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rfc:rfc6157

Internet Engineering Task Force (IETF) G. Camarillo Request for Comments: 6157 Ericsson Updates: 3264 K. El Malki Category: Standards Track Athonet ISSN: 2070-1721 V. Gurbani

                                             Bell Labs, Alcatel-Lucent
                                                            April 2011
      IPv6 Transition in the Session Initiation Protocol (SIP)

Abstract

 This document describes how the IPv4 Session Initiation Protocol
 (SIP) user agents can communicate with IPv6 SIP user agents (and vice
 versa) at the signaling layer as well as exchange media once the
 session has been successfully set up.  Both single- and dual-stack
 (i.e., IPv4-only and IPv4/IPv6) user agents are considered.

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 in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6157.

Copyright Notice

 Copyright (c) 2011 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 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.

Camarillo, et al. Standards Track [Page 1] RFC 6157 IPv6 Transition in SIP April 2011

 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008.  The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow
 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
 2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
 3.  The Signaling Layer  . . . . . . . . . . . . . . . . . . . . .  4
   3.1.  Proxy Behavior . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.1.  Relaying Requests across Different Networks  . . . . .  5
   3.2.  User Agent Behavior  . . . . . . . . . . . . . . . . . . .  7
 4.  The Media Layer  . . . . . . . . . . . . . . . . . . . . . . .  7
   4.1.  Updates to RFC 3264  . . . . . . . . . . . . . . . . . . .  9
   4.2.  Initial Offer  . . . . . . . . . . . . . . . . . . . . . .  9
   4.3.  Connectivity Checks  . . . . . . . . . . . . . . . . . . . 10
 5.  Contacting Servers: Interaction of RFC 3263 and RFC 3484 . . . 10
 6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
 7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 11
 8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   8.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
   8.2.  Informative References . . . . . . . . . . . . . . . . . . 12
 Appendix A.  Sample IPv4/IPv6 DNS File . . . . . . . . . . . . . . 14

1. Introduction

 SIP [3] is a protocol to establish and manage multimedia sessions.
 After the exchange of signaling messages, SIP endpoints generally
 exchange session or media traffic, which is not transported using SIP
 but a different protocol.  For example, audio streams are typically
 carried using the Real-Time Transport Protocol (RTP) [13].
 Consequently, a complete solution for IPv6 transition needs to handle
 both the signaling layer and the media layer.  While unextended SIP
 can handle heterogeneous IPv6/IPv4 networks at the signaling layer as
 long as proxy servers and their Domain Name System (DNS) entries are
 properly configured, user agents using different networks and address
 spaces must implement extensions in order to exchange media between
 them.

Camarillo, et al. Standards Track [Page 2] RFC 6157 IPv6 Transition in SIP April 2011

 This document addresses the system-level issues in order to make SIP
 work successfully between IPv4 and IPv6.  Sections 3 and 4 provide
 discussions on the topics that are pertinent to the signaling layer
 and media layer, respectively, to establish a successful session
 between heterogeneous IPv4/IPv6 networks.

2. Terminology

 In this document, the key words "MUST", "MUST NOT", "REQUIRED",
 "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
 RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
 described in BCP 14, RFC 2119 [1] and indicate requirement levels for
 compliant implementations.
 IPv4-only user agent:  An IPv4-only user agent supports SIP signaling
    and media only on the IPv4 network.  It does not understand IPv6
    addresses.
 IPv4-only node:  A host that implements only IPv4.  An IPv4-only node
    does not understand IPv6.  The installed base of IPv4 hosts
    existing before the transition begins are IPv4-only nodes.
 IPv6-only user agent:  An IPv6-only user agent supports SIP signaling
    and media only on the IPv6 network.  It does not understand IPv4
    addresses.
 IPv6-only node:  A host that implements IPv6 and does not implement
    IPv4.
 IPv4/IPv6 node:  A host that implements both IPv4 and IPv6; such
    hosts are also known as "dual-stack" hosts [17].
 IPv4/IPv6 user agent:  A user agent that supports SIP signaling and
    media on both IPv4 and IPv6 networks.
 IPv4/IPv6 proxy:  A proxy that supports SIP signaling on both IPv4
    and IPv6 networks.

