Speermint Working Group                                   A.Uzelac(Ed.)
Internet Draft
SPEERMINT                                                 A. Uzelac, Ed.
Internet-Draft                                           Global Crossing
Intended status: Informational                                  R. Penno
Expires: May 2010
                                                       November September 10, 2009 2010                             Juniper Networks
                                                               M. Hammer
                                                           Cisco Systems
                                                                D. Malas
                                                               CableLabs
                                                                 S. Khan
                                                                 Comcast
                                                               H. Kaplan
                                                             Acme Packet
                                                            J. Livingood
                                                                 Comcast
                                                             D. Schwartz
                                                XConnect Global Networks
                                                              R. Shockey
                                                      Shockey Consulting
                                                           March 9, 2010

                     SPEERMINT Peering Architecture
                     draft-ietf-speermint-architecture-09
                  draft-ietf-speermint-architecture-10

   This document may contain material from IETF Documents or IETF
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   it for publication as an RFC or to translate it into languages other
   than English.

Abstract

   This document defines a peering architecture for the Session
   Initation Protocol (SIP) [RFC3261], it's functional components and
   interfaces.  It also describes the steps necessary to establish a
   session between two peering domains in the context of the functions
   defined.

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Abstract

   This document defines the SPEERMINT peering architecture, its functional
   components and peering interface functions. It also describes the steps taken
   to establish a session between two peering domains in the context of the
   functions defined. License.

Table of Contents

   1. Introduction...................................................2  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Reference SPEERMINT Architecture...............................4 Architecture . . . . . . . . . . . . . . . . . . . .  4
   3.  Procedures of Inter-domain SSP Session Establishment...........4
      3.1. Establishment . . . . .  5
   4.  Relationships between functions/elements..................5
   4. functions/elements . . . . . . . . . . .  6
   5.  Recommended SSP Procedures.....................................5
      4.1. Procedures . . . . . . . . . . . . . . . . . .  6
     5.1.  Originating SSP Procedures................................5
         4.1.1. Procedures . . . . . . . . . . . . . . . .  7
       5.1.1.  The Look-Up Function (LUF)...........................5
            4.1.1.1. (LUF) . . . . . . . . . . . . . .  7
         5.1.1.1.  Target Address Analysis.........................6
            4.1.1.2. Analysis  . . . . . . . . . . . . .  7
         5.1.1.2.  ENUM Lookup.....................................6
         4.1.2. Lookup  . . . . . . . . . . . . . . . . . . .  7
       5.1.2.  Location Routing Function (LRF)......................6
            4.1.2.1. (LRF)  . . . . . . . . . . .  8
         5.1.2.1.  DNS Resolution..................................7
            4.1.2.2. resolution . . . . . . . . . . . . . . . . . .  8
         5.1.2.2.  Routing Table...................................7
            4.1.2.3. Table  . . . . . . . . . . . . . . . . . .  8
         5.1.2.3.  LRF to LRF Routing..............................7
         4.1.3. The Routing . . . . . . . . . . . . . . . .  8
       5.1.3.  Signaling Path Border Element (SBE)..............7
            4.1.3.1. (SBE)  . . . . . . . . .  8
       5.1.4.  Establishing a Trusted Relationship.............8
            4.1.3.2. Relationship  . . . . . . . . .  9
         5.1.4.1.  IPSec  . . . . . . . . . . . . . . . . . . . . . .  9
         5.1.4.2.  Co-Location  . . . . . . . . . . . . . . . . . . .  9
         5.1.4.3.  Sending the SIP request.........................8
      4.2. Request  . . . . . . . . . . . . .  9
     5.2.  Target SSP Procedures.....................................8
         4.2.1. Procedures  . . . . . . . . . . . . . . . . . .  9
       5.2.1.  The Ingress Signaling Path Border Element (SBE)......8
            4.2.1.1. TLS.............................................8
            4.2.1.2. SBE  . . . . . . . . . . . . . . . . . . . 10
         5.2.1.1.  TLS  . . . . . . . . . . . . . . . . . . . . . . . 10
         5.2.1.2.  Receive SIP requests............................9
      4.3. Requests . . . . . . . . . . . . . . . 10
     5.3.  Data Path Border Element (DBE)............................9
   5. Address space considerations...................................9 (DBE) . . . . . . . . . . . . . . 10
   6. Security Considerations........................................9  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 10
   7.  IANA Considerations...........................................10 Considerations  . . . . . . . . . . . . . . . . . . . . . 11
   8. Acknowledgments...............................................10  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   9. References....................................................11
      9.1.  Normative References.....................................11
      9.2. Informative References...................................12
   Author's Addresses...............................................13 References . . . . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12

