Subject: Re: [sipcore] Happy Eyeballs -- UDP and RTT

From: Brett Tate <[email-masked]>
Date: Thu, 10 Mar 2016 14:16:58 -0500

> > Happy Eyeballs has a mess of issues surrounding UDP.
> > [etc.]

I agree.  In addition to the issues that have already been raised, the
solution potentially would need to update RFC 4320 concerning sending 100
over UDP for non-INVITE.

> What I'm looking for here is some feedback:  Is adding
> one or two RTT of delay to SIP signaling a problem or not?
> If two RTT of additional delay is not a problem, we can be
> much more restrictive regarding what mechanisms we define.

It likely depends upon the reason and frequency.  The
draft-ietf-sipcore-dns-dual-stack recommendation already has the potential
to double the amount of time it takes to advance from primary to secondary
when primary is down.  For example, trying primary AAAA and A before
advancing to SRV record for secondary which also has AAAA and A.
Hopefully, the Happy Eyeballs resolution allows hitting the forth location
(secondary A record) within an acceptable amount of time.  And hopefully
the Happy Eyeballs resolution doesn't introduce too much extra traffic.