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          13 14 15 16 17 18 19 rfc6406                                  
SPEERMINT                                                  D. Malas, Ed.
Internet-Draft                                                 CableLabs
Intended status: Informational                         J. Livingood, Ed.
Expires: August 22, 2011                                         Comcast
                                                       February 18, 2011

        Session PEERing for Multimedia INTerconnect Architecture


   This document defines a peering architecture for the Session
   Initiation Protocol (SIP), its functional components and interfaces.
   It also describes the components and the steps necessary to establish
   a session between two SIP Service Provider (SSP) peering domains.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on August 22, 2011.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

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   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.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  New Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Session Border Controller (SBC)  . . . . . . . . . . . . .  4
     2.2.  Carrier-of-Record  . . . . . . . . . . . . . . . . . . . .  5
   3.  Reference Architecture . . . . . . . . . . . . . . . . . . . .  5
   4.  Procedures of Inter-Domain SSP Session Establishment . . . . .  7
   5.  Relationships Between Functions/Elements . . . . . . . . . . .  8
   6.  Recommended SSP Procedures . . . . . . . . . . . . . . . . . .  8
     6.1.  Originating or Indirect SSP Procedures . . . . . . . . . .  8
       6.1.1.  The Look-Up Function (LUF) . . . . . . . . . . . . . .  9  Target Address Analysis  . . . . . . . . . . . . .  9  ENUM Lookup  . . . . . . . . . . . . . . . . . . .  9
       6.1.2.  Location Routing Function (LRF)  . . . . . . . . . . . 10  DNS Resolution . . . . . . . . . . . . . . . . . . 10  Routing Table  . . . . . . . . . . . . . . . . . . 10  LRF to LRF Routing . . . . . . . . . . . . . . . . 11
       6.1.3.  The Signaling Path Border Element (SBE)  . . . . . . . 11  Establishing a Trusted Relationship  . . . . . . . 11  IPSec  . . . . . . . . . . . . . . . . . . . . . . 11  Co-Location  . . . . . . . . . . . . . . . . . . . 11  Sending the SIP Request  . . . . . . . . . . . . . 12
     6.2.  Target SSP Procedures  . . . . . . . . . . . . . . . . . . 12
       6.2.1.  TLS  . . . . . . . . . . . . . . . . . . . . . . . . . 12
       6.2.2.  Receive SIP Requests . . . . . . . . . . . . . . . . . 12
     6.3.  Data Path Border Element (DBE) . . . . . . . . . . . . . . 13
   7.  Address Space Considerations . . . . . . . . . . . . . . . . . 13
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 13
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14
   12. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 15
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 16
     13.2. Informative References . . . . . . . . . . . . . . . . . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18

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1.  Introduction

   This document defines a reference peering architecture for the
   Session Initiation Protocol (SIP)[RFC3261], it's functional
   components and interfaces, in the context of session peering for
   multimedia interconnects.  In this process, we define the peering
   reference architecture, its functional components, and peering
   interface functions from the perspective of a SIP Service Provider's
   (SSP) [RFC5486] network.  Thus, it also describes the components and
   the steps necessary to establish a session between two SSP peering

   An SSP may also be referred to as an Internet Telephony Service
   Provider (ITSP).  While the terms ITSP and SSP are frequently used
   interchangeably, this document and other subsequent SIP peering-
   related documents should use the term SSP.  SSP more accurately
   depicts the use of SIP as the underlying layer 5 signaling protocol.

   This architecture enables the interconnection of two SSPs in layer 5
   peering, as defined in the SIP-based session peering requirements

   Layer 3 peering is outside the scope of this document.  Hence, the
   figures in this document do not show routers so that the focus is on
   layer 5 protocol aspects.

   This document uses terminology defined in the Session Peering for
   Multimedia Interconnect (SPEERMINT) Terminology document [RFC5486].
   Apart from normative references included herein, readers may also
   find [I-D.ietf-speermint-voip-consolidated-usecases] informative.

