstream TCP SYN ACK reply comes back from   the public Internet.3.  Operation of the PCP Proxy   Upon receipt of a PCP mapping-creation request from a downstream   PCP client, a PCP proxy first examines its local mapping table to see   if it already has a valid active mapping matching the internal   address and internal port (and in the case of PEER requests, the   remote peer) given in the request.   If the PCP proxy does not already have a valid active mapping for   this mapping-creation request, then it allocates an available port on   its external interface.  We assume for the sake of this description   that the address of its external interface is itself a private   address, subject to translation by an upstream NAT.  The PCP proxy   then constructs an appropriate corresponding PCP request of its own   (as described below) and sends it to its upstream NAT, and the newly   created local mapping is considered temporary until a confirming   reply is received from the upstream PCP server.   If the PCP proxy does already have a valid active mapping for this   mapping-creation request and the lifetime remaining on the local   mapping is at least 3/4 of the lifetime requested by the PCP client,   then the PCP proxy SHOULD send an immediate reply giving the   outermost external address and port (previously learned using PCP   recursively, as described below) and the actual lifetime remaining   for this mapping.  If the lifetime remaining on the local mapping is   less than 3/4 of the lifetime requested by the PCP client, then the   PCP proxy MUST generate an upstream request as described below.   For mapping-deletion requests (lifetime = 0), the local mapping, if   any, is deleted, and then (regardless of whether or not a local   mapping existed) a corresponding upstream request is generated.   The PCP proxy knows the destination IP address for its upstream   PCP request using the same means that are available for provisioning   a PCP client.  In particular, the PCP proxy MUST follow the procedure   defined inSection 8.1 of the PCP specification [RFC6887] to discover   its PCP server.  This does not preclude other means from being used   in addition.Perreault, et al.            Standards Track                    [Page 6]

RFC 7648                        PCP Proxy                 September 2015   In the upstream PCP request:   o  The PCP client's IP address and internal port are the PCP proxy's      own external address and port just allocated for this mapping.   o  The suggested external address and port in the upstream      PCP request SHOULD be copied from the original PCP request.  On a      typical renewal request, this will be the outermost external      address and port previously learned by the client.   o  The requested lifetime is as requested by the client if it falls      within the acceptable range for this PCP server; otherwise, it      SHOULD be capped to appropriate minimum and maximum values      configured for this PCP server.   o  The mapping nonce is copied from the original PCP request.   o  For PEER requests, the remote peer IP address and port are copied      from the original PCP request.   Upon receipt of a PCP reply giving the outermost (i.e., publicly   routable) external address, port, and lifetime, the PCP proxy records   this information in its own mapping table and relays the information   to the requesting downstream PCP client in a PCP reply.  The   PCP proxy therefore records, among other things, the following   information in its mapping table:   o  Client's internal address and port.   o  External address and port allocated by this PCP proxy.   o  Outermost external address and port allocated by the upstream      PCP server.   o  Mapping lifetime (also dictated by the upstream PCP server).   o  Mapping nonce.   In the downstream PCP reply:   o  The lifetime is as granted by the upstream PCP server, or less if      the granted lifetime exceeds the maximum lifetime this PCP server      is configured to grant.  If the proxy chooses to grant a      downstream lifetime greater than the lifetime granted by the      upstream PCP server (which is NOT RECOMMENDED), then this      PCP proxy MUST take responsibility for renewing the upstream      mapping itself.Perreault, et al.            Standards Track                    [Page 7]