3. The Signaling Layer

 An autonomous domain sends and receives SIP traffic to and from its
 user agents as well as to and from other autonomous domains.  This
 section describes the issues related to such traffic exchanges at the
 signaling layer, i.e., the flow of SIP messages between participants
 in order to establish the session.  We assume that the network
 administrators appropriately configure their networks such that the

Camarillo, et al. Standards Track [Page 3] RFC 6157 IPv6 Transition in SIP April 2011

 SIP servers within an autonomous domain can communicate between
 themselves.  This section contains system-level issues; a companion
 document [15] addresses IPv6 parser torture tests in SIP.

3.1. Proxy Behavior

 User agents typically send SIP traffic to an outbound proxy, which
 takes care of routing it forward.  In order to support both IPv4-only
 and IPv6-only user agents, it is RECOMMENDED that domains deploy
 dual-stack outbound proxy servers or, alternatively, deploy both
 IPv4-only and IPv6-only outbound proxies.  Furthermore, there SHOULD
 exist both IPv6 and IPv4 DNS entries for outbound proxy servers.
 This allows the user agent to query DNS and obtain an IP address most
 appropriate for its use (i.e., an IPv4-only user agent will query DNS
 for A resource records (RRs), an IPv6-only user agent will query DNS
 for AAAA RRs, and a dual-stack user agent will query DNS for all RRs
 and choose a specific network.)
 Some domains provide automatic means for user agents to discover
 their proxy servers.  It is RECOMMENDED that domains implement
 appropriate discovery mechanisms to provide user agents with the IPv4
 and IPv6 addresses of their outbound proxy servers.  For example, a
 domain may support both the DHCPv4 [11] and the DHCPv6 [10] options
 for SIP servers.
 On the receiving side, user agents inside an autonomous domain
 receive SIP traffic from sources external to their domain through an
 inbound proxy, which is sometimes co-located with the registrar of
 the domain.  As was the case previously, it is RECOMMENDED that
 domains deploy dual-stack inbound proxies or, alternatively, deploy
 both IPv4-only and IPv6-only inbound proxy servers.  This allows a
 user agent external to the autonomous domain to query DNS and receive
 an IP address of the inbound proxy most appropriate for its use
 (i.e., an IPv4-only user agent will query DNS for A RRs, an IPv6-only
 user agent will query DNS for AAAA RRs, and a dual-stack user agent
 will query DNS for all RRs and choose a specific network).  This
 strategy, i.e., deploying dual-stack proxies, also allows for an
 IPv6-only user agent in the autonomous domain to communicate with an
 IPv4-only user agent in the same autonomous domain.  Without such a
 proxy, user agents using different networks identifiers will not be
 able to successfully signal each other.
 Proxies MUST follow the recommendations in Section 5 to determine the
 order in which to contact the downstream servers when routing a
 request.

Camarillo, et al. Standards Track [Page 4] RFC 6157 IPv6 Transition in SIP April 2011

3.1.1. Relaying Requests across Different Networks

 A SIP proxy server that receives a request using IPv6 and relays it
 to a user agent (or another downstream proxy) using IPv4, and vice
 versa, needs to remain in the path traversed by subsequent requests.
 Therefore, such a SIP proxy server MUST be configured to Record-Route
 in that situation.
    Note that while this is the recommended practice, some problems
    may still arise if an RFC 2543 [14] endpoint is involved in
    signaling.  Since the ABNF in RFC 2543 did not include production
    rules to parse IPv6 network identifiers, there is a good chance
    that an RFC 2543-only compliant endpoint is not able to parse or
    regenerate IPv6 network identifiers in headers.  Thus, despite a
    dual-stack proxy inserting itself into the session establishment,
    the endpoint itself may not succeed in the signaling establishment
    phase.
    This is generally not a problem with RFC 3261 endpoints; even if
    such an endpoint runs on an IPv4-only node, it still is able to
    parse and regenerate IPv6 network identifiers.
 Relaying a request across different networks in this manner has other
 ramifications.  For one, the proxy doing the relaying must remain in
 the signaling path for the duration of the session; otherwise, the
 upstream client and the downstream server would not be able to
 communicate directly.  Second, to remain in the signaling path, the
 proxy MUST insert one or two Record-Route headers: if the proxy is
 inserting a URI that contains a Fully Qualified Domain Name (FQDN) of
 the proxy, and that name has both IPv4 and IPv6 addresses in DNS,
 then inserting one Record-Route header suffices.  But if the proxy is
 inserting an IP address in the Record-Route header, then it must
 insert two such headers; the first Record-Route header contains the
 proxy's IP address that is compatible with the network type of the
 downstream server, and the second Record-Route header contains the
 proxy's IP address that is compatible with the upstream client.
 An example helps illustrate this behavior.  In the example, we use
 only those headers pertinent to the discussion.  Other headers have
 been omitted for brevity.  In addition, only the INVITE request and
 final response (200 OK) are shown; it is not the intent of the
 example to provide a complete call flow that includes provisional
 responses and other requests.
 In this example, proxy P, responsible for the domain example.com,
 receives a request from an IPv4-only upstream client.  It proxies
 this request to an IPv6-only downstream server.  Proxy P is running
 on a dual-stack host; on the IPv4 interface, it has an address of

