[SR-Users] Upstream ignores reply, because To-tag doesn't match?

Sergiu Pojoga pojogas at gmail.com
Sat Apr 6 17:25:54 CEST 2019

Hi ppl,

Scenario: invite from upstream is t_relayed to a client gateway. After
`fr_inv_timeout` occurs, in a failure route I simply t_reply with "503 -
Service unavailable", then exit().

However, the upstream provider simply ignores this reply, call doesn't hang
up. This doesn't happen when the client's gateway generates identical 503
or other negative replies.

I suspect this is happening because the To-tag in the Kam generated 503
reply doesn't match with the To-tag that previously was forwarded from the
client's gateway to the upstream provider in the `180 Ringing`.

Any suggestions what can be done about it?

2019/04/06 10:42:46.127177 65.39.xxx.xxx:5060 -> 208.72.xxx.xxx:5060

SIP/2.0 180 Ringing

Via: SIP/2.0/UDP

Record-Route: <sip:65.39.xxx.xxx;lr=on;did=915.8af1>

From: "SERGIU" <sip:514XXXXXXX at 208.72.xxx.xxx>;isup-oli=00;tag=1975755942

To: <sip:514XXXXXXX at 65.39.xxx.xxx>;tag=as2ab54180

Call-ID: DID-28270826 at 208.72.xxx.xx

CSeq: 477023 INVITE

Supported: replaces, timer, path

Contact: <sip:1514XXXXXXX at 65.39.xxx.xxx:5060>

Content-Length: 0

2019/04/06 10:42:51.072516 65.39.xxx.xxx:5060 -> 208.72.xxx.xxx:5060

SIP/2.0 503 Service Unavailable

Call-ID: DID-28270826 at 208.72.xxx.xx

Via: SIP/2.0/UDP

From: "SERGIU" <sip:514XXXXXXX at 208.72.xxx.xxx>;isup-oli=00;tag=1975755942

To: <sip:514XXXXXXX at 65.39.xxx.xxx>;tag=a6a1c5f60faecf035a1ae5b6e96e979a-8e82

CSeq: 477023 INVITE

Server: KAM

Content-Length: 0

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