draft-ietf-speermint-requirements-07.txt   draft-ietf-speermint-requirements-08.txt 
SPEERMINT Working Group J-F. Mule SPEERMINT Working Group J-F. Mule
Internet-Draft CableLabs Internet-Draft CableLabs
Intended status: Informational October 17, 2008 Intended status: Informational October 26, 2009
Expires: April 20, 2009 Expires: April 29, 2010
SPEERMINT Requirements for SIP-based Session Peering SPEERMINT Requirements for SIP-based Session Peering
draft-ietf-speermint-requirements-07.txt draft-ietf-speermint-requirements-08.txt
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Abstract Abstract
This memo captures protocol requirements to enable session peering of This memo captures protocol requirements to enable session peering of
voice, presence, instant messaging and other types of multimedia voice, presence, instant messaging and other types of multimedia
traffic. It is based on the use cases that have been described in traffic. It is based on the use cases that have been described in
the SPEERMINT working group. This informational document is intended the SPEERMINT working group. This informational document is intended
to link the session peering use cases to protocol solutions. to link the session peering use cases to protocol solutions.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. General Requirements . . . . . . . . . . . . . . . . . . . . . 5 3. General Requirements . . . . . . . . . . . . . . . . . . . . . 5
3.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Border Elements . . . . . . . . . . . . . . . . . . . . . 5 3.2. Border Elements . . . . . . . . . . . . . . . . . . . . . 5
3.3. Session Establishment Data . . . . . . . . . . . . . . . . 8 3.3. Session Establishment Data . . . . . . . . . . . . . . . . 9
3.3.1. User Identities and SIP URIs . . . . . . . . . . . . . 8 3.3.1. User Identities and SIP URIs . . . . . . . . . . . . . 9
3.3.2. URI Reachability . . . . . . . . . . . . . . . . . . . 9 3.3.2. URI Reachability . . . . . . . . . . . . . . . . . . . 10
4. Requirements for Session Peering of Presence and Instant 4. Requirements for Session Peering of Presence and Instant
Messaging . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Messaging . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 5. Security Considerations . . . . . . . . . . . . . . . . . . . 13
5.1. Security Properties for the Acquisition of Session 5.1. Security Properties for the Acquisition of Session
Establishment Data . . . . . . . . . . . . . . . . . . . . 12 Establishment Data . . . . . . . . . . . . . . . . . . . . 13
5.2. Security Properties for the SIP signaling exchanges . . . 13 5.2. Security Properties for the SIP signaling exchanges . . . 14
5.3. End-to-End Media Security . . . . . . . . . . . . . . . . 14 5.3. End-to-End Media Security . . . . . . . . . . . . . . . . 15
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8.1. Normative References . . . . . . . . . . . . . . . . . . . 17 8.1. Normative References . . . . . . . . . . . . . . . . . . . 18
8.2. Informative References . . . . . . . . . . . . . . . . . . 17 8.2. Informative References . . . . . . . . . . . . . . . . . . 18
Appendix A. Policy Parameters for Session Peering . . . . . . . . 20 Appendix A. Policy Parameters for Session Peering . . . . . . . . 22
A.1. Categories of Parameters for VoIP Session Peering and A.1. Categories of Parameters for VoIP Session Peering and
Justifications . . . . . . . . . . . . . . . . . . . . . . 20 Justifications . . . . . . . . . . . . . . . . . . . . . . 22
A.2. Summary of Parameters for Consideration in Session A.2. Summary of Parameters for Consideration in Session
Peering Policies . . . . . . . . . . . . . . . . . . . . . 23 Peering Policies . . . . . . . . . . . . . . . . . . . . . 25
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 25 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 27
Intellectual Property and Copyright Statements . . . . . . . . . . 26
1. Introduction 1. Introduction
Peering at the session level represents an agreement between parties Peering at the session level represents an agreement between parties
to exchange multimedia traffic. It is assumed that these sessions to exchange multimedia traffic. In this document, we assume that the
use the Session Initiation Protocol (SIP) protocol to enable peering Session Initiation Protocol (SIP) is used to establish sessions
between two or more actors. These actors are called SIP Service between SIP Service Providers (SSPs). SIP Service Providers are
Providers (SSPs) and they are typically represented by users, user referred to as peers and they are typically represented by users,
groups such as enterprises, real-time collaboration service user groups, enterprises, real-time collaboration service
communities, or other service providers offering voice or multimedia communities, or other service providers offering voice or multimedia
services using SIP. services using SIP.
A reference architecture for SIP session peering is described in A number of documents have been developed to provide background
[I-D.ietf-speermint-architecture]. A number of use cases describe information about SIP session peering. It is expected that the
how session peering has been or could be deployed based on the reader is familiar with the reference architecture described in
reference architecture [I-D.ietf-speermint-architecture], use cases for voice
([I-D.ietf-speermint-voip-consolidated-usecases] and ([I-D.ietf-speermint-voip-consolidated-usecases]) and instant
[I-D.ietf-speermint-consolidated-presence-im-usecases]). messaging and presence ([RFC5344]).
Peering at the session layer can be achieved on a bilateral basis Peering at the session layer can be achieved on a bilateral basis
(direct peering established directly between two SSPs), or on an (direct peering established directly between two SSPs), or on an
indirect basis via a session intermediary (indirect peering via a indirect basis via a session intermediary (indirect peering via a
third-party SSP that has a trust relationship with the SSPs) - see third-party SSP that has a trust relationship with the SSPs) - see
the terminology document for more details. the terminology document for more details.
