Re: [sipcore] Happy Eyeballs for SIP / Summa Beatitudinem

[[e-mail] (Dale R. Worley)]

"Asveren, Tolga" <[e-mail]> writes:
> I think it would be useful to get on a common understanding/consensus
> on "what needs to be covered and in which document" as far as use of
> multiple IP Address Families/Multiple Interfaces are concerned. Here
> is a first attempt for "Summary of Happiness":

The current plan has been to discuss topics incrementally in order to
keep the scope of each incremental technical discussion small enough
that it will come to an end.  If we throw everything into the discussion
at once, it will be difficult to both discuss things thoroughly and come
to a consensus.

> ii- RFC6555 
> Defines parallel connection attempt for different IP address families. 
> Restricts itself -I don't know exactly why- to a single hostname for
> IPv4/IPv6 and does not cover other ways of learning IP Addresses,
> e.g. provisioning, DHCP based. AFAICS, procedure described in this
> specification can be applied for those cases as well. 

That's because RFC 6555 discusses the case of HTTP, where there is a
single host name, the domain name from the HTTP URL.  There *are* no
other ways of learning an IP address in HTTP.

> iv- draft-worley-sip-he-connection-00

> Would any "fast-failover after connection failure", e.g. toward the
> standby server after failure of the primary server, related procedures
> be in scope? For connection oriented protocols, any possible
> recommendations/improvements in this area would probably be limited to
> reusing the TLS connection. Is there anything SIP specific, which
> could help here?

Fast failover is, in effect, in scope because in a failure situation,
what Happy Eyeballs attempts to do with the next SIP message is deliver
it quickly.

> B) Use of Multiple Interfaces
> v- I think the ideal place to cover this would be RFC6555-bis (also by
> considering other restrictions as mentioned in ii- above). I wouldn't
> think that there would be a need for defining anything new in
> draft-worley-sip-he-connection-00 (?).

The subtle problem with multiple interfaces is that there can be
multiple interfaces that might be able to connect to a particular target
address.  Currently in IPv6, the source address selection algorithm of
RFC 6724 chooses which interface is to be used to contact a particular
target address.  But IIRC Roman Shpount noted that there are times when
RFC 6724 gives a non-working result.  It looks like in the long run we
want H.E. to be able to use alternative source addresses if necessary.

Dale