One document matched: draft-ietf-speermint-architecture-16.txt
Differences from draft-ietf-speermint-architecture-15.txt
SPEERMINT D. Malas, Ed.
Internet-Draft CableLabs
Intended status: Informational J. Livingood, Ed.
Expires: May 12, 2011 Comcast
November 8, 2010
SPEERMINT Peering Architecture
draft-ietf-speermint-architecture-16
Abstract
This document defines a peering architecture for the Session
Initiation Protocol (SIP) [RFC3261], it's 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.
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This Internet-Draft will expire on May 12, 2011.
Copyright Notice
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described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Reference Architecture . . . . . . . . . . . . . . . . . . . . 4
3. Procedures of Inter-Domain SSP Session Establishment . . . . . 5
4. Relationships Between Functions/Elements . . . . . . . . . . . 6
5. Recommended SSP Procedures . . . . . . . . . . . . . . . . . . 6
5.1. Originating or Indirect SSP Procedures . . . . . . . . . . 6
5.1.1. The Look-Up Function (LUF) . . . . . . . . . . . . . . 7
5.1.1.1. Target Address Analysis . . . . . . . . . . . . . 7
5.1.1.2. ENUM Lookup . . . . . . . . . . . . . . . . . . . 7
5.1.2. Location Routing Function (LRF) . . . . . . . . . . . 8
5.1.2.1. DNS Resolution . . . . . . . . . . . . . . . . . . 8
5.1.2.2. Routing Table . . . . . . . . . . . . . . . . . . 8
5.1.2.3. LRF to LRF Routing . . . . . . . . . . . . . . . . 9
5.1.3. The Signaling Path Border Element (SBE) . . . . . . . 9
5.1.3.1. Establishing a Trusted Relationship . . . . . . . 9
5.1.3.2. IPSec . . . . . . . . . . . . . . . . . . . . . . 9
5.1.3.3. Co-Location . . . . . . . . . . . . . . . . . . . 9
5.1.3.4. Sending the SIP Request . . . . . . . . . . . . . 10
5.2. Target SSP Procedures . . . . . . . . . . . . . . . . . . 10
5.2.1. TLS . . . . . . . . . . . . . . . . . . . . . . . . . 10
5.2.2. Receive SIP Requests . . . . . . . . . . . . . . . . . 10
5.3. Data Path Border Element (DBE) . . . . . . . . . . . . . . 10
6. Address Space Considerations . . . . . . . . . . . . . . . . . 11
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 11
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 11
11. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 13
12. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 13
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
13.1. Normative References . . . . . . . . . . . . . . . . . . . 14
13.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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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 providers
[RFC5486] network. Thus, it also describes the components and the
steps necessary to establish a session between two SIP Service
Provider (SSP) peering domains.
This architecture enables the interconnection of two SSPs in layer 5
peering, as defined in the 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.
This document uses terminology defined in the Session Peering for
Multimedia Interconnect (SPEERMINT) Terminology document [RFC5486].
2. Reference Architecture
The following figure depicts the architecture and logical functions
that form peering between two SSPs.
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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
For further details on the elements and functions described in this
figure, please refer to [RFC5486].
3. Procedures of Inter-Domain SSP Session Establishment
This document assumes that in order for a session to be established
from a 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
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4. Exchange the media, which could include voice, video, text, etc.
5. End the session (BYE)
The originating or indirect 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 1 that shows the target SSP with its own
peering functions.
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 Session Border Controller, 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:
* SF can communicate with LUF, LRF, SBE and SF
* LUF can communicator with SF and SBE
* LRF can communicate with SF and SBE
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
[I-D.ietf-speermint-requirements] and is put here for continuity
purposes.
5.1. Originating or Indirect SSP Procedures
This section describes the procedures of the originating or indirect
SSP.
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5.1.1. 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.
5.1.1.1. 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 is 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 5.1.2.1.
This may be the case, to use one example, with
"sips:bob@biloxi.example.com".
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.
5.1.1.2. 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 for 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 a 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.
5.1.2. 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 may be used.
5.1.2.1. 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 5.2.1.
5.1.2.2. 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 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.
5.1.2.3. 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.
5.1.3. 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, a 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 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.
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.
5.1.3.2. 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.
5.1.3.3. 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.
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5.1.3.4. Sending the SIP Request
Once a trust relationship between the peers is established, the
originating (or indirect) SSP sends the request.
5.2. Target SSP Procedures
This section describes the Target SSP Procedures.
5.2.1. TLS
The section defines uses 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.
5.2.2. 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".
5.3. 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
encryption.
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6. 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.
7. 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.
8. IANA Considerations
This memo includes no request to IANA.
9. 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.
Additional security considerations have been documented separately in
[I-D.ietf-speermint-voipthreats].
10. Contributors
Mike Hammer
Cisco Systems
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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
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
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Shockey Consulting
USA
Email: Richard@shockey.us
--------------------------------------------------------------
Adam Uzelac
Global Crossing
Rochester, NY - USA
Email: adam.uzelac@globalcrossing.com
11. Change Log
NOTE TO RFC EDITOR: PLEASE REMOVE THIS SECTION PRIOR TO PUBLICATION.
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
notes.
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
soon.
12. Open Issues
NOTE TO RFC EDITOR: PLEASE REMOVE THIS SECTION PRIOR TO PUBLICATION.
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o NONE!
13. References
13.1. Normative References
[I-D.ietf-speermint-requirements]
Mule, J., "Requirements for SIP-based Session Peering",
draft-ietf-speermint-requirements-10 (work in progress),
October 2010.
[I-D.ietf-speermint-voipthreats]
Seedorf, J., Niccolini, S., Chen, E., and H. Scholz,
"Session Peering for Multimedia Interconnect (SPEERMINT)
Security Threats and Suggested Countermeasures",
draft-ietf-speermint-voipthreats-06 (work in progress),
November 2010.
[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.
[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.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
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(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.
[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
[I-D.ietf-speermint-voip-consolidated-usecases]
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)
CableLabs
Louisville, CO
US
Email: d.malas@cablelabs.com
Jason Livingood (editor)
Comcast
Philadelphia, PA
US
Email: Jason_Livingood@cable.comcast.com
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