[reSIProcate] RFC 5923 alias

[Daniel Pocock <daniel@xxxxxxxxxxxxx>]

I'm just trying repro with a Polycom device that is behind NAT, using TLS

When the device tries to register, I notice that repro can't send the
407 challenge back to the device over the TLS connection.  The log just
says `discarding stray response: SipResp: 407 tid=8b5....'

The Polycom device appears to support the `alias' attribute in the Via
header, for re-use of the TLS connection:
http://tools.ietf.org/html/rfc5923

repro supports RFC 5626 (reg-id in the Contact header), but I'm not sure
if the Polycom handset supports that

Can anyone comment on either of these solutions, i.e. is 5923
appropriate, has anyone got support for it in a branch somewhere perhaps?