One document matched: draft-ietf-speermint-voip-consolidated-usecases-02.txt
Differences from draft-ietf-speermint-voip-consolidated-usecases-01.txt
Internet Draft A.Uzelac
SPEERMINT Global Crossing
Intended status: Standards Track Y.Lee
Expires: Dec 2007 Comcast
D.Schwartz
Kayote Networks
E. Katz
Xconnect
O.Lendl
enum.at
R.Mahy
Plantronics
June 8, 2007
VoIP SIP Peering Use Cases
draft-ietf-speermint-voip-consolidated-usecases-02.txt
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Copyright (C) The IETF Trust (2007)
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Abstract
This document will capture VoIP use case for SIP Peering. It is a
consolidation of Speermint use cases drafts.
Table of Contents
1. Introduction...................................................3
2. Terminology....................................................3
3. Use Cases......................................................6
3.1. Direct Use Cases..........................................7
3.1.1. Minimalist Direct.......................................7
3.1.1.1. Administrative characteristics........................8
3.1.2. Direct with one SBE.....................................8
3.1.2.1. Options and Nuances...................................9
3.1.2.2. Administrative characteristics........................9
3.1.3. Direct with two SBEs....................................9
3.1.3.1. Options and Nuances..................................10
3.1.3.2. Administrative characteristics.......................11
3.2. Indirect.................................................11
3.2.1. Transit PSP............................................11
3.2.1.1. Administrative Characteristics.......................12
3.3. Assisted.................................................13
3.3.1. Assisted PSP...........................................13
4. Federations...................................................14
4.1. Federation Considerations................................15
4.2. Federation Examples......................................16
4.2.1. Trivial Federations....................................16
4.2.2. Access List based......................................17
4.2.3. TLS based Federations..................................17
4.2.4. Central SIP Proxy......................................17
4.2.4.1. Architecture, scalability and business scalability...18
4.2.5. Private Layer 3 Network................................18
4.2.6. Peer to Peer SIP.......................................18
4.2.7. DUNDi..................................................19
5. Security Considerations.......................................19
6. IANA Considerations...........................................19
References.......................................................20
Normative References..........................................20
Informative References........................................21
Author's Addresses............................................21
Full Copyright Statement......................................22
Intellectual Property.........................................22
Acknowledgment................................................22
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1. Introduction
This document attempts to capture VoIP use cases for Session
Initiation Protocol (SIP)[1] based peering. These use cases will
assist in identifying requirements for VoIP Peering using SIP and
provide a perspective on future specifications.
Only use cases related to VoIP are considered in this document.
Other real-time SIP communications use cases, like Instant Messaging
(IM) and presence are out of scope for this document. In describing
use cases, the intent is descriptive, not prescriptive.
There are existing documents [2][3][4][5][6] that have captured use
case scenarios. This draft draws from those documents. The document
contains three categories of use cases; Direct, Indirect and
Assisted. The use cases contained in this document attempts to be as
comprehensive as possible, but should not be considered complete.
2. Terminology
The terminology for this draft will draw from the Speermint
terminology draft. [15]
o Direct Peering: Direct peering describes those cases in which two
service providers interconnect without using an intervening layer
5 network. This peering model can also be considered a bi-
lateral relationship historically.
o Indirect Peering: Indirect, or Transit peering refers to the
establishment of a secure signaling and bearer path via one (or
more) referral or transit network(s).
o Assisted Peering: In this case, some entity employs a central SIP
proxy (which is not itself a VSP) to facilitate direct calls
between participating networks.
o Federations: A federation is a group of SPs which agree to receive
calls from each other. A Federation may use a Peering Service
Provider, (in any modes Direct, Indirect, Assisted) to facilitate
some or all of the Assisted Peering services.
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o Voice Service Provider (VSP): A Voice Service Provider (or VSP) is
an entity that provides transport of SIP signaling to its
customers. In the event that the VSP is also an SP, it may also
provide media streams to its customers. Such a service provider
may additionally be interconnected with other service providers;
that is, it may "peer" with other service providers. A VSP may
also interconnect with the PSTN.
o Originating VSP (O-VSP): A VSP where the calling party resides.
