Source Port/Destination Port for SIP messages

[rime]

When tracing on a Session Manager (putty as "cust" to the security module IP address, then run traceSM, filter on the IP address of the peer with "-i <ip address>"), I see that the Session Manager sends messages with ports widely different from the configured 5061 for that particular signaling connection. Is it predictable which ports will be used? Can't they be nailed down to 5061 or other configured values? I ask because priority on the router is based on IP addresses, protocols and also source and destination ports. Here an interpreted trace extract where the issue is visible:

SESSION MGR............................ PEER
-----------............................-----
Source port: .....0 ....-----INVITE---> Destination Port: 5061
Destination port: 45561 <--- TRYING --- Source Port: .....5061
Destination port: 45561 <--- RINGING -- Source Port: .....5061
Source port: .....0 ....-----PRACK----> Destination Port: 5061
Destination port: 45561 <--- OK ------- Source Port: .....5061

[ilalpatidar]

The ports shown in the trace seems to be from the originating device and I think they cant be controlled as these will be random UDP port from the range defined on the communication controller. (For example H.323 Avaya phones ports are controlled through the ip- network region form)

I hope this helps.

[rime]

Source Port/Destination Port for SIP messages

In the trace shown, both endpoints are Session Manager systems, of different enterprises, interconnected by a SIP trunk. So it is the Session Managers which decide to use port 0 to initiate a dialogue, respectively 45561 (or other) to reply to it. The SIP entity links explicitly list TLS port 5061 for both ends of the links, on both Session Managers of both enterprises. But in reality, we see different ports in protocol traces. Building a reliable ACL is the challenge that results.