draft-ietf-speermint-requirements-04.txt   draft-ietf-speermint-requirements-05.txt 
SPEERMINT Working Group J-F. Mule SPEERMINT Working Group J-F. Mule
Internet-Draft CableLabs Internet-Draft CableLabs
Intended status: Informational February 25, 2008 Intended status: Informational June 27, 2008
Expires: August 28, 2008 Expires: December 29, 2008
SPEERMINT Requirements for SIP-based VoIP Interconnection SPEERMINT Requirements for SIP-based Session Peering
draft-ietf-speermint-requirements-04.txt draft-ietf-speermint-requirements-05.txt
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2008). Copyright (C) The IETF Trust (2008).
Abstract Abstract
A number of use cases have been described for session peering of This memo captures protocol requirements identified for enabling
voice, presence, instant messaging and other types of multimedia session peering of voice, presence, instant messaging and other types
traffic. This memo captures some of the requirements identified by of multimedia traffic. It is an informational document linking the
these use case scenarios. It is intended to become an informational session peering use cases to protocol solutions.
document linking the use cases to potential 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. Session Peering Points . . . . . . . . . . . . . . . . . . 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
3.4. Other Considerations . . . . . . . . . . . . . . . . . . . 10
4. Considerations and Requirements for Session Peering of 4. Considerations and Requirements for Session Peering of
Presence and Instant Messaging . . . . . . . . . . . . . . . . 12 Presence and Instant Messaging . . . . . . . . . . . . . . . . 10
5. Security Requirements . . . . . . . . . . . . . . . . . . . . 14 5. Security Requirements . . . . . . . . . . . . . . . . . . . . 12
5.1. Security in SIP networks in the context of session 5.1. Security Properties for the Acquisition of Session
peering . . . . . . . . . . . . . . . . . . . . . . . . . 14 Establishment Data . . . . . . . . . . . . . . . . . . . . 12
5.2. Security Requirements for the Lookup and Location 5.2. Security Properties for the SIP exchanges . . . . . . . . 13
Routing Data . . . . . . . . . . . . . . . . . . . . . . . 14 5.3. End-to-End Media Security . . . . . . . . . . . . . . . . 13
5.3. Hop-by-hop Security for SIP Signaling and TLS 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
Considerations . . . . . . . . . . . . . . . . . . . . . . 15 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
5.4. End-to-End Media Security . . . . . . . . . . . . . . . . 16 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 9.1. Normative References . . . . . . . . . . . . . . . . . . . 17
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 9.2. Informative References . . . . . . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Appendix A. Policy Parameters for Session Peering . . . . . . . . 20
9.1. Normative References . . . . . . . . . . . . . . . . . . . 20 A.1. Categories of Parameters and Justifications . . . . . . . 20
9.2. Informative References . . . . . . . . . . . . . . . . . . 20
Appendix A. Policy Parameters for Session Peering . . . . . . . . 23
A.1. Categories of Parameters and Justifications . . . . . . . 23
A.2. Summary of Parameters for Consideration in Session A.2. Summary of Parameters for Consideration in Session
Peering Policies . . . . . . . . . . . . . . . . . . . . . 26 Peering Policies . . . . . . . . . . . . . . . . . . . . . 23
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 27 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 25
Intellectual Property and Copyright Statements . . . . . . . . . . 28 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 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.
Common terminology for SIP session peering is defined Common terminology for SIP session peering is defined in
([I-D.ietf-speermint-terminology]) and a reference architecture is [I-D.ietf-speermint-terminology] and a reference architecture is
described in [I-D.ietf-speermint-architecture]. A number of use described in [I-D.ietf-speermint-architecture]. A number of use
cases have been exposed by users of SIP services and various other cases describe how session peering has been or could be deployed
actors describing how layer-5 peering has been or could be deployed
based on the 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 an intermediary (indirect peering via a third- indirect basis via a session intermediary (indirect peering via a
party SSP that has a trust relationship with the SSPs) - see the third-party SSP that has a trust relationship with the SSPs) - see
terminology document for more details. the terminology document for more details.