Camarillo, et al. Standards Track [Page 5] RFC 6157 IPv6 Transition in SIP April 2011

 192.0.2.1, and on the IPv6 interface, it is configured with an
 address of 2001:db8::1 (Appendix A contains a sample DNS zone file
 entry that has been populated with both IPv4 and IPv6 addresses.)
   UAC            Proxy           UAS
  (IPv4)            P           (IPv6)
    |          (IPv4/IPv6)         |
    |               |              |
    +---F1--------->|              |
    |               +---F2-------->|
    |               |              |
    |               |<--F3---------+
    |<--F4----------+              |
   ...             ...            ...
    |               |              |
    V               V              V
 F1: INVITE sip:alice@example.com SIP/2.0
     ...
 F2: INVITE sip:alice@2001:db8::10 SIP/2.0
     Record-Route: <sip:2001:db8::1;lr>
     Record-Route: <sip:192.0.2.1;lr>
     ...
 F3: SIP/2.0 200 OK
     Record-Route: <sip:2001:db8::1;lr>
     Record-Route: <sip:192.0.2.1;lr>
     ...
 F4: SIP/2.0 200 OK
     Record-Route: <sip:2001:db8::1;lr>
     Record-Route: <sip:192.0.2.1;lr>
     ...
 Figure 1: Relaying requests across different networks
 When the User Agent Server (UAS) gets an INVITE and it accepts the
 invitation, it sends a 200 OK (F3) and forms a route set.  The first
 entry in its route set corresponds to the proxy's IPv6 interface.
 Similarly, when the 200 OK reaches the User Agent Client (UAC) (F4),
 it creates a route set by following the guidelines of RFC 3261 and
 reversing the Record-Route headers.  The first entry in its route set
 corresponds to the proxy's IPv4 interface.  In this manner, both the
 UAC and the UAS will have the correct address of the proxy to which
 they can target subsequent requests.

Camarillo, et al. Standards Track [Page 6] RFC 6157 IPv6 Transition in SIP April 2011

 Alternatively, the proxy could have inserted its FQDN in the Record-
 Route URI and the result would have been the same.  This is because
 the proxy has both IPv4 and IPv6 addresses in the DNS; thus, the URI
 resolution would have yielded an IPv4 address to the UAC and an IPv6
 address to the UAS.

3.2. User Agent Behavior

 User agent clients MUST follow the normative text specified in
 Section 4.2 to gather IP addresses pertinent to the network.  Having
 done that, clients MUST follow the recommendations in Section 5 to
 determine the order of the downstream servers to contact when routing
 a request.
 Autonomous domains SHOULD deploy dual-stack user agent servers, or
 alternatively, deploy both IPv4-only and IPv6-only servers.  In
 either case, the RR in DNS for reaching the server should be
 specified appropriately.

4. The Media Layer

 SIP establishes media sessions using the offer/answer model [4].  One
 endpoint, the offerer, sends a session description (the offer) to the
 other endpoint, the answerer.  The offer contains all the media
 parameters needed to exchange media with the offerer: codecs,
 transport addresses, protocols to transfer media, etc.
 When the answerer receives an offer, it elaborates an answer and
 sends it back to the offerer.  The answer contains the media
 parameters that the answerer is willing to use for that particular
 session.  Offer and answer are written using a session description
 protocol.  The most widespread protocol to describe sessions at
 present is called, aptly enough, the Session Description Protocol
 (SDP) [2].
 A direct offer/answer exchange between an IPv4-only user agent and an
 IPv6-only user agent does not result in the establishment of a
 session.  The IPv6-only user agent wishes to receive media on one or
 more IPv6 addresses, but the IPv4-only user agent cannot send media
 to these addresses, and generally does not even understand their
 format.  Consequently, user agents need a means to obtain both IPv4
 and IPv6 addresses to receive media and to place them in offers and
 answers.
    This IP version incompatibility problem would not exist if hosts
    implementing IPv6 also implemented IPv4, and were configured with
    both IPv4 and IPv6 addresses.  In such a case, a UA would be able