1.  Introduction

   The objective of this document is to define a reference peering
   architecture in the context of Session PEERing session peering for Multimedia INTerconnect (SPEERMINT). 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.

   This architecture allows the interconnection of two SSPs in layer 5
   peering as defined in the SPEERMINT Requirements [14] and Terminology [13] documents. SIP-based session peering requirements
   [I-D.ietf-speermint-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. functions and
   elements.

   This document uses terminology defined in the SPEERMINT Session Peering for
   Multimedia Interconnect Terminology document
   [13], so [RFC5486].

2.  Reference Architecture

   Figure 1 depicts the reader should be familiar with all the terms defined there.

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",   "SHALL",
   "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are
   to be interpreted as described in [RFC2119].

2. Reference SPEERMINT Architecture

   Figure 2 depicts the SPEERMINT architecture and logical functions that form the
   peering between two SSPs.

              ---------------                          ---------------
             /               \                        /               \
           |    +--LUF-+     |       +------+       |     +--LUF-+    |
           | |->|      |     |       |  The terms used in the diagram are expanded
   here for reference:

   o  SBE - Signaling Path Border Element is described in Section 5.1.3

   o  LUF - Look-up Function is described in Section 5.1.1

   o  LRF - Location Routing Function is described in Section 5.1.2

   o  SF - Signaling Function is defined in [RFC5486]

   o  SIP - Session Initiation Protocol is defined in [RFC3261]

   o  DBE - Data Path Border Element is described in Section 5.3

   o  DNS - Domain Name Service is described in Section 5.1.2.1

   o  ENUM |       |     |      |<-| |
           | |  |      +------------>| - E.164 Number Mapping is described in Section 5.1.1.2

   o  FQDN - Fully Qualified Domain Name

   o  TN DB|<------------+      |  | |
           | |  |      |     |       +------+       |     |      | DB - Telephone Number Database
   o  IP - IPv4/v6 Address

   o  RTP - Real-time Transport Protocol is defined in [RFC3550]

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

                                 Figure 1: Reference SPEERMINT Architecture 1

   For further details on the elements and functions described in this
   figure, please refer to [RFC 5486]. [RFC5486].

3.  Procedures of Inter-domain SSP Session Establishment

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

   1.  Determine the target SSP via the LUF.

          a.  (Note: If the target
       address represents an intra-SSP resource, a resource within the originating SSP, the
       behavior is out-of-scope with respect to this draft. 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, tec, text, etc.

   5.  End the session (BYE)

   The originating SSP would likely perform steps 1-4, and the target
   SSP would likely perform steps 4-5.

   In the case

   If the target SSP changes, is also an indirect peer, then steps 1-4 would may be
   repeated.  This is reflected in Figure 2 1 that shows the target SSP
   with its own peering functions.

  3.1.

4.  Relationships between functions/elements

      -

   o  An SBE can contain a SF function.
      -

   o  An SF can perform LUF and LRF functions.
      -

   o  As an additional consideration, a in current Session Border
      Controller [SBC RFC], (SBC) implementations, an SBC can contain an SF, SBE
      and DBE, and may perform the LUF and LRF functions.
      -

   o  The following functions can communicate as follows, depending upon
      various real-world implementations:
           o

      *  SF can communicate with LUF, LRF, SBE LRF and another SF
           o

      *  LUF can communicator communicate with SF and SBE
           o

      *  LRF can communicate with SF and SBE

4.