This document first describes general requirements. The use cases This document first describes general requirements. The use cases
are then analyzed in the spirit of extracting relevant protocol are then analyzed in the spirit of extracting relevant protocol
requirements that must be met to accomplish the use cases. These requirements that must be met to accomplish the use cases. These
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a session peering policy, provided in an informative appendix. It a session peering policy, provided in an informative appendix. It
should be considered as an example of the information SIP Service should be considered as an example of the information SIP Service
Providers may have to discuss or agree on to exchange SIP traffic. Providers may have to discuss or agree on to exchange SIP traffic.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
This document also reuses the terminology defined in This document also reuses the terminology defined in [RFC5486]. It
[I-D.ietf-speermint-terminology]. It is assumed that the reader is is assumed that the reader is familiar with the Session Description
familiar with the Session Description Protocol (SDP) [RFC4566] and Protocol (SDP) [RFC4566] and the Session Initiation Protocol (SIP)
the Session Initiation Protocol (SIP) [RFC3261]. Finally, when used [RFC3261]. Finally, when used with capital letters, the terms
with capital letters, the terms 'Authentication Service' are to be 'Authentication Service' are to be understood as defined by SIP
understood as defined by SIP Identity [RFC4474]. Identity [RFC4474].
3. General Requirements 3. General Requirements
The following sub-sections contain general requirements applicable to The following sub-sections contain general requirements applicable to
multiple use cases for multimedia session peering. multiple use cases for multimedia session peering.
3.1. Scope 3.1. Scope
The primary focus of this document is on the requirements applicable The primary focus of this document is on the requirements applicable
to the boundaries of Layer 5 SIP networks: SIP entities, Signaling to the boundaries of Layer 5 SIP networks: SIP entities, Signaling
path Border Elements (SBEs), and the associated protocol requirements path Border Elements (SBEs), and the associated protocol requirements
for the look-up and location routing of the session establishment for the look-up and location routing of the session establishment
data. The requirements applicable to SIP UAs or related to the data. The requirements applicable to SIP User Agents or related to
provisioning of the session data are considered out of scope. the provisioning of the session data are considered out of scope.
SSPs desiring to establish session peering relationships have to SIP Service Providers have to reach an agreement on numerous points
reach an agreement on numerous points. when establishing session peering relationships .
This document highlights only certain aspects of a session peering This document highlights only certain aspects of a session peering
agreement, mostly the requirements relevant to protocols: the agreement, mostly the requirements relevant to protocols: the
declaration, advertisement and management of ingress and egress declaration, advertisement and management of ingress and egress
border elements for session signaling and media, information related border elements for session signaling and media, information related
to the Session Establishment Data (SED), and the security properties to the Session Establishment Data (SED), and the security properties
that may be desirable for secure session exchanges. that may be desirable for secure session exchanges.
Numerous other considerations of session peering arrangements are Numerous other considerations of session peering arrangements are
critical to reach a successful agreement but they are considered out critical to reach a successful agreement but they are considered out
of scope of the SPEERMINT working group. They include information of scope of this document. They include information about SIP
about SIP protocol support (e.g. SIP extensions and field protocol support (e.g. SIP extensions and field conventions), media
conventions), media (e.g., type of media traffic to be exchanged, (e.g., type of media traffic to be exchanged, compatible media codecs
compatible media codecs and transport protocols, mechanisms to ensure and transport protocols, mechanisms to ensure differentiated quality
differentiated quality of service for media), layer-3 IP connectivity of service for media), layer-3 IP connectivity between the Signaling
between the Signaling and Data path Border Elements, accounting and and Data path Border Elements, accounting and traffic capacity
traffic capacity control (e.g. the maximum number of SIP sessions at control (e.g. the maximum number of SIP sessions at each ingress
each ingress point, or the maximum number of concurrent IM or VoIP point, or the maximum number of concurrent IM or VoIP sessions).
sessions).
The informative Appendix A lists parameters that may be considered The informative Appendix A lists parameters that may be considered
when discussing the technical parameters of SIP session peering. The when discussing the technical parameters of SIP session peering. The
purpose of this list is to capture the parameters that are considered purpose of this list is to capture the parameters that are considered
outside the scope of the protocol requirements. outside the scope of the protocol requirements.
3.2. Border Elements 3.2. Border Elements
For border elements to be operationally manageable, maximum For border elements to be operationally manageable, maximum
flexibility should be given for how they are declared or dynamically flexibility should be given for how they are declared or dynamically
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o Requirement #1: o Requirement #1:
Protocol mechanisms MUST be provided to enable a SIP Service Protocol mechanisms MUST be provided to enable a SIP Service
Provider to communicate the ingress Signaling Path Border Elements Provider to communicate the ingress Signaling Path Border Elements
of its service domain. of its service domain.
Notes on solution space: Notes on solution space:
The SBEs may be advertised to session peers using static The SBEs may be advertised to session peers using static
mechanisms or they may be dynamically advertised. There is mechanisms or they may be dynamically advertised. There is
general agreement that [RFC3263] provides a solution for general agreement that [RFC3263] provides a solution for
dynamically advertising ingress SBEs in most cases of Direct or dynamically advertising ingress SBEs in most cases of Direct or
Indirect peering. However, this DNS-based solution may be limited Indirect peering. We discussed the DNS-based solution space
in cases where the DNS response varies based on who sends the further in Requirement #4 below, especially in cases where the DNS
query (peer-dependent SBEs, see below). response varies based on who sends the query (peer-dependent
SBEs).
o Requirement #2: o Requirement #2:
Protocol mechanisms MUST be provided to enable a SIP Service Protocol mechanisms MUST be provided to enable a SIP Service
Provider to communicate the egress SBEs of its service domain. Provider to communicate the egress SBEs of its service domain.
Notes on motivations for this requirement: Notes on motivations for this requirement:
For the purposes of capacity planning, traffic engineering and For the purposes of capacity planning, traffic engineering and
call admission control, a SIP Service Provider may be asked where call admission control, a SIP Service Provider may be asked where
it will generate SIP calls from. The SSP accepting calls from a it will generate SIP calls from. The SSP accepting calls from a
peer may wish to know where SIP calls will originate from (this peer may wish to know where SIP calls will originate from (this
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policies and accept media traffic from anywhere outside their network policies and accept media traffic from anywhere outside their network
to anywhere inside their network, some SSPs may want to optimize to anywhere inside their network, some SSPs may want to optimize
media delivery and identify media paths between peers prior to media delivery and identify media paths between peers prior to
traffic being sent (layer 5 to layer 3 QoS mapping). traffic being sent (layer 5 to layer 3 QoS mapping).
o Requirement #3: o Requirement #3:
Protocol mechanisms MUST be provided to allow a SIP Service Protocol mechanisms MUST be provided to allow a SIP Service
Provider to communicate its DBEs to its peers. Provider to communicate its DBEs to its peers.
