RV130 SIP ALG

[sharpegary]

Does anyone have any idea as to "what" the RV130 SIP ALG "actually" writes to the header and/or body of the SIP message/packet?

I mean, exactly what does the Cisco RV130 SIP ALG modify in a SIP message?

I don not have any way of tracing, so I can't see the modifications.

I realize that VOIP over NAT ain't perfect....however; someone must have figured out some sort of solution in the twelve years that VOIP has been marketed?  And one would think that Cisco would be leading the pack.

[Saurabh Gera]

When a user initiates a call, a SIP request is sent to a SIP server (either a proxy or a redirect server). The request includes the address of the caller (in the "from" header field) and the address of the intended callee (in the "to" header field). The following sections provide simple examples of successful point-to-point calls established using a proxy and a redirect server.

Over time, a SIP end user might move between end systems. The location of the end user can be dynamically registered with the SIP server. The location server can use one or more protocols (including finger, rwhois, and LDAP) to locate the end user. Because the end user can be logged in at more than one station and because the location server can sometimes have inaccurate information, the SIP server might return more than one address for the end user. If the request is coming through a SIP proxy server, the proxy server will try each of the returned addresses until it locates the end user. If the request is coming through a SIP redirect server, the redirect server forwards all the addresses to the caller in the "contact" header field of the invitation response.

[sharpegary]

Thanks for the input...

I understand SIP, and I didn't ask for an explanation, I am sure you were just trying to assist.

I was asking, EXACTLY what does the Cisco RV130 SIP ALG piece add/replace in the SIP message?

Example, from what I believe to be a Fortinet router:

Normal SIP INVITE from the LAN client (with private IP)

INVITE sip:destino@example.com SIP/2.0
Via: SIP/2.0/UDP 192.168.1.33:5060;branch=z9hG4bKjyofoqmp
Max-Forwards: 70
To: <sip:destino@example.com>
From: "Iñaki" <sip:ibc@example.com>;tag=nrrrx
Call-ID: xetazdjyktlpsfo@192.168.1.33
CSeq: 800 INVITE
Contact: <sip:ibc@192.168.1.33:5060>
Content-Type: application/sdp
Allow: INVITE,ACK,BYE,CANCEL,OPTIONS,PRACK,REFER,NOTIFY,SUBSCRIBE,INFO,MESSAGE
Supported: replaces,norefersub,100rel
User-Agent: Twinkle/1.1
Content-Length: 312

v=0
o=ibc 1090098764 894503441 IN IP4 192.168.1.33
s=-
c=IN IP4 192.168.1.33
t=0 0
m=audio 8000 RTP/AVP 98 97 8 0 3 101
a=rtpmap:98 speex/16000
a=rtpmap:97 speex/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:3 GSM/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=ptime:20
a=zrtp

The same INVITE modified by the ALG router:

INVITE sip:destino@example.com SIP/2.0
Via: SIP/2.0/UDP 192.0.2.200:12345;branch=z9hG4bKjyofoqmp
Max-Forwards: 70
To: <sip:destino@example.com>
From: "Iñaki" <sip:ibc@example.com>;tag=nrrrx
Call-ID: xetazdjyktlpsfo@192.168.1.33
CSeq: 800 INVITE
Contact: <sip:ibc@192.0.2.200:12345>
Content-Type: application/sdp
Allow: INVITE,ACK,BYE,CANCEL,OPTIONS,PRACK,REFER,NOTIFY,SUBSCRIBE,INFO,MESSAGE
Supported: replaces,norefersub,100rel
User-Agent: Twinkle/1.1
Content-Length: 312

v=0
o=ibc 1090098764 894503441 IN IP4 192.168.1.33
s=-
c=IN IP4 192.0.2.200
t=0 0
m=audio 33445 RTP/AVP 98 97 8 0 3 101
a=rtpmap:98 speex/16000
a=rtpmap:97 speex/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:3 GSM/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-15
a=ptime:20
a=zrtp