2.  New Terminology

   [RFC5486] is a key reference for the majority of the SPEERMINT-
   related terminology used in this document.  However, some additional
   new terms are used here as follows in this section.

2.1.  Session Border Controller (SBC)

   A Session Border Controller (SBC) is referred to in Section 5.  An
   SBC can contain a Signaling Function (SF), Signaling Path Border
   Element (SBE) and Data Path Border Element (DBE), and may perform the
   Look-Up Function (LUF) and Location Routing Function (LRF) functions,
   as described in Section 3.  Whether the SBC performs one or more of
   these functions is generally speaking dependent upon how a SIP
   Service Provider (SSP) configures such a network element.  In
   addition, requirements for an SBC can be found in [RFC5853].

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2.2.  Carrier-of-Record

   A carrier-of-record, as used in Section, is defined in
   [RFC5067].  That document describes the term to refer to the entity
   having discretion over the domain and zone content and acting as the
   registrant for a telephone number, as represented in ENUM.  This can

   o  the Service Provider to which the E.164 number was allocated for
      end user assignment, whether by the National Regulatory Authority
      (NRA) or the International Telecommunication Union (ITU), for
      instance, a code under "International Networks" (+882) or
      "Universal Personal Telecommunications (UPT)" (+878) or,

   o  if the number is ported, the service provider to which the number
      was ported, or

   o  where numbers are assigned directly to end users, the service
      provider that the end user number assignee has chosen to provide a
      Public Switched Telephone Network/Public Land Mobile Network
      (PSTN/ PLMN) point-of-interconnect for the number.

   It is understood that the definition of carrier-of-record within a
   given jurisdiction is subject to modification by national

3.  Reference Architecture

   The following figure depicts the architecture and logical functions
   that form peering between two SSPs.

   For further details on the elements and functions described in this
   figure, please refer to [RFC5486].  The following terms, which appear
   in Figure 1, which are documented in [RFC5486] are reproduced here
   for simplicity.

   - Data Path Border Element (DBE): A data path border element (DBE) is
   located on the administrative border of a domain through which flows
   the media associated with an inter-domain session.  It typically
   provides media-related functions such as deep packet inspection and
   modification, media relay, and firewall-traversal support.  The DBE
   may be controlled by the SBE.

   - E.164 Number Mapping (ENUM): See [RFC3761].

   - Fully Qualified Domain Name (FQDN): See Section 5.1 of [RFC1035].

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   - Location Routing Function (LRF): The Location Routing Function
   (LRF) determines for the target domain of a given request the
   location of the SF in that domain, and optionally develops other SED
   required to route the request to that domain.  An example of the LRF
   may be applied to either example in Section 4.3.3 of [RFC5486].  Once
   the ENUM response or SIP 302 redirect is received with the
   destination's SIP URI, the LRF must derive the destination peer's SF
   from the FQDN in the domain portion of the URI.  In some cases, some
   entity (usually a 3rd party or federation) provides peering
   assistance to the originating SSP by providing this function.  The
   assisting entity may provide information relating to direct (Section
   4.2.1 of [RFC5486]) or indirect (Section 4.2.2 of [RFC5486]) peering
   as necessary.

   - Look-Up Function (LUF): The Look-Up Function (LUF) determines for a
   given request the target domain to which the request should be
   routed.  An example of an LUF is an ENUM [4] look-up or a SIP INVITE
   request to a SIP proxy providing redirect responses for peers.  In
   some cases, some entity (usually a 3rd party or federation) provides
   peering assistance to the originating SSP by providing this function.
   The assisting entity may provide information relating to direct
   (Section 4.2.1 of [RFC5486]) or indirect (Section 4.2.2 of [RFC5486])
   peering as necessary.

   - Real-Time Transport Protocol (RTP): See [RFC3550].

   - Session Initiation Protocol (SIP): See [RFC3261].