Camarillo, et al. Standards Track [Page 7] RFC 6157 IPv6 Transition in SIP April 2011

    to pick a compatible media transport address type to enable the
    hosts to communicate with each other.
 Pragmatism dictates that IPv6 user agents undertake the greater
 burden in the transition period.  Since IPv6 user agents are not
 widely deployed yet, it seems appropriate that IPv6 user agents
 obtain IPv4 addresses instead of mandating an upgrade on the
 installed IPv4 base.  Furthermore, IPv6 user agents are expected to
 be dual-stacked and thus also support IPv4, unlike the larger IPv4-
 only user agent base that does not or cannot support IPv6.
 An IPv6 node SHOULD also be able to send and receive media using IPv4
 addresses, but if it cannot, it SHOULD support Session Traversal
 Utilities for NAT (STUN) relay usage [8].  Such a relay allows the
 IPv6 node to indirectly send and receive media using IPv4.
 The advantage of this strategy is that the installed base of IPv4
 user agents continues to function unchanged, but it requires an
 operator that introduces IPv6 to provide additional servers for
 allowing IPv6 user agents to obtain IPv4 addresses.  This strategy
 may come at an additional cost to SIP operators deploying IPv6.
 However, since IPv4-only SIP operators are also likely to deploy STUN
 relays for NAT (Network Address Translator) traversal, the additional
 effort to deploy IPv6 in an IPv4 SIP network should be limited in
 this aspect.
 However, there will be deployments where an IPv4/IPv6 node is unable
 to use both interfaces natively at the same time, and instead, runs
 as an IPv6-only node.  Examples of such deployments include:
 1.  Networks where public IPv4 addresses are scarce and it is
     preferable to make large deployments only on IPv6.
 2.  Networks utilizing Layer-2's that do not support concurrent IPv4
     and IPv6 usage on the same link.

4.1. Updates to RFC 3264

 This section provides a normative update to RFC 3264 [4] in the
 following manner:
 1.  In some cases, especially those dealing with third party call
     control (see Section 4.2 of [12]), there arises a need to specify
     the IPv6 equivalent of the IPv4 unspecified address (0.0.0.0) in
     the SDP offer.  For this, IPv6 implementations MUST use a domain
     name within the .invalid DNS top-level domain instead of using
     the IPv6 unspecified address (i.e., ::).

Camarillo, et al. Standards Track [Page 8] RFC 6157 IPv6 Transition in SIP April 2011

 2.  Each media description in the SDP answer MUST use the same
     network type as the corresponding media description in the offer.
     Thus, if the applicable "c=" line for a media description in the
     offer contained a network type with the value "IP4", the
     applicable "c=" line for the corresponding media description in
     the answer MUST contain "IP4" as the network type.  Similarly, if
     the applicable "c=" line for a media description in the offer
     contained a network type with the value "IP6", the applicable
     "c=" line for the corresponding media description in the answer
     MUST contain "IP6" as the network type.

4.2. Initial Offer

 We now describe how user agents can gather addresses by following the
 Interactive Connectivity Establishment (ICE) [7] procedures.  ICE is
 protocol that allows two communicating user agents to arrive at a
 pair of mutually reachable transport addresses for media
 communications in the presence of NATs.  It uses the STUN [18]
 protocol, applying its binding discovery and relay usages.
 When following the ICE procedures, in addition to local addresses,
 user agents may need to obtain addresses from relays; for example, an
 IPv6 user agent would obtain an IPv4 address from a relay.  The relay
 would forward the traffic received on this IPv4 address to the user
 agent using IPv6.  Such user agents MAY use any mechanism to obtain
 addresses in relays, but, following the recommendations in ICE, it is
 RECOMMENDED that user agents support STUN relay usage [6] [8] for
 this purpose.
 IPv4/IPv6 user agents SHOULD gather both IPv4 and IPv6 addresses
 using the ICE procedures to generate all their offers.  This way,
 both IPv4-only and IPv6-only answerers will be able to generate a
 mutually acceptable answer that establishes a session (having used
 ICE to gather both IPv4 and IPv6 addresses in the offer reduces the
 session establishment time because all answerers will find the offer
 valid.)
    Implementations are encouraged to use ICE; however, the normative
    strength of the text above is left at a SHOULD since in some
    managed networks (such as a closed enterprise network) it is
    possible for the administrator to have control over the IP version
    utilized in all nodes and thus deploy an IPv6-only network, for
    example.  The use of ICE can be avoided for signaling messages
    that stay within such managed networks.