The O-VSP is in the Originating Domain, and/or defines the
Originating Domain.
o Terminating VSP (T-VSP): A VSP of the called party. The T-VSP is
in the Terminating Domain, and/or defines the Originating Domain.
o Peering Service Provider (PSP): A logical entity providing peering
functions.
o Direct PSP (D-PSP): PSP providing location function or service
enabling direct peering relationship.
o Assisting PSP (A-PSP): An Assisting VSP is some entity that
employs a central SIP proxy (which is not itself a VSP) to bridge
calls between participating networks.
o Signaling Border Element (SBE): A signaling border element (SBE)
[15] provides signaling-related functions. A SBE is frequently
deployed on a domain's border as a B2BUA.
o Originating SBE (O-SBE): SBE in originating domain.
o Terminating SBE (T-SBE): SBE in terminating domain.
o Transit SBE (t-SBE): SBE in the transit domain.
o Assisted SBE (A-SBE): SBE in Assisted domain.
o Data Path Border Element: A data path border element (DBE) [15]
provides media-related functions such as deep packet inspection
and modification, media relay, and firewall support under SBE
control. As was the case with the SBE, a DBE is frequently
deployed on a domain's border.
o Originating DBE (O-DBE): The DBE connects to the terminating DBE.
o Terminating DBE (T-DBE): The DBE connects to the originating DBE.
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o Transit DBE (t-DBE): The DBE that is located in the transit
domain. This is NOT to be confused with the T-DBE of the
terminating domain.
o Location Server (LS): A server called upon by O-VSP, either Local
or Remote, to translate an E.164 number into a SIP URI. The O-
VSP's client may call the Location Function using ENUM
Query/Response, SIP Invite/Redirect, or other method depending on
O-VSP's infrastructure and methods available for the data being
interrogated, with the response format being appropriate to the
Query format. In the case of an ENUM Query, the response should
be a NAPTR record containing the sip URI that can be resolved by
the client. In the case of a SIP Invite/Redirect, the response
should be a SIP Redirect (30X) message containing the URI.
o Session Manager (SM): A SM is the entity responsible for sending
and receiving the SIP messages from or to Signaling Path Border
Element (SBE). It is also responsible for locating the user home
proxy. SM is logical, it MAY contain one functional entity or
multiple functional entities.
o Originating SM (O-SM): The SM originates the call. In this
context, it is Alice's SM.
o Terminating SM (T-SM): The SM terminates the call. In this
context, it is Bob's SM.
o Transit SM (t-SM): The SM of the transit domain.
o User Endpoint (UE): User Endpoint is the client that makes or
receives calls. UE can be sip based or non-sip based. For non-sip
based UE, SM acts as a signaling gateway and translates the non-
sip signaling to sip signaling before sending to SBE.
o Originating UE (O-UE): Alice's UE.
o Terminating UE (T-UE): Bob's UE.
o Federations: A federation is a group of VSPs which agree to
receive calls from each other using pre-agreed technical and
administrative procedures.
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+-------------+-------------------------------------+------------+
| \ Transit Domain / |
| \ / |
| \ +------+ +------+ / |
| \ + t-LS + + t-SM | / |
| \ +------+ +-----++ / |
| \ +------+ +------+ / |
| +------+ \ | t-SBE| | t-DBE| /+------+ |
| +-----+ O-LS + \ +------+ +------+ / + T-LS +-----+ |
| | +------+ \ / +------+ | |
| | \ / | |
| | \ / | |
| | +------+ \ / +------+ | |
| | | O-SBE+ \ / + T-SBE| | |
| | +---+--+ \ / +------+ | |
| | | \ / | |
| | | \ / | |
| | +---+--+ \ / +------+ | |
| +-----+ O-SM | \ / | T-SM +-----+ |
| +-----++ + ++-----+ |
| +----+ | | | +----+ |
| |O-UE+---------+ | +---------+T-UE| |
| +----+ +------+ | +------+ +----+ |
| | O-DBE| | | T-DBE| |
| +------+ | +------+ |
| Originating Domain | Terminating Domain |
+----------------------------------------------------------------+
Figure 1 Generalized Overview
PLEASE NOTE: In figure one – the elements defined are optional in
many use cases.
3. Use Cases
Use cases are sorted into 3 general groupings: Direct, Indirect and
Assisted. Though there may be some overlap among the use cases in
these categories, there are different requirements between the
scenarios and this document serves to help identify the requirements
for SIP Peering for VoIP.