   - Signaling Path Border Element (SBE): A signaling path border
   element (SBE) is located on the administrative border of a domain
   through which inter-domain session layer messages will flow.  It
   typically provides signaling functions such as protocol inter-working
   (for example, H.323 to SIP), identity and topology hiding, and
   Session Admission Control for a domain.

   - Signaling Function (SF): The Signaling Function (SF) performs
   routing of SIP requests for establishing and maintaining calls, and
   to assist in the discovery or exchange of parameters to be used by
   the Media Function (MF).  The SF is a capability of SIP processing
   elements such as SIP proxies, SBEs, and user agents.

   - SIP Service Provider (SSP): A SIP Service Provider (SSP) is an
   entity that provides session services utilizing SIP signaling to its
   customers.  In the event that the SSP is also a function of the SP,
   it may also provide media streams to its customers.  Such an SSP may
   additionally be peered with other SSPs.  An SSP may also interconnect
   with the PSTN.

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         +=============++                          ++=============+
                       ||                          ||
                 +-----------+                +-----------+
                 |    SBE    |       +-----+  |    SBE    |
                 |  +-----+  | SIP   |Proxy|  |  +-----+  |
                 |  | LUF |<-|------>|ENUM |  |  | LUF |  |
                 |  +-----+  | ENUM  |TN DB|  |  +-----+  |
            SIP  |           |       +-----+  |           |
          ------>|  +-----+  | DNS   +-----+  |  +-----+  |
                 |  | LRF |<-|------>|FQDN |  |  | LRF |  |
                 |  +-----+  |       |IP   |  |  +-----+  |
                 |  +-----+  | SIP   +-----+  |  +-----+  |
                 |  | SF  |<-|----------------|->|  SF |  |
                 |  +-----+  |                |  +-----+  |
                 +-----------+                +-----------+
                      ||                           ||
                 +-----------+                +-----------+
            RTP  |    DBE    | RTP            |    DBE    |
          ------>|           |--------------->|           |
                 +-----------+                +-----------+
                       ||                          ||
          SSP1 Network ||                          || SSP2 Network
         +=============++                          ++=============+

   Reference Architecture

                                 Figure 1

4.  Procedures of Inter-Domain SSP Session Establishment

   This document assumes that in order for a session to be established
   from a User Agent (UA) in the originating (or indirect) SSP's network
   to an UA in the Target SSP's network the following steps are taken:

   1.  Determine the target or indirect SSP via the LUF.  (Note: If the
       target address represents an intra-SSP resource, the behavior is
       out-of-scope with respect to this draft.)

   2.  Determine the address of the SF of the target SSP via the LRF.

   3.  Establish the session

   4.  Exchange the media, which could include voice, video, text, etc.

   5.  End the session (BYE)

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   The originating or indirect SSP would perform steps 1-4, the target
   SSP would perform steps 4, and either one can perform step 5.

   In the case the target SSP changes, then steps 1-4 would be repeated.
   This is reflected in Figure 1 that shows the target SSP with its own
   peering functions.

5.  Relationships Between Functions/Elements

   Please also refer to Figure 1.

   o  An SBE can contain a Signaling Function (SF).

   o  An SF can perform a Look-Up Function (LUF) and Location Routing
      Function (LRF).

   o  As an additional consideration, a Session Border Controller, can
      contain an SF, SBE and DBE, and may act as both an LUF and LRF.

   o  The following functions may communicate as follows in an example
      SSP network, depending upon various real-world implementations:

      *  SF may communicate with LUF, LRF, SBE and SF

      *  LUF may communicate with SF and SBE

      *  LRF may communicate with SF and SBE

6.  Recommended SSP Procedures

   This section describes the functions in more detail and provides some
   recommendations on the role they would play in a SIP call in a Layer
   5 peering scenario.

   Some of the information in the section is taken from
   [I-D.ietf-speermint-requirements] and is included here for continuity
   purposes.  It is also important to refer to Section 3.2 of
   [I-D.ietf-speermint-voipthreats], particularly with respect to the
   use of IPSec and TLS.

