draft-ietf-speermint-requirements-05.txt   draft-ietf-speermint-requirements-06.txt 
SPEERMINT Working Group J-F. Mule SPEERMINT Working Group J-F. Mule
Internet-Draft CableLabs Internet-Draft CableLabs
Intended status: Informational June 27, 2008 Intended status: Informational July 14, 2008
Expires: December 29, 2008 Expires: January 15, 2009
SPEERMINT Requirements for SIP-based Session Peering SPEERMINT Requirements for SIP-based Session Peering
draft-ietf-speermint-requirements-05.txt draft-ietf-speermint-requirements-06.txt
Status of this Memo Status of this Memo
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This Internet-Draft will expire on December 29, 2008. This Internet-Draft will expire on January 15, 2009.
Copyright Notice
Copyright (C) The IETF Trust (2008).
Abstract Abstract
This memo captures protocol requirements identified for enabling This memo captures protocol requirements to enable session peering of
session peering of voice, presence, instant messaging and other types voice, presence, instant messaging and other types of multimedia
of multimedia traffic. It is an informational document linking the traffic. It is based on the use cases that have been described in
session peering use cases to protocol solutions. the speermint working group. This informational document is intended
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 . . . . . . . . . . . . . . . . 8
3.3.1. User Identities and SIP URIs . . . . . . . . . . . . . 8 3.3.1. User Identities and SIP URIs . . . . . . . . . . . . . 8
3.3.2. URI Reachability . . . . . . . . . . . . . . . . . . . 9 3.3.2. URI Reachability . . . . . . . . . . . . . . . . . . . 9
4. Considerations and Requirements for Session Peering of 4. Considerations and Requirements for Session Peering of
Presence and Instant Messaging . . . . . . . . . . . . . . . . 10 Presence and Instant Messaging . . . . . . . . . . . . . . . . 10
5. Security Requirements . . . . . . . . . . . . . . . . . . . . 12 5. Security Requirements . . . . . . . . . . . . . . . . . . . . 12
5.1. Security Properties for the Acquisition of Session 5.1. Security Properties for the Acquisition of Session
Establishment Data . . . . . . . . . . . . . . . . . . . . 12 Establishment Data . . . . . . . . . . . . . . . . . . . . 12
5.2. Security Properties for the SIP exchanges . . . . . . . . 13 5.2. Security Properties for the SIP signaling exchanges . . . 13
5.3. End-to-End Media Security . . . . . . . . . . . . . . . . 13 5.3. End-to-End Media Security . . . . . . . . . . . . . . . . 14
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 8. Security Considerations . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . . 17 9.1. Normative References . . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . . 17 9.2. Informative References . . . . . . . . . . . . . . . . . . 19
Appendix A. Policy Parameters for Session Peering . . . . . . . . 20 Appendix A. Policy Parameters for Session Peering . . . . . . . . 22
A.1. Categories of Parameters and Justifications . . . . . . . 20 A.1. Categories of Parameters for VoIP Session Peering and
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 Intellectual Property and Copyright Statements . . . . . . . . . . 28
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 allow the exchange of multimedia traffic. It is assumed that to allow the exchange of multimedia traffic. It is assumed that
these sessions use the Session Initiation Protocol (SIP) protocol to these sessions use the Session Initiation Protocol (SIP) protocol to
enable peering between two or more actors. These actors are called enable peering between two or more actors. These actors are called
SIP Service Providers (SSPs) and they are typically represented by SIP Service Providers (SSPs) and they are typically represented by
users, user groups such as enterprises, real-time collaboration users, user groups such as enterprises, real-time collaboration
service communities, or other service providers offering voice or service communities, or other service providers offering voice or
multimedia services. multimedia services using SIP.
Common terminology for SIP session peering is defined in A reference architecture for SIP session peering is described in
[I-D.ietf-speermint-terminology] and a reference architecture is [I-D.ietf-speermint-architecture]. A number of use cases describe
described in [I-D.ietf-speermint-architecture]. A number of use how session peering has been or could be deployed based on the
cases describe how session peering has been or could be deployed reference architecture
based on the reference architecture
([I-D.ietf-speermint-voip-consolidated-usecases] and ([I-D.ietf-speermint-voip-consolidated-usecases] and
[I-D.ietf-speermint-consolidated-presence-im-usecases]). [I-D.ietf-speermint-consolidated-presence-im-usecases]).
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
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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 [I-D.ietf- This document also reuses the terminology defined in [I-D.ietf-
speermint-terminology]. It is assumed that the reader is familiar speermint-terminology]. It is assumed that the reader is familiar
with the Session Description Protocol (SDP) [RFC4566] and the Session with the Session Description Protocol (SDP) [RFC4566] and the Session
Initiation Protocol (SIP) [RFC3261]. Initiation Protocol (SIP) [RFC3261]. Finally, when used with capital
letters, the terms 'Authentication Service' are to be understood as
defined by SIP 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 and Signaling to the boundaries of Layer 5 SIP networks: SIP entities, Signaling
path Border Elements (SBEs); any requirements touching SIP UA or end- path Border Elements (SBEs), and the associated protocol requirements
devices are considered out of scope. for the look-up and location routing of the session establishment
data. The requirements related to SIP UAs, the provisioning of the
session data are considered out of scope.
