T.38 reinvite and 488 Inacceptable Here relay problem; codec issue with proxy_media=true

30 Mar 2011

      Hi All!

I'm trying to launch t.38 passthough on FS.
I have two sip profiles - local and external, one on customer side looking
to ATAs, and one looking to PSTN gateways.
On both profiles I have enabled t38-passthrough, and this works when T.38 is
enabled on ATA and PSTN gateway.

Problems come when T.38 is turned off on ATA, so PSTN gateway detects fax on
its side and tries to re-invite ATA behind freeswitch with T.38. ATA answers
488 Inacceptable Here, but this answer doesn't get relayed to PSTN gateway,
so while ATA transmits fax signals inband, PSTN gateway still doesn't know
that re-invite is failed and fax machines can't negotiate t.30.

My question is how to allow relay this 488 to another side of bridge?

I thought that maybe proxy_media=true will help, and this is where second
issue comes. I enabled late negotiation and proxy_media, the only codec I
use is PCMA. But when I get incoming call, initially in PCMA and it goes to
outbound ESL app via socket, in the middle of processing I get strange
errors:

EXECUTE sofia/external/1234567@XXXXX.199 set(continue_on_fail=true)
2011-03-30 18:59:30.172363 [DEBUG] mod_dptools.c:1060
sofia/external/1234567@XX.XX.XX.199 SET [continue_on_fail]=[true]
EXECUTE sofia/external/1234567@XXXXX.199 socket(localhost:8006 async full)
*2011-03-30 18:59:30.184605 [DEBUG] switch_ivr.c:766 Codec Activated
L16@0hz0 channels 0ms
*
2011-03-30 18:59:30.188640 [DEBUG] switch_core_session.c:954 Send signal
sofia/external/1234567@XXXXX.199 [BREAK]
2011-03-30 18:59:30.205638 [DEBUG] switch_ivr.c:563 sofia/external/
1234567@85.114.2.199 Command Execute limit(hash OutboundExternalLimit 1)
EXECUTE sofia/external/1234567@XXXXX.199 limit(hash OutboundExternalLimit 1)
2011-03-30 18:59:30.205638 [INFO] switch_limit.c:126 incr called:
OutboundExternalLimit_1 max:-1, interval:0
2011-03-30 18:59:30.205638 [INFO] mod_hash.c:200 Usage for
OutboundExternalLimit_1 is now 1
*2011-03-30 18:59:30.205638 [ERR] switch_core_io.c:724
sofia/external/1234567@XXXXX.199 has no write codec.*
2011-03-30 18:59:30.205638 [DEBUG] switch_channel.c:2563
(sofia/external/1234567@XXXXX.199) Callstate Change RINGING -> HANGUP
2011-03-30 18:59:30.205638 [NOTICE] switch_core_io.c:725 Hangup
sofia/external/1234567@XXXXX.199 [CS_EXECUTE] [INCOMPATIBLE_DESTINATION]

I don't answer channel in my script, it doesn't even try to execute bridge,
failing somewhere in the middle.
Is this a bug or misconfiguration of my FS?

I tried latest git FreeSWITCH Version 1.0.head (git-6e78f6f 2011-03-30
11-41-45 +0200) with same result.

-- 
Best regards,

Dmitry Sytchev,
IT Engineer

Dmitry Sytchev

Anthony Minessale

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