5.  Recommended SSP Procedures

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

   Some of the information in the section is taken from [14]
   [I-D.ietf-speermint-requirements] and is put here for continuity
   purposes.

  4.1.

5.1.  Originating SSP Procedures

4.1.1.

5.1.1.  The Look-Up Function (LUF)

   Purpose is to determine the SF of the target domain of a given
   request and optionally develop Session Establishment Data.

     4.1.1.1.

5.1.1.1.  Target Address Analysis

   When the originating SSP receives a request to communicate, SIP request, 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 SSP's administrative domain or federation of domains, domain, then the originating SSP
   performs a Lookup Function (LUF) to determine a the target address, domain, and then is it
   resolves the call routing data by using the Location routing Function Routing (LRF).

   For example, if the request to communicate is for an im: or pres: URI
   type, the originating SSP follows the procedures in [8]. [RFC3861].  If
   the highest priority supported URI scheme is sip: or sips: the
   originating SSP skips to SIP DNS
   resolution in Section 5.1.3. resolution.  Likewise, if the target
   address is already a sip: or sips: URI in an external domain, the
   originating SSP skips to SIP DNS resolution in Section 4.1.2.1. 5.1.2.1

   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.

     4.1.1.2.

5.1.1.2.  ENUM Lookup

   If an external E.164 address is the target, the originating SSP
   consults the a private or public "User ENUM" rooted at e164.arpa, ENUM server, according to the procedures
   described in RFC 3761. [RFC3761].  The SSP must query for the "E2U+sip"
   enumservice as described in
   RFC 3764 [11], [RFC3764], but MAY check for other
   enumservices.  The originating SSP MAY consult a cache or alternate
   representation of the ENUM data rather than actual DNS queries.
   Also, the SSP may skip actual DNS queries if the originating SSP
   is sure that the target address country code domain is not
   represented in e164.arpa.
   If a sip: or sips: URI is chosen the SSP skips to Section 5.1.6. as an IPv4/v6 address.

   If an im: or pres: URI is chosen for based on an "E2U+im" [8] [RFC3861]
   or "E2U+pres" [9] [RFC3953] enumserver, the SSP follows the procedures
   for resolving these URIs to URIs for specific protocols such a SIP or XMPP as described in the previous section.

4.1.2.
   XMPP.

5.1.2.  Location Routing Function (LRF)

   The LRF of an Originating SSP analyzes the 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 indirect 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 may be used.

     4.1.2.1.

5.1.2.1.  DNS Resolution resolution

   The originating SSP uses the procedures in RFC 3263 [4] Section 4 [RFC3263] to determine how
   to contact the receiving target SSP.  To summarize the RFC 3263 procedure:
   unless these are explicitly encoded in the target URI, a transport is
   chosen using
   NAPTR Naming Authority Pointer (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 Originating SSP to the receiving target SSP if available.

     4.1.2.2.

5.1.2.2.  Routing Table

   If there are no End User ENUM records and the Originating SSP cannot
   discover the carrier-of-record or if the Originating SSP cannot reach
   the carrier-of-
   record carrier-of-record via SIP peering, the Originating SSP may
   deliver the call to the PSTN or reject it.  Note that the originating
   SSP may forward the call to another SSP for PSTN gateway termination
   by prior arrangement using the routing table.

   If so, the originating 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.

     4.1.2.3.

5.1.2.3.  LRF to LRF Routing

   Communications

   Communication 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.

4.1.3. The

5.1.3.  Signaling Path Border Element (SBE)

   The purpose of signaling function path border element 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
   optional termination and re-initiation of calls may be performed by
   the signaling path Session Border Element (SBE), or other signaling
   elements.

   Optionally, a the SF of a SBE 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 a 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.  Signaling function may
   optionally communicate with the network to pass Layer 3 related policies [10]

     4.1.3.1.
   policies.