SSPs desiring to establish session peering relationships have to SSPs desiring to establish session peering relationships have to
reach an agreement on numerous aspects. reach an agreement on numerous points.
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, including agreement, mostly the requirements relevant to protocols: the
the declaration, advertisement and management of ingress and egress declaration, advertisement and management of ingress and egress for
for session signaling and media, information related to the Session session signaling and media, information related to the Session
Establishment Data (SED), and the security mechanisms a peer may use Establishment Data (SED), and the security mechanisms a peer may use
to accept and secure session exchanges. to accept and secure session exchanges.
Numerous other aspects of session peering arrangement are critical to Numerous other considerations of session peering arrangement are
reach a successful agreement but they are considered out of scope of critical to reach a successful agreement but they are considered out
the SPEERMINT working group. They include aspects such as SIP of scope of the SPEERMINT working group. They include information
protocol support (e.g. SIP extensions and field conventions), media about SIP protocol support (e.g. SIP extensions and field
(e.g., type of media traffic to be exchanged, compatible media codecs conventions), media (e.g., type of media traffic to be exchanged,
and media transport protocols, mechanisms to ensure differentiated compatible media codecs and media transport protocols, mechanisms to
quality of service for media), SIP layer-3 IP connectivity between ensure differentiated quality of service for media), SIP layer-3 IP
the Signaling Path and Data Path Border Elements, traffic capacity connectivity between the Signaling Path and Data Path Border
control (e.g. maximum number of SIP sessions at each ingress point, Elements, traffic capacity control (e.g. maximum number of SIP
maximum number of concurrent IM or VoIP sessions), and accounting. sessions at each ingress point, maximum number of concurrent IM or
VoIP sessions), and accounting.
The informative Appendix A lists parameters that may considered when The informative Appendix A lists parameters that may be considered
discussing the technical aspects of SIP session peering. The purpose when discussing the technical parameters of SIP session peering. The
of this list which has evolved through the working group use case purpose of this list is to capture the parameters that are considered
discussions is to capture the parameters that are considered outside outside the scope of the protocol requirements.
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 border elements are declared or flexibility should be given for how they are declared or dynamically
dynamically advertised. advertised.
Indeed, in any session peering environment, there is a need for a SIP Indeed, in any session peering environment, there is a need for a SIP
Service Provider to declare or dynamically advertise the SIP entities Service Provider to declare or dynamically advertise the SIP entities
that will face the peer's network. The data path border elements are that will face the peer's network. The data path border elements are
typically signaled dynamically in the session description. typically signaled dynamically in the session description.
The use cases defined The use cases defined
([I-D.ietf-speermint-voip-consolidated-usecases]) catalog the various ([I-D.ietf-speermint-voip-consolidated-usecases]) catalog the various
border elements between SIP Service Providers; they include Signaling border elements between SIP Service Providers; they include Signaling
Path Border Elements (SBEs) and SIP proxies (or any SIP entity at the Path Border Elements (SBEs) and SIP proxies (or any SIP entity at the
boundary of the Layer 5 network). boundary of the Layer 5 network).
o Requirement #1: o Requirement #1:
Protocol mechanisms must exist for a SIP Service Provider (SSP) to Protocol mechanisms must exist for a SIP Service Provider to
communicate the ingress Signaling Path Border Elements of its communicate the ingress Signaling Path Border Elements of its
service domain. 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 seems to mechanisms or they may be dynamically advertised. There is
be 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. However, this DNS-based solution may be limited
in cases where the DNS response varies based on who sends the in cases where the DNS response varies based on who sends the
query (peer-dependent SBEs, see below). query (peer-dependent SBEs, see below).
o Requirement #2: o Requirement #2:
Protocol mechanisms should exist for a SIP Service Provider (SSP) Protocol mechanisms must exist for a SIP Service Provider to
to communicate the egress SBEs of its service domain. 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
information is typically used by the terminating SSP). information is typically used by the terminating SSP).
Note that this may not be applicable to all types of session
peering (voice may be a particular case where this is needed -- at
least based on current practices).
While provisioning requirements are out-of-scope of this document, While provisioning requirements are out-of-scope of this document,
some SSPs may find use for a mechanism to dynamically advertise or some SSPs may find use for a mechanism to dynamically advertise or
discover the egress SBEs of a peer. discover the egress SBEs of a peer.
If the SSP also provides media streams to its users as shown in the If the SSP also provides media streams to its users as shown in the
use cases for "Originating" and "Terminating" SSPs, a mechanism use cases for "Originating" and "Terminating" SSPs, a mechanism
should exist to allow SSPs to advertise their egress and ingress data should exist to allow SSPs to advertise their egress and ingress data
path border elements (DBEs), if applicable. While some SSPs may have path border elements (DBEs), if applicable. While some SSPs may have
open policies and accept media traffic from anywhere outside their open policies and accept media traffic from anywhere outside their
network to anywhere inside their network, some SSPs may want to network to anywhere inside their network, some SSPs may want to
optimize media delivery and identify media paths between peers prior optimize media delivery and identify media paths between peers prior
to traffic being sent (layer 5 to layer 3 QoS mapping). to traffic being sent (layer 5 to layer 3 QoS mapping).
o Requirement #3: o Requirement #3:
Protocol mechanisms should be available to allow a SIP Service Protocol mechanisms must allow a SIP Service Provider to
Provider to communicate its DBEs to its peers. 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 today in a static manner. Some SSPs do
not. not.
