Speermint Working Group A.Uzelac(Ed.)
Internet Draft Global Crossing
Intended status: Informational
Expires: September 2009
March 2, 2009
SPEERMINT Peering Architecture
draft-ietf-speermint-architecture-08
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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.
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Table of Contents
1. Introduction...................................................3
2. Network Context................................................3
3. Reference SPEERMINT Architecture...............................4
4. Procedures of Interdomain SSP Session Establishment............6
5. Recommended SSP Procedures.....................................7
5.1. Originating SSP Procedures................................7
5.1.1. The Look-Up Function (LUF)...........................7
5.1.1.1. Target address analysis.........................7
5.1.1.2. End User ENUM Lookup............................8
5.1.1.3. Infrastructure ENUM lookup......................8
5.1.2. Location Routing Function (LRF)......................8
5.1.2.1. SIP DNS Resolution..............................8
5.1.2.2. Routing Table...................................9
5.1.2.3. SIP Redirect Server.............................9
5.1.3. The Signaling Function (SF)..........................9
5.1.3.1. Establishing a Trusted Relationship.............9
5.1.3.2. Sending the SIP request........................10
5.2. Terminating SSP Procedures...............................10
5.2.1. The Location Function (LF)..........................10
5.2.1.1. Publish ENUM records...........................10
5.2.1.2. Publish SIP DNS records........................11
5.2.1.3. Subscribe Notify...............................11
5.2.2. Signaling Function (SF).............................11
5.2.2.1. TLS............................................11
5.2.2.2. Receive SIP requests...........................11
5.3. Target SSP Procedures....................................12
5.3.1. Signaling Function (SF).............................12
5.3.1.1. TLS............................................12
5.3.1.2. Receive SIP requests...........................12
5.4. Media Function (MF)......................................12
5.5. Policy Considerations....................................12
6. Call Control and Media Control Deployment Options.............13
7. Address space considerations..................................14
8. Security Considerations.......................................15
9. IANA Considerations...........................................15
10. Acknowledgments..............................................15
11. References...................................................16
11.1. Normative References....................................16
11.2. Informative References..................................17
Author's Addresses...............................................18
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1. Introduction
The objective of this document is to define a reference peering architecture in
the context of Session PEERing for Multimedia INTerconnect (SPEERMINT). 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) network.
This architecture allows the interconnection of two SSPs in layer 5 peering as
defined in the SPEERMINT Requirements [14] and Terminology [13] documents.
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 SPEERMINT Terminology document
[13], so 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. Network Context
Figure 1 allows for the following potential SPEERMINT peering scenarios:
o Enterprise to Enterprise across the public Internet
o Enterprise to SSP across the public Internet
o SSP to SSP across the public Internet
o Enterprise to enterprise across a private Layer 3 network
o Enterprise to SSP across a private Layer 3 network
o SSP to SSP across a private Layer 3 network
+-------------------+
| |
| Public |
| SIP |
| Peering |
| |
+-------------------+
|
-----
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+-----------+ / \ +-----------+
|Enterprise | -- -- |Enterprise |
|Provider A |-----------/ \-----------|Provider B |
+-----------+ -- -- +-----------+
/ Public \
| Internet |
\ (Layer 3) /
+-----------+ -- -- +-----------+
| SSP C |-----------\ /-----------| SSP D |
| | -- -- | |
+-----------+ \_____/ +-----------+
| Layer 3 Peering
| Point (out of scope)
-----
+-----------+ / \ +-----------+
|Enterprise | -- -- |Enterprise |
|Provider E |-----------/ \-----------|Provider F |
+-----------+ -- Private -- +-----------+
/ Network \
| (Layer 3) |
\ /
+-----------+ -- -- +-----------+
| SSP G |-----------\ /-----------| SSP H |
| | -- -- | |
+-----------+ \____/ +-----------+
|
+-------------------+
| Private |
| SIP |
| Peering |
| |
+-------------------+
Figure 1: SPEERMINT Network Context
3. Reference SPEERMINT Architecture
Figure 2 depicts the SPEERMINT architecture and logical functions that form the
peering between two SSPs.
