On 01/08/2016 04:32 PM, Benjamin Fitzgerald wrote:
I think #1 fixed it for me! Thank you so much! I changed the RTP timeout
on a test account SIP account and immediately it resolved the issue.
Excellent! Happy to help.
You're right, sending a BYE would effectively synchronize them
however I did not think keepalive using OPTIONS scheme would send a
BYE message in the event of a dead RTP session. That's why I thought
this scheme may not work.
No, indeed it would not; Kamailio has no awareness of RTP whatsoever.
All such schemes, including this one, as well as SSTs, are aimed at
detecting dead peers purely from signalling (that is, SIP) alone.
The way the OPTIONS keepalive flow works, for example, is:
UA A Proxy UA B
==================================
---- OPTIONS ---->
<---- 200 OK -----
<--- OPTIONS ----
--- 200 OK ---->
If UA B goes away:
UA A Proxy UA B
==================================
---- OPTIONS ---->
[no response]
...
------- BYE ------->
<---- BYE -----
--- 200 OK --->
The BYEs are crafted by Kamailio to (a) look to UA A like they came from
UA B and (b) to look to UA B like they came from UA A. This is because a
proxy cannot, formally speaking, endogenously originate in-dialog
requests. So, it's definitely a spoof-hack, but it works.
This mimics the more typical B2BUA-based approach of periodically
hitting both ends with empty reinvites whose effect is nullary (i.e. no
SDP amendments or remote dialog URI changes), and whose sole purpose is
to see if a 200 OK response is returned. If not, you can assume the
endpoint's dead or unreachable.
All proxy-side measures are going to operate on SIP solely.
I suppose I phrased this incorrectly as Kamailio thinks the endpoint
is in a call, when really it is just Asterisk and I am personally
associating the state with these transactions.
Well, it's understandable that you think in call-centric terms; we all
do. It just becomes important when illuminating distinctions tied up in
protocol semantics. It's a task requiring some pedantry.
-- Alex
--
Alex Balashov | Principal | Evariste Systems LLC
303 Perimeter Center North, Suite 300
Atlanta, GA 30346
United States
Tel: +1-800-250-5920 (toll-free) / +1-678-954-0671 (direct)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/
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