Notes: Some SSPs engaged in SIP interconnects do exchange this Notes: Some SSPs engaged in SIP interconnects do exchange this
type of DBE information today in a static manner. Some SSPs do type of DBE information in a static manner. Some SSPs do not.
not.
In some SIP networks, SSPs operate the same border elements for all In some SIP networks, SSPs may expose the same border elements to all
peers. In other SIP networks, it is common for SSPs to advertise peers. In other environments, it is common for SSPs to advertise
specific SBEs and DBEs to certain peers: the advertisement of SBEs specific SBEs and DBEs to certain peers. This is done by SSPs to
and DBEs may be peer-dependent. meet specific objectives for a given peer: routing optimization of
the signaling and media exchanges, optimization of the latency or
throughput based on the 'best' SBE and DBE combination, and other
service provider policy parameters. These are some of the reasons
why advertisement of SBEs and DBEs may be peer-dependent.
o Requirement #4: o Requirement #4:
The mechanisms recommended for the declaration or advertisement of The mechanisms recommended for the declaration or advertisement of
SBE and DBE entities MUST allow for peer variability. SBE and DBE entities MUST allow for peer variability.
Notes on solution space: Notes on solution space:
For advertising peer-dependent SBEs (peer variability), the A simple solution is to advertise SBE entities using DNS and
solution space based on [RFC3263] is under specified and there are [RFC3263] by providing different DNS names to different peers.
no know best current practices. Is DNS the right place for This approach has some practical limitations because the SIP URIs
putting data that varies based on who asks? containing the DNS names used to resolve the SBEs may be
propagated by users, for example in the form of sip:user@domain.
It is impractical to ask users to use different target URIs based
upon their SIP service provider's desire to receive incoming
session signaling at different ingress SBEs based upon the
originator. The solution described in [RFC3263] and based on DNS
to advertise SBEs is therefore under-specified for this
requirement.
Other DNS mechanisms have been used extensively in other areas of
the Internet, in particular in Content Distribution
Internetworking to make the DNS responses vary based on the
originator of the DNS query (see [RFC3466], [RFC3568] and
[RFC3570]). The applicability of such solutions needs for session
peering needs further analysis.
Finally, other techniques such as Anycast services ([RFC4786]) may
be employed at lower layers than Layer 5 to provide a solution to
this requirement. For example, anycast nodes could be defined by
SIP service providers to expose a common address for SBEs into
DNS, allowing the resolution of the anycast node address to the
appropriate peer-dependent service address based on the routing
topology or other criteria gathered from the combined use of
anycast and DNS techniques.
Notes on media-variability of such advertisements: Notes on variability of the SBE advertisements based on the media
capabilities:
Some SSPs may have some restrictions on the type of media traffic Some SSPs may have some restrictions on the type of media traffic
their SBEs can accept. For SIP sessions however, it is not their SBEs can accept. For SIP sessions however, it is not
possible to communicate those restrictions in advance of the possible to communicate those restrictions in advance of the
session initiation: a SIP target may support voice-only media, session initiation: a SIP target may support voice-only media,
voice and video, or voice and instant messaging communications. voice and video, or voice and instant messaging communications.
While the inability to find out whether a particular type of SIP While the inability to find out whether a particular type of SIP
session can be terminated by a certain SBE can cause failed session can be terminated by a certain SBE can cause failed
session establishment attempts, there is consensus to not add a session establishment attempts, there is consensus to not add a
new requirement for this. These aspects are essentially covered new requirement in this document. These aspects are essentially
by SSPs when discussing traffic exchange policies (out of scope of covered by SSPs when discussing traffic exchange policies and are
this document). deemed out of scope of this document.
In the use cases provided as part of direct and indirect peering In the use cases provided as part of direct and indirect peering
scenarios, an SSP deals with multiple SIP entities and multiple SBEs scenarios, an SSP deals with multiple SIP entities and multiple SBEs
in its own domain. There is often a many-to-many relationship in its own domain. There is often a many-to-many relationship
between the SIP Proxies considered inside the trusted network between the SIP Proxies considered inside the trusted network
boundary of the SSP and its Signaling path Border Elements at the boundary of the SSP and its Signaling path Border Elements at the
network boundaries. network boundaries.
It should be possible for an SSP to define which egress SBE a SIP It should be possible for an SSP to define which egress SBE a SIP
entity must use based on a given peer destination. entity must use based on a given peer destination.
For example, in the case of an indirect peering scenario (section 5. For example, in the case of an indirect peering scenario (section 5.
of [I-D.ietf-speermint-voip-consolidated-usecases], Figure 5), it of [I-D.ietf-speermint-voip-consolidated-usecases]), it should be
should be possible for the SIP proxy in the originating network possible for the SIP proxy in the originating network (O-Proxy) to
(O-Proxy) to select the appropriate egress SBE (O-SBE) to reach the select the appropriate egress SBE (O-SBE) to reach the SIP target
SIP target based on the information the proxy receives from the based on the information the proxy receives from the Lookup Function
Lookup Function (O-LUF) and/or Location Routing Function (O-LRF) - (O-LUF) and/or Location Routing Function (O-LRF) - message response
message response labeled (2). Note that this example also applies to labeled (2). Note that this example also applies to the case of
the case of Direct Peering when a service provider has multiple Direct Peering when a service provider has multiple service areas and
service areas and each service area involves multiple SIP Proxies and each service area involves multiple SIP Proxies and a few SBEs.
a few SBEs.
o Requirement #5: o Requirement #5:
The mechanisms recommended for the Look-Up Function (LUF) and the The mechanisms recommended for the Look-Up Function (LUF) and the
Location Routing Functions (LRF) MUST be capable of returning both Location Routing Functions (LRF) MUST be capable of returning both
a target URI destination and a value providing the next SIP a target URI destination and a value providing the next SIP
hop(s). hop(s).
