No rport in SIP REGISTER req

[eng_ali_83]

Hi ,

What is the meaning when cisco CUBE has rport feild empty or has no value , for instance :

Received:
REGISTER sip:XX.XX.XX.XX;transport=UDP SIP/2.0Via: SIP/2.0/UDP 10.230.42.209:1028;branch=z9hG4bK-524287-1---95f6b53cbf63ec4a;rport

Max-Forwards: 70Contact: <sip:1119@10.230.42.209:1028;rinstance=990a591ef73bbb18;transport=UDP>

is it ISP problem or from my cisco CUBE  ?

I appreciate your help

[Vivek Batra]

Hi,

rport is included in 'via' header and doesn't need to include anything. I don't see any issue with the message you've posted.

rport basically enables the symmetric response routing so that response can go back through NAT router. In absence of rport header OR if proxy doesn't support 'rport', SIP response will be sent to port indicated in via header and probably will not go back to UAC if there was NAT in between.

- Vivek

[eng_ali_83]

this rport should have a port number and this port number should be used with the public ip address to get back to the source , in my case the port that is used with public ip is the one that is in the sip msg not the one in the received UDP header

Thanks

[Vivek Batra · Accepted solution]

rport is only header and doesn't include any port. Port is included as a part of URI in via. So in your message, if rport is not included, the 200 OK will be sent to private IP and port 1028. Now if your device is behind the NAT router, 200 OK will never reach there. Once we add rport in via (not adding actual port), now proxy will ignore the URI in via field and will send 200 OK to NATted IP and Port and hence sender will get 200 OK successfully.

- Vivek

[eng_ali_83]

Hi,Yes I got it now , so report is just like a flag , just to tell the UAS (in my case cisco CUBE) to use the port that in UDP header .
so now my problem is more complicated , after I used the following debug cmd on my cisco cube:
debug ccsip message
eventhough rport field is appeared in the 200 OK msg , wireshark gave me that the port used in the UDP header is the one of the sip msg port , and that's why I am not receiving any response to my UAC ! 

PBX---CUBE (Public IP) --- Wireshark --- Internet Rtr---Internet--HomeRtr-- my phone

Any suggestion 

Regards,

[Vivek Batra]

I can't think that 'rpot' is not implemented in CME unless there is some command controls the behavior of 'rport' which I am not aware of.

- Vivek