5.1.4.  Establishing a Trusted Relationship

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

4.1.3.1.1.

5.1.4.1.  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.

4.1.3.1.2.

5.1.4.2.  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 would be sent
   as clear text.

     4.1.3.2.

5.1.4.3.  Sending the SIP request Request

   Once a trust relationship between the peers is established, the
   originating SSP sends the request.

  4.2.

5.2.  Target SSP Procedures

4.2.1.
5.2.1.  The Ingress Signaling Path Border Element (SBE)

     4.2.1.1. SBE

5.2.1.1.  TLS

   When the receiving target SSP receives a TLS client hello, it responds with its
   certificate.  The Target Originating SSP certificate should be valid and
   rooted in a well-
   known well-known certificate authority.  The procedures to
   authenticate the SSP's originating domain are specified in [24].
   [I-D.ietf-sip-domain-certs].

   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.

     4.2.1.2.

5.2.1.2.  Receive SIP requests 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 SSP is not
   authorized to peer, the receiving SSP should respond with a 403
   response with the reason phrase "Unsupported Peer".

  4.3.

5.3.  Data Path Border Element (DBE)

   The purpose of the DBE [RFC 5486] [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). Enhanced Variable Rate Codec (EvRC)).
   Additionally, the MF may perform media relaying, media security,
   privacy, and encryption.

5. 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. 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.

6.  Acknowledgments

   The only requirement is working group thanks Sohel Khan for his initial architecture
   draft that all
   associated entities across the peering interface are reachable.

6. helped to initiate work on this draft.

   Other contributors include Rohan Mahy, Otmar Lendl, Jim McEachern and
   John Elwell for detailed comments and feedback.

7.  IANA Considerations

   This memo includes no request to IANA.

8.  Security Considerations

   In all cases, cryptographic-based security should be maintained as an
   optional requirement between peering providers conditioned on the
   presence or absence of underlying physical security of SSP
   connections, e.g. within the same secure physical building.

   In order to maintain a consistent approach, unique and specialized
   security requirements common for the majority of peering
   relationships, should be standardized within the IETF.  These
   standardized methods may enable capabilities such as dynamic peering
   relationships across publicly maintained interconnections.

7. IANA Considerations

   There are no IANA considerations at this time.

8. Acknowledgments

   The working group thanks Sohel Khan for his initial architecture
   draft that helped to initiate work on this draft.

   A significant portion of this draft is taken from [14] with
   permission from the author R. Mahy. The other important contributor
   is Otmar Lendl. Special thanks to Jim McEachern for detailed comments and
   feedback.

9. References

  9.1.  Normative References

   [1]   Bradner,

   [I-D.ietf-sip-domain-certs]
              Gurbani, V., Lawrence, S., "Key words for use and B. Laboratories, "Domain
              Certificates in RFCs to Indicate Requirement Levels",
         BCP 14, RFC 2119, the Session Initiation Protocol (SIP)",
              draft-ietf-sip-domain-certs-05 (work in progress),
              March 1997.

   [2]   Mealling, M. and R. Daniel, "The Naming Authority Pointer (NAPTR) DNS
         Resource Record", RFC 2915, September 2000.

   [3] 2010.

   [I-D.ietf-speermint-requirements]
              Mule, J., "SPEERMINT Requirements for SIP-based Session
              Peering", draft-ietf-speermint-requirements-09 (work in
              progress), October 2009.

   [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.

   [4]

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

   [5]   Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and T.
         Wright, "Transport Layer Security (TLS) Extensions", RFC 4366, April
         2006.

   [6]

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

   [7]   Peterson, J., Liu, H., Yu, J.,

   [RFC3761]  Faltstrom, P. and B. Campbell, "Using M. Mealling, "The E.164 numbers
         with the 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)", (SIP) Addresses-of-Record", RFC 3824, June 3764,
              April 2004.

