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Date:      Tue, 21 Jul 1998 10:56:33 +0200 (METDST)
From:      hm@hcs.de (Hellmuth Michaelis)
To:        leo@wau.mis.ah.nl (Leo Weppelman)
Cc:        freebsd-isdn@FreeBSD.ORG
Subject:   Re: Can't get dialback to work [ long ]
Message-ID:  <m0yyYDq-0000f8C@hcswork.hcs.de>
In-Reply-To: <19980720162306.38929@wau.mis.ah.nl> from Leo Weppelman at "Jul 20, 98 04:23:07 pm"

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>From the keyboard of Leo Weppelman:
> On Wed 15 Jul 1998, Hellmuth Michaelis wrote:
> > >From the keyboard of Leo Weppelman:
> > > 
> > > At the company, we have a Linux system that we use for dialin. It is
> > > configured for dialback (reject the incoming call, dialback thereafter).
> > > Somehow, I can't get the dialback to work on my NetBSD/Atari with i4b-00.62.
> > > 
> > > My config entry looks like:
> > >   dialretries             = 1
> >     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > 
> > Try to increase the number of dialretries. I don't know if the behaviour with
> > your settings is a bug or a feature ... ;-)
> > 
> > Also, configure callbackwait or calledbackwait explicitely, whichever is 
> > appropriate for your setup.
> 
> Ok, I did this and it works (more or less.... ;-). Somehow it takes a
> tremendous time to get the connection established. 

[...]
>   - my isdn.rc entry:
>       calledbackwait          = 3
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^



What happenes is:

a) frame:000006 - time:20.07 15:16:30.81 0 secs - outgoing SETUP to remote
b) frame:000013 - time:20.07 15:16:39.21 9 secs - line cleared
c) frame:000016 - time:20.07 15:16:43.78 13 secs - outgoing SETUP to remote
d) frame:000023 - time:20.07 15:16:49.90 19 secs - line cleared
e) frame:000026 - time:20.07 15:16:52.71 22 secs - remote calls in

The time between b) and c) is your calledbackwait time parameter (set to 3)

The time between d) and e) is the time, the remote needs to be able to call
in (both participating exchanges need to free the lines and other resources
on both ends) which also close to 3 seconds.

The calledbackwait parameter specifies how long isdnd will wait between b) and
c) until another call is made to the remote to make the remote call back. This
time is the time-window the remote is able to call back. In case this window
is too small (as it is in your case), you'll get the problems you describe.

You need a larger calledbackwait (and/or a shorted callbackwait or equivalent
at the remote side) in your setup!

A good strategy to find out the time required for calledbackwait is to set 
it to a large value, i.e. 30 or 60 seconds (be patient ... :-) ).

Then you measure the time it takes usually (in case the ISDN network is very
loaded, i.e. during daytime, it takes more time to callback; during nighttimes
it is usually much faster!) getting from the RELEASE_COMPLETE message to the
time the calling back remote calls in. Add some seconds to this and use it as 
the calledbackwait time.





