Unable to complete calls using SPA9K

jwashline1 · ‎11-30-2010

I have a simple VoiP configuration using SPA9K, SPA400, SPA921 phones. I am trying to add a TEO TSG-6 phone into the configuration. The TSG-6 registers correctly however when I try to initiate a call to a local extension the receiving phone set never connects, only shows answering until it times out. Phone calls between SPA921 and SPA921 work correctly. Calls initiated from SPA921 to TSG-6 work correctly. Only calls initiated by the TSG-6 don't seem to work properly. Does anyone have any explanation?

Daniele Giordano · ‎12-04-2010

Can you capture the traffic between two phones with wireshark?
You can do it configuring a span port on your switch.
Post also phones configuration.

Thanks.

jwashline1 · ‎12-06-2010

I have run wireshark and what appears is between the SPA921 and TSG-6 phone the ACK is :

No. Time Source Destination Protocol Info

49 11.015128 193.104.0.53 193.104.0.52 SIP Request: ACK sip:1002@193.104.0.52:5060;transport=udp

This works correctly the phones connect and converstation is possible.

When I try between TSG-6 to TSG-6 or SPA921 the ack is:

No. Time Source Destination Protocol Info

11 3.080554 193.104.0.51 193.104.0.41 SIP Request: ACK sip:1002@193.104.0.52:5060;transport=udp

It appears the TSG-6 phone is expecting the ACK to come from the SPA9000 (193.104.0.41) instead of the other TSG-6 (193-104.0.52). The connection never completes. I have not found any setting in the SPA9000 where it could respond to the ACK as a proxy. Does anyone know of any other setting that may have an impact?

No. Time Source Destination Protocol Info

11 3.080554 193.104.0.51 193.104.0.41 SIP Request: ACK sip:1002@193.104.0.52:5060;transport=udp

It appears the TSG-6 phone is expecting the ACK to come from the SPA9000 (193.104.0.41) instead of the other TSG-6 (193-104.0.52). The connection never completes. I have not found any setting in the SPA9000 where it could respond to the ACK as a proxy. Does anyone know of any other setting that may have an impact?

Daniele Giordano · ‎12-06-2010

I think that the problem is in your TGS-6 configuration. Can you post it?
Do you have configured Outbound Proxy?

jwashline1 · ‎12-07-2010

TSG6 settings as follows:

SIP tab:

Proxy id - 192.168.0.1

Proxy udp port - 6060

Registrar enable on

Registrar id 192.168.0.1

Registrar port 6060

Registrar expiration 3600 seconds

Backup proxy id

Backup proxy port 5060

Backup registrar enable off

Backup registrar id

Backup registrar port 5060

Backup registrar expiration 3600 seconds

Outbound proxy

Outbound port 5060

Port 5060

RTP port 16392

RTP packet rate 10 milliseconds

Subscription expiration 3600 seconds

SIP call settings

Session timer unsupported

Session timer interval minimum 120 seconds

Session timer interval 3600 seconds

session refresher ANY

User Agent TEO

Call deflect id ALU_CALL_DEFLECTION

Loc call fwd id

Loc call fwd option off

Loc call fwd no-anwer time 12 seconds

emergency number

Hot-warm line number LU-FS5000-HOT_WARM

Phone context

Endpoint mode Normal

BusyLamp console base 0

Max rph r priority 2 (0-9)

Server type GENERIC

Session method is update OFF

Silence Supression OFF

Compact Headers OFF

Early Media detection ON

Message summary Subscription OFF

Prack Unsupported

Preconditions Unsupported

Privacy Values none

Resource Priority tag unsupported

Transport UDP

trys before using backup 8 times

Url Type SIP

line mode Normal

Dial plan

I have tried removing the Proxy id/leaving it blank but the phone won't register with the SPA9000.

Daniele Giordano · ‎12-07-2010

I need more info.

Can you post both full wireshark traces?

Thanks.

jwashline1 · ‎12-08-2010

The spa.pcap is a capture between SPA921 and TSG-6 phone, the tsg.pcap is a capture between TSG-6 and TSG-6.

Daniele Giordano · ‎12-08-2010

Strange issue.
In your working scenario, the SPA921 receive a 200 message forwarded by SPA9000. This message contains the ip address of TEO phone in the contact field. The SPA921 should send an ACK to proxy (SPA9000) but it sends the ACK direct to TEO. This is not correct.
The RTP flow starts correctly but in closing phase, when TEO sends a BYE to the proxy (SPA9000) receives a 404 error message because SPA9000 doesn't know that the call started.

Correct scenario:

In your not working scenario the flow of sip messages is correct.
It seems that the problem is in the proxy (SPA9000). It receives the ACK message from TEO but doesn't forward it to the other phone.

Can you try your TEO phones with other proxy? I think that they will work properly.

Can you post your SPA9000 config?

jwashline1 · ‎12-09-2010

The attached zip file contains screen captures from the SPA9000. Yes, I agree that the problem is the ACK is not being forwarded by SPA9000, I have not found any setting on the SPA9000 that seems to affect/change the problem. The SPA921 works because it send the ACK directly back to the TEO. The TEO dont work because they are expecting the SPA9000 to forward the ACK but it doesn't.

Daniele Giordano · ‎12-09-2010

Try to enable PRACK on all equipments.
In SPA devices you can enable 100rel PRACK support under EXT -> SIP Settings -> SIP 100REL Enable menu.
In TEO phones change the option "Prack Unsupported".

After these changes re-capture the traffic with wireshark. This is not a workaround but I think that Provisional Response ACK modifies the behavior of devices.