Subject: [tsv-area] non-SIP usage of ICE

From: Lars Eggert <[email-masked]>
Date: Mon, 19 May 2008 12:03:53 +0300

Hi,

the MMUSIC WG is discussing whether they should take on a work item on  
using ICE in non-SIP/RTP environments. This subset of ICE specified in  
draft-rosenberg-mmusic-ice-nonsip (called NICE) would be a general- 
purpose NAT traversal mechanism, and is for example being considered  
by the HIP WG as a NAT traversal solution for HIP.

I strongly encourage transport-area folks to join this discussion on  
the MMUSIC mailing list. The proponents of ICE argue to develop it  
into the IETF-preferred NAT traversal protocol, for which it IMO is  
currently not sufficiently developed.

There are some challenges here that are of immediate interest to  
transport folks. One is that ICE-for-SIP had been pacing its  
connectivity checks such that they use bandwidth in way that is not  
more aggressive than a following RTP media stream. With NICE, this  
approach is no longer possible, because NICE has no knowledge of the  
transmission behavior of arbitrary flows.

Another is that if NICE chooses candidates that it has obtained via  
STUN and TURN, non-RTP traffic may be tunneled through such relays,  
which is currently (at least to me) not a well-understood operation.

Because ICE handles gathering of candidate IP addresses and ports, it  
is undefined how ICE/NICE would intersect with layer-3 mobility and  
multihoming solutions, or transport protocols like SCTP.

Finally, ICE has so far mostly focused on relaying UDP traffic, with a  
draft on relaying TCP still under WG discussion (draft-ietf-mmusic-ice- 
tcp), which so far is still SIP/RTP-specific. There is currently no  
possibility to relay SCTP or DCCP with ICE.

Lars