Per information in the Speermint terminology draft, the direct use
cases involve those cases in which two service providers interconnect
without using an intervening layer 5 network. This approach is also
considered a bi-lateral peering agreement.
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Indirect or transit peering involves a third party proxying both
signaling and bearer between the Originating and Terminating Domains.
It is generally required that a trust relationship is established
between the originating service provider and the transit network on
one side, and the transit network and the termination network on the
other side, so there is no requirement for a trust relationship
directly between the originating and terminating.
Assisted use cases involve the use of a third party for signaling.
This third party may or may not have a pre-existing relationship with
the O-VSP, and/or T-VSP. The A-VSP may only provide next-hop
discovery for the O-VSP on behalf of the T-VSP and proxy all
communications, or may be more intimately involved by maintaining
session state in the signaling plane. Other functions which may be
provided in Assisted Peering include, peering policies, and
administrative rules for such sessions (settlement, abuse-handling,
security requirements) and the specific rules for the technical
details of the interconnection (signaling, media, layers 1-4 etc.)
3.1. Direct Use Cases
There are intra-domain message flows within the use cases to serve as
supporting background information. Only inter-domain communications
is germane to Speermint.
3.1.1. Minimalist Direct
1. O-UE initiates a call via SIP INVITE
2. O-SM queries for next-hop information from a routing database.
3. Routing database entity replies with route to called party
4. Call sent to terminating domains session manager.
5. Session manager determines called party status and directs call
to called party.
6. RTP is established between O-UE and T-UE.
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+------------------+-------------------+
| Orig Domain | Term Domain |
| +--------+ | +--------+ |
| | O-LS | | | T-LS | |
| +--------+ | +--------+ |
| (2) / | |
| /(3) | |
| +-----+ | +-----+ |
| |O-SM |--------(4)---------|T-SM | |
| +-----+ | +-----+ |
| | | | |
| (1) | (5) |
| | | | |
| +----+ | +----+ |
| |O-UE+===(6)=(RTP)=========+T-UE+ |
| +----+ | +----+ |
+------------------+-------------------+
Figure 2 Minimalist Direct
3.1.1.1. Administrative characteristics
The minimalist direct use case is typically implemented in a scenario
where exists a strong degree of trust between the 2 administrative
domains. Neither the Originating nor Terminating domains have a
dedicated network element (i.e. Session Border Element - SBE) that
serves any domain demarcation purpose. This can and should be
considered an “Open” peering model.
3.1.2. Direct with one SBE
In this type of interconnection scenario, the SBE is owned and
operated within the originating administrative domain for purposes of
domain demarcation, security, and trust boundry.
1. O-UE initiates a call.
2. The O-SM performs next-hop determination for the called party
via the O-LS. This can be done via ENUM/DNS/Redirect 3XX
multiple choices and/or static routing.
3. The result of the query will be O-SBE that is logically
interconnected to the terminating domain.
4. O-SM will signal O-SBE.
5. O-SBE routes call to T-SM within terminating domain.
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6. T-SM signals the called party, T-UE.
7. RTP established between the O-UE and T-UE.
+------------------+-------------------+
| Orig Domain | Term Domain |
| +--------+ | +--------+ |
| | O-LS | | | T-LS | |
| +--------+ | +--------+ |
| (2) / | |
| /(3) | |
|+-----+ +-----+ +-----+ |
||O-SM |-(4)-|O-SBE+----(5)---|T-SM | |
|+-----+ +--+--+ +-----+ |
| | | | |
| (1) | (6) |
| | | | |
| +----+ | +----+ |
| |O-UE+=====(7)=(RTP)=========+T-UE+ |
| +----+ | +----+ |
+------------------+-------------------+
Figure 3 Direct with one SBEs
3.1.2.1. Options and Nuances
There is evidence that both the signaling and the media would
traverse a single element, and in this case, there would be an
element that would be both the SBE and DBE.
3.1.2.2. Administrative characteristics
The direct peering with a single SBE is typically implemented in the
scenario where the Originating domain is a VoIP Service Provider
(VSP) and the Terminating domain is an Enterprise IP telephony
deployment. The SBE(s) provides the VSP with the ability to support
overlapping RFC1918 address space via NAT, Session limiting, Session
“scrubbing” to permit only certain SDP options, etc.