Notes: solutions may exist depending on the choice of the protocol Notes: solutions may exist depending on the choice of the protocol
used between the Proxy and its LUF/LRF. The idea is for the used between the Proxy and its LUF/LRF. The idea is for the
O-Proxy to be provided with the next SIP hop and the equivalent of O-Proxy to be provided with the next SIP hop and the equivalent of
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protocol for the LUF, the solution space is undefined. protocol for the LUF, the solution space is undefined.
It is desirable for an SSP to be able to communicate how It is desirable for an SSP to be able to communicate how
authentication of a peer's SBEs will occur (see the security authentication of a peer's SBEs will occur (see the security
requirements for more details). requirements for more details).
o Requirement #6: o Requirement #6:
The mechanisms recommended for locating a peer's SBE MUST be able The mechanisms recommended for locating a peer's SBE MUST be able
to convey how a peer should initiate secure session establishment. to convey how a peer should initiate secure session establishment.
Notes : some mechanisms exist. For example, the required protocol Notes: some mechanisms exist. For example, the required protocol
use of SIP over TLS may be discovered via [RFC3263]. use of SIP over TLS may be discovered via [RFC3263] and guidelines
concerning the use of the SIPS URI scheme in SIP have been
documented in [RFC5630].
3.3. Session Establishment Data 3.3. Session Establishment Data
The Session Establishment Data (SED) is defined in The Session Establishment Data (SED) is defined in [RFC5486] as the
[I-D.ietf-speermint-terminology] as the data used to route a call to data used to route a call to the next hop associated with the called
the next hop associated with the called domain's ingress point. The domain's ingress point. The following paragraphs capture some
following paragraphs capture some general requirements on the SED general requirements on the SED data.
data.
3.3.1. User Identities and SIP URIs 3.3.1. User Identities and SIP URIs
User identities used between peers can be represented in many User identities used between peers can be represented in many
different formats. Session Establishment Data should rely on URIs different formats. Session Establishment Data should rely on URIs
(Uniform Resource Identifiers, [RFC3986]) and SIP URIs should be (Uniform Resource Identifiers, [RFC3986]) and SIP URIs should be
preferred over tel URIs ([RFC3966]) for session peering of VoIP preferred over tel URIs ([RFC3966]) for session peering of VoIP
traffic. traffic.
The use of DNS domain names and hostnames is recommended in SIP URIs The use of DNS domain names and hostnames is recommended in SIP URIs
and they should be resolvable on the public Internet. As for the and they should be resolvable on the public Internet. As for the
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possible to avoid extra protocol round trips. possible to avoid extra protocol round trips.
o Requirement #9: o Requirement #9:
The mechanisms for session peering MUST allow an SBE to locate its The mechanisms for session peering MUST allow an SBE to locate its
peer SBE given a URI type and the target SSP domain name. peer SBE given a URI type and the target SSP domain name.
4. Requirements for Session Peering of Presence and Instant Messaging 4. Requirements for Session Peering of Presence and Instant Messaging
This section describes requirements for presence and instant This section describes requirements for presence and instant
messaging session peering. Several use cases for presence and messaging session peering. Several use cases for presence and
instant messaging peering are described in instant messaging peering are described in [RFC5344], a document
[I-D.ietf-speermint-consolidated-presence-im-usecases], a document authored by A. Houri, E. Aoki and S. Parameswar. Credits for the
authored by A. Houri, E. Aoki and S. Parameswar. Credits for this original content captured in this section must go to them.
section must go to A. Houri, E. Aoki and S. Parameswar.
The following requirements for presence and instant messaging session
peering are derived from
[I-D.ietf-speermint-consolidated-presence-im-usecases] and an initial
set of related requirements published by A. Houri, E. Aoki and S.
Parameswar:
o Requirement #10: o Requirement #10:
The mechanisms recommended for the exchange of presence The mechanisms recommended for the exchange of presence
information between SSPs MUST allow a user of one SSP's presence information between SSPs SHOULD allow a user of one presence
community to subscribe presentities served by another SSP via its community to send a presence subscription request to presentities
local community, including subscriptions to a single presentity, a served by another SSP via its local community, including
personal, public or ad-hoc group list of presentities. subscriptions to a single presentity, a personal, public or ad-hoc
group list of presentities.
Notes: see section 2.2 of Notes: see section 2.2 of [RFC5344].
[I-D.ietf-speermint-consolidated-presence-im-usecases].
o Requirement #11: o Requirement #11:
The mechanisms recommended for Instant Messaging message exchanges The mechanisms recommended for Instant Messaging exchanges between
between SSPs MUST allow a user of one SSP's community to SSPs SHOULD allow a user of one SSP's community to communicate
communicate with users of the other SSP community via their local with users of the other SSP community via their local community
community using various methods. Such methods include sending a using the various methods. Note that some SSPs may exercise some
one-time IM message, initiating a SIP session for transporting control over which methods are allowed based on service policies.
sessions of messages, participating in n-way chats using chat Such methods include sending a one-time IM message, initiating a
rooms with users from the peer SSPs, sending a file or sharing a SIP session for transporting sessions of messages, participating
document. in n-way chats using chat rooms with users from the peer SSPs,
etc.
Notes: see section 2.6 of Notes: see section 2.6 of [RFC5344].