Camarillo, et al. Standards Track [Page 9] RFC 6157 IPv6 Transition in SIP April 2011

4.3. Connectivity Checks

 Once the answerer has generated an answer following the ICE
 procedures, both user agents perform the connectivity checks as
 specified by ICE.  These checks help prevent some types of flooding
 attacks and allow user agents to discover new addresses that can be
 useful in the presence of NATs.

5. Contacting Servers: Interaction of RFC 3263 and RFC 3484

 RFC 3263 maps a SIP or SIPS URI to a set of DNS SRV records for the
 various servers that can handle the URI.  The Expected Output, given
 an Application Unique String (the URI) is one or more SRV records,
 sorted by the "priority" field, and further ordered by the "weight"
 field in each priority class.
    The terms "Expected Output" and "Application Unique String", as
    they are to be interpreted in the context of SIP, are defined in
    Section 8 of RFC 3263 [5].
 To find a particular IP address to send the request to, the client
 will eventually perform an A or AAAA DNS lookup on a target.  As
 specified in RFC 3263, this target will have been obtained through
 NAPTR and SRV lookups, or if NAPTR and SRV lookup did not return any
 records, the target will simply be the domain name of the Application
 Unique String.  In order to translate the target to the corresponding
 set of IP addresses, IPv6-only or dual-stack clients MUST use the
 newer getaddrinfo() name lookup function, instead of gethostbyname()
 [16].  The new function implements the Source and Destination Address
 Selection algorithms specified in RFC 3484 [9], which is expected to
 be supported by all IPv6 hosts.
 The advantage of the additional complexity is that this technique
 will output an ordered list of IPv6/IPv4 destination addresses based
 on the relative merits of the corresponding source/destination pairs.
 This will guarantee optimal routing.  However, the Source and
 Destination Selection algorithms of RFC3484 are dependent on broad
 operating system support and uniform implementation of the
 application programming interfaces that implement this behavior.
    Developers should carefully consider the issues described by Roy
    et al. [19] with respect to address resolution delays and address
    selection rules.  For example, implementations of getaddrinfo()
    may return address lists containing IPv6 global addresses at the
    top of the list and IPv4 addresses at the bottom, even when the
    host is only configured with an IPv6 local scope (e.g., link-
    local) and an IPv4 address.  This will, of course, introduce a
    delay in completing the connection.

Camarillo, et al. Standards Track [Page 10] RFC 6157 IPv6 Transition in SIP April 2011

6. Security Considerations

 This document describes how IPv4 SIP user agents can communicate with
 IPv6 user agents (and vice versa).  To do this, it uses additional
 protocols (STUN relay usage [6], ICE [7], SDP [2]); the threat model
 of each such protocol is included in its respective document.  The
 procedures introduced in this document do not introduce the
 possibility of any new security threats; however, they may make hosts
 more amenable to existing threats.  Consider, for instance, a UAC
 that allocates an IPv4 and an IPv6 address locally and inserts these
 into the SDP.  Malicious user agents that may intercept the request
 can mount a denial-of-service attack targeted to the different
 network interfaces of the UAC.  In such a case, the UAC should use
 mechanisms that protect confidentiality and integrity of the
 messages, such as using the SIPS URI scheme as described in Section
 26.2.2 of RFC3261 [3], or secure MIME as described in Section 23 of
 RFC3261 [3].  If HTTP Digest is used as an authentication mechanism
 in SIP, then the UAC should ensure that the quality of protection
 also includes the SDP payload.

7. Acknowledgments

 The authors would like to thank Mohamed Boucadair, Christine Fischer,
 Cullen Jennings, Aki Niemi, Jonathan Rosenberg, and Robert Sparks for
 discussions on the working group list that improved the quality of
 this document.
 Additionally, Francois Audet, Mary Barnes, Keith Drage, and Dale
 Worley provided invaluable comments as part of the working group Last
 Call review process.  Jari Arkko, Lars Eggert, Tobias Gondrom, Suresh
 Krishnan, and Tim Polk conducted an in-depth review of the work as
 part of the IESG and Gen-ART reviews.

8. References

8.1. Normative References

 [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.
 [2]   Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
       Description Protocol", RFC 4566, July 2006.
 [3]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
       Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
       Session Initiation Protocol", RFC 3261, June 2002.