This document first describes general requirements that have been This document first describes general requirements. The use cases
derived from the working group discussions. The use cases are then are then analyzed in the spirit of extracting relevant protocol
analyzed in the spirit of extracting relevant protocol requirements requirements that must be met to accomplish the use cases. These
that must be met to accomplish the use cases. These requirements are requirements are intended to be independent of the type of media
intended to be independent of the type of media exchanged such as exchanged such as Voice over IP (VoIP), video telephony, and instant
Voice over IP (VoIP), video telephony, and instant messaging. In the messaging. Media-specific requirements are defined in separate
case where some requirements are media-specific, we define them in a sections.
separate section.
It is not the goal of this document to mandate any particular use of It is not the goal of this document to mandate any particular use of
IETF protocols by SIP Service Providers in order to establish session IETF protocols by SIP Service Providers in order to establish session
peering. Instead, the document highlights what requirements should peering. Instead, the document highlights what requirements should
be met and what protocols may be used to define the solution space. be met and what protocols may be used to define the solution space.
Finally, we conclude with a list of parameters for the definition of Finally, we conclude with a list of parameters for the definition of
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 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
NOT","SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
this document are to be interpreted as described in RFC 2119 document are to be interpreted as described in [RFC2119].
[RFC2119].
This document also reuses the SIP 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].
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
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reach a successful agreement but they are considered out of scope of reach a successful agreement but they are considered out of scope of
the SPEERMINT working group. They include aspects such as SIP the SPEERMINT working group. They include aspects such as SIP
protocol support (e.g. SIP extensions and field conventions), media protocol support (e.g. SIP extensions and field conventions), media
(e.g., type of media traffic to be exchanged, compatible media codecs (e.g., type of media traffic to be exchanged, compatible media codecs
and media transport protocols, mechanisms to ensure differentiated and media transport protocols, mechanisms to ensure differentiated
quality of service for media), SIP layer-3 IP connectivity between quality of service for media), SIP layer-3 IP connectivity between
the Signaling Path and Data Path Border Elements, traffic capacity the Signaling Path and Data Path Border Elements, traffic capacity
control (e.g. maximum number of SIP sessions at each ingress point, control (e.g. maximum number of SIP sessions at each ingress point,
maximum number of concurrent IM or VoIP sessions), and accounting. maximum number of concurrent IM or VoIP sessions), and accounting.
The informative Appendix A lists parameters that SPPs may consider The informative Appendix A lists parameters that may considered when
when discussing the technical aspects of SIP session peering. The discussing the technical aspects of SIP session peering. The purpose
purpose of this list which has evolved through the working group use of this list which has evolved through the working group use case
case discussions 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. Session Peering Points 3.2. Border Elements
For session peering to be scalable and operationally manageable, For border elements to be operationally manageable, maximum
maximum flexibility should be given for how signaling path and media flexibility should be given for how border elements are declared or
path border elements are declared, dynamically advertised and dynamically advertised.
updated.
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 media or data path border that will face the peer's network. The data path border elements are
elements are typically signaled dynamically in the session typically signaled dynamically in the session description.
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
session peering points between SIP Service Providers; they include border elements between SIP Service Providers; they include Signaling
Signaling Path Border Elements (SBEs) and SIP proxies (or any SIP Path Border Elements (SBEs) and SIP proxies (or any SIP entity at the
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 (SSP) 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 seems to
be general agreement that [RFC3263] provides a solution for be general agreement that [RFC3263] provides a solution for
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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 should exist for a SIP Service Provider (SSP)
to communicate the egress SBEs of its service domain. 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. Note that this may not be it will generate SIP calls from. The SSP accepting calls from a
applicable to all types of session peering (voice may be a peer may wish to know where SIP calls will originate from (this
particular case where this is needed -- at least based on current information is typically used by the terminating SSP).
practices). 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,
some SSPs may find use for a mechanism to dynamically advertise or
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 media border elements should exist to allow SSPs to advertise their egress and ingress data
responsible for egress and ingress data path border elements (DBEs), path border elements (DBEs), if applicable. While some SSPs may have
if applicable. While some SPPs may have open policies and accept open policies and accept media traffic from anywhere outside their
media traffic from anywhere outside their network to anywhere inside network to anywhere inside their network, some SSPs may want to
their network, some SSPs may want to optimize media delivery and optimize media delivery and identify media paths between peers prior
identify media paths between peers prior to traffic being sent (layer to traffic being sent (layer 5 to layer 3 QoS mapping).