6.1.  Originating or Indirect SSP Procedures

   This section describes the procedures of the originating or indirect

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6.1.1.  The Look-Up Function (LUF)

   The purpose of the LUF is to determine the SF of the target domain of
   a given request and optionally to develop Session Establishment Data.
   It is important to note that the LUF may utilize the public e164.arpa
   ENUM root, as well as one or more private roots.  When private roots
   are used specialized routing rules may be implemented, and these
   rules may vary depending upon whether an originating or indirect SSP
   is querying the LUF.  Target Address Analysis

   When the originating (or indirect) SSP receives a request to
   communicate, it analyzes the target URI to determine whether the call
   needs to be routed internal or external to its network.  The analysis
   method is internal to the SSP; thus, outside the scope of SPEERMINT.

   If the target address does not represent a resource inside the
   originating (or indirect) SSP's administrative domain or federation
   of domains, then the originating (or indirect) SSP performs a Lookup
   Function (LUF) to determine a target address, and then it resolves
   the call routing data by using the Location routing Function (LRF).

   For example, if the request to communicate is for an im: or pres: URI
   type [RFC3861] [RFC3953], the originating (or indirect) SSP follows
   the procedures in [RFC3861].  If the highest priority supported URI
   scheme is sip: or sips: the originating (or indirect) SSP skips to
   SIP DNS resolution in Section 5.1.3.  Likewise, if the target address
   is already a sip: or sips: URI in an external domain, the originating
   (or indirect) SSP skips to SIP DNS resolution in Section
   This may be the case, to use one example, with

   If the target address corresponds to a specific E.164 address, the
   SSP may need to perform some form of number plan mapping according to
   local policy.  For example, in the United States, a dial string
   beginning "011 44" could be converted to "+44", or in the United
   Kingdom "00 1" could be converted to "+1".  Once the SSP has an E.164
   address, it can use ENUM.  ENUM Lookup

   If an external E.164 address is the target, the originating (or
   indirect) SSP consults the public "User ENUM" rooted at e164.arpa,
   according to the procedures described in [RFC3761].  The SSP must
   query for the "E2U+sip" enumservice as described in [RFC3764], but
   may check for other enumservices.  The originating (or indirect) SSP
   may consult a cache or alternate representation of the ENUM data

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   rather than actual DNS queries.  Also, the SSP may skip actual DNS
   queries if the originating (or indirect) SSP is sure that the target
   address country code is not represented in e164.arpa.

   If an im: or pres: URI is chosen based on an "E2U+im" [RFC3861] or
   "E2U+pres" [RFC3953] enumserver, the SSP follows the procedures for
   resolving these URIs to URIs for specific protocols such as SIP or
   XMPP as described in the previous section.

   The NAPTR response to the ENUM lookup may be a SIP AoR (such as
   "sips:bob@example.com") or SIP URI (such as
   "sips:bob@sbe1.biloxi.example.com").  In the case of when a SIP URI
   is returned, the originating (or indirect) SSP has sufficient routing
   information to locate the target SSP.  In the case of when a SIP AoR
   is returned, the SF then uses the LRF to determine the URI for more
   explicitly locating the target SSP.

6.1.2.  Location Routing Function (LRF)

   The LRF of an originating (or indirect) SSP analyzes target address
   and target domain identified by the LUF, and discovers the next hop
   signaling function (SF) in a peering relationship.  The resource to
   determine the SF of the target domain might be provided by a third-
   party as in the assisted-peering case.  The following sections define
   mechanisms which may be used by the LRF.  These are not in any
   particular order and, importantly, not all of them have to be used.  DNS Resolution

   The originating (or indirect) SSP uses the procedures in Section 4 of
   [RFC3263] to determine how to contact the receiving SSP.  To
   summarize the [RFC3263] procedure: unless these are explicitly
   encoded in the target URI, a transport is chosen using NAPTR records,
   a port is chosen using SRV records, and an address is chosen using A
   or AAAA records.