3.1.3. Direct with two SBEs
Multiple SBCs are implemented in this interconnection scenario. The
SBEs are operated within different administrative domains.
1. O-UE initiates a call.
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2. The O-SM performs next-hop determination for the called party
via the O-LS. This can be done via ENUM/DNS/Redirect 3XX
multiple choices and/or static routing.
3. The result of the query will be O-SBE that is interconnected to
the terminating domain, but administered in the originating
domain.
4. O-SM will signal O-SBE.
5. O-SBE routes call to T-SBE within terminating domain.
6. T-SBE signals T-SM.
7. T-SM signals the called party, T-UE.
8. RTP is established between UEs via Data Border Edge elements.
+---------------------+ +-----------------------+
| Orig Domain | | Term Domain |
| +--------+ | | +--------+ |
| | O-LS | | | | T-LS | |
| +--------+ | | +--------+ |
| (2) / | | |
| /(3) | | |
|+-----+ +-----+ +-----+ +-----+ |
||O-SM |---(4)--|O-SBE|--(5)--|T-SBE+---(6)---|T-SM | |
|+-----+ +-----+ +-----+ +-----+ |
| | | | | |
| (1) | | (7) |
| | | | | |
| +----+ +-----+ +-----+ +----+ |
| |O-UE+========+O-DBE+==(8)==+T-DBE+==========+O-UE| |
| +----+ +-----+ +-----+ +----+ |
+---------------------+ +-----------------------+
Figure 4 Direct with two SBEs
3.1.3.1. Options and Nuances
There is evidence that both the signaling and the media would
traverse a single element, and in this case, there would be an
element that would be both the SBE and DBE. (note: this is not
depicted in figure above) There may also be a single or multiple
DBEs as depicted in the diagram.
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3.1.3.2. Administrative characteristics
The direct peering use case with 2 SBEs is typically seen in where
both the originating and terminating domain are VSPs. Both maintain
that there is perceived value in “protecting” their VSP network cores
via SBEs/DBEs/etc. This use case is also applicable where one or both
domains are enterprises.
3.2. Indirect Use Cases
3.2.1. Transit PSP
This call flow is similar to the minimalist approach, but with a
Peering Service Provider (PSP) providing signaling(i.e. SIP
“normalizing”) and bearer (i.e. transcoding) services to facilitate
communications between the originating and terminating domains. For
this call flow all signaling and bearer to and from the
Originating/Terminating domains traverses the Transit Domain,
possibly for services like Q0S, interoperability and security.
1. O-UE initiates a call.
2. The O-SM performs next-hop determination for the called party
via the LS within the Transit domain. This can be done via
ENUM/DNS/Redirect 3XX multiple choices and/or static routing.
3. The result of the query will be the transit provider’s SBE (t-
SBE) that is interconnected to the transit domain via the O-SBE.
4. O-SM signals the t-SBE via the O-SBE.
5. t-SBE routes call to T-SBE within terminating domain.
6. T-SBE signals T-SM.
7. T-SM signals the called party, T-UE.
8. RTP is established between UEs via DBE path typically
coordinated by the Transit Domain.
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+------------------+
| Transit Domain |
| |
| +------+ |
| +--+ t-SM | |
| / +-+ t-LS | |
| / / +------+ |
+------------------+ / / +----------------------+
| Orig Domain |/ / | Term Domain |
| +-----------+ / | +--------+ |
| / |/ | | T-LS | |
| / +----(3)---+ | +--------+ |
| (2) / | | |
| / / | | |
|+-----+ +-----+ +-----+ +-----+ +-----+|
||O-SM |-(4)-|O-SBE|------+t-SBE+-(5)-+T-SBE+---(6)---|T-SM ||
|+-----+ +-----+ +-----+ +-----+ +-----+|
| | | | | | |
| (1) | | | (7) |
| | | | | | |
| +----+ +-----+ +-----+ +-----+ +----+|
| |O-UE+=====|0-DBE|=(8)==+t-DBE+=====+T-DBE+==========+T-UE||
| +----+ +-----+ +-----+ +-----+ +----+|
+------------------------------------------------------------+
Figure 5 Indirect via Transit PSP
3.2.1.1. Administrative Characteristics
The transit peering use case is normally implemented in cases where
no direct interconnection exists between originating and terminating
domains due to either business or physical constraints.