[I-D.ietf-speermint-consolidated-presence-im-usecases].
o Requirement #12: Privacy Sharing o Requirement #12: Privacy Sharing
In order to enable sending less notifications between communities, In some presence communities, users can define the list of
there should be a mechanism that will enable sharing privacy watchers that receive presence notifications for a given
information of users between the communities. This will enable presentity. Such privacy settings for watcher notifications per
sending a single notification per presentity that will be sent to presentity are typically not shared across SSPs causing multiple
the appropriate watchers on the other community according to the notifications to be sent for one presentity change between SSPs.
The sharing of those privacy settings per presentity between SSPs
would allow fewer notifications: a single notification would be
sent per presentity and the terminating SSP would send
notifications to the appropriate watchers according to the
presentity's privacy information. presentity's privacy information.
The privacy sharing mechanism must be done in a way that will The mechanisms recommended for Presence information exchanges
enable getting the consent of the user whose privacy will be sent between SSPs SHOULD allow the sharing of some user privacy
to the other community prior to sending the privacy information. settings in order for users to convey the list of watchers that
can receive notification of presence information changes on a per
if user consent is not give, it should not be possible to this presentity basis.
optimization. In addition to getting the consent of users The privacy sharing mechanism must be done with the express
regarding privacy sharing, the privacy data must be sent only via consent of the user whose privacy settings will be shared with to
secure channels between communities. the other community. Because of the privacy-sensitive information
exchanged between SSPs, the protocols used for the exchange of
presence information must follow the security recommendations
defined in section 6 of [RFC3863].
Notes: see section 2.3 of Notes: see section 2.3 of [RFC5344].
[I-D.ietf-speermint-consolidated-presence-im-usecases].
o Requirement #13: Multiple Recipients o Requirement #13: Multiple Watchers
It should be possible to send a presence document with a list of It should be possible to send a presence document with a list of
watchers on the other community that should receive the presence watchers on the other community that should receive the presence
document notification. This will enable sending less presence document notification. This will enable sending less presence
document notifications between the communities while avoiding the document notifications between the communities while avoiding the
need to share privacy information of presentities from one need to share privacy information of presentities from one
community to the other. community to the other.
The systems used to exchange presence documents between SSPs
SHOULD allow more than one watchers to be passed with a presence
document.
o Requirement #14: Mappings o Requirement #14: Standard PIDF Documents and Mappings
Early deployments of SIP based presence and IM gateways are done Early deployments of SIP-based presence and Instant Messaging
in front of legacy proprietary systems that use different names gateways have been done in front of legacy proprietary systems
for different properties that exist in PIDF. For example "Do Not that use different naming schemes or name values for the elements
Disturb" may be translated to "Busy" in another system. In order and properties defined in a Presence Information Data Format
to make sure that the meaning of the status is preserved, there is (PIDF) document ([RFC3863]). For example the value "Do Not
a need that either each system will translate its internal Disturb" in one presence service may be mapped to "Busy" in
statuses to standard PIDF based statuses of a translation table of another system for the status element. Beyond this example of
proprietary statuses to standard based PIDF statuses will be status values, it is important to ensure that the meaning of the
provided from one system to the other. presence information is preserved between SSPs.
The systems used to exchange presence documents between SSPs
SHOULD use standard PIDF documents and translate any non-standard
value of a PIDF element to a standard one.
5. Security Considerations 5. Security Considerations
This section describes the security properties that are desirable for This section describes the security properties that are desirable for
the protocol exchanges in scope of session peering. Three types of the protocol exchanges in scope of session peering. Three types of
information flows are described in the architecture and use case information flows are described in the architecture and use case
documents: the acquisition of the Session Establishment Data (SED) documents: the acquisition of the Session Establishment Data (SED)
based on a destination target via the Lookup and Location Routing based on a destination target via the Lookup and Location Routing
Functions (LUF and LRF), the SIP signaling between SIP Service Functions (LUF and LRF), the SIP signaling between SIP Service
Providers, and the associated media exchanges. Providers, and the associated media exchanges.
skipping to change at page 12, line 28 skipping to change at page 13, line 28
security mechanisms as required by [RFC3365]; this is left for future security mechanisms as required by [RFC3365]; this is left for future
protocol solutions that meet the requirements. protocol solutions that meet the requirements.
A security threat analysis provides additional guidance for session A security threat analysis provides additional guidance for session
peering ([I-D.niccolini-speermint-voipthreats]). peering ([I-D.niccolini-speermint-voipthreats]).
5.1. Security Properties for the Acquisition of Session Establishment 5.1. Security Properties for the Acquisition of Session Establishment
Data Data
The Look-Up Function (LUF) and Location Routing Function (LRF) are The Look-Up Function (LUF) and Location Routing Function (LRF) are
defined in [I-D.ietf-speermint-terminology]. They provide mechanisms defined in [RFC5486]. They provide mechanisms for determining the
for determining the SIP target address and domain the request should SIP target address and domain the request should be sent to, and the
be sent to, and the associated SED to route the request to that associated SED to route the request to that domain.
domain.
o Requirement #15: o Requirement #15:
The protocols used to query the Lookup and Location Routing The protocols used to query the Lookup and Location Routing
Functions MUST support mutual authentication. Functions SHOULD support mutual authentication.
Motivations: Motivations:
A mutual authentication service is desirable for the LUF and LRF A mutual authentication service is desirable for the LUF and LRF
protocol exchanges. The content of the response returned by the protocol exchanges. The content of the response returned by the
LUF and LRF may depend on the identity of the requestor: the LUF and LRF may depend on the identity of the requestor: the
authentication of the LUF & LRF requests is therefore a desirable authentication of the LUF & LRF requests is therefore a desirable
property. Mutual authentication is also desirable: the requestor property. Mutual authentication is also desirable: the requestor
may verify the identity of the systems that provided the LUF & LRF may verify the identity of the systems that provided the LUF & LRF
responses given the nature of the data returned in those responses given the nature of the data returned in those
responses. Authentication also provides some protection for the responses. Authentication also provides some protection for the
skipping to change at page 14, line 23 skipping to change at page 15, line 23
The establishment of media security may be achieved along the media The establishment of media security may be achieved along the media
path and not over the signaling path given the indirect peering use path and not over the signaling path given the indirect peering use
cases. cases.