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+------+
| DNS, |
+---------->| Db, |<---------+
| | etc | |
| +------+ |
| |
------|-------- -------|-------
/ v \ / v \
| +--LUF-+ | | +--LUF-+ |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| +------+ | | +------+ |
| | | |
| +--LRF-+ | | +--LRF-+ |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| +------+ | | +------+ |
| | | |
| | | |
| +---SF--+ +---SF--+ |
| | | | | |
| | SBE | | SBE | |
| Originating | | | | Target |
| +---SF--+ +---SF--+ |
| SSP | | SSP |
| +---MF--+ +---MF--+ |
| | | | | |
| | DBE | | DBE | |
| | | | | |
| +---MF--+ +---MF--+ |
\ / \ /
--------------- ---------------
Figure 2: Reference SPEERMINT Architecture
The following procedures are implemented by a set of peering functions:
The Look-Up Function (LUF) provides a mechanism for determining for a given
request the target domain to which the request should be routed.
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
Session Establishment Data (SED) required to route the request to that domain.
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The Signaling Function (SF) provides SIP call routing, to optionally perform
termination and re-initiation of call, to 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 Media Function (MF) provides media related functions such as media
transcoding, topology hiding and media security implementation between two
SSPs.
The intention of defining these functions is to provide a framework for design
segmentation and allow each one to evolve independently.
4. Procedures of Interdomain SSP Session Establishment
This document assumes that in order for a session to be established from a UA
in the originating SSP's network to an UA in the Target SSP's network the
following steps are taken:
1. analyze the target address.
a. If the target address represents an intra-SSP resource, the
behavior is out-of-scope with respect to this draft.
2. determine the target SSP (LUF)
3. determine the SF next-hop in the target SSP (LRF)
4. enforce authentication and potentially other policies
5. determine of the UA
6. establish the session,
7. transfer of media which could include voice, video, text and others,
8. terminate 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 the target SSP changes, then steps 1-4 would be repeated. This is
reflected in Figure 2 that shows the target SSP with its own peering functions.
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5. 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 [14] and is put here for
continuity purposes.
5.1. Originating SSP Procedures
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.
5.1.1.1. Target address analysis
When the originating 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. Note that the SSP may also consult any manner
of private data sources to make this determination.
If the target address does not represent a resource inside the originating
SSP's administrative domain or federation of domains, the originating SSP
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, the
originating SSP follows the procedures in [8]. If the highest priority
supported URI scheme is sip: or sips: the originating 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 SSP skips to SIP DNS
resolution in Section 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.
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5.1.1.2. End User ENUM Lookup
If an external E.164 address is the target, the originating SSP consults the
public "User ENUM" rooted at e164.arpa, according to the procedures described
in RFC 3761. The SSP must query for the "E2U+sip" enumservice as described in
RFC 3764 [11], 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 is not represented in e164.arpa.
If a sip: or sips: URI is chosen the SSP skips to Section 5.1.6.
If an im: or pres: URI is chosen for based on an "E2U+im" [8] or "E2U+pres" [9]
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.
5.1.1.3. Infrastructure ENUM lookup
An originating SSP may check for a carrier-of-record in an Infrastructure ENUM
domain according to the procedures described in [12]. As in the previous step,
the SSP may consult a cache or alternate representation of the ENUM data in
lieu of actual DNS queries. The SSP first checks for records for the "E2U+sip"
enumservice, then for the "E2U+pstn" enumservice as defined in [21]. If a
terminal record is found with a sip: or sips: URI, the SSP skips to Section
5.1.2.1. , otherwise the SSP continues processing according to the next
section.
5.1.2. Location Routing Function (LRF)
The LRF of an Originating 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.
5.1.2.1. SIP DNS Resolution
Once a sip: or sips: in an external domain is identified as the target, the
originating SSP may apply local policy to decide whether forwarding requests to
the target domain is acceptable. The originating SSP uses the procedures in
RFC 3263 [4] Section 4 to determine how to contact the receiving SSP. To
summarize the RFC 3263 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. Note that these
are queries of records in the global DNS.
