IP Telephony (iptel)

In addition to this official charter maintained by the IETF Secretariat, there is additional informati on about this working group on the Web at:

       Additional IPTEL Page

Last Modified: 2007-10-15

Additional information is available at tools.ietf.org/wg/iptel


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Description of Working Group:

The focus of the IP Telephony (iptel) group is on the problems related
to naming and routing for Voice over IP (VoIP) protocols.
Naming is accomplished through the use of the tel URI, which specifies
a URI for telephone numbers. The tel URI was originally defined in RFC
2806, which was developed outside of any IETF working group. The iptel
working group is responsible for updating the specification based on
extensive experience with the tel URI. It is chartered to develop any
extensions to the tel URI, such as support for number portability
indicators and trunk groups.

Routing protocols for VoIP allow intermediaries, such as SIP proxies
and H.323 gatekeepers, to make call routing decisions based on
reachability information learned from peer elements. The iptel group
has already defined a protocol, Telephony Routing over IP (TRIP), RFC
3219, which solves one aspect of this problem. Specifically, it
the case where calls need to be routed between domains. It allows for
the exchange of routing information between these providers, so that
policies can be applied to the resulting data to create a forwarding
information base.

However, this protocol does not address all the scenarios of route
information exchange between servers. One important scenario is the
propagation of routing information between gateways and the signaling
servers in front of them. This is also known as "gateway
It allows the signaling server to make a routing decision about which
gateway to use based on dynamic information about the gateway
resources. Vendors have deployed proprietary solutions for this
communications interface. A standard is needed. The group will
a standards track document that defines a protocol (possibly based on
TRIP) for this interface.

TRIP and the gateway registration protocol are orthogonal to the
DNS-based mechanisms specified in ENUM and RFC 3264. Those mechanisms
are used to translate a URI, representing a name, to an address. If
that address is a phone number in the telephone network, trip and
can be used to assist in determining the right route (through various
gateways) to that number.

The group will also generate a MIB document for TRIP.

Note that the group is not working on elevating TRIP to Draft Standard
at this time.


1. A proposed standard specification for gateway to server route

2. A proposed standard TRIP MIB specification, based heavily on the
existing BGP-4 MIB documents.

3. A standards track update to the tel URI.

4. Standards track extensions to the tel URI for PSTN
such as number portability and trunk group identification.

Goals and Milestones:

Done    Submit gateway location framework document to IESG for consideration as an RFC.
Done    Submit call processing syntax framework document to IESG for consideration as an RFC.
Done    Submit call processing syntax document to IESG for consideration as a Proposed Standard.
Done    Submit gateway location protocol document to IESG for consideration as an RFC.
Done    TRIP MIB Document submitted to IESG for consideration as proposed standard
Done    Tel URI revisions submitted to IESG
Done    Number portability extensions submitted to IESG for consideration as proposed standard
Done    Gateway to Server Route Exchange document submitted to IESG for consideration as proposed standard.
Done    Consider closing

No Current Internet-Drafts

Request For Comments:

Call Processing Language Framework and Requirements (RFC 2824) (58711 bytes)
A Framework for a Gateway Location Protocol (RFC 2871) (60664 bytes)
Telephony Routing over IP (TRIP) (RFC 3219) (184618 bytes)
Management Information Base for Telephony Routing over IP (TRIP) (RFC 3872) (98614 bytes)
CPL: A Language for User Control of Internet Telephony Services (RFC 3880) (154991 bytes)
The tel URI for Telephone Numbers (RFC 3966) (40783 bytes) obsoletes RFC 2806/ updated by RFC 5341
Number Portability Parameters for the (RFC 4694) (36910 bytes)
The ENUM Dip Indicator Parameter for the (RFC 4759) (15062 bytes)
Representing trunk groups in tel/sip Uniform Resource Identifiers (URIs) (RFC 4904) (41027 bytes)
A Telephony Gateway REgistration Protocol (TGREP) (RFC 5140) (59511 bytes)
The Internet Assigned Number Authority (IANA) tel Uniform Resource Identifier (URI) Parameter Registry (RFC 5341) (13944 bytes) updates RFC 3966