For example, media carried over the Real-Time Protocol (RTP) can be For example, media carried over the Real-Time Protocol (RTP) can be
secured using secure RTP (SRTP [RFC3711]). A framework for secured using secure RTP (SRTP [RFC3711]). A framework for
establishing SRTP security using Datagram TLS [RFC4347] is described establishing SRTP security using Datagram TLS [RFC4347] is described
in [I-D.ietf-sip-dtls-srtp-framework]: it allows for end-to-end media in [I-D.ietf-sip-dtls-srtp-framework]: it allows for end-to-end media
security establishment using extensions to DTLS security establishment using extensions to DTLS
([I-D.ietf-avt-dtls-srtp]). ([I-D.ietf-avt-dtls-srtp]).
It should also be noted that media can be carried in numerous It should also be noted that media can be carried in numerous
protocols other than RTP such as SIP (SIP MESSAGE method), MSRP, protocols other than RTP such as SIP (SIP MESSAGE method), MSRP (the
XMPP, etc., over TCP ([RFC4571]), and that it can be encrypted over Message Session Relay Protocol, [RFC4975], XMPP (the Extensible
secure connection-oriented transport sessions over TLS ([RFC4572]). Messaging and Presence Protocol, [RFC3920]) and many others. Media
may also be carried over TCP ([RFC4571]), and it can be encrypted
over secure connection-oriented transport sessions over TLS
([RFC4572]).
A desirable security property for session peering is for SIP entities A desirable security property for session peering is for SIP entities
to be transparent to the end-to-end media security negotiations: SIP to be transparent to the end-to-end media security negotiations: SIP
entities should not intervene in the Session Description Protocol entities should not intervene in the Session Description Protocol
(SDP) exchanges for end-to-end media security. (SDP) exchanges for end-to-end media security.
o Requirement #17: o Requirement #17:
The protocols used to enable session peering MUST NOT interfere The protocols used to enable session peering MUST NOT interfere
with the exchanges of media security attributes in SDP. Media with the exchanges of media security attributes in SDP. Media
attribute lines that are not understood by SBEs MUST be ignored attribute lines that are not understood by SBEs MUST be ignored
and passed along the signaling path untouched. and passed along the signaling path untouched.
6. Acknowledgments 6. Acknowledgments
This document is based on the input and contributions made by a large This document is based on the input and contributions made by a large
number of people in the SPEERMINT working group, including: Edwin number of people including: Bernard Aboba, Edwin Aoki, Scott Brim,
Aoki, Scott Brim, John Elwell, Mike Hammer, Avshalom Houri, Richard John Elwell, Mike Hammer, Avshalom Houri, Richard Shocky, Henry
Shocky, Henry Sinnreich, Richard Stastny, Patrik Faltstrom, Otmar Sinnreich, Richard Stastny, Patrik Faltstrom, Otmar Lendl, Daryl
Lendl, Daryl Malas, Dave Meyer, Sriram Parameswar, Jon Peterson, Malas, Dave Meyer, Sriram Parameswar, Jon Peterson, Jason Livingood,
Jason Livingood, Bob Natale, Benny Rodrig, Brian Rosen, Eric Bob Natale, Benny Rodrig, Brian Rosen, Eric Rosenfeld, Peter Saint-
Rosenfeld, Adam Uzelac, and David Schwartz. Andre, David Schwartz and Adam Uzelac.
Specials thanks go to Rohan Mahy, Brian Rosen, John Elwell for their Specials thanks go to Rohan Mahy, Brian Rosen, John Elwell for their
initial drafts describing guidelines or best current practices in initial drafts describing guidelines or best current practices in
various environments, to Avshalom Houri, Edwin Aoki and Sriram various environments, to Avshalom Houri, Edwin Aoki and Sriram
Parameswar for authoring the presence and instant messaging Parameswar for authoring the presence and instant messaging
requirements and to Dan Wing for providing detailed feedback on the requirements and to Dan Wing for providing detailed feedback on the
security consideration sections. security consideration sections.
7. IANA Considerations 7. IANA Considerations
skipping to change at page 17, line 18 skipping to change at page 18, line 18
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References 8.2. Informative References
[I-D.ietf-avt-dtls-srtp] [I-D.ietf-avt-dtls-srtp]
McGrew, D. and E. Rescorla, "Datagram Transport Layer McGrew, D. and E. Rescorla, "Datagram Transport Layer
Security (DTLS) Extension to Establish Keys for Secure Security (DTLS) Extension to Establish Keys for Secure
Real-time Transport Protocol (SRTP)", Real-time Transport Protocol (SRTP)",
draft-ietf-avt-dtls-srtp-05 (work in progress), draft-ietf-avt-dtls-srtp-07 (work in progress),
September 2008. February 2009.
[I-D.ietf-pmol-sip-perf-metrics] [I-D.ietf-pmol-sip-perf-metrics]
Malas, D., "SIP End-to-End Performance Metrics", Malas, D. and A. Morton, "SIP End-to-End Performance
draft-ietf-pmol-sip-perf-metrics-01 (work in progress), Metrics", draft-ietf-pmol-sip-perf-metrics-04 (work in
June 2008. progress), September 2009.
[I-D.ietf-sip-connect-reuse] [I-D.ietf-sip-connect-reuse]
Mahy, R., Gurbani, V., and B. Tate, "Connection Reuse in Gurbani, V., Mahy, R., and B. Tate, "Connection Reuse in
the Session Initiation Protocol (SIP)", the Session Initiation Protocol (SIP)",
draft-ietf-sip-connect-reuse-11 (work in progress), draft-ietf-sip-connect-reuse-14 (work in progress),
July 2008. August 2009.
