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Summary:ASTERISK-17284: T38 passthrough doesn't work in glare reinvite situation
Reporter:mdu113 (mdu113)Labels:
Date Opened:2011-01-25 16:02:55.000-0600Date Closed:
Priority:MinorRegression?No
Status:Open/NewComponents:Channels/chan_sip/T.38
Versions:Frequency of
Occurrence
Related
Issues:
Environment:Attachments:( 0) debug.log
Description:Have the following situation:
000011206003 (cisco 1751+fxs with t38 enabled) <-> asterisk <-> sipp1 (ITSP)
ITSP is using Cisco AS5400 to terminate sip calls to PSTN and has T38 enabled
The problem is that both cisco devices detect fax tones (and send T38 reinvites) almost concurrently and that seems to confuse asterisk. I see the following logged on the console:
[Jan 25 16:03:21] WARNING[5956] chan_sip.c: Failed to read an alternate host or port in SDP. Expect audio problems
[Jan 25 16:03:21] WARNING[5956] chan_sip.c: Failed to set an alternate media source on glared reinvite. Audio may not work properly on this call.
When it happens fax 100% fails. When it doesn't happen fax works very reliably


****** ADDITIONAL INFORMATION ******

Attached is asterisk's debug.log.
I've made the following sip messaging diagram:
000011206003 asterisk sipp1
-> INVITE
<- 407 Proxy Authentication Required
-> ACK
-> INVITE with auth
<- 100 Trying
INVITE ->
100 Trying <-
183 Session Progress <-
<- 183 Session Progress
200 OK <-
ACK ->
<- 200 OK
-> ACK
INVITE with T38 (by sipp1) <-
100 Trying ->
<- INVITE with T38
-> INVITE with T38 (by 000011206003)
[Jan 25 16:03:21] WARNING[5956] chan_sip.c: Failed to read an alternate host or port in SDP. Expect audio problems
[Jan 25 16:03:21] WARNING[5956] chan_sip.c: Failed to set an alternate media source on glared reinvite. Audio may not work properly on this call.
<- 491 Request Pending
-> 491 Request Pending
<- ACK
-> ACK

<- INVITE without T38
-> 100 Trying
-> 200 OK without T38
<- ACK
-> INVITE with T38
<- 100 Trying
<- 200 OK with T38
-> ACK

Also cisco debugging (debug fax relay t30 all-level-1) in this case shows that fax negotiation fails:

Jan 25 16:09:14: 2/2  96067571 fr-entered=10(ms)
   timestamp=96075370 fr-msg-det TSI
   timestamp=96076070 fr-msg-det DCS
   timestamp=96086030 fr-msg-det TSI
   timestamp=96086720 fr-msg-det DCS

Successful fax debugging looks like the following:
Jan 25 16:01:00: 2/2  95573302 fr-entered=10(ms)
   timestamp=95579990 fr-msg-tx CSI
   timestamp=95580680 fr-msg-tx DIS
   timestamp=95582460 fr-msg-det TSI
   timestamp=95583150 fr-msg-det DCS
   timestamp=95589140 fr-msg-tx CFR
   timestamp=95630240 fr-msg-det EOP
   timestamp=95632830 fr-msg-tx MCF
   timestamp=95634540 fr-msg-det DCN
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