> 
> The trace:
> =========== isdntrace controller #0 =========== started Mon Jul 20 15:16:26 1998
> 
> -- NT->TE - unit:0 - frame:000001 - time:20.07 15:16:30.32 - length:4 ----------
> Dump:000  02 a1 01 05                                           ....
> Q921: SAP=0 (Call Control), C, TEI=80, S-Frame: RR N(R) 2 PF 1 
> 
> -- TE->NT - unit:0 - frame:000002 - time:20.07 15:16:30.78 - length:8 ----------
> Dump:000  fc ff 03 0f 7f 9d 01 ff                               ........
> Q921: SAP=63 (TEI-Management), C, TEI=127, Ri=0x7f9d, IdRequest, Ai=127
> 
> -- NT->TE - unit:0 - frame:000003 - time:20.07 15:16:30.79 - length:8 ----------
> Dump:000  fe ff 03 0f 7f 9d 02 c3                               ........
> Q921: SAP=63 (TEI-Management), C, TEI=127, Ri=0x7f9d, IdAssign, Ai=97
> 
> -- TE->NT - unit:0 - frame:000004 - time:20.07 15:16:30.79 - length:3 ----------
> Dump:000  00 c3 7f                                              ...
> Q921: SAP=0 (Call Control), C, TEI=97, U-Frame: SABME PF 1 
> 
> -- NT->TE - unit:0 - frame:000005 - time:20.07 15:16:30.81 - length:3 ----------
> Dump:000  00 c3 73                                              ..s
> Q921: SAP=0 (Call Control), R, TEI=97, U-Frame: UA PF 1 
> 
> -- TE->NT - unit:0 - frame:000006 - time:20.07 15:16:30.81 - length:42 ---------
> Dump:000  00 c3 00 00                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 0 N(R) 0 P 0 
> Dump:004  08 01 51 05 a1 04 02 88 90 18 01 81 6c 0b 81 30       ..Q.........l..0
> Dump:020  33 30 32 34 34 38 39 33 37 70 0b 81 30 37 35 36       302448937p..0756
> Dump:036  31 32 32 33 33 39                                     122339
> Q931: pd=Q.931/I.451, cr=0x51 (from origination), message=SETUP: 
>      [sending complete]
>      [bearer capability: 
>           cap=unrestricted digital information
>           std=CCITT
>           rate=64 kbit/s
>           mode=circuit]
>      [channel id: channel=B-1 (preferred)]
>      [calling party number: 0302448937 (type=unknown, plan=ISDN)]
>      [called party number: 0756122339 (type=unknown, plan=ISDN)]
> 
> -- NT->TE - unit:0 - frame:000007 - time:20.07 15:16:30.84 - length:4 ----------
> Dump:000  00 c3 01 02                                           ....
> Q921: SAP=0 (Call Control), R, TEI=97, S-Frame: RR N(R) 1 PF 0 
> 
> -- NT->TE - unit:0 - frame:000008 - time:20.07 15:16:31.09 - length:11 ---------
> Dump:000  02 c3 00 02                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 0 N(R) 1 P 0 
> Dump:004  08 01 d1 02 18 01 89                                  .......
> Q931: pd=Q.931/I.451, cr=0x51 (from destination), message=CALL PROCEEDING: 
>      [channel id: channel=B-1 (exclusive)]
> 
> -- TE->NT - unit:0 - frame:000009 - time:20.07 15:16:31.09 - length:4 ----------
> Dump:000  02 c3 01 02                                           ....
> Q921: SAP=0 (Call Control), R, TEI=97, S-Frame: RR N(R) 1 PF 0 
> 
> -- NT->TE - unit:0 - frame:000010 - time:20.07 15:16:39.17 - length:12 ---------
> Dump:000  02 c3 02 02                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 1 N(R) 1 P 0 
> Dump:004  08 01 d1 45 08 02 80 9f                               ...E....
> Q931: pd=Q.931/I.451, cr=0x51 (from destination), message=DISCONNECT: 
>      [cause: 31: Normal, unspecified (Q.850) 
>           (location=user, std=CCITT)]
> 
> -- TE->NT - unit:0 - frame:000011 - time:20.07 15:16:39.17 - length:8 ----------
> Dump:000  00 c3 02 04                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 1 N(R) 2 P 0 
> Dump:004  08 01 51 4d                                           ..QM
> Q931: pd=Q.931/I.451, cr=0x51 (from origination), message=RELEASE: 
> 
> -- NT->TE - unit:0 - frame:000012 - time:20.07 15:16:39.18 - length:4 ----------