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When communicating with another SSP, entities compliant to this document should
select a TLS-protected transport for communication from the originating SSP to
the receiving SSP if available.
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 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.
5.1.2.3. SIP Redirect Server
A SIP Redirect Server using 3XX SIP Redirect is another option in resolving the
next-hop SF of the target domain.
5.1.3. The Signaling Function (SF)
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 optional
termination and re-initiation of calls may be performed by the signaling path
Session Border Element (SBE).
Optionally, a SF may perform additional functions such as Session Admission
Control, SIP Denial of Service protection, SIP Topology Hiding, SIP header
normalization, and 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]
5.1.3.1. 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.
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5.1.3.1.1. TLS connection
Once a transport, port, and address are found, the originating SSP will open or
find a reusable TLS connection to the peer. The procedures to authenticate the
SSP's target domain is specified in [24]
5.1.3.1.2. TLS
If the trust relationship was established through TLS, the originating SSP can
optionally verify and assert the senders identity using the SIP Identity
mechanism.
In addition, new requests should contain a valid Identity and Identity-Info
header as described in [12]. The Identity-Info header must present a domain
name that is represented in the certificate provided when establishing the TLS
connection over which the request is sent. The originating SSP should include
an Identity header on in-dialog requests as well if the From header field value
matches an identity the originating SSP is willing to assert.
5.1.3.1.3. 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.
5.1.3.1.4. 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.
5.1.3.2. Sending the SIP request
Once a trust relationship between the peers is established, the originating SSP
sends the request.
5.2. Terminating SSP Procedures
5.2.1. The Location Function (LF)
5.2.1.1. Publish ENUM records
The receiving SSP should participate by publishing "E2U+sip" and "E2U+pstn"
records with sip: or sips: URIs wherever a public Infrastructure ENUM root is
available. This assumes that the receiving SSP wants to peer by default. When
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the receiving SSP does not want to accept traffic from specific originating
SSPs, it may still reject requests on a call-by-call basis.
5.2.1.2. Publish SIP DNS records
To receive SSP requests, the receiving SSP must insure that it publishes
appropriate NAPTR, SRV, and address (A and/or AAAA) records in the LF relevant
to the SSP's SF.
5.2.1.3. Subscribe Notify
Policies function may also be optionally implemented by dynamic subscribe,
notify, and exchange of policy information and feature information among SSPs
[21].
5.2.2. Signaling Function (SF)
5.2.2.1. TLS
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 [24].
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.
5.2.2.2. 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 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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5.3. Target SSP Procedures
5.3.1. Signaling Function (SF)
5.3.1.1. TLS
When the receiving SSP receives a TLS client hello, it responds with its
certificate. The Target SSP's certificate should be valid and rooted in a
well-known certificate authority. The procedures to authenticate the SSP's
originating domain are specified in [24].
If the requests should contain a valid Identity and Identity-Info header as
described in [24] the target SF 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.
5.3.1.2. Receive SIP requests
The procedures of the SF of the target SSP are the same as the ones described
in section 5.2.2.2 with the addition that it might establish a connection to
another target SSP, and in this case use the procedures recommended to an
originating SS (section 5.1).
5.4. Media Function (MF)
The purpose of the MF 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, privacy, and encryption.
5.5. Policy Considerations
In the context of the SPEERMINT working group when two SSPs peer, there MAY be
a desire to exchange peering policy information dynamically. There are
specifications in progress in the SIPPING working group to define policy
exchange between an UA and a domain [23] and providing profile data to SIP user
agents [24] These considerations borrow from both.
Following the terminology introduced in [12], this package uses the terms
Peering Session-Independent and Session-Specific policies in the following
context.
o Peering Session-Independent policies include Diffserv Marking, Policing,
Session Admission Control, and domain reachabilities, amongst others. The
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time period between Peering Session-Independent policy changes is much
greater than the time it takes to establish a call.
o Peering Session-Specific polices includes supported connection/call rate,
total number of connections/calls available, current utilization, amongst
others. Peering Session-specific policies can change within the time it
takes to establish a call.
