Subject: [Sipping] draft-ietf-sipping-sip-offeranswer-11: 491 with Retry-After

From: Brett Tate <[email-masked]>
Date: Wed, 20 Jan 2010 04:47:49 -0800

Draft-ietf-sipping-sip-offeranswer-11 section 4.1 indicates sending 491 response with Retry-After.  The Retry-After header has not been defined for inclusion within a 491 response.  The 491 response has an explicit back-off algorithm discussed within rfc3261 and rfc3311.  Within various glare and race conditions, both RFCs discuss sending things like 500 response with Retry-After or a 491 response; however neither indicates to send a 491 response with Retry-After header.

Thus concerning section 4.1 of the draft, "491 response with Retry-After header field" should likely be changed to "491 response"; and "491 response with Retry-After" should likely be "491 response".

If not changed, what is the purpose of the Retry-After within a 491 response since it would be ignored per rfc3261 and rfc3311?

Thanks,
Brett