   When communicating with another SSP, entities compliant to this
   document should select a TLS-protected transport for communication
   from the originating (or indirect) SSP to the receiving SSP if
   available, as described further in Section 6.2.1.  Routing Table

   If there are no End User ENUM records and the originating (or
   indirect) SSP cannot discover the carrier-of-record or if the
   originating (or indirect) SSP cannot reach the carrier-of-record via
   SIP peering, the originating (or indirect) SSP may deliver the call
   to the PSTN or reject it.  Note that the originating (or indirect)

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   SSP may forward the call to another SSP for PSTN gateway termination
   by prior arrangement using the local SIP proxy routing table.

   If so, the originating (or indirect) SSP rewrites the Request-URI to
   address the gateway resource in the target SSP's domain and may
   forward the request on to that SSP using the procedures described in
   the remainder of these steps.  LRF to LRF Routing

   Communications between the LRF of two interconnecting SSPs may use
   DNS or statically provisioned IP Addresses for reachability.  Other
   inputs to determine the path may be code-based routing, method-based
   routing, Time of day, least cost and/or source-based routing.

6.1.3.  The Signaling Path Border Element (SBE)

   The purpose of signaling function is to perform routing of SIP
   messages as well as optionally implement security and policies on SIP
   messages, and to assist in discovery/exchange of parameters to be
   used by the Media Function (MF).  The signaling function performs the
   routing of SIP messages.  The SBE may be a B2BUA or it may act as a
   SIP proxy.  Optionally, an SF may perform additional functions such
   as Session Admission Control, SIP Denial of Service protection, SIP
   Topology Hiding, SIP header normalization, SIP security, privacy, and
   encryption.  The SF of an SBE can also process SDP payloads for media
   information such as media type, bandwidth, and type of codec; then,
   communicate this information to the media function.  Establishing a Trusted Relationship

   Depending on the security needs and trust relationships between SSPs,
   different security mechanisms can be used to establish SIP calls.
   These are discussed in the following subsections.  IPSec

   In certain deployments the use of IPSec between the signaling
   functions of the originating and terminating domains can be used as a
   security mechanism instead of TLS.  However, such IPSec use should be
   the subject of a future document as additional specification is
   necessary to use IPSec properly and effectively.  Co-Location

   In this scenario the SFs are co-located in a physically secure
   location and/or are members of a segregated network.  In this case
   messages between the originating and terminating SSPs could be sent

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   as clear text (unencrypted).  However, even in these semi-trusted co-
   location facilities, other security or access control mechanisms may
   be appropriate, such as IP access control lists or other mechanisms.  Sending the SIP Request

   Once a trust relationship between the peers is established, the
   originating (or indirect) SSP sends the request.

6.2.  Target SSP Procedures

   This section describes the Target SSP Procedures.

6.2.1.  TLS

   The section defines the usage of TLS between two SSPs [RFC5246]
   [RFC5746] [RFC5878].  When the receiving SSP receives a TLS client
   hello, it responds with its certificate.  The Target SSP certificate
   should be valid and rooted in a well-known certificate authority.
   The procedures to authenticate the SSP's originating domain are
   specified in [RFC5922].

   The SF of the Target SSP verifies that the Identity header is valid,
   corresponds to the message, corresponds to the Identity-Info header,
   and that the domain in the From header corresponds to one of the
   domains in the TLS client certificate.

   As noted above in Section, some deployments may utilize IPSec
   rather than TLS.

6.2.2.  Receive SIP Requests

   Once a trust relationship is established, the Target SSP is prepared
   to receive incoming SIP requests.  For new requests (dialog forming
   or not) the receiving SSP verifies if the target (request-URI) is a
   domain that for which it is responsible.  For these requests, there
   should be no remaining Route header field values.  For in-dialog
   requests, the receiving SSP can verify that it corresponds to the
   top-most Route header field value.

   The receiving SSP may reject incoming requests due to local policy.
   When a request is rejected because the originating (or indirect) SSP
   is not authorized to peer, the receiving SSP should respond with a
   403 response with the reason phrase "Unsupported Peer".