RFC 7648                        PCP Proxy                 September 2015   o  The Epoch Time is this PCP proxy's Epoch Time, not the Epoch Time      of the upstream PCP server.  Each PCP server has its own      independent Epoch Time.  However, if the Epoch Time received from      the upstream PCP server indicates a loss of state in that      PCP server, the PCP proxy can either (1) recreate the lost      mappings itself or (2) reset its own Epoch Time to cause its      downstream clients to perform such state repairs themselves.  A      PCP proxy MUST NOT simply copy the upstream PCP server's      Epoch Time into its downstream PCP replies, because if it suffers      its own state loss it needs the ability to communicate that state      loss to clients.  Thus, each PCP server has its own independent      Epoch Time.  However, as a convenience, a downstream PCP proxy may      simply choose to reset its own Epoch Time whenever it detects that      its upstream PCP server has lost state.  Thus, in this case, the      PCP proxy's Epoch Time always resets whenever its upstream      PCP server loses state; it may reset at other times as well.   o  The mapping nonce is copied from the reply received from the      upstream PCP server.   o  The assigned external port and assigned external IP address are      copied from the reply received from the upstream PCP server (i.e.,      they are the outermost external IP address and port, not the      locally assigned external address and port).  By recursive      application of this procedure, the outermost external IP address      and port are relayed from the outermost NAT, through one or more      intervening PCP proxies, until they ultimately reach the      downstream client.   o  For PEER requests, the remote peer IP address and port are copied      from the reply received from the upstream PCP server.3.1.  Optimized Hairpin Routing   A PCP proxy SHOULD implement optimized hairpin routing.  What this   means is the following:   o  If a PCP proxy observes an outgoing packet arriving on its      internal interface that is addressed to an external address and      port appearing in the NAT gateway's own mapping table, then the      NAT gateway SHOULD (after creating a new outbound mapping if one      does not already exist) rewrite the packet appropriately and      deliver it to the internal client to which that external address      and port are currently allocated.Perreault, et al.            Standards Track                    [Page 8]

RFC 7648                        PCP Proxy                 September 2015   o  Similarly, if a PCP proxy observes an outgoing packet arriving on      its internal interface that is addressed to an *outermost*      external address and port appearing in the NAT gateway's own      mapping table, then the NAT gateway SHOULD do as described above:      create a new outbound mapping if one does not already exist, and      then rewrite the packet appropriately and deliver it to the      internal client to which that outermost external address and port      are currently allocated.  This is not necessary for successful      communication, but it provides efficiency.  Without this optimized      hairpin routing, the packet will be delivered all the way to the      outermost NAT gateway, which will then perform standard hairpin      translation and send it back.  Using knowledge of the outermost      external address and port, this rewriting can be anticipated and      performed locally.  This rewriting technique will typically offer      higher throughput and lower latency than sending packets all the      way to the outermost NAT gateway and back.   Note that traffic counters maintained by an upstream PCP server will   differ from the counters of a PCP proxy implementing optimized   hairpin routing.3.2.  Termination of Recursion   Any recursive algorithm needs a mechanism to terminate the recursion   at the appropriate point.  This termination of recursion can be   achieved in a variety of ways.  The following (non-exhaustive)   examples are provided for illustration purposes:   o  An ISP's PCP-controlled gateway (which may embed a NAT, firewall,      or any function that can be controlled with PCP) could be      configured to know that it is the outermost PCP-controlled      gateway, and consequently it does not need to relay PCP requests      upstream.   o  A PCP-controlled gateway could determine automatically that if its      external address is not one of the known private addresses      [RFC1918] [RFC6598], then its external address is a public      routable IP address, and consequently it does not need to relay      PCP requests upstream.   o  Recursion may be terminated if there is no explicit list of      PCP servers configured (manually, using DHCP [RFC7291], or      otherwise) or if its default router is not responsive to      PCP requests.   o  Recursion may also be terminated if the upstream PCP-controlled      device does not embed a PCP proxy.Perreault, et al.            Standards Track                    [Page 9]