[I-D.ietf-sip-dtls-srtp-framework] [I-D.ietf-sip-dtls-srtp-framework]
Fischl, J., Tschofenig, H., and E. Rescorla, "Framework Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
for Establishing an SRTP Security Context using DTLS", for Establishing an SRTP Security Context using DTLS",
draft-ietf-sip-dtls-srtp-framework-04 (work in progress), draft-ietf-sip-dtls-srtp-framework-07 (work in progress),
October 2008. March 2009.
[I-D.ietf-sip-hitchhikers-guide]
Rosenberg, J., "A Hitchhiker's Guide to the Session
Initiation Protocol (SIP)",
draft-ietf-sip-hitchhikers-guide-05 (work in progress),
February 2008.
[I-D.ietf-speermint-architecture] [I-D.ietf-speermint-architecture]
Penno, R., "SPEERMINT Peering Architecture", Penno, R. and S. Khan, "SPEERMINT Peering Architecture",
draft-ietf-speermint-architecture-06 (work in progress), draft-ietf-speermint-architecture-08 (work in progress),
May 2008. March 2009.
[I-D.ietf-speermint-consolidated-presence-im-usecases]
Houri, A., "Presence & Instant Messaging Peering Use
Cases",
draft-ietf-speermint-consolidated-presence-im-usecases-05
(work in progress), July 2008.
[I-D.ietf-speermint-terminology]
Malas, D. and D. Meyer, "SPEERMINT Terminology",
draft-ietf-speermint-terminology-16 (work in progress),
February 2008.
[I-D.ietf-speermint-voip-consolidated-usecases] [I-D.ietf-speermint-voip-consolidated-usecases]
Uzelac, A. and Y. Lee, "VoIP SIP Peering Use Cases", Uzelac, A. and Y. Lee, "VoIP SIP Peering Use Cases",
draft-ietf-speermint-voip-consolidated-usecases-10 (work draft-ietf-speermint-voip-consolidated-usecases-14 (work
in progress), August 2008. in progress), August 2009.
[I-D.niccolini-speermint-voipthreats] [I-D.niccolini-speermint-voipthreats]
Niccolini, S., Chen, E., and J. Seedorf, "SPEERMINT Niccolini, S., Chen, E., Seedorf, J., and H. Scholz,
Security Threats and Suggested Countermeasures", "SPEERMINT Security Threats and Suggested
draft-niccolini-speermint-voipthreats-04 (work in Countermeasures", draft-niccolini-speermint-voipthreats-05
progress), July 2008. (work in progress), October 2008.
[RFC2198] Perkins, C., Kouvelas, I., Hodson, O., Hardman, V., [RFC2198] Perkins, C., Kouvelas, I., Hodson, O., Hardman, V.,
Handley, M., Bolot, J., Vega-Garcia, A., and S. Fosse- Handley, M., Bolot, J., Vega-Garcia, A., and S. Fosse-
Parisis, "RTP Payload for Redundant Audio Data", RFC 2198, Parisis, "RTP Payload for Redundant Audio Data", RFC 2198,
September 1997. September 1997.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002. June 2002.
skipping to change at page 18, line 45 skipping to change at page 19, line 28
[RFC3365] Schiller, J., "Strong Security Requirements for Internet [RFC3365] Schiller, J., "Strong Security Requirements for Internet
Engineering Task Force Standard Protocols", BCP 61, Engineering Task Force Standard Protocols", BCP 61,
RFC 3365, August 2002. RFC 3365, August 2002.
[RFC3455] Garcia-Martin, M., Henrikson, E., and D. Mills, "Private [RFC3455] Garcia-Martin, M., Henrikson, E., and D. Mills, "Private
Header (P-Header) Extensions to the Session Initiation Header (P-Header) Extensions to the Session Initiation
Protocol (SIP) for the 3rd-Generation Partnership Project Protocol (SIP) for the 3rd-Generation Partnership Project
(3GPP)", RFC 3455, January 2003. (3GPP)", RFC 3455, January 2003.
[RFC3466] Day, M., Cain, B., Tomlinson, G., and P. Rzewski, "A Model
for Content Internetworking (CDI)", RFC 3466,
February 2003.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003. Applications", STD 64, RFC 3550, July 2003.
[RFC3603] Marshall, W. and F. Andreasen, "Private Session Initiation [RFC3568] Barbir, A., Cain, B., Nair, R., and O. Spatscheck, "Known
Protocol (SIP) Proxy-to-Proxy Extensions for Supporting Content Network (CN) Request-Routing Mechanisms",
the PacketCable Distributed Call Signaling Architecture", RFC 3568, July 2003.
RFC 3603, October 2003.
[RFC3570] Rzewski, P., Day, M., and D. Gilletti, "Content
Internetworking (CDI) Scenarios", RFC 3570, July 2003.
[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", RFC 3611, Protocol Extended Reports (RTCP XR)", RFC 3611,
November 2003. November 2003.
[RFC3702] Loughney, J. and G. Camarillo, "Authentication, [RFC3702] Loughney, J. and G. Camarillo, "Authentication,
Authorization, and Accounting Requirements for the Session Authorization, and Accounting Requirements for the Session
Initiation Protocol (SIP)", RFC 3702, February 2004. Initiation Protocol (SIP)", RFC 3702, February 2004.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)", Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004. RFC 3711, March 2004.
[RFC3824] Peterson, J., Liu, H., Yu, J., and B. Campbell, "Using [RFC3824] Peterson, J., Liu, H., Yu, J., and B. Campbell, "Using
E.164 numbers with the Session Initiation Protocol (SIP)", E.164 numbers with the Session Initiation Protocol (SIP)",
RFC 3824, June 2004. RFC 3824, June 2004.
[RFC3863] Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr,
W., and J. Peterson, "Presence Information Data Format
(PIDF)", RFC 3863, August 2004.
[RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
[RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers", [RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
RFC 3966, December 2004. RFC 3966, December 2004.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005. RFC 3986, January 2005.