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 SIP entities acting as SBEs are capable of establishing. In their SIP entities acting as SBEs are capable of establishing. In
order to avoid a failed attempt to establish a session, a mechanism order to avoid a failed attempt to establish a session, a mechanism
may be provided to allow SSPs to indicate if some restrictions exist may be provided to allow SSPs to indicate if some restrictions exist
on the type of media traffic: ingress and egress SBE points may be on the type of media traffic: ingress and egress SBE points may be
peer-dependent, and/or media-dependent. peer-dependent, and/or media-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 For advertising peer-dependent SBEs (peer variability), the
solution space based on [RFC3263] is under specified and there are solution space based on [RFC3263] is under specified and there are
no know best current practices. Is DNS the right place for no know best current practices. Is DNS the right place for
putting data that varies based on who asks? putting data that varies based on who asks?
In the use cases provided as part of direct and indirect scenarios, In the use cases provided as part of direct and indirect scenarios,
an SSP deals with multiple SIP entities and multiple SBEs in its own an SSP deals with multiple SIP entities and multiple SBEs in its own
domain. There is often a many-to-many relationship between SIP domain. There is often a many-to-many relationship between SIP
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[I-D.ietf-speermint-voip-consolidated-usecases], Figure 5), it should [I-D.ietf-speermint-voip-consolidated-usecases], Figure 5), it should
be possible for the O-Proxy to choose the appropriate O-SBE based on be possible for the O-Proxy to choose the appropriate O-SBE based on
the information the O-Proxy receives from the Lookup Function (LUF) the information the O-Proxy receives from the Lookup Function (LUF)
and/or Location Routing Function (LRF) - message response labeled and/or Location Routing Function (LRF) - message response labeled
(3). Note that this example also applies to the case of Direct (3). Note that this example also applies to the case of Direct
Peering when a service provider has multiple service areas and each Peering when a service provider has multiple service areas and each
service area involves multiple SIP Proxies and a few SBEs. service area involves multiple SIP Proxies and a few SBEs.
o Requirement #5: o Requirement #5:
The mechanisms recommended for the lookup and location routing The mechanisms recommended for the lookup and location routing
service must be capable or returning both a target URI destination functions MUST be capable of returning both a target URI
and a value for the SIP Route header. destination and a value for the SIP Route header.
Notes: solutions exist if the protocol used between the Proxy and Notes: solutions exist if the protocol used between the Proxy and
the LUF/LRF is SIP; if ENUM is used, the author of this document the LUF/LRF is SIP; if ENUM is used, the author of this document
does not know of any solution today. does not know of any solution today.
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 : certain mechanisms exist; for example, the required Notes : certain mechanisms exist; for example, the required
protocol use of SIP over TLS may be discovered via [RFC3263]. protocol use of SIP over TLS may be discovered via [RFC3263].
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
[I-D.ietf-speermint-terminology] as the data used to route a call to [I-D.ietf-speermint-terminology] as the data used to route a call to
the next hop associated with the called domain's ingress point. The the next hop associated with the called domain's ingress point. The
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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. It is and they should be resolvable on the public Internet. As for the
recommended that the host part of SIP URIs contain a fully-qualified
domain name instead of a numeric IPv4 or IPv6 address. As for the
user part of the SIP URIs, the mechanisms for session peering should user part of the SIP URIs, the mechanisms for session peering should
not require an SSP to be aware of which individual user identities not require an SSP to be aware of which individual user identities
are valid within its peer's domain. are valid within its peer's domain.
o Requirement #7: o Requirement #7:
The protocols used for session peering must accommodate the use of The protocols used for session peering MUST accommodate the use of
different types of URIs. URIs with the same domain-part should different types of URIs. URIs with the same domain-part SHOULD
share the same set of peering policies, thus the domain of the SIP share the same set of peering policies, thus the domain of the SIP
URI may be used as the primary key to any information regarding URI may be used as the primary key to any information regarding
the reachability of that SIP URI. the reachability of that SIP URI. The host part of SIP URIs
SHOULD contain a fully-qualified domain name instead of a numeric
IPv4 or IPv6 address.
o Requirement #8: o Requirement #8:
The mechanisms for session peering should not require an SSP to be The mechanisms for session peering should not require an SSP to be
aware of which individual user identities are valid within its aware of which individual user identities are valid within its
peer's domain. peer's domain.
o Notes on the solution space for #7 and #8: o Notes on the solution space for #7 and #8:
This is generally well supported by IETF protocols. When This is generally well supported by IETF protocols. When
telephone numbers are in tel URIs, SIP requests cannot be routed telephone numbers are in tel URIs, SIP requests cannot be routed
in accordance with the traditional DNS resolution procedures in accordance with the traditional DNS resolution procedures
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to locate and retrieve the domain's policy and SBE entities. to locate and retrieve the domain's policy and SBE entities.