5 to layer 3 QoS mapping).
o Requirement #3: o Requirement #3:
Protocol mechanisms should be available to allow a SIP Service Protocol mechanisms should be available 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 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 and media 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?
For advertising media-dependent SBEs, solutions exist as long as
URIs are protocol-dependent URIs. A protocol-dependent URI like a
SIP URI can be mapped to more than one types of media. It should
be noted that some URIs like the IM URI are abstract ([RFC3428])
and need to be translated to protocol dependent URIs. It is also
not possible to know what media is supported by the SIP SBE before
initiating a query by using mechanisms like [RFC3263].
The following example provides some additional motivations for the
above requirement on advertising media-dependent SBEs to peers.
In large multi-service SIP networks, an SSP chooses to have several
SBEs for receiving incoming SIP session requests (ingress SBEs), and
several SBEs for outgoing SIP session requests (egress SBEs). In
order to facilitate the operations, feature management, and
maintenance of its SBEs, the SSP opts for having distinct SBEs for
voice, real-time collaboration, etc. Some SBEs are therefore
dedicated to exchanging certain types of media traffic due to
specific SIP extensions required for certain media types (e.g.
SIMPLE, the SIP MESSAGE Method for Instant Messaging [RFC3428] or the
Message Sessions Relay Protocol (MSRP)). Note that this example is
applicable to some enterprise networks where IP voice traffic hits
different SIP gateways and voice servers (e.g. IP-PBX) than Instant
Messaging and real-time collaboration servers (e.g. real-time
collaboration and IM server supporting SIMPLE and XMPP).
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
Proxies and Signaling path Border Elements. Proxies and Signaling path Border Elements.
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. For example, in entity must use based on a given peer destination. For example, in
the case of an indirect peering scenario (section 5.1.5 of the case of an indirect peering scenario (section 5.1.5 of
[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)
or Location Routing Function (LRF) - message response labeled (3). and/or Location Routing Function (LRF) - message response labeled
Note that this example also applies to the case of Direct Peering (3). Note that this example also applies to the case of Direct
when a service provider has multiple service areas and each service Peering when a service provider has multiple service areas and each
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 service must be capable or returning both a target URI destination
and a SIP Route. 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:
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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.
3.4. Other Considerations
The considerations listed below were gathered early on in the
SPEERMINT working group as part of discussions to define the scope of
the working group. They have not been updated in this revision of
the draft.
o It is assumed that session peering is independent of lower layers.
The mechanisms used to establish session peering should
accommodate diverse supporting lower layers. It should not matter
whether lower layers rely on the public Internet or are
implemented by private L3 connectivity, using firewalls or L2/L3
Virtual Private Networks (VPNs), IPSec tunnels or Transport Layer
Security (TLS) connections [RFC3546]...
o Session Peering Policies and Extensibility:
Mechanisms developed for session peering should be flexible and
extensible to cover existing and future session peering models.
It is also recommended that SSP policies be published via local
configuration choices in a distributed system like DNS rather than
in a centralized system like a 'peering registry'.
In the context of session peering, a policy is defined as the set
of parameters and other information needed by an SPP to connect to
another. Some of the session policy parameters may be statically
exchanged and set throughout the lifetime of the peering
relationship. Others parameters may be discovered and updated
dynamically using by some explicit protocol mechanisms. These
dynamic parameters may also relate to an SSP's session-dependent
or session independent policies as defined in
[I-D.ietf-sipping-session-policy].
o Administrative and Technical Policies:
Various types of policy information may need to be discovered or
exchanged in order to establish session peering. At a minimum, a
policy should specify information related to session establishment
data in order to avoid session establishment failures. A policy
may also include information related to QoS, billing and
accounting, layer-3 related interconnect requirements which are
out of the scope of this document, see examples in Section
Appendix A.
Motivations:
The reasons for declining or accepting incoming calls from a
prospective peering partner can be both administrative
(contractual, legal, commercial, or business decisions) and
technical (certain QoS parameters, TLS keys, domain keys, ...).
The objectives are to provide a baseline framework to define,
publish and optionally retrieve policy information so that a
session establishment does not need to be attempted to know that
incompatible policy parameters will cause the session to fail
(this was originally referred to as "no blocked calls").