[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, April 2006. Security", RFC 4347, April 2006.
skipping to change at page 19, line 47 skipping to change at page 20, line 42
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[RFC4571] Lazzaro, J., "Framing Real-time Transport Protocol (RTP) [RFC4571] Lazzaro, J., "Framing Real-time Transport Protocol (RTP)
and RTP Control Protocol (RTCP) Packets over Connection- and RTP Control Protocol (RTCP) Packets over Connection-
Oriented Transport", RFC 4571, July 2006. Oriented Transport", RFC 4571, July 2006.
[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572, July 2006. Description Protocol (SDP)", RFC 4572, July 2006.
[RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast
Services", BCP 126, RFC 4786, December 2006.
[RFC4916] Elwell, J., "Connected Identity in the Session Initiation [RFC4916] Elwell, J., "Connected Identity in the Session Initiation
Protocol (SIP)", RFC 4916, June 2007. Protocol (SIP)", RFC 4916, June 2007.
[RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message
Session Relay Protocol (MSRP)", RFC 4975, September 2007.
[RFC5344] Houri, A., Aoki, E., and S. Parameswar, "Presence and
Instant Messaging Peering Use Cases", RFC 5344,
October 2008.
[RFC5411] Rosenberg, J., "A Hitchhiker's Guide to the Session
Initiation Protocol (SIP)", RFC 5411, February 2009.
[RFC5486] Malas, D. and D. Meyer, "Session Peering for Multimedia
Interconnect (SPEERMINT) Terminology", RFC 5486,
March 2009.
[RFC5503] Andreasen, F., McKibben, B., and B. Marshall, "Private
Session Initiation Protocol (SIP) Proxy-to-Proxy
Extensions for Supporting the PacketCable Distributed Call
Signaling Architecture", RFC 5503, March 2009.
[RFC5630] Audet, F., "The Use of the SIPS URI Scheme in the Session
Initiation Protocol (SIP)", RFC 5630, October 2009.
Appendix A. Policy Parameters for Session Peering Appendix A. Policy Parameters for Session Peering
This informative section lists various types of parameters that This informative section lists various types of parameters that
should be considered by implementers when deciding what configuration should be considered by implementers when deciding what configuration
variables to expose to system administrators or management stations, variables to expose to system administrators or management stations,
as well as SSPs or federations of SSPs when discussing the technical as well as SSPs or federations of SSPs when discussing the technical
part of a session peering policy. part of a session peering policy.
In the context of session peering, a policy can be defined as the set In the context of session peering, a policy can be defined as the set
of parameters and other information needed by an SSP to exchange of parameters and other information needed by an SSP to exchange
skipping to change at page 21, line 45 skipping to change at page 23, line 45
* A session peering policy should include the list of supported * A session peering policy should include the list of supported
and required SIP RFCs, supported and required SIP methods and required SIP RFCs, supported and required SIP methods
(including private p headers if applicable), error response (including private p headers if applicable), error response
codes, supported or recommended format of some header field codes, supported or recommended format of some header field
values , etc. values , etc.
* It should also be possible to describe the list of supported * It should also be possible to describe the list of supported
SIP RFCs by various functional groupings. A group of SIP RFCs SIP RFCs by various functional groupings. A group of SIP RFCs
may represent how a call feature is implemented (call hold, may represent how a call feature is implemented (call hold,
transfer, conferencing, etc.), or it may indicate a functional transfer, conferencing, etc.), or it may indicate a functional
grouping as in [I-D.ietf-sip-hitchhikers-guide]. grouping as in [RFC5411].
o Accounting: o Accounting:
Methods used for call or session accounting should be specified. Methods used for call or session accounting should be specified.
An SSP may require a peer to track session usage. It is critical An SSP may require a peer to track session usage. It is critical
for peers to determine whether the support of any SIP extensions for peers to determine whether the support of any SIP extensions
for accounting is a pre-requisite for SIP interoperability. In for accounting is a pre-requisite for SIP interoperability. In
some cases, call accounting may feed data for billing purposes but some cases, call accounting may feed data for billing purposes but
not always: some operators may decide to use accounting as a 'bill not always: some operators may decide to use accounting as a 'bill
and keep' model to track session usage and monitor usage against and keep' model to track session usage and monitor usage against
service level agreements. service level agreements.
[RFC3702] defines the terminology and basic requirements for [RFC3702] defines the terminology and basic requirements for
accounting of SIP sessions. A few private SIP extensions have accounting of SIP sessions. A few private SIP extensions have
also been defined and used over the years to enable call also been defined and used over the years to enable call
accounting between SSP domains such as the P-Charging* headers in accounting between SSP domains such as the P-Charging* headers in
[RFC3455], the P-DCS-Billing-Info header in [RFC3603], etc. [RFC3455], the P-DCS-Billing-Info header in [RFC5503], etc.
o Performance Metrics: o Performance Metrics:
Layer-5 performance metrics should be defined and shared between Layer-5 performance metrics should be defined and shared between
peers. The performance metrics apply directly to signaling or peers. The performance metrics apply directly to signaling or
media; they may be used pro-actively to help avoid congestion, media; they may be used pro-actively to help avoid congestion,
call quality issues or call signaling failures, and as part of call quality issues or call signaling failures, and as part of
monitoring techniques, they can be used to evaluate the monitoring techniques, they can be used to evaluate the
performance of peering exchanges. performance of peering exchanges.
Examples of SIP performance metrics include the maximum number of Examples of SIP performance metrics include the maximum number of
SIP transactions per second on per domain basis, Session SIP transactions per second on per domain basis, Session
skipping to change at page 26, line 4 skipping to change at line 1018
Author's Address Author's Address
Jean-Francois Mule Jean-Francois Mule
CableLabs CableLabs
858 Coal Creek Circle 858 Coal Creek Circle
Louisville, CO 80027 Louisville, CO 80027
USA USA
Email: jf.mule@cablelabs.com Email: jf.mule@cablelabs.com
Full Copyright Statement
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this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
 End of changes. 55 change blocks. 
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