[MMUSIC] Updating the pacing of ICE connectivity checks

[Ari Keränen <[e-mail]>]

Hi all,

Updating the pacing parameter, Ta, of ICE for non-RTP traffic (for 
background, see [1] and [2]), as discussed at the Atlanta meeting, will 
be one of the important changes in the new version of ICE.

Currently the RFC5245 says (for non-RTP traffic) "Ta SHOULD be 
configurable, SHOULD have a default of 500 ms, and MUST NOT be 
configurable to be less than 500 ms."

This results in very slow pace of starting connectivity checks if ICE is 
used with non-RTP traffic. With RTP, the Ta is calculated based on the 
expected bandwidth used by the RTP stream and can be down to 20 ms. 
Therefore, many current implementations apparently ignore the "MUST NOT" 
above and set Ta to something lower.

The quite conservative value of 500 ms was originally chosen because of 
the fear of congesting the links with the connectivity check messages. 
This is obviously still a valid concern, but would suggesting something 
lower still make sense? How low would it be reasonably safe to go? What 
is currently used in practice? Can we come up with a formula similar to 
RTP (perhaps based on expected bandwidth usage)?


Cheers,
Ari

[1] http://tools.ietf.org/html/rfc5245#appendix-B.1
[2] http://tools.ietf.org/html/rfc5245#section-16.2