For example, an originating service provider must be able to For example, an originating service provider must be able to
determine whether a SIP URI is open for direct interconnection determine whether a SIP URI is open for direct interconnection
without requiring an SBE to initiate a SIP request. Furthermore, without requiring an SBE to initiate a SIP request. Furthermore,
since each call setup implies the execution of any proposed since each call setup implies the execution of any proposed
algorithm, the establishment of a SIP session via peering should algorithm, the establishment of a SIP session via peering should
incur minimal overhead and delay, and employ caching wherever incur minimal overhead and delay, and employ caching wherever
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. Considerations and Requirements for Session Peering of Presence and 4. Considerations and Requirements for Session Peering of Presence and
Instant Messaging 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
[I-D.ietf-speermint-consolidated-presence-im-usecases], a document [I-D.ietf-speermint-consolidated-presence-im-usecases], a document
authored by A. Houri, E. Aoki and S. Parameswar. Credits for this authored by A. Houri, E. Aoki and S. Parameswar. Credits for this
section must go to A. Houri, E. Aoki and S. Parameswar. section must go to A. Houri, E. Aoki and S. Parameswar.
The following requirements for presence and instant messaging session The following requirements for presence and instant messaging session
peering are derived from peering are derived from
[I-D.ietf-speermint-consolidated-presence-im-usecases] and [I-D.ietf-speermint-consolidated-presence-im-usecases] and an initial
[I-D.houri-speermint-presence-im-requirements]: 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 MUST allow a user of one SSP's presence
community to subscribe presentities served by another SSP via its community to subscribe presentities served by another SSP via its
local community, including subscriptions to a single presentity, a local community, including subscriptions to a single presentity, a
personal, public or ad-hoc group list of presentities. personal, public or ad-hoc group list of presentities.
Notes: see section 2.2 of Notes: see section 2.2 of
[I-D.ietf-speermint-consolidated-presence-im-usecases]. [I-D.ietf-speermint-consolidated-presence-im-usecases].
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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.
This section is focused on three security services, authentication, This section is focused on three security services, authentication,
data confidentiality and data integrity as summarized in [RFC3365]. data confidentiality and data integrity as summarized in [RFC3365].
However, this text does not specify the mandatory-to-implement However, this text does not specify the mandatory-to-implement
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 guidance for session peering A security threat analysis provides guidance for session peering
([I-D.draft-niccolini-speermint-voipthreats]). ([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 [I-D.ietf-speermint-terminology]. They provide mechanisms
for determining the SIP target address and domain the request should for determining the SIP target address and domain the request should
be sent to, and the associated SED to route the request to that be sent to, and the associated SED to route the request to that
domain. domain.
o Requirement #15:
The protocols used to query the Lookup and Location Routing
Functions MUST support mutual authentication.
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 response from the LUF and LRF may depend on protocol exchanges. The response from the LUF and LRF may depend
the identity of the requestor: the authentication of the LUF/LRF on the identity of the requestor: the authentication of the LUF/
requests is therefore a desirable property. Mutual authentication is LRF requests is therefore a desirable property. Mutual
also desirable: the requestor may verify the identity of the systems authentication is also desirable: the requestor may verify the
that provided the LUF/LRF responses given the nature of the data identity of the systems that provided the LUF/LRF responses given
returned in those responses. Authentication also provides some the nature of the data returned in those responses.
protection for the availability of the LUF and LRF against attackers Authentication also provides some protection for the availability
that would attempt to launch DoS attacks by sending bogus requests of the LUF and LRF against attackers that would attempt to launch
causing the LUF to perform a lookup and consume resources. DoS attacks by sending bogus requests causing the LUF to perform a
lookup and consume resources.
o Requirement #16:
The protocols used to query the Lookup and Location Routing
Functions MUST provide support for data confidentiality and
integrity.
Motivations:
Given the sensitive nature of the session establishment data Given the sensitive nature of the session establishment data
exchanged with the LUF and LRF functions, the protocol mechanisms exchanged with the LUF and LRF functions, the protocol mechanisms
chosen for the lookup and location routing should offer data chosen for the lookup and location routing should offer data
confidentiality and integrity protection (SED data may contain user confidentiality and integrity protection (SED data may contain
addresses, SIP URI, location of SIP entities at the boundaries of SIP user addresses, SIP URI, location of SIP entities at the
Service Provider domains, etc.). boundaries of SIP Service Provider domains, etc.).
Requirement #15: o Notes on the solution space for Requirements #15 and #16: ENUM,
The data exchanges for the lookup and location routing MUST support SIP and proprietary protocols are typically used today for
mutual authentication, data confidentiality and integrity. accessing these functions. Even though SSPs may use lower layer
security mechanisms to guarantee some of those security
properties, candidate protocols for the LUF and LRF must meet the
above requirements.
Notes on the solution space: ENUM, SIP and proprietary protocols are 5.2. Security Properties for the SIP signaling exchanges
typically used today for accessing these functions. SSPs may use
lower layer security mechanisms to guarantee some of those security
properties.
5.2. Security Properties for the SIP exchanges While the SIP signaling exchanges are out of scope of speermint, this
section describes some of the security properties that are desirable
in the context of SIP interconnects between SSPs.
