CUPC7 SIP and STUN SRV DNS Queries

[Jonathan Schulenberg]

If I perform a packet capture of a CUPC 7 login I see that the client performs SRV DNS queries for:

• _sip._tcp.cups-servername.proxydomain.local.
• _sip._udp.cups-servername.proxydomain.local.
• _stun._udp.proxydomain.local.

I have two questions that arrise from this observation:

1. Why would the client perform a SIP SRV query against the servername instead of the SIP proxy domain? Unless I am missing something, querying the proxy domain would make a lot more sense.
   Note that this behavior does not change regardless of the SIP Proxy service parameters SRV Cluster Name or Address Resolution Type being changed from their default values of null and IP respectively.
   
2. Does CUPS run a STUN server service and if so on what port; or, is the customer environment expected to provide its own STUN server if needed?

[htluo]

1. This is by designed (of CUPC).  I agree with you that it makes more sense to use proxy domain instead of FQDN.

2. If I remember it right, CUPS does not host a STUN server.  Default port for STUN was UDP port 3478.

Michael

http://htluo.blogspot.com