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.
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for different properties that exist in PIDF. For example "Do Not for different properties that exist in PIDF. For example "Do Not
Disturb" may be translated to "Busy" in another system. In order Disturb" may be translated to "Busy" in another system. In order
to make sure that the meaning of the status is preserved, there is to make sure that the meaning of the status is preserved, there is
a need that either each system will translate its internal a need that either each system will translate its internal
statuses to standard PIDF based statuses of a translation table of statuses to standard PIDF based statuses of a translation table of
proprietary statuses to standard based PIDF statuses will be proprietary statuses to standard based PIDF statuses will be
provided from one system to the other. provided from one system to the other.
5. Security Requirements 5. Security Requirements
Session peering does bring a new environment in which security This section describes the security properties that are desirable for
requirements should be analyzed but the fundamental mechanisms for the protocol exchanges in scope of session peering. Three types of
securing SIP and media exchanges remain applicable (see Section 26.2 information flows are described in the architecture and use case
of [RFC3261]. The issues are less in the mechanisms that do exist documents: the acquisition of the Session Establishment Data (SED)
and can be used to mitigate threats than they are in getting two SSPs based on a destination target via the Lookup and Location Routing
to agree on which ones to use. Functions (LUF and LRF), the SIP signaling between SIP Service
Providers, and the associated media exchanges.
This section first provides a broad picture of the various mechanisms
used today in the context of SIP session peering. We then describe
security considerations for the three types of information flows
described in the use cases: the data queried from the Lookup or
Location Routing Functions, data exchanged in the SIP signaling
between SSPs (directly and indirectly), and media.
5.1. Security in SIP networks in the context of session peering
In today's SIP deployments, various approaches exist to secure This section is focused on three security services, authentication,
exchanges between SIP Service Providers. Lookup, signaling and media data confidentiality and data integrity as summarized in [RFC3365].
security are the three primary topics for consideration in most However, this text does not specify the mandatory-to-implement
deployments. security mechanisms as required by [RFC3365]; this is left for future
A number of transport, network and session-level mechanisms are used protocol solutions that meet the requirements.
for SIP by some categories of SSPs. TLS is used in the enterprise
networks for applications such as VoIP and secure Instant Messaging
and session-level security is used end-to-end for some instant
messaging systems or in service provider networks for Instant
Messaging and presence applications. At the network-level, IPsec and
L2/L3 VPNs are widely used in some SSP networks where there is a
desire to secure all signaling and media traffic at or below the IP
layer.
Media level security between providers is not widely used today for
media transported using the Real-Time Protocol (RTP), even though it
is in use in few deployments where the privacy of voice and other RTP
media is critical.
A security threat analysis provides guidance for session peering A security threat analysis provides guidance for session peering
([I-D.draft-niccolini-speermint-voipthreats]). More discussions ([I-D.draft-niccolini-speermint-voipthreats]).
based on this threat analysis and use cases continue to be required
in the working group to define what hop-by-hop or end-to-end security
requirements are necessary in the context of session peering.
5.2. Security Requirements for the Lookup and Location Routing Data 5.1. Security Properties for the Acquisition of Session Establishment
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 a defined in [I-D.ietf-speermint-terminology]. They provide mechanisms
mechanism for determining for a given request the target domain to for determining the SIP target address and domain the request should
which the request should be routed, and SED required to route the be sent to, and the associated SED to route the request to that
request to that domain. domain.
Requirement #15:
The protocols used for the LUF and LRF must allow the look-up and SED
data to be exchanged securely (authentication and encryption services
should be provided).
Notes on the solution space: ENUM, SIP and proprietary protocols are
typically used today for accessing these functions.
5.3. Hop-by-hop Security for SIP Signaling and TLS Considerations
Given the direct and indirect peering uses cases referenced in the
previous sections of this document, hop-by-hop security between two
SSPs using Transport Layer Security (TLS) is desirable.
The Transport Layer Security (TLS) is a standard way to secure
signaling between SIP entities. TLS can be used in direct peering to
mutually authenticate SSPs and provide message confidentiality and
integrity protection. The remaining paragraphs explore how TLS could
be deployed and used between 2 SSPs to secure SIP exchanges. The
intent is to capture what two SSPs should discuss and agree on in
order to establish TLS connections for SIP session peering.