The fundamental mechanisms for securing SIP are applicable (see In general, the security properties desirable for the SIP exchanges
Section 26.2 of [RFC3261], and [RFC4474]). in an inter-domain context apply to session peering. These include:
Authentication of SIP communications are desirable, especially in the o securing the transport of SIP messages between the peers' SBEs.
context of session peering involving SIP intermediaries. Data Authentication of SIP communications is desirable, especially in
the context of session peering involving SIP intermediaries. Data
confidentiality and integrity of the SIP message body may be confidentiality and integrity of the SIP message body may be
desirable given some of the levels of session peering indirection desirable as well given some of the levels of session peering
(indirect/assisted peering), but they could be harmful as they may indirection (indirect/assisted peering), but they could be harmful
prevent intermediary SSPs from "inserting" SBEs/DBEs along the as they may prevent intermediary SSPs from "inserting" SBEs/DBEs
signaling and data paths. along the signaling and data paths.
o providing an Authentication Service to authenticate the identity
of connected users based on the SIP Service Provider domains (for
both the SIP requests and the responses).
The fundamental mechanisms for securing SIP between proxy servers
intra- and inter-domain are applicable to session peering; refer to
Section 26.2 of [RFC3261] for transport-layer security of SIP
messages using TLS, [I-D.ietf-sip-connect-reuse] for establishing TLS
connections between proxies, [RFC4474] for the protocol mechanisms to
verify the identity of the senders of SIP requests in an inter-domain
context, and [RFC4916] for verifying the identity of the sender of
SIP responses).
o Requirement #17:
The security properties provided by the protocol mechanisms
defined in Section 26.2 of [RFC3261] and
[I-D.ietf-sip-connect-reuse] for transport-layer security, and by
[RFC4474], and [RFC4916] for SIP identity MUST be met in the
context of the speermint architecture.
Motivations:
The motivations for this requirement are provided in the above
paragraphs.
o Discussion points around Requirement #17:
The above text captures the super-set of security properties that
2 SSPs would ever want. The question is why would SSPs need RFC
4474 if they have hop-by-hop security and connection reuse
underneath? What additional properties would RFC4474 provide in
this context?
On a different note, is it reasonable to say that SSPs need the
validation of the sender of the request using SIP Identity RFC
4474 for every request? If yes, have folks considered the impact
of requiring the computation and verification of the SIP Identity
field value for every request?
5.3. End-to-End Media Security 5.3. End-to-End Media Security
Media security is critical to guarantee end-to-end confidentiality of Media security is critical to guarantee end-to-end confidentiality of
the communication between the end-users' devices, independently of the communication between the end-users' devices, independently of
how many direct or indirect peers are along the signaling path. how many direct or indirect peers are present along the signaling
path. A number of desirable security properties emerge from this
It is recommended that the establishment of media security be goal.
provided along the media path and not over the signaling path given
the indirect peering use cases.
Notes on the solution space: The establishment of media security may be achieved along the media
Media carried over the Real-Time Protocol (RTP) can be secured using path and not over the signaling path given the indirect peering use
secure RTP or sRTP ([RFC3711]). A framework for establishing sRTP cases.
security using Datagram TLS [RFC4347] is described in For example, media carried over the Real-Time Protocol (RTP) can be
[I-D.ietf-sip-dtls-srtp-framework]: it allows for end-to-end media secured using secure RTP (SRTP [RFC3711]). A framework for
establishing SRTP security using Datagram TLS [RFC4347] is described
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]). This DTLS-SRTP framework meets the above ([I-D.ietf-avt-dtls-srtp]).
requirement. It should also be noted that media can be carried in numerous
protocols other than RTP such as SIP (SIP MESSAGE method), MSRP,
XMPP, etc., over TCP ([RFC4571]), and that it can be encrypted over
secure connection-oriented transport sessions over TLS ([RFC4572]).
Note that media can also be carried in numerous protocols other than A desirable security property for session peering is that SIP
RTP such as SIP (SIP MESSAGE method), MSRP, XMPP, etc. In these entities should not intervene in the Session Description Protocol
cases, it is desirable those those protocols offer data (SDP) exchanges for end-to-end media security.
confidentiality protection at a minimum.
o Requirement #18:
The protocols used to enable session peering MUST NOT interfere
with the exchanges of media security attributes in SDP. Media
attribute lines that are not understood by SBEs MUST be ignored
and passed along the signaling path untouched.
6. Acknowledgments 6. Acknowledgments
This document is a work-in-progress and it is based on the input and This document is based on the input and contributions made by a large
contributions made by a large number of people in the SPEERMINT number of people in the SPEERMINT working group, including: Edwin
working group, including: Edwin Aoki, Scott Brim, John Elwell, Mike Aoki, Scott Brim, John Elwell, Mike Hammer, Avshalom Houri, Richard
Hammer, Avshalom Houri, Richard Shocky, Henry Sinnreich, Richard Shocky, Henry Sinnreich, Richard Stastny, Patrik Faltstrom, Otmar
Stastny, Patrik Faltstrom, Otmar Lendl, Daryl Malas, Dave Meyer, Lendl, Daryl Malas, Dave Meyer, Sriram Parameswar, Jon Peterson,
Sriram Parameswar, Jon Peterson, Jason Livingood, Bob Natale, Benny Jason Livingood, Bob Natale, Benny Rodrig, Brian Rosen, Eric
Rodrig, Brian Rosen, Eric Rosenfeld, Adam Uzelac and Dan Wing. Rosenfeld, Adam Uzelac, and David Schwartz.