RFC 7648                        PCP Proxy                 September 20153.3.  Source Address for PCP Requests Sent Upstream   As with a regular PCP server, the PCP-controlled device can be a NAT,   a firewall, or even some sort of hybrid.  In particular, a PCP proxy   that simply relays all requests upstream can be thought of as the   degenerate case of a PCP server controlling a wide-open firewall   back-to-back with a regular PCP client.   One important property of the PCP-controlled device will affect the   PCP proxy's behavior: when the proxy's server part instructs the   device to create a mapping, that mapping's external address may or   may not be one that belongs to the proxy node.   o  When the mapping's external address belongs to the proxy node, as      would presumably be the case for a NAT, then the proxy's client      side sends out an upstream PCP request using the mapping's      external IP address as the source.   o  When the mapping's external address does not belong to the proxy      node, as would presumably be the case for a firewall, then the      proxy's client side needs to install upstream mappings on behalf      of its downstream clients.  To do this, it MUST insert a      THIRD_PARTY option in its upstream PCP request carrying the      mapping's external address.   Note that hybrid PCP-controlled devices may create NAT-like mappings   in some circumstances and firewall-like mappings in others.  A proxy   controlling such a device would adjust its behavior dynamically,   depending on the kind of mapping created.3.4.  Unknown Opcodes and Options3.4.1.  No NAT Is Co-located with the PCP Proxy   When no NAT is co-located with the PCP proxy, the port numbers   included in received PCP messages (from the PCP server or   PCP client(s)) are not altered by the PCP proxy.  The PCP proxy   relays to the PCP server unknown options and Opcodes because there is   no reachability failure risk.3.4.2.  PCP Proxy Co-located with a NAT Function   By default, the proxy MUST relay unknown Opcodes and mandatory-to-   process unknown options.  Rejecting unknown options and Opcodes has   the drawback of preventing a PCP client from making use of new   capabilities offered by the PCP server but not supported by the   PCP proxy, even if no IP address and/or port is included in the   option/Opcode.Perreault, et al.            Standards Track                   [Page 10]

RFC 7648                        PCP Proxy                 September 2015   Because PCP messages with an unknown Opcode or mandatory-to-process   unknown options can carry a hidden internal address or internal port   that will not be translated, a PCP proxy MUST be configurable to   disable relaying unknown Opcodes and mandatory-to-process unknown   options.  If the PCP proxy is configured to disable relaying unknown   Opcodes and mandatory-to-process unknown options, the PCP proxy MUST   behave as follows:   o  a PCP proxy co-located with a NAT MUST reject, via an      UNSUPP_OPCODE error response, a received request with an unknown      Opcode.   o  a PCP proxy co-located with a NAT MUST reject, via an      UNSUPP_OPTION error response, a received request with a mandatory-      to-process unknown option.3.5.  Mapping Repair   ANNOUNCE requests received from PCP clients are handled locally; as   such, these requests MUST NOT be relayed to the provisioned   PCP server.   Upon receipt of an unsolicited ANNOUNCE response from a PCP server,   the PCP proxy proceeds to renew the mappings and checks to see   whether or not there are changes compared to a local cache if it is   maintained by the PCP proxy.  If no change is detected, no   unsolicited ANNOUNCE is generated towards PCP clients.  If a change   is detected, the PCP proxy MUST generate unsolicited ANNOUNCE   message(s) to appropriate PCP clients.  If the PCP proxy does not   maintain a local cache for the mappings, unsolicited multicast   ANNOUNCE messages are sent to PCP clients.   Upon change of its external IP address, the PCP proxy SHOULD renew   the mappings it maintained.  If the PCP server assigns a different   external port, the PCP proxy SHOULD follow the PCP mapping repair   procedure [RFC6887].  This can be achieved only if a full state table   is maintained by the PCP proxy.3.6.  Multiple PCP Servers   A PCP proxy MAY handle multiple PCP servers at the same time.  Each   PCP server is associated with its own epoch value.  PCP clients are   not aware of the presence of multiple PCP servers.   Following the PCP Server Selection process [RFC7488], if several   PCP servers are configured to the PCP proxy, it will contact in   parallel all these PCP servers.Perreault, et al.            Standards Track                   [Page 11]

