[Serusers] proxy + nat in the same box
Eduard San Anselmo Mateu
esananselmo at albasoft.com
Fri Feb 27 10:50:01 CET 2004
I have read lots of posts to this list and whitepapers about NAT traversal with
SIP, but all of them refer to the same problem: the endpoint is behind a nat box
and SER is after that box. My question is regarding the situation in which SER
resides at the same box than NAT. Here's a diagram (sorry for that awful
ascii-art, never been a good artist):
_____ ______ ______ _____
| | | | | | | |
| A |------| FW |----- INTERNET ----| |-------| B |
|_____| | NAT | | NAT | |_____|
| SER | | |
192.168.0.90 |______| IPpA IPpB |______| 10.0.0.70
IPpA and IPpB are the public IP addresses of A and B, respectively. SER is
listening on its private IP. Of course, the SER box also has an RTP proxy.
I think there's no problem with RTP, because nathelper's exported functions can
deal with the problem of changing SDP's fields. My problem has to deal with SIP,
specially when B invites A into a conversation, and A has to give an answer. In
that case, when SER has to repeat that answer to B, what will it write in the
Record-Route header field? It should write IPpA so that B can get to SER in the
future, but if SER's listening on its private IP, I'm afraid it will write that
public IP in Record-Route.
Can anybody please point me in the right direction, or at least address me to a
place where all this may be explained (not the RFC, please!)?.
Thanks in advance.
Eduard San Anselmo
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