[Users] differ DNS between proxy-proxy and client-proxy connections

[Klaus Darilion]

Hi!

This is a little bit OT, but maybe you can help me out. Consider the 
following setup: I have a SIP service running on mydomain.com.

My sip AoR is sip:klaus at mydomain.com

mydomain.com resolves to my main SIP proxy (registrar, proxy, used by 
all local clients) using NAPTRs, SRV and A records.

Further, I do want to have a separate proxy (edge proxy) which handles 
signaling from/to external domains, TLS, white/blacklisting ....

Thus, the domain mydomain.com should resolve to:
- the main proxy for SIP clients
- the edge proxy for SIP proxies

Of course I could use different domains or the clients have to configure 
an outbound proxy (which points directly to the main proxy), but this 
complicates configuration.

AFAIK, Microsoft solved this problem within the LCS using different 
prefixes during the SRV lookup. The Live Communicator (client) uses 
_sipinternal._udp.mydomain.com to find the main proxy, whereas the LCS 
uses _sip._udp.domain.com to find the edge proxy (access proxy in 
Microsoft terms) of mydomain.com.

Thus, I would like to raise discussion: Have you an idea how to solve 
this? Are you aware of any RFCs/drafts addressing this problem?

regards
klaus