Orig Domain .--. Transit = Relationship O-T
In the O-T relationship, typical policies, features or functions that
deem this relationship necessary are NP, Ubiquity of termination
options, and masquerading of originating VoIP network gear.
Term Domain .--. Transit = Relationship T-T
In the T-T relationship, typical policies, features or functions
observed consist of codec “scrubbing”, anonimizing, and transcoding.
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3.3. Assisted Use Cases
Assisted use cases involve an assisting PSP (A-PSP) that facilitates
direct session establishment between the O-VSP and T-VSP. There may
be elements that provide SIP proxy functionality, and are often
implemented in practice by SBE(s) and DBE(s) which may "filter" or
"normalize" and provide network-hiding for incoming messages en route
to their final destination. Fear and distrust coupled with continued
interoperability and security concerns have revived the need for the
neutral central element role enabled by this peering model.
Popularity of this model can be attributed to the concentration of
functions provided by A-PSP. As an external element, A-PSP can
provide the full set of services for VSPs, and through its own
relationships with the VSP, eliminate the need of all VSPs for pair-
wise service relationships. A-PSP can potentially encompass a large
namespace of users that is accessible in one query to external VSP
members (or not -depending on policy).
In addition there is an interoperability function usually performed
by an SBE, almost guaranteeing interoperability and protocol
interchangeability between member VSPs. As part of the
interoperability there is also is media sub-function enabling the
federation to enforce a standard set of codecs or alternatively
provide transcoding functionality to make sure there is media
interoperability as well. Finally, A-PSP can implement the routing
function enabling traffic shaping and throttling across the
federation.
3.3.1. Assisted PSP
This is a direct call flow, as in the minimalist approach, but with
an A-PSP aiding the originating to terminating domain relationship.
The A-PSP may have a relationship with the originating and/or
terminating domain.
1. O-UE initiates a call.
2. The O-SM performs next-hop determination for the called party
via the A-LS within the Assisting domain. This can be done via
ENUM/DNS/Redirect 3XX multiple choices and/or static routing.
3. The result of the query will be the T-SBE that is accessible via
the O-SBE. There must be a common IP denominator between the
originating and terminating domains. (i.e. Internet)
4. Signaling will traverse the O-SM onwards to the O-SBE.
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5. O-SBE routes call to T-SBE.
6. T-SBE signals T-SM.
7. T-SM signals the called party, T-UE.
8. Bearer path established between O-UE and T-UE through O/A/T DBE.
+------------------------+
| Assist Domain |
| |
| +--------+ |
| | A-LS | |
| ++---+---+ |
| | | |
+---------------+ | | +-----------------+
| Orig Domain \ | | / Term Domain |
| +----------+------+ | / +--------+ |
| / \ | / | LS-t | |
| / +----(3)----+--------+ / +--------+ |
| (2) / \ / |
| / / +------------+ |
|+-----+ +-----+ +-----+ +-----+ |
||O-SM |---(4)--|O-SBE+-----(5)----+T-SBE+---(6)---|T-SM | |
|+-----+ +-----+ +-----+ +-----+ |
| | | | | |
| (1) | (common IP | (7) |
| | |denominator)| | |
| +----+ +-----+ +-----+ +----+ |
| |O-UE+========+O-DBE+=====(8)====+T-DBE+==========+T-UE| |
| +----+ +-----+ +-----+ +----+ |
+----------------------------------------------------------+
Figure 6 Direct with Assisted PSP
PLEASE NOTE – elements depicted are optional.
4. Federations
This section discusses the federation concept, explains which
technical parameters make up the foundation of a federation and
provides examples.
Contrary to the previous section, this section does not focus on
specific implementation details like the presence of SBCs or other
border elements. The aim here is to provide a broader view on what
kinds of arrangements are possible.
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The concrete implementation details (e.g. "direct with one SBC"
versus "direct with two SBCs") can involve all the use cases thus
far described in the document.
4.1. Federation Considerations
Each federation has to specify how a few core operations which are
to be performed by its members.
These include:
1. Peer Discovery
This specifies how a VSPs discovers that he can place a specify
call to a peering partner in this federation.
Possible solution are e.g.: a manually configured list of TN-
prefixes and domain names, automatically obtained list of reachable
prefixes/domains by some sort if intra-federation route
announcements, trial queries to the federation's LS, trial lookups
in federation-internal databases (e.g. private DNS),public database
lookups (e.g. I-ENUM).