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, and 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. requirements and to Dan Wing for providing detailed feedback on the
security consideration sections.
7. IANA Considerations 7. IANA Considerations
This document does not register any values in IANA registries. This document does not register any values in IANA registries.
8. Security Considerations 8. Security Considerations
Securing session peering communications involves numerous protocol Securing session peering communications involves numerous protocol
exchanges, first and foremost, the securing of SIP signaling and exchanges, first and foremost, the securing of SIP signaling and
media sessions. The security considerations contained in [RFC3261], media sessions. The security considerations contained in [RFC3261],
skipping to change at page 17, line 14 skipping to change at page 19, line 14
9. References 9. References
9.1. Normative References 9.1. Normative References
[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.
9.2. Informative References 9.2. Informative References
[I-D.draft-ietf-pmol-sip-perf-metrics] [I-D.ietf-avt-dtls-srtp]
Malas, D., "SIP End-to-End Performance Metrics", McGrew, D. and E. Rescorla, "Datagram Transport Layer
draft-ietf-pmol-sip-perf-metrics-01.txt (work in Security (DTLS) Extension to Establish Keys for Secure
progress), June 2008. Real-time Transport Protocol (SRTP)",
draft-ietf-avt-dtls-srtp-02 (work in progress),
[I-D.draft-niccolini-speermint-voipthreats] February 2008.
Niccolini, S., Chen, E., and J. Seedorf, "VoIP Security
Threats relevant to SPEERMINT",
draft-niccolini-speermint-voipthreats-03.txt (work in
progress), February 2008.
[I-D.houri-speermint-presence-im-requirements] [I-D.ietf-pmol-sip-perf-metrics]
Houri, A., Aoki, E., and S. Parameswar, "Presence and IM Malas, D., "SIP End-to-End Performance Metrics",
Requirements", May 2007. draft-ietf-pmol-sip-perf-metrics-01 (work in progress),
June 2008.
[I-D.ietf-avt-dtls-srtp] [I-D.ietf-sip-connect-reuse]
McGrew, D. and E. Rescorla, "DTLS Extensions to Establish Mahy, R., Gurbani, V., and B. Tate, "Connection Reuse in
Keys for SRTP", draft-ietf-avt-dtls-srtp-02.txt (work in the Session Initiation Protocol (SIP)",
progress), February 2008. draft-ietf-sip-connect-reuse-10 (work in progress),
May 2008.
[I-D.ietf-sip-dtls-srtp-framework] [I-D.ietf-sip-dtls-srtp-framework]
Fischl, J., Tschofenig, H., and E. Rescorla, "DTLS-SRTP Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
Framework", draft-ietf-sip-dtls-srtp-framework-01 (work in for Establishing an SRTP Security Context using DTLS",
progress), February 2008. draft-ietf-sip-dtls-srtp-framework-01 (work in progress),
February 2008.
[I-D.ietf-sip-hitchhikers-guide] [I-D.ietf-sip-hitchhikers-guide]
Rosenberg, J., "A Hitchhikers Guide to the Session Rosenberg, J., "A Hitchhiker's Guide to the Session
Initiation Protocol (SIP)", July 2007. 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 et al., R., "SPEERMINT Peering Architecture", Penno, R., "SPEERMINT Peering Architecture",
draft-ietf-speermint-architecture-06.txt (work in draft-ietf-speermint-architecture-06 (work in progress),
progress), May 2008. May 2008.
[I-D.ietf-speermint-consolidated-presence-im-usecases] [I-D.ietf-speermint-consolidated-presence-im-usecases]
Houri, A., Aoki, E., and S. Parameswar, "Presence & Houri, A., "Presence & Instant Messaging Peering Use
Instant Messaging Peering Use Cases", Cases",
draft-ietf-speermint-consolidated-presence-im-usecases-04 draft-ietf-speermint-consolidated-presence-im-usecases-05
(work in progress), February 2008. (work in progress), July 2008.
[I-D.ietf-speermint-terminology] [I-D.ietf-speermint-terminology]
Meyer, R. and D. Malas, "SPEERMINT Terminology", Malas, D. and D. Meyer, "SPEERMINT Terminology",
draft-ietf-speermint-terminology-16.txt (work in draft-ietf-speermint-terminology-16 (work in progress),
progress), February 2008. February 2008.
[I-D.ietf-speermint-voip-consolidated-usecases] [I-D.ietf-speermint-voip-consolidated-usecases]
Uzelac et al., A., "VoIP SIP Peering Use Cases", Uzelac, A. and Y. Lee, "VoIP SIP Peering Use Cases",
draft-ietf-speermint-voip-consolidated-usecases-08.txt draft-ietf-speermint-voip-consolidated-usecases-08 (work
(work in progress), May 2008. in progress), May 2008.
[I-D.niccolini-speermint-voipthreats]
Niccolini, S., Chen, E., and J. Seedorf, "SPEERMINT
Security BCPs", draft-niccolini-speermint-voipthreats-03
(work in progress), February 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 20, line 5 skipping to change at page 21, line 38
[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.