   [8]

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

   [9]

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

   [10]  ETSI TS 102 333: " Telecommunications and Internet converged Services
         and Protocols for Advanced Networking (TISPAN); Gate control protocol".

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

   [12]  Livingood, J. and R. Shockey, "IANA Registration for an
         Enumservice Containing PSTN Signaling Information", RFC 4769, November
         2006.

  9.2. Informative References

   [13]

   [RFC5486]  Malas, D., "SPEERMINT Terminology", draft-ietf-speermint-terminology-16
         (work in progress), February 2008.

   [14]  Mule, J-F., "SPEERMINT Requirements for SIP-based VoIP Interconnection",
         draft-ietf-speermint-requirements-04.txt, February 2008.

   [15]  Mahy, R., "A Minimalist Approach to Direct Peering", draft-
         mahy-speermint-direct-peering-02.txt, July 2007.

   [16]  Penno, R., et al., "SPEERMINT Routing Architecture Message
         Flows", draft-ietf-speermint-flows-02.txt", April 2007.

   [17]  Houri, A., et al., "RTC Provisioning Requirements", draft-
         houri-speermint-rtc-provisioning-reqs-00.txt, June, 2006.

   [18]  Habler, M., et al., "A Federation based VOIP Peering
         Architecture", draft-lendl-speermint-federations-03.txt, September 2006.

   [19]  Mahy, R., "A Telephone Number Mapping (ENUM) Service
         Registration for Instant Messaging (IM) Services", draft-ietf-
         enum-im-service-03 (work in progress), March 2006.

   [20]  Haberler, M. and R. Stastny, "Combined User and Carrier ENUM in the
         e164.arpa tree", draft-haberler-carrier-enum-03 (work in progress),
         March 2006.

   [21]  Penno, R., Malas D., and Melampy, P., "A Session Initiation
         Protocol (SIP) Event package for Peering", draft-penno-sipping-peering-
         package-00 (work in progress), September 2006.

   [22]  Hollander, D., Bray, T., D. and A. Layman, "Namespaces in XML", W3C REC
         REC-xml-names-19990114, January 1999.

   [23]  Burger, E (Ed.), "A Mechanism D. Meyer, "Session Peering for Content Indirection in
         Session Initiation Protocol (SIP) Messages", Multimedia
              Interconnect (SPEERMINT) Terminology", RFC 4483, May 2006

   [24]  Gurbani, V., Lawrence, S., and B. Laboratories, "Domain Certificates in
         the Session Initiation Protocol (SIP)", draft-ietf-sip-domain-certs-00
         (work in progress), November 2007.

Author's 5486,
              March 2009.

Authors' Addresses

   Adam Uzelac (editor)
   Global Crossing
   Rochester, NY - USA
   US

   Email: adam.uzelac@globalcrossing.com

   Reinaldo

   Reinadlo Penno
   Juniper Networks
   Sunnyvale, CA - USA
   US

   Email: rpenno@juniper.net

   Mike Hammer
   Cisco Systems
   Herndon, VA - USA
   US

   Email: mhammer@cisco.com

   Sohel Khan, Ph.D.
   Comcast Cable Communications
   USA
   Email: sohel_khan@cable.comcast.com
   Daryl Malas
   CableLabs
   Louisville, CO - USA
   US

   Email: d.malas@cablelabs.com

   Sohel Khan
   Comcast
   Philadelphia, PA
   US

   Email: sohel_khan@cable.comcast.com

   Hadriel Kaplan
   Acme Packet
   Burlington, MA
   US

   Email: hkaplan@acmepacket.com

   Jason Livingood
   Comcast
   Philadelphia, PA
   US

   Email: Jason_livingood@cable.comcast.com Jason_Livingood@cable.comcast.com

   David Schwartz
   Kayote Systems
   XConnect Global Networks
   Jerusalem
   Israel

   Email: david.schwartz@kayote.com

   Rich dschwartz@xconnnect.net

   Richard Shockey
   Shockey
   Unaffiliated Consulting
   US

   Email: Richard@shockey.us