2. Location Server
What methods are used for TN to URI mapping?
Examples: Public User-ENUM, public Infrastructure ENUM, private
ENUM tree, SIP Redirect, DUNDi.
3. Next Hop Domain Resolution
If the LS did not return an URI of the form sip:user@IP-address,
then the originating VSP has to translate the domain part of the
URI to an IP-address (plus perhaps fall-backs) in order to contact
the next hop.
Examples: RFC3263 in the public DNS. RFC3263 in a federation
private DNS. RFC3263 in the public DNS with split-DNS, P2P SIP,
modified RFC3263 in the public DNS (e.g. a federation-specific
prefix to the domain name).
4. Call Setup
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The federation may also define specifics on what SIP features need
to be used when contacting the next hop in order to a) reach the
next hop at all and b) to prove that the sender is a legitimate
peering partner.
Examples: hard-code transport (TCP/UDP/TLS), non-standard port
number, specific source IP address (e.g. in a private L3 network),
which TLS client certificate to use, other authentication scheme.
5. Filtering Incoming Calls
On the receiving side, the border element needs to determine
whether the INVITE it just received really came from a member of
the federation. This is the flip side of 4.
Example: verify TLS cert, check incoming interface/VLAN,check
source IP address against a configured list of valid ones.
4.2. Federation Examples
This section lists some examples of how federations can operate.
4.2.1. Trivial Federations
A private peering arrangement between two VSPs is a special case of
a federation. These two VSP have agreed to exchange calls amongst
themselves and they have set up whatever SBC/LS/SBE plus Layer
3infrastructure they need to route and complete the calls.
It is thus not needed to treat bi-lateral peerings as conceptually
different to federation-based peering.
On the other extreme, the set of all VSPs implementing an open SIP
service according to RFCs 3261/3263/3761 also fulfills the
definition of a federation. In that case, the technical rules are
contained in these three RFCs, the LS is the public DNS. Whether
some of these VSPs use SBCs as border elements is not relevant.
The administrative model of this federation is the "email model":
There is no "member list", any SIP server operating on the Internet
which implements call routing according to these RFCs is implicitly
a member of that federation. No business relationship is needed
between "members", thus no money is likely to change hands for
terminating calls. There is no contractual protection against
nuisance calls, SPIT, or denial of service attacks.
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4.2.2. Access List based
If running an open SIP proxy is not desired, then a group of VSPs
which want to allow calls from each other can collect the list of
IP addresses of all their border elements.
This list is redistributed to all members which use it to configure
firewalls in front of their ingress elements. Thus calls from
other members of this federation are accepted while calls from
other hosts on the Internet are blocked.
Whether VSPs deploy SBCs as border elements is not relevant. Call
routing can still be done via standard RFC rules.
Whenever a new member joins this club every other VSP needs to
adapt its filter rules.
4.2.3. TLS based Federations
Another option to restrict incoming calls to federation members is
to use Transport Layer Security (TLS) certificates as access
control. This works best if the federation runs a certificate
authority (CA) which signs the TLS keys of each member VSP. Thus
the ingress element of a VSP needs to check only whether the client
certificate presented by the calling SIP proxy contains a proper
signature from that CA.
Adding support for Certificate Revocation Lists solves the issue of
blocking calls from former members of that federation. The main
benefit of this model is that no changes need to be made at the
ingress element of all old members whenever a VSP joins that
federation.
4.2.4. Central SIP Proxy
One way to simplify the management of these firewall rules is to
route all SIP messages via a central proxy.
In that case, all federation members just need to open up their
ingress elements to requests from that central server. A new VSP
just triggers a change in the configuration of this box and not at
all other VSPs.
While centralized solutions may entail typical hub-and-spoke
architecture considerations, the added overall federation
scalability with respect to the number of interconnects required,
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their associated policies and management make this approach quite
popular today.
This is an example of Assisted Peering.
4.2.4.1. Architecture, scalability and business scalability
The network architecture which in the case centralized model would
reflect a hub and spoke model - should be weighed against a
distributed model. While such a centralized model presents well-
known network and server scalability challenges, a distributed
model requires higher interconnection complexity, reflected in
provisioning and the need for the maintenance of such
relationships.