[RFC4474] Peterson, J. and C. Jennings, "Enhancements for [RFC4474] Peterson, J. and C. Jennings, "Enhancements for
Authenticated Identity Management in the Session Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 4474, August 2006. Initiation Protocol (SIP)", RFC 4474, August 2006.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[RFC4571] Lazzaro, J., "Framing Real-time Transport Protocol (RTP)
and RTP Control Protocol (RTCP) Packets over Connection-
Oriented Transport", RFC 4571, July 2006.
[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572, July 2006.
[RFC4916] Elwell, J., "Connected Identity in the Session Initiation
Protocol (SIP)", RFC 4916, June 2007.
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
parameters 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
aspects 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
traffic with another peer. Some of the session policy parameters may traffic with another peer. Some of the session policy parameters may
be statically exchanged and set throughout the lifetime of the be statically exchanged and set throughout the lifetime of the
peering relationship. Others parameters may be discovered and peering relationship. Others parameters may be discovered and
updated dynamically using by some explicit protocol mechanisms. updated dynamically using by some explicit protocol mechanisms.
These dynamic parameters may also relate to an SSP's session- These dynamic parameters may be session-dependent, or the may apply
dependent or session independent policies as defined in [I-D.ietf- over multiple sessions or peers.
sipping-session-policy].
Various types of policy information may need to be discovered or Various types of policy information may need to be discovered or
exchanged in order to establish session peering. At a minimum, a exchanged in order to establish session peering. At a minimum, a
policy should specify information related to session establishment policy should specify information related to session establishment
data in order to avoid session establishment failures. A policy may data in order to avoid session establishment failures. A policy may
also include information related to QoS, billing and accounting, also include information related to QoS, billing and accounting,
layer-3 related interconnect requirements which are out of the scope layer-3 related interconnect requirements which are out of the scope
of this document. of this document.
Some aspects of session peering policies must be agreed to and Some aspects of session peering policies must be agreed to and
skipping to change at page 20, line 45 skipping to change at page 22, line 44
capabilities, standard ways of expressing those policy parameters may capabilities, standard ways of expressing those policy parameters may
be defined among SSP and exchanged dynamically. For e.g., templates be defined among SSP and exchanged dynamically. For e.g., templates
could be created in various document formats so that it could be could be created in various document formats so that it could be
possible to dynamically discover some of the domain policy. Such possible to dynamically discover some of the domain policy. Such
templates could be initiated by implementers (for each software/ templates could be initiated by implementers (for each software/
hardware release, a list of supported RFCs, RFC parameters is hardware release, a list of supported RFCs, RFC parameters is
provided in a standard format) and then adapted by each SSP based on provided in a standard format) and then adapted by each SSP based on
its service description, server or device configurations and variable its service description, server or device configurations and variable
based on peer relationships. based on peer relationships.
A.1. Categories of Parameters and Justifications A.1. Categories of Parameters for VoIP Session Peering and
Justifications
The following list should be considered as an initial list of The following list should be considered as an initial list of
"discussion topics" to be addressed by peers when initiating a VoIP "discussion topics" to be addressed by peers when initiating a VoIP
peering relationship. peering relationship.
o IP Network Connectivity: o IP Network Connectivity:
Session peers should define how the IP network connectivity Session peers should define how the IP network connectivity
between their respective SBEs and DBEs. While this is out of between their respective SBEs and DBEs. While this is out of
scope of session peering, SSPs must agree on a common mechanism scope of session peering, SSPs must agree on a common mechanism
for IP transport of session signaling and media. This may be for IP transport of session signaling and media. This may be
accomplish via private (e.g. IPVPN, IPsec, etc.) or public IP accomplish via private (e.g. IPVPN, IPsec, etc.) or public IP
networks. networks.
o Media-related Parameters: o Media-related Parameters:
* Media Codecs: list of supported media codecs for audio, real- * Media Codecs: list of supported media codecs for audio, real-
time fax (version of T.38, if applicable), real-time text (RFC time fax (version of T.38, if applicable), real-time text (RFC
4103), DTMF transport, voice band data communications (as 4103), DTMF transport, voice band data communications (as
applicable) along with the supported or recommended codec applicable) along with the supported or recommended codec
packetization rates, level of RTP paylod redundancy, audio packetization rates, level of RTP payload redundancy, audio
volume levels, etc. volume levels, etc.
* Media Transport: level of support for RTP-RTCP [RFC3550], RTP * Media Transport: level of support for RTP-RTCP [RFC3550], RTP
Redundancy (RTP Payload for Redundant Audio Data - [RFC2198]) , Redundancy (RTP Payload for Redundant Audio Data - [RFC2198]) ,
T.38 transport over RTP, etc. T.38 transport over RTP, etc.
* Other: support of the VoIP metric block as defined in RTP * Other: support of the VoIP metric block as defined in RTP
Control Protocol Extended Reports [RFC3611] , etc. Control Protocol Extended Reports [RFC3611] , etc.
o SIP: o SIP:
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(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 [I-D.ietf-sip-hitchhikers-guide].
o Presence and Instant Messaging: TBD
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
skipping to change at page 22, line 22 skipping to change at page 24, line 20
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
Completion Rate (SCR), Session Establishment Rate (SER), etc. Completion Rate (SCR), Session Establishment Rate (SER), etc.