These policies can be SSP dependent or independent, creating the following
peering policy definition:
o SSP Independent or Dependent
Session dependent Session
independent
6. Call Control and Media Control Deployment Options
The peering functions can be deployed along the following two dimensions
depending upon how the signaling and the media functions along with IP layer
are implemented:
Composed or Decomposed: Addresses the question whether the media must flow
through the same physical and geographic elements as SIP dialogs and sessions.
Centralized or Distributed: Addresses the question whether the logical and
physical interconnections are in one geographical location or distributed to
multiple physical locations on the SSP's network.
In a composed model, SF and MF functions are implemented in one peering logical
element.
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Provider A Provider B
---------- . . ----------
/ \ . . / \
| | . _ . | |
| +----+ . / \_ . +----+ |
| | SF |<-----/ \------| SF | |
| +-+--+ . /Transit\ . | | |
| | | . / IP \ . | | |
| +-+--+ . | Provider| . | | |
| | MF |<~~~| (Option)|~~~~| MF | |
| +----+ . \ / . +----+ |
| | . \ __ _ / . | |
\_________ / . . \________ _/
---------- ----------
--- Signal (SIP)
~~~ Bearer (RTP/IP)
... Scope of peering
Figure 3: Decomposed v. Collapsed Peering
The advantage of a collapsed peering architecture is that one-element solves
all peering issues. Disadvantage examples of this architecture are single point
of failure, bottleneck, and complex scalability.
In a decomposed model, SF and MF are implemented in separate peering logical
elements. SFs are implemented in a proxy and MFs are implemented in another
logical element. The scaling of signaling versus scaling of media may differ
between applications. Decomposing allows each to follow a separate migration
path.
This model allows the implementation of M:N model where one SF is associated
with multiple peering MF and one peering MF is associated with multiple SFs.
Generally, a vertical protocol associates the relationship between a SF and a
MF. This architecture reduces the potential of a single point of failure. It
allows separation of the policy decision point and the policy enforcement
point. An example of disadvantages is the scaling complexity because of the M:N
relationship and latency due to the vertical control messages between entities.
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. The origination or termination networks may or may not entirely
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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. 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.
9. IANA Considerations
There are no IANA considerations at this time.
10. 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.
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11. References
11.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",
BCP 14, RFC 2119, March 1997.
[2] Mealling, M. and R. Daniel, "The Naming Authority Pointer (NAPTR) DNS
Resource Record", RFC 2915, September 2000.
[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.
[4] 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] 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., and B. Campbell, "Using E.164 numbers
with the Session Initiation Protocol (SIP)", RFC 3824, June 2004.
[8] Peterson, J., "Address Resolution for Instant Messaging and
Presence",RFC 3861, August 2004.
[9] 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.
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11.2. Informative References
[13] 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., and A. Layman, "Namespaces in XML", W3C REC
REC-xml-names-19990114, January 1999.
[23] Burger, E (Ed.), "A Mechanism for Content Indirection in
Session Initiation Protocol (SIP) Messages", 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.
Uzelac Expires September 2, 2009 [Page 17]
Internet-Draft SPEERMINT peering architecture February 2009
Author's Addresses
Adam Uzelac
Global Crossing
Rochester, NY - USA
Email: adam.uzelac@globalcrossing.com
Reinaldo Penno
Juniper Networks
Sunnyvale, CA - USA
Email: rpenno@juniper.net
Mike Hammer
Cisco Systems
Herndon, VA - USA
Email: mhammer@cisco.com
Sohel Khan, Ph.D.
Comcast Cable Communications
USA
Email: sohel_khan@cable.comcast.com
Daryl Malas
CableLabs
Louisville, CO - USA
Email: d.malas@cablelabs.com
Uzelac Expires September 2, 2009 [Page 18]