1. One or more Certificate Authorities (CAs) should be agreed A mutual authentication service is desirable for the LUF and LRF
between SSPs for securing session peering exchanges. protocol exchanges. The response from the LUF and LRF may depend on
Alternatively, self-signed certificates may also be used. the identity of the requestor: the authentication of the LUF/LRF
requests is therefore a desirable property. Mutual authentication is
also desirable: the requestor may verify the identity of the systems
that provided the LUF/LRF responses given the nature of the data
returned in those responses. Authentication also provides some
protection for the availability of the LUF and LRF against attackers
that would attempt to launch DoS attacks by sending bogus requests
causing the LUF to perform a lookup and consume resources.
Motivations: Given the sensitive nature of the session establishment data
An SSP should have control over which root CAs it trusts for SIP exchanged with the LUF and LRF functions, the protocol mechanisms
communications. This may imply creating a certificate trust list chosen for the lookup and location routing should offer data
and including the peer's CA for each authorized domain. In the confidentiality and integrity protection (SED data may contain user
case of a federation, this requirement allows for the initiating addresses, SIP URI, location of SIP entities at the boundaries of SIP
side to verify that the server certificate chains up to a trusted Service Provider domains, etc.).
root CA. This also means that SIP servers should allow the
configuration of a certificate trust list in order to allow an SSP
to control which peer's CAs are trusted for TLS connections. Note
that these considerations seem to be around two themes: one is
trusting a root, the other is trusting intermediate CAs.
There are various use cases of direct peering where there is no
pre-established trust relationship that can rely on self-signed
certificates.
2. Peers should indicate whether their domain policies require Requirement #15:
proxy servers to inspect and verify the identity provided in SIP The data exchanges for the lookup and location routing MUST support
requests as defined in [RFC4474]. Federations supporting mutual authentication, data confidentiality and integrity.
[RFC4474] and CA(s) must specify the CA(s) permitted to issue
certificates of the authentication service.
3. SIP entities and SBEs involved in the secure session Notes on the solution space: ENUM, SIP and proprietary protocols are
establishment over TLS must have valid X.509 certificates and must typically used today for accessing these functions. SSPs may use
be able to receive a TLS connection on a well-known port as lower layer security mechanisms to guarantee some of those security
defined in [RFC3261]. properties.
4. The following SIP and TLS protocol parameters should be agreed 5.2. Security Properties for the SIP exchanges
upon as part of session peering policies: the version of TLS
supported by SIP entities and SBEs (TLSv1, TLSv1.1), the SIP TLS
port (default 5061), the server-side session timeout (default 300
seconds), the list of supported or recommended ciphersuites, the
list of trusted root CAs if applicable or whether self-signed
certs are acceptable.
5. SIP entities and SBEs involved in the session establishment The fundamental mechanisms for securing SIP are applicable (see
over TLS must verify and validate the client certificates. See Section 26.2 of [RFC3261], and [RFC4474]).
section 9 and 9.3 of [I-D.ietf-sip-certs].
6. A session peering policy should include details on SIP session Authentication of SIP communications are desirable, especially in the
establishment over TLS if TLS is supported. context of session peering involving SIP intermediaries. Data
confidentiality and integrity of the SIP message body may be
desirable given some of the levels of session peering indirection
(indirect/assisted peering), but they could be harmful as they may
prevent intermediary SSPs from "inserting" SBEs/DBEs along the
signaling and data paths.
5.4. 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 along the signaling path.
o Requirement #16:
It is recommended that the establishment of media security be It is recommended that the establishment of media security be
provided along the media path and not over the signaling path provided along the media path and not over the signaling path given
given the indirect peering use cases. the indirect peering use cases.
Notes on the solution space: Notes on the solution space:
Media carried over the Real-Time Protocol (RTP) can be secured Media carried over the Real-Time Protocol (RTP) can be secured using
using secure RTP or sRTP ([RFC3711]). A framework for secure RTP or sRTP ([RFC3711]). A framework for establishing sRTP
establishing sRTP security using Datagram TLS [RFC4347] is security using Datagram TLS [RFC4347] is described in
described in [I-D.ietf-sip-dtls-srtp-framework]: it allows for [I-D.ietf-sip-dtls-srtp-framework]: it allows for end-to-end media
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 ([I-D.ietf-avt-dtls-srtp]). This DTLS-SRTP framework meets the above
above requirement. requirement.