Camarillo, et al. Standards Track [Page 11] RFC 6157 IPv6 Transition in SIP April 2011

 [4]   Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
       the Session Description Protocol (SDP)", RFC 3264, June 2002.
 [5]   Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol
       (SIP): Locating SIP Servers", RFC 3263, June 2002.
 [6]   Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
       Relays around NAT (TURN): Relay Extensions to Session Traversal
       Utilities for NAT (STUN)", RFC 5766, April 2010.
 [7]   Rosenberg, J., "Interactive Connectivity Establishment (ICE): A
       Protocol for Network Address Translator (NAT) Traversal for
       Offer/Answer Protocols", RFC 5245, April 2010.
 [8]   Camarillo, G., Novo, O., and S. Perreault, "Traversal Using
       Relays around NAT (TURN) Extension for IPv6", RFC 6156, April
       2011.
 [9]   Draves, R., "Default Address Selection for Internet Protocol
       version 6 (IPv6)", RFC 3484, February 2003.

8.2. Informative References

 [10]  Schulzrinne, H. and B. Volz, "Dynamic Host Configuration
       Protocol (DHCPv6) Options for Session Initiation Protocol (SIP)
       Servers", RFC 3319, July 2003.
 [11]  Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCP-
       for-IPv4) Option  for Session Initiation Protocol (SIP)
       Servers", RFC 3361, August 2002.
 [12]  Rosenberg, J., Peterson, J., Schulzrinne, H., and G. Camarillo,
       "Best Current Practices for Third Party Call Control (3pcc) in
       the Session Initiation Protocol (SIP)", BCP 85, RFC 3725,
       April 2004.
 [13]  Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
       "RTP: A Transport Protocol for Real-Time Applications", STD 64,
       RFC 3550, July 2003.
 [14]  Handley, M., Schulzrinne, H., Schooler, E., and J. Rosenberg,
       "SIP: Session Initiation Protocol", RFC 2543, March 1999.
 [15]  Gurbani, V., Boulton, C., and R. Sparks, "Session Initiation
       Protocol (SIP) Torture Test Messages for Internet Protocol
       Version 6 (IPv6)", RFC 5118, February 2008.

Camarillo, et al. Standards Track [Page 12] RFC 6157 IPv6 Transition in SIP April 2011

 [16]  Shin, M-K., Hong, Y-G., Hagino, J., Savola, P., and E. Castro,
       "Application Aspects of IPv6 Transition", RFC 4038, March 2005.
 [17]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms for
       IPv6 Hosts and Routers", RFC 4213, October 2005.
 [18]  Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, "Session
       Traversal Utilities for NAT (STUN)", RFC 5389, October 2008.
 [19]  Roy, S., Durand, A., and J. Paugh, "IPv6 Neighbor Discovery On-
       Link Assumption Considered Harmful", RFC 4943, September 2007.

Camarillo, et al. Standards Track [Page 13] RFC 6157 IPv6 Transition in SIP April 2011

Appendix A. Sample IPv4/IPv6 DNS File

 A portion of a sample DNS zone file entry is reproduced below that
 has both IPv4 and IPv6 addresses.  This entry corresponds to a proxy
 server for the domain "example.com".  The proxy server supports the
 Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)
 transport for both IPv4 and IPv6 networks.
     ...
     _sip._tcp  SRV  20 0 5060 sip1.example.com
                SRV   0 0 5060 sip2.example.com
     _sip._udp  SRV  20 0 5060 sip1.example.com
                SRV   0 0 5060 sip2.example.com
     sip1 IN A     192.0.2.1
     sip1 IN AAAA  2001:db8::1
     sip2 IN A     192.0.2.2
     sip2 IN AAAA  2001:db8::2
     ...

Camarillo, et al. Standards Track [Page 14] RFC 6157 IPv6 Transition in SIP April 2011

Authors' Addresses

 Gonzalo Camarillo
 Ericsson
 Hirsalantie 11
 Jorvas  02420
 Finland
 EMail: Gonzalo.Camarillo@ericsson.com
 Karim El Malki
 Athonet
 AREA Science Park
 Padriciano 99
 Trieste (TS)  34149
 Italy
 EMail: karim@athonet.com
 Vijay K. Gurbani
 Bell Laboratories, Alcatel-Lucent
 1960 Lucent Lane
 Rm 9C-533
 Naperville, IL  60563
 USA
 Phone: +1 630 224 0216
 EMail: vkg@bell-labs.com

Camarillo, et al. Standards Track [Page 15]

/data/webs/external/dokuwiki/data/pages/rfc/rfc6157.txt · Last modified: 2011/04/27 21:37 (external edit)