RFC 7648                        PCP Proxy                 September 2015   In some contexts (e.g., PCP-controlled Carrier-Grade NATs (CGNs)),   the PCP proxy MAY load-balance the PCP clients among available   PCP servers.  The PCP proxy MUST ensure that requests of a given   PCP client are relayed to the same PCP server.   The PCP proxy MAY rely on some fields (e.g., Zone-ID [PCP-ZONES]) in   the PCP request to redirect the request to a given PCP server.4.  Security Considerations   The PCP proxy MUST follow the security considerations detailed in the   PCP specification [RFC6887] for both the client and server side.Section 3.3 specifies the cases where a THIRD_PARTY option is   inserted by the PCP proxy.  In those cases, ways to prevent a   malicious user from creating mappings on behalf of a third party must   be employed as discussed inSection 13.1 of the PCP specification   [RFC6887].  In particular, THIRD_PARTY options MUST NOT be enabled   unless the network on which the PCP messages are to be sent is fully   trusted (via physical or cryptographic security, or both) -- for   example, if access control lists (ACLs) are installed on the   PCP proxy, the PCP server, and the network between them so that those   ACLs allow only communications from a trusted PCP proxy to the   PCP server.   A received request carrying an unknown Opcode or option SHOULD be   dropped (or, in the case of an unknown option that is not mandatory   to process, the option SHOULD be removed) if it is not compatible   with security controls provisioned to the PCP proxy.   The device embedding the PCP proxy MAY block PCP requests directly   sent to the upstream PCP server(s).  This can be enforced using ACLs.5.  References5.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119,              DOI 10.17487/RFC2119, March 1997,              <http://www.rfc-editor.org/info/rfc2119>.   [RFC6887]  Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and              P. Selkirk, "Port Control Protocol (PCP)",RFC 6887,              DOI 10.17487/RFC6887, April 2013,              <http://www.rfc-editor.org/info/rfc6887>.Perreault, et al.            Standards Track                   [Page 12]

RFC 7648                        PCP Proxy                 September 20155.2.  Informative References   [PCP-ANYCAST]              Kiesel, S., Penno, R., and S. Cheshire, "Port Control              Protocol (PCP) Anycast Addresses", Work in Progress,draft-ietf-pcp-anycast-07, August 2015.   [PCP-DEPLOY]              Boucadair, M., "Port Control Protocol (PCP) Deployment              Models", Work in Progress,draft-boucadair-pcp-deployment-cases-03, July 2014.   [PCP-ZONES]              Penno, R.,"PCP Support for Multi-Zone Environments", Work              in Progress,draft-penno-pcp-zones-01, October 2011.   [RFC1918]  Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,              and E. Lear, "Address Allocation for Private Internets",BCP 5,RFC 1918, DOI 10.17487/RFC1918, February 1996,              <http://www.rfc-editor.org/info/rfc1918>.   [RFC6598]  Weil, J., Kuarsingh, V., Donley, C., Liljenstolpe, C., and              M. Azinger, "IANA-Reserved IPv4 Prefix for Shared Address              Space",BCP 153,RFC 6598, DOI 10.17487/RFC6598, April              2012, <http://www.rfc-editor.org/info/rfc6598>.   [RFC7291]  Boucadair, M., Penno, R., and D. Wing, "DHCP Options for              the Port Control Protocol (PCP)",RFC 7291,              DOI 10.17487/RFC7291, July 2014,              <http://www.rfc-editor.org/info/rfc7291>.   [RFC7488]  Boucadair, M., Penno, R., Wing, D., Patil, P., and T.              Reddy, "Port Control Protocol (PCP) Server Selection",RFC 7488, DOI 10.17487/RFC7488, March 2015,              <http://www.rfc-editor.org/info/rfc7488>.Acknowledgements   Many thanks to C. Zhou, T. Reddy, and D. Thaler for their review and   comments.   Special thanks to F. Dupont, who contributed to this document.Perreault, et al.            Standards Track                   [Page 13]

RFC 7648                        PCP Proxy                 September 2015Authors' Addresses   Simon Perreault   Jive Communications   Quebec, QC   Canada   Email: sperreault@jive.com   Mohamed Boucadair   France Telecom   Rennes  35000   France   Email: mohamed.boucadair@orange.com   Reinaldo Penno   Cisco   United States   Email: repenno@cisco.com   Dan Wing   Cisco Systems, Inc.   170 West Tasman Drive   San Jose, California  95134   United States   Email: dwing@cisco.com   Stuart Cheshire   Apple Inc.   1 Infinite Loop   Cupertino, California  95014   United States   Phone: +1 408 974 3207   Email: cheshire@apple.comPerreault, et al.            Standards Track                   [Page 14]

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