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6.3.  Data Path Border Element (DBE)

   The purpose of the DBE [RFC5486] is to perform media related
   functions such as media transcoding and media security implementation
   between two SSPs.

   An example of this is to transform a voice payload from one codec
   (e.g., G.711) to another (e.g., EvRC).  Additionally, the MF may
   perform media relaying, media security [RFC3711], privacy, and

7.  Address Space Considerations

   Peering must occur in a common IP address space, which is defined by
   the federation, which may be entirely on the public Internet, or some
   private address space [RFC1918].  The origination or termination
   networks may or may not entirely be in the same address space.  If
   they are not, then a network address translation (NAT) or similar may
   be needed before the signaling or media is presented correctly to the
   federation.  The only requirement is that all associated entities
   across the peering interface are reachable.

8.  Acknowledgments

   The working group would like to thank John Elwell, Otmar Lendl, Rohan
   Mahy, Alexander Mayrhofer, Jim McEachern, Jean-Francois Mule,
   Jonathan Rosenberg, and Dan Wing for their valuable contributions to
   various versions of this document.

9.  IANA Considerations

   This memo includes no request to IANA.

10.  Security Considerations

   The level (or types) of security mechanisms implemented between
   peering providers is in practice dependent upon on the underlying
   physical security of SSP connections.  This means, as noted in
   Section, whether peering equipment is in a secure facility or
   not may bear on other types of security mechanisms which may be
   appropriate.  Thus, if two SSPs peered across public Internet links,
   they are likely to use IPSec or TLS since the link between the two
   domains should be considered untrusted.

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   Many detailed and highly relevant security requirements for SPEERMINT
   have been documented in Section 5 of
   [I-D.ietf-speermint-requirements].  As a result, that document should
   be considered required reading.

   Additional and important security considerations have been documented
   separately in [I-D.ietf-speermint-voipthreats].  This document
   describes the many relevant security threats to SPEERMINT, as well
   the relevant countermeasures and security protections which are
   recommended to combat any potential threats or other risks.  This
   includes a wide range of detailed threats in Section 2 of
   [I-D.ietf-speermint-voipthreats].  It also includes key requirements
   in Section 3.1 of [I-D.ietf-speermint-voipthreats], such as the
   requirement for the LUF and LRF to support mutual authentication for
   queries, among other requirements which are related to
   [I-D.ietf-speermint-requirements].  Section 3.2 of
   [I-D.ietf-speermint-voipthreats] explains how to meet these security
   requirements, and then Section 4 explores a wide range of suggested

11.  Contributors

   Mike Hammer

   Cisco Systems

   Herndon, VA - USA

   Email: mhammer@cisco.com


   Hadriel Kaplan

   Acme Packet

   Burlington, MA - USA

   Email: hkaplan@acmepacket.com


   Sohel Khan, Ph.D.

   Comcast Cable

   Philadelphia, PA - USA

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Internet-Draft       SPEERMINT Peering Architecture        February 2011

   Email: sohel_khan@cable.comcast.com


   Reinaldo Penno

   Juniper Networks

   Sunnyvale, CA - USA

   Email: rpenno@juniper.net


   David Schwartz

   XConnect Global Networks

   Jerusalem - Israel

   Email: dschwartz@xconnnect.net


   Rich Shockey

   Shockey Consulting


   Email: Richard@shockey.us


   Adam Uzelac

   Global Crossing

   Rochester, NY - USA

   Email: adam.uzelac@globalcrossing.com

12.  Change Log


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Internet-Draft       SPEERMINT Peering Architecture        February 2011

   o  19: Additional change to the IPSec section at Jari Arkko's

   o  18: Made several changes based on feedback from Adrian Farrel,
      Bert Wijnen, Dan Romascanu, Avshalom Houri, Russ Housley, Sean
      Turner, Tim Polk, and Russ Mundy during IESG review.