Note that media can also be carried in numerous protocols other than Note that media can also be carried in numerous protocols other than
RTP such as SIP (SIP MESSAGE method), MSRP, XMPP, etc. In these RTP such as SIP (SIP MESSAGE method), MSRP, XMPP, etc. In these
cases, the above requirement is also met given the security features cases, it is desirable those those protocols offer data
of these protocols. confidentiality protection at a minimum.
6. Acknowledgments 6. Acknowledgments
This document is a work-in-progress and it is based on the input and This document is a work-in-progress and it is based on the input and
contributions made by a large number of people in the SPEERMINT contributions made by a large number of people in the SPEERMINT
working group, including: Edwin Aoki, Scott Brim, John Elwell, Mike working group, including: Edwin Aoki, Scott Brim, John Elwell, Mike
Hammer, Avshalom Houri, Richard Shocky, Henry Sinnreich, Richard Hammer, Avshalom Houri, Richard Shocky, Henry Sinnreich, Richard
Stastny, Patrik Faltstrom, Otmar Lendl, Daryl Malas, Dave Meyer, Stastny, Patrik Faltstrom, Otmar Lendl, Daryl Malas, Dave Meyer,
Sriram Parameswar, Jon Peterson, Jason Livingood, Bob Natale, Benny Sriram Parameswar, Jon Peterson, Jason Livingood, Bob Natale, Benny
Rodrig, Brian Rosen, Eric Rosenfeld, Adam Uzelac and Dan Wing. Rodrig, Brian Rosen, Eric Rosenfeld, Adam Uzelac and Dan Wing.
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, and 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.
7. IANA Considerations 7. IANA Considerations
None. 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],
and [RFC4474] are applicable to the SIP protocol exchanges. A number and [RFC4474] are applicable to the SIP protocol exchanges. A number
of security considerations are also described in Section Section 5. of security considerations are also described in Section Section 5.
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-malas-performance-metrics] [I-D.draft-ietf-pmol-sip-perf-metrics]
Malas, D., "SIP End-to-End Performance Metrics", Malas, D., "SIP End-to-End Performance Metrics",
December 2007. draft-ietf-pmol-sip-perf-metrics-01.txt (work in
progress), June 2008.
[I-D.draft-niccolini-speermint-voipthreats] [I-D.draft-niccolini-speermint-voipthreats]
Niccolini, S., Chen, E., and J. Seedorf, "VoIP Security Niccolini, S., Chen, E., and J. Seedorf, "VoIP Security
Threats relevant to SPEERMINT", Threats relevant to SPEERMINT",
draft-niccolini-speermint-voipthreats-03.txt (work in draft-niccolini-speermint-voipthreats-03.txt (work in
progress), February 2008. progress), February 2008.
[I-D.houri-speermint-presence-im-requirements] [I-D.houri-speermint-presence-im-requirements]
Houri, A., Aoki, E., and S. Parameswar, "Presence and IM Houri, A., Aoki, E., and S. Parameswar, "Presence and IM
Requirements", May 2007. Requirements", May 2007.
[I-D.ietf-avt-dtls-srtp] [I-D.ietf-avt-dtls-srtp]
McGrew, D. and E. Rescorla, "DTLS Extensions to Establish McGrew, D. and E. Rescorla, "DTLS Extensions to Establish
Keys for SRTP", draft-ietf-avt-dtls-srtp-01.txt (work in Keys for SRTP", draft-ietf-avt-dtls-srtp-02.txt (work in
progress), November 2007. progress), February 2008.
[I-D.ietf-sip-certs]
Jennings, C., Peterson, J., and J. Fischl, "Certificate
Management Service for The Session Initiation Protocol
(SIP)", draft-ietf-sip-certs-05.txt (work in progress),
January 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, "DTLS-SRTP
Framework", draft-ietf-sip-dtls-srtp-framework-01 (work in Framework", draft-ietf-sip-dtls-srtp-framework-01 (work in
progress), February 2008. 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 Hitchhikers Guide to the Session
Initiation Protocol (SIP)", July 2007. Initiation Protocol (SIP)", July 2007.