4.2.5. Private Layer 3 Network
Federations can also establish a separate layer 3 network for their
peering traffic. This could be implemented e.g. by creating a new
VLAN at an Internet exchange point to which all members of that
federation connect their SBEs.
Alternatively, a federation can establish a smaller version of the
Internet to which only members are allowed to connect. The GRX
network of the mobile operators is an example of a dedicated layer
3 infrastructure.
Such a private layer 3 network can also be implemented using
virtual private network (VPN) technologies like IPsec.
In all these cases the SBE can assume that any SIP requests it
receives via an interfaces located in this L3 network comes from
legitimate peering partner.
The separation of the peering network from the Internet makes it
easier to protect the peering arrangement from attacks and to
ensure QoS.
4.2.6. Peer to Peer SIP
P2PSIP replaces the RFC3263 rules by a lookup in a distributed hash
table (DHT). A federation could use this technology to implement
call routing between the peers: the border elements of all members
participate in the DHT algorithm and distribute routing information
this way.
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Only members of the federation thus can use information stored in
the DHT which could be the basis of both call routing within the
federation as well as access control between members.
4.2.7. DUNDi
Distributed Universal Number Discovery (DUNDi)
[http://www.dundi.com/dundi.txt] can also be used to build
federations: DUNDi itself acts as a distributed LS which can add
dynamically generated passwords to the URIs it returns.
This way, the T-SBE can verify that an incoming calls comes from a
member of this DUNDi cloud.
5. Security Considerations
This document introduces no new security considerations. However,
it is important to note that session interconnect, as described in
this document, has a wide variety of security issues that should be
considered in documents addressing both protocol and use case
analyzes.
6. IANA Considerations
This document creates no new requirements on IANA namespaces
[RFC2434].
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References
Normative References
[1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[2] Schwartz, David, draft-schwartz-speermint-use-cases-federations
[3] Mahy, Rohan, draft-mahy-speermint-direct-peering
[4] Lendl, Otmar, draft-lendl-speermint-federations
[5] Lee, Yiu, draft-lee-speermint-use-case-cable
[6] Uzelac, Adam, draft-uzelac-speermint-use-cases
[7] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol
(SIP): Locating SIP Servers", RFC 3263, June 2002.
[8] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and
T. Wright, "Transport Layer Security (TLS) Extensions", RFC
3546, June 2003.
[9] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", STD 64,
RFC 3550, July 2003.
[10] Peterson, J., Liu, H., Yu, J., and B. Campbell, "Using E.164
numbers with the Session Initiation Protocol (SIP)", RFC 3824,
June 2004.
[11] Peterson, J., “Address Resolution for Instant Messaging and
Presence”,RFC 3861, August 2004.
[12] Peterson, J., "Telephone Number Mapping (ENUM) Service
Registration for Presence Services", RFC 3953, January 2005.
[13] ETSI TS 102 333: " Telecommunications and Internet converged
Services and Protocols for Advanced Networking (TISPAN); Gate
control protocol".
[14] Peterson, J., "enumservice registration for Session Initiation
Protocol (SIP) Addresses-of-Record", RFC 3764, April 2004.
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Informative References
[15] Meyer, D., "SPEERMINT Terminology", draft-ietf-speermint-
terminology-06 (work in progress), 2006.
[16] Mule, J-F., “SPEERMINT Requirements for SIP-based VoIP
Interconnection”, draft-ietf-speermint-requirements-00.txt,
June 2006.
[17] Camarillo, G. “Requirements from SIP (Session Initiation
Protocol) Session Border Control Deployments“, draft-camarillo-
sipping-sbc-funcs-04.txt, June, 2006.
[18] Habler, M., et al., “A Federation based VOIP Peering
Architecture”, draft-lendl-speermint-federations-03.txt,
September 2006.
Author's Addresses
Adam Uzelac
Global Crossing
Email: adam.uzelac@globalcrossing.com
Rohan Mahy
Plantronics
Email: rohan@ekabal.com
Yiu L. Lee
Comcast Cable Communications
Email: yiu_lee@cable.comcast.com
David Schwartz
Kayote Networks
Email: david.schwartz@kayote.com
Eli Katz
Xconnect Global Networks
Email: ekatz@xconnect.net
Otmar Lendl
enum.at GmbH
Email: otmar.lendl@enum.at
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