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IP Telephony

Document Charter IP Telephony WG (iptel)
Title IP Telephony
Last updated 2009-03-11
State Approved
WG State Concluded
IESG Responsible AD (None)
Charter edit AD (None)
Send notices to (None)

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.