[I-D.ietf-sipping-session-policy]
Hilt, V. and G. Camarillo, "A Session Initiation Protocol
(SIP) Event Package for Session-Specific Session
Policies", draft-ietf-sipping-policy-package-04.txt (work
in progress), August 2007.
[I-D.ietf-speermint-architecture] [I-D.ietf-speermint-architecture]
Penno et al., R., "SPEERMINT Peering Architecture", Penno et al., R., "SPEERMINT Peering Architecture",
draft-ietf-speermint-architecture-04.txt (work in draft-ietf-speermint-architecture-06.txt (work in
progress), August 2007. progress), 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., Aoki, E., and S. Parameswar, "Presence &
Instant Messaging Peering Use Cases", Instant Messaging Peering Use Cases",
draft-ietf-speermint-consolidated-presence-im-usecases-04 draft-ietf-speermint-consolidated-presence-im-usecases-04
(work in progress), February 2008. (work in progress), February 2008.
[I-D.ietf-speermint-terminology] [I-D.ietf-speermint-terminology]
Meyer, R. and D. Malas, "SPEERMINT Terminology", Meyer, R. and D. Malas, "SPEERMINT Terminology",
draft-ietf-speermint-terminology-16.txt (work in draft-ietf-speermint-terminology-16.txt (work in
progress), February 2008. progress), 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 et al., A., "VoIP SIP Peering Use Cases",
draft-ietf-speermint-voip-consolidated-usecases-05.txt draft-ietf-speermint-voip-consolidated-usecases-08.txt
(work in progress), February 2008. (work in progress), May 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.
[RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation [RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation
Protocol (SIP): Locating SIP Servers", RFC 3263, Protocol (SIP): Locating SIP Servers", RFC 3263,
June 2002. June 2002.
[RFC3428] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C., [RFC3365] Schiller, J., "Strong Security Requirements for Internet
and D. Gurle, "Session Initiation Protocol (SIP) Extension Engineering Task Force Standard Protocols", BCP 61,
for Instant Messaging", RFC 3428, December 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.
[RFC3546] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
and T. Wright, "Transport Layer Security (TLS)
Extensions", RFC 3546, June 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 [RFC3603] Marshall, W. and F. Andreasen, "Private Session Initiation
Protocol (SIP) Proxy-to-Proxy Extensions for Supporting Protocol (SIP) Proxy-to-Proxy Extensions for Supporting
the PacketCable Distributed Call Signaling Architecture", the PacketCable Distributed Call Signaling Architecture",
RFC 3603, October 2003. RFC 3603, October 2003.
[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
skipping to change at page 23, line 8 skipping to change at page 20, line 8
[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.
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 first considered by implementers when deciding what should be considered by implementers when deciding what configuration
configuration parameters to expose to system admins or management parameters to expose to system administrators or management stations,
stations, and second, by SSPs or federations of SSPs when discussing as well as SSPs or federations of SSPs when discussing the technical
the technical aspects of a session peering policy. aspects of a session peering policy.
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
traffic with another peer. Some of the session policy parameters may
be statically exchanged and set throughout the lifetime of the
peering relationship. Others parameters may be discovered and
updated dynamically using by some explicit protocol mechanisms.
These dynamic parameters may also relate to an SSP's session-
dependent or session independent policies as defined in [I-D.ietf-
sipping-session-policy].
Various types of policy information may need to be discovered or
exchanged in order to establish session peering. At a minimum, a
policy should specify information related to session establishment
data in order to avoid session establishment failures. A policy may
also include information related to QoS, billing and accounting,
layer-3 related interconnect requirements which are out of the scope
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
manually implemented; they are static and are typically documented as manually implemented; they are static and are typically documented as
part of a business contract, technical document or agreement between part of a business contract, technical document or agreement between
parties. For some parameters linked to protocol support and parties. For some parameters linked to protocol support and
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/
skipping to change at page 24, line 50 skipping to change at page 22, line 22
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-malas-performance-metrics]; a subset of these may be [I-D.draft-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
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