[Asterisk-Dev] Q.931 SERVice messages

[C. Maj]

I'm trying to add better support to libpri for maintenance
protocol SERVice and SERVice ACKnowledgement messages.  The
code is marked in q931.c as being a 'KLUDGE' and should be
ripe by now for fixing.

Things work great on my test machine with a T400 and a loop
back cable.  B-Channels are able to go in and out of
service, and the state is stored in chan_zap.c so that
channels out of service are immediately skipped when
attempting a call on them (similar to Do Not Disturb.)

Problem is, I can't get it to work in the real world.  And
given that this is a non-ITU message type, I'm not sure if
it's me or the switch that doesn't want to play nice.  As
best I can tell, these SERVice messages are defined in ANSI
T1.607 with a list price of $360 -- no 3 freebie downloads
like the ITU specs.  Thus, I've scoured various other web
resources to cobble together the implementation.

If I'm correct in my assumptions so far, these NFAS/CCS
SERVice messages are required for proper operation of backup
D-Channels, in addition to maintenance of B-Channels.
Currently, it appears although * supports the use of a
backup D-Channel, it is not able to initiate a backup
procedure -- only follow what the far-end switch does.

I'm attaching a patch of what I have so far, but what I
could really, really use from some kind soul is a PRI trace
of a proper SERV exchange for maintenance on a B-Channel.
If you want to try the patch, it adds CLI commands:
"zap service enable|disable|loop channel <chan num>"
(Very similar to the Cisco IOS Dial Technologies command:
"isdn service <chan num> state 0|1|2")

--Chris


-- 
Chris Maj, Rochester
cmaj_at_freedomcorpse_dot_com
Pronunciation Guide: Maj == May
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