   o  17: Misc. updates at the request of Gonzalo, the RAI AD, in order
      to clear his review and move to the IESG.  This included adding
      terminology from RFC 5486 and expanding the document name.

   o  16: Yes, one final outdated reference to fix.

   o  15: Doh!  Uploaded the wrong doc to create -14.  Trying again. :-)

   o  14: WGLC ended.  Ran final nits check prior to sending proto to
      the AD and sending the doc to the IESG.  Found a few very minor
      nits, such as capitalization and replacement of an obsoleted RFC,
      which were corrected per nits tool recommendation.  The -14 now
      moves to the AD and the IESG.

   o  13: Closed out all remaining tickets, resolved all editorial

   o  12: Closed out several open issues.  Properly XML-ized all
      references.  Updated contributors list.

   o  11: Quick update to refresh the I-D since it expired, and cleaned
      up some of the XML for references.  A real revision is coming

13.  References

13.1.  Normative References

              Mule, J., "Requirements for SIP-based Session Peering",
              draft-ietf-speermint-requirements-10 (work in progress),
              October 2010.

              Seedorf, J., Niccolini, S., Chen, E., and H. Scholz,
              "Session Peering for Multimedia Interconnect (SPEERMINT)
              Security Threats and Suggested Countermeasures",
              draft-ietf-speermint-voipthreats-07 (work in progress),
              January 2011.

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   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets",
              BCP 5, RFC 1918, February 1996.

   [RFC3261]  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.

   [RFC3263]  Rosenberg, J. and H. Schulzrinne, "Session Initiation
              Protocol (SIP): Locating SIP Servers", RFC 3263,
              June 2002.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, July 2003.

   [RFC3761]  Faltstrom, P. and M. Mealling, "The E.164 to Uniform
              Resource Identifiers (URI) Dynamic Delegation Discovery
              System (DDDS) Application (ENUM)", RFC 3761, April 2004.

   [RFC3764]  Peterson, J., "enumservice registration for Session
              Initiation Protocol (SIP) Addresses-of-Record", RFC 3764,
              April 2004.

   [RFC3861]  Peterson, J., "Address Resolution for Instant Messaging
              and Presence", RFC 3861, August 2004.

   [RFC3953]  Peterson, J., "Telephone Number Mapping (ENUM) Service
              Registration for Presence Services", RFC 3953,
              January 2005.

   [RFC5067]  Lind, S. and P. Pfautz, "Infrastructure ENUM
              Requirements", RFC 5067, November 2007.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

   [RFC5486]  Malas, D. and D. Meyer, "Session Peering for Multimedia
              Interconnect (SPEERMINT) Terminology", RFC 5486,
              March 2009.

   [RFC5746]  Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,
              "Transport Layer Security (TLS) Renegotiation Indication
              Extension", RFC 5746, February 2010.

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   [RFC5853]  Hautakorpi, J., Camarillo, G., Penfield, R., Hawrylyshen,
              A., and M. Bhatia, "Requirements from Session Initiation
              Protocol (SIP) Session Border Control (SBC) Deployments",
              RFC 5853, April 2010.

   [RFC5878]  Brown, M. and R. Housley, "Transport Layer Security (TLS)
              Authorization Extensions", RFC 5878, May 2010.

   [RFC5922]  Gurbani, V., Lawrence, S., and A. Jeffrey, "Domain
              Certificates in the Session Initiation Protocol (SIP)",
              RFC 5922, June 2010.

13.2.  Informative References

              Uzelac, A. and Y. Lee, "VoIP SIP Peering Use Cases",
              draft-ietf-speermint-voip-consolidated-usecases-18 (work
              in progress), April 2010.

   [RFC3711]  Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
              Norrman, "The Secure Real-time Transport Protocol (SRTP)",
              RFC 3711, March 2004.

Authors' Addresses

   Daryl Malas (editor)
   Louisville, CO

   Email: d.malas@cablelabs.com

   Jason Livingood (editor)
   Philadelphia, PA

   Email: Jason_Livingood@cable.comcast.com

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