Some SIP end-to-end performance metrics are defined in Some SIP end-to-end performance metrics are defined in
[I-D.draft-ietf-pmol-sip-perf-metrics]; a subset of these may be [I-D.ietf-pmol-sip-perf-metrics]; a subset of these may be
applicable to session peering and interconnects. applicable to session peering and interconnects.
Some media-related metrics for monitoring VoIP calls have been Some media-related metrics for monitoring VoIP calls have been
defined in the VoIP Metrics Report Block, in Section 4.7 of defined in the VoIP Metrics Report Block, in Section 4.7 of
[RFC3611]. [RFC3611].
o Security: o Security:
An SSP should describe the security requirements that other peers An SSP should describe the security requirements that other peers
must meet in order to terminate calls to its network. While such must meet in order to terminate calls to its network. While such
a list of security-related policy parameters often depends on the a list of security-related policy parameters often depends on the
security models pre-agreed to by peers, it is expected that these security models pre-agreed to by peers, it is expected that these
skipping to change at page 22, line 44 skipping to change at page 24, line 42
session peering outside SSP clubs. The list of security session peering outside SSP clubs. The list of security
parameters may be long and composed of high-level requirements parameters may be long and composed of high-level requirements
(e.g. authentication, privacy, secure transport) and low level (e.g. authentication, privacy, secure transport) and low level
protocol configuration elements like TLS parameters. protocol configuration elements like TLS parameters.
The following list is not intended to be complete, it provides a The following list is not intended to be complete, it provides a
preliminary list in the form of examples: preliminary list in the form of examples:
* Call admission requirements: for some providers, sessions can * Call admission requirements: for some providers, sessions can
only be admitted if certain criteria are met. For example, for only be admitted if certain criteria are met. For example, for
some providers' networks, only incoming SIP sessions signaled some providers' networks, only incoming SIP sessions signaled
over established IPSec tunnels or presented to the well-known over established IPsec tunnels or presented to the well-known
TLS ports are admitted. Other call admission requirements may TLS ports are admitted. Other call admission requirements may
be related to some performance metrics as descrived above. be related to some performance metrics as described above.
Finally, it is possible that some requiremetns be imposed on Finally, it is possible that some requirements be imposed on
lower layers, but these are considered out of scope of session lower layers, but these are considered out of scope of session
peering. peering.
* Call authorization requirements and validation: the presence of * Call authorization requirements and validation: the presence of
a caller or user identity may be required by an SSP. Indeed, a caller or user identity may be required by an SSP. Indeed,
some SSPs may further authorize an incoming session request by some SSPs may further authorize an incoming session request by
validating the caller's identity against white/black lists validating the caller's identity against white/black lists
maintained by the service provider or users (traditional caller maintained by the service provider or users (traditional caller
ID screening applications or IM white list). ID screening applications or IM white list).
* Privacy requirements: an SSP may demand that its SIP messages * Privacy requirements: an SSP may demand that its SIP messages
be securely transported by its peers for privacy reasons so be securely transported by its peers for privacy reasons so
that the calling/called party information be protected. Media that the calling/called party information be protected. Media
sessions may also require privacy and some SSP policies may sessions may also require privacy and some SSP policies may
include requirements on the use of secure media transport include requirements on the use of secure media transport
protocols such as sRTP, along with some contraints on the protocols such as SRTP, along with some constraints on the
minimum authentication/encryption options for use in sRTP. minimum authentication/encryption options for use in SRTP.
* Network-layer security parameters: this covers how IPSec * Network-layer security parameters: this covers how IPsec
security associated may be established, the IPSec key exchange security associated may be established, the IPsec key exchange
mechanisms to be used and any keying materials, the lifetime of mechanisms to be used and any keying materials, the lifetime of
timed Security Associated if applicable, etc. timed Security Associated if applicable, etc.
* Transport-layer security parameters: this covers how TLS * Transport-layer security parameters: this covers how TLS
connections should be established as described in Section connections should be established as described in Section
Section 5. Section 5.
A.2. Summary of Parameters for Consideration in Session Peering A.2. Summary of Parameters for Consideration in Session Peering
Policies Policies
skipping to change at page 24, line 4 skipping to change at page 25, line 48
* Codecs for audio, video, real time text, instant messaging * Codecs for audio, video, real time text, instant messaging
media sessions media sessions
* Modes of communications for audio (voice, fax, DTMF), IM (page * Modes of communications for audio (voice, fax, DTMF), IM (page
mode, MSRP) mode, MSRP)
* Media transport and means to establish secure media sessions * Media transport and means to establish secure media sessions
* List of ingress and egress DBEs where applicable, including * List of ingress and egress DBEs where applicable, including
STUN Relay servers if present STUN Relay servers if present
o SIP
o SIP
* SIP RFCs, methods and error responses * SIP RFCs, methods and error responses
* headers and header values * headers and header values
* possibly, list of SIP RFCs supported by groups (e.g. by call * possibly, list of SIP RFCs supported by groups (e.g. by call
feature) feature)
o Accounting o Accounting
o Capacity Control and Performance Management: any limits on, or, o Capacity Control and Performance Management: any limits on, or,
skipping to change at page 26, line 44 skipping to change at line 1003
attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at
ietf-ipr@ietf.org. ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
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