Blogs

Showing 1 - 5 of 21 results.
Items per Page 5
of 5
First Previous Last

Forums

« Back to SIP Trunk Questions

Re-SUBSCRIBE request dropped when monitoring multiple phones

Combination View Flat View Tree View
Threads [ Previous | Next ]
Re-SUBSCRIBE request dropped when monitoring multiple phones
Answer
8/17/10 11:32 PM
I'm using SIP SUBSCRIBE to get presence information about phones.  When I only monitor one one phone it works fine.  I sent a SUBSCRIBE, get a 200 OK response, then an initial NOTIFY with the phone's busy/idle status.  Shortly before the subscription's expiration time I send another SUBSCRIBE with the same Call-ID, event ID, and From tag as the first one and the same To tag as in the servers 200 response.  (I increment the CSeq.)  I again get a 200 OK response, and a NOTIFY.
 
If I send 2 SUBSCRIBEs to monitor 2 different phones, each initial SUBSCRIBE gets a 200 OK and a NOTIFY, but the second set of SUBSCRIBES get dropped.  I get no response back from the server.  Eventually (30 minutes after the expiration time) I get a NOTIFY that the subscription has been terminated (reason=timeout).
 
Any idea what's going on?

Here's the initial SUBSCRIBE: (192.168.97.54 is the server; 192.168.11.167 is my client)
SUBSCRIBE sip:2040@192.168.97.54 SIP/2.0
Contact: <sip:192.168.11.167:5060;transport=UDP>
Via: SIP/2.0/UDP 192.168.11.167:5060;branch=z9hG4bK-1-0-1-6061766
From: <sip:3200@192.168.97.54>;tag=729305
To: <sip:2040@192.168.97.54>
Supported: 100rel, path
Max-Forwards: 70
Content-Length: 0
Expires: 600
Call-ID: 1-2907@192.168.11.167
Cseq: 4842 SUBSCRIBE
Event: presence;id=422488

Here's the server's response to the initial SUBSCRIBE:
SIP/2.0 200 OK
Date: Tue, 17 Aug 2010 13:36:09 GMT
From: <sip:3200@192.168.97.54>;tag=729305
Content-Length: 0
To: <sip:2040@192.168.97.54>;tag=1281814172
Contact: <sip:2040@192.168.97.54:5060>
Expires: 600
Call-ID: 1-2907@192.168.11.167
Via: SIP/2.0/UDP 192.168.11.167:5060;branch=z9hG4bK-1-0-1-6061766
CSeq: 4842 SUBSCRIBE

Here's the re-SUBSCRIBE:
SUBSCRIBE sip:2040@192.168.97.54 SIP/2.0
Contact: <sip:192.168.11.167:5060;transport=UDP>
Via: SIP/2.0/UDP 192.168.11.167:5060;branch=z9hG4bK-1-0-1-6061766
From: <sip:3200@192.168.97.54>;tag=729305
To: <sip:2040@192.168.97.54>;tag=1281814172
Supported: 100rel, path
Call-ID: 1-2907@192.168.11.167
Content-Length: 0
Expires: 600
Cseq: 4844 SUBSCRIBE
Event: presence;id=422488
Flag

RE: Re-SUBSCRIBE request dropped when monitoring multiple phones
Answer
9/2/10 7:15 PM as a reply to Eric Rubin.
I finally figured out the problem.  It's with the Cseq.  I was incrementing the Cseq for every SUBSCRIBE I sent.  But the Cseq is supposed to increment by 1 WITHIN EACH DIALOG (section 12.2.1.1 of RFC 3261).  So when I had only 1 subscription (and thus 1 dialog) it worked, but when I had 2 subscriptions the Cseq was higher then the previous Cseq for the dialog.  (In the example below the first Cseq is 4842 and the second is 4844.)  The Call Manager drops requests when the Cseq is not 1 higher than the previous Cseq for the dialog.  (I don't know why it doesn't send an "Invalid Cseq" response.)  I was able to fix the problem by having Cseqs for each dialog that each incremented independently, or by having all the subscriptions within a single dialog.
 
 
I'm using SIP SUBSCRIBE to get presence information about phones.  When I only monitor one one phone it works fine.  I sent a SUBSCRIBE, get a 200 OK response, then an initial NOTIFY with the phone's busy/idle status.  Shortly before the subscription's expiration time I send another SUBSCRIBE with the same Call-ID, event ID, and From tag as the first one and the same To tag as in the servers 200 response.  (I increment the CSeq.)  I again get a 200 OK response, and a NOTIFY.
 
If I send 2 SUBSCRIBEs to monitor 2 different phones, each initial SUBSCRIBE gets a 200 OK and a NOTIFY, but the second set of SUBSCRIBES get dropped.  I get no response back from the server.  Eventually (30 minutes after the expiration time) I get a NOTIFY that the subscription has been terminated (reason=timeout).
 
Any idea what's going on?

Here's the initial SUBSCRIBE: (192.168.97.54 is the server; 192.168.11.167 is my client)
SUBSCRIBE sip:2040@192.168.97.54 SIP/2.0
Contact: <sip:192.168.11.167:5060;transport=UDP>
Via: SIP/2.0/UDP 192.168.11.167:5060;branch=z9hG4bK-1-0-1-6061766
From: <sip:3200@192.168.97.54>;tag=729305
To: <sip:2040@192.168.97.54>
Supported: 100rel, path
Max-Forwards: 70
Content-Length: 0
Expires: 600
Call-ID: 1-2907@192.168.11.167
Cseq: 4842 SUBSCRIBE
Event: presence;id=422488

Here's the server's response to the initial SUBSCRIBE:
SIP/2.0 200 OK
Date: Tue, 17 Aug 2010 13:36:09 GMT
From: <sip:3200@192.168.97.54>;tag=729305
Content-Length: 0
To: <sip:2040@192.168.97.54>;tag=1281814172
Contact: <sip:2040@192.168.97.54:5060>
Expires: 600
Call-ID: 1-2907@192.168.11.167
Via: SIP/2.0/UDP 192.168.11.167:5060;branch=z9hG4bK-1-0-1-6061766
CSeq: 4842 SUBSCRIBE

Here's the re-SUBSCRIBE:
SUBSCRIBE sip:2040@192.168.97.54 SIP/2.0
Contact: <sip:192.168.11.167:5060;transport=UDP>
Via: SIP/2.0/UDP 192.168.11.167:5060;branch=z9hG4bK-1-0-1-6061766
From: <sip:3200@192.168.97.54>;tag=729305
To: <sip:2040@192.168.97.54>;tag=1281814172
Supported: 100rel, path
Call-ID: 1-2907@192.168.11.167
Content-Length: 0
Expires: 600
Cseq: 4844 SUBSCRIBE
Event: presence;id=422488
Flag

Collateral


No files available