Re: [OpenSIPS-Users] multiple retransmissions on 4XX after ACK

Mon, 10 Oct 2016 09:34:22 -0700

Hi All

I've made tha call from an internal machine and opensips still appears to ignore the ACKs

The ACK looks to be OK

2016/10/10 17:28:20.183387 192.168.36.92:5060 -> 192.168.36.141:5060
ACK sip:[email protected] SIP/2.0
Via: SIP/2.0/UDP 192.168.36.92:5060;branch=z9hG4bK665e6330;rport
Max-Forwards: 70
From: <sip:[email protected]>;tag=as27a256cc
To: <sip:[email protected]>;tag=gK0ca8d98e
Contact: <sip:[email protected]:5060>
Call-ID: [email protected]:5060
CSeq: 103 ACK
User-Agent: FPBX-12.0.76.2(11.7.0)
Content-Length: 0

this is from an asterisk box in response to a 404 from the Opensips Box.
Opensips sends several 404s and there are ACKs to the fist four and it still sends subsequebt ones
Regards

Richard

On 07/10/2016 19:46, Richard Robson wrote:

The ack is from the cp. opensips is sending the 4xx.
I'll try the same on another provider. Thanks for the info


On 7 Oct 2016 18:27, "Newlin, Ben" <[email protected]> wrote:

The most likely cause is that there is something wrong in the format of the ACK which is causing the far end to not recognize it as being the ACK for that 4XX response. So the far end will continue to retransmit the 4XX response. On the OpenSIPS side, these are recognized as retransmissions so the previous response is resent without triggering the failure route.

 

The reason it happens on 4XX but not on 200 OK is that ACKs within a dialog – for 200 OK responses to INVITE or BYE – are actually requests themselves and are sent end-to-end just like INVITEs and BYEs. These ACKs are constructed following the rules for any request within a dialog [1].

 

ACKs to failure responses, however, are transmitted at the transaction layer which means in this case they are being generated by OpenSIPS directly. Transactional ACKs are not requests and the rules for constructing them are different [2]. The most important parts are that the Via and Request-URI headers must match those in the initial request exactly.

 

I have encountered this problem several times when my manipulations of messages in the routing script cause the ACKs to be malformed. I would suggest capturing a SIP trace of the failing transaction and verify the ACK is constructed properly.

 

[1] https://tools.ietf.org/html/rfc3261#section-12.2.1.1

[2] https://tools.ietf.org/html/rfc3261#section-17.1.1.3

 

Ben Newlin

 

From: <[email protected].org> on behalf of Richard Robson <[email protected]>
Organization: Greenlight Innovation
Reply-To: OpenSIPS users mailling list <[email protected]>
Date: Friday, October 7, 2016 at 12:46 PM
To: OpenSIPS users mailling list <[email protected]>
Subject: [OpenSIPS-Users] multiple retransmissions on 4XX after ACK

 

Hi Guys,

 

Not sure if this a problem or normal behaviour or I'm doing something wrong.

 

 

after a 4XX is sent and the ACK recieved I can see 3 retransmissions of

the 4XX message all with corresponding ACKs. Whywould it re transmit

after an ACK

 

in the logs in the reply route I only see one. Is there something I

should be doing or is this normal behaviour. It doesnt do it with BYEs

 

We are testing with BT next wee and I'd like everything to be shipshape

 

this is from the carrier to opensips

 

              PSTN CARRIER                       OPENSIPS    

│Record-Route: <sip:109.239.96.133;lr;ftag=0UUHS0000030000E

           ──────────┬─────────

──────────┬─────────│01001u1J9XWPK0DDUY6X;did=e7f.7bf9fe87>

                     │        INVITE (SDP) │         │Via: SIP/2.0/UDP

109.239.96.133:5060;branch=z9hG4bK547c.48

   17:42:38.425641   │ ──────────────────────────> │         │a4d4.0

         +0.004634   │      100 Giving a try │         │Via: SIP/2.0/UDP

194.145.191.131:5060;branch=z9hG4bK00E0F5

   17:42:38.430275   │ <────────────────────────── │        

│0E45333EAEE2FDC3E18D

         +0.105251   │         180 Ringing │         │From:

<sip:[email protected].131>;tag=0UUHS000003000

   17:42:38.535526   │ <────────────────────────── │        

│1D01001u1J9XWPK0DDUY6X

         +0.128720   │         180 Ringing │         │To:

   17:42:38.664246   │ <<<──────────────────────── │         │Call-ID:

4515e0000ef5-57f7d085-4d7d4603-f256d18-48e7f14@12

        +10.118555   │     408 Request Timeout │         │0.0.1

   17:42:48.782801   │ <────────────────────────── │         │CSeq:

33717 INVITE

         +0.000610   │             ACK │         │Contact:

   17:42:48.783411   │ ──────────────────────────> │        

│Allow-Events: refer

         +0.436750   │     408 Request Timeout │         │Allow: INVITE,

ACK, BYE, CANCEL, OPTIONS, PRACK, INFO, REF

   17:42:49.220161   │ <<<──────────────────────── │         │, NOTIFY,

SUBSCRIBE, UPDATE

         +0.000636   │             ACK │         │Content-Type:

application/sdp

   17:42:49.220797   │ ────────────────────────>>> │        

│Max-Forwards: 69

         +1.003961   │     408 Request Timeout │         │Supported:

timer, replaces, histinfo, 100rel

   17:42:50.224758   │ <<<──────────────────────── │        

│User-Agent: TELES-SBC

         +0.000705   │             ACK │         │Content-Length:   463

   17:42:50.225463   │ ────────────────────────>>> │         │

         +2.005938   │     408 Request Timeout │         │v=0

   17:42:52.231401   │ <<<──────────────────────── │         │o=-

1890151066 0 IN IP4 194.145.191.134

         +0.000651   │             ACK │         │s=TELES-SBC

   17:42:52.232052   │ ────────────────────────>>> │         │c=IN IP4

194.145.191.134

                     │ │         │t=0 0

                                                             │

 

Regards,

 

 

--

Richard Robson

Greenlight Support

01382 843843

 

 

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-- 
Richard Robson
Greenlight Support
01382 843843
[email protected]



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