> Dump:000  00 c3 01 04                                           ....
> Q921: SAP=0 (Call Control), R, TEI=97, S-Frame: RR N(R) 2 PF 0 
> 
> -- NT->TE - unit:0 - frame:000013 - time:20.07 15:16:39.21 - length:12 ---------
> Dump:000  02 c3 04 04                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 2 N(R) 2 P 0 
> Dump:004  08 01 d1 5a 08 02 80 9f                               ...Z....
> Q931: pd=Q.931/I.451, cr=0x51 (from destination), message=RELEASE COMPLETE: 
>      [cause: 31: Normal, unspecified (Q.850) 
>           (location=user, std=CCITT)]
> 
> -- TE->NT - unit:0 - frame:000014 - time:20.07 15:16:39.21 - length:4 ----------
> Dump:000  02 c3 01 06                                           ....
> Q921: SAP=0 (Call Control), R, TEI=97, S-Frame: RR N(R) 3 PF 0 
> 
> -- NT->TE - unit:0 - frame:000015 - time:20.07 15:16:40.53 - length:4 ----------
> Dump:000  02 a1 01 05                                           ....
> Q921: SAP=0 (Call Control), C, TEI=80, S-Frame: RR N(R) 2 PF 1 
> 
> -- TE->NT - unit:0 - frame:000016 - time:20.07 15:16:43.78 - length:42 ---------
> Dump:000  00 c3 04 06                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 2 N(R) 3 P 0 
> Dump:004  08 01 2c 05 a1 04 02 88 90 18 01 81 6c 0b 81 30       ..,.........l..0
> Dump:020  33 30 32 34 34 38 39 33 37 70 0b 81 30 37 35 36       302448937p..0756
> Dump:036  31 32 32 33 33 39                                     122339
> Q931: pd=Q.931/I.451, cr=0x2c (from origination), message=SETUP: 
>      [sending complete]
>      [bearer capability: 
>           cap=unrestricted digital information
>           std=CCITT
>           rate=64 kbit/s
>           mode=circuit]
>      [channel id: channel=B-1 (preferred)]
>      [calling party number: 0302448937 (type=unknown, plan=ISDN)]
>      [called party number: 0756122339 (type=unknown, plan=ISDN)]
> 
> -- NT->TE - unit:0 - frame:000017 - time:20.07 15:16:43.81 - length:4 ----------
> Dump:000  00 c3 01 06                                           ....
> Q921: SAP=0 (Call Control), R, TEI=97, S-Frame: RR N(R) 3 PF 0 
> 
> -- NT->TE - unit:0 - frame:000018 - time:20.07 15:16:44.04 - length:11 ---------
> Dump:000  02 c3 06 06                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 3 N(R) 3 P 0 
> Dump:004  08 01 ac 02 18 01 89                                  .......
> Q931: pd=Q.931/I.451, cr=0x2c (from destination), message=CALL PROCEEDING: 
>      [channel id: channel=B-1 (exclusive)]
> 
> -- TE->NT - unit:0 - frame:000019 - time:20.07 15:16:44.04 - length:4 ----------
> Dump:000  02 c3 01 08                                           ....
> Q921: SAP=0 (Call Control), R, TEI=97, S-Frame: RR N(R) 4 PF 0 
> 
> -- NT->TE - unit:0 - frame:000020 - time:20.07 15:16:49.84 - length:12 ---------
> Dump:000  02 c3 08 06                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 4 N(R) 3 P 0 
> Dump:004  08 01 ac 45 08 02 80 d8                               ...E....
> Q931: pd=Q.931/I.451, cr=0x2c (from destination), message=DISCONNECT: 
>      [cause: 88: Incompatible destination (Q.850) 
>           (location=user, std=CCITT)]
> 
> -- TE->NT - unit:0 - frame:000021 - time:20.07 15:16:49.84 - length:8 ----------
> Dump:000  00 c3 06 0a                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 3 N(R) 5 P 0 
> Dump:004  08 01 2c 4d                                           ..,M
> Q931: pd=Q.931/I.451, cr=0x2c (from origination), message=RELEASE: 
> 
> -- NT->TE - unit:0 - frame:000022 - time:20.07 15:16:49.85 - length:4 ----------
> Dump:000  00 c3 01 08                                           ....
> Q921: SAP=0 (Call Control), R, TEI=97, S-Frame: RR N(R) 4 PF 0 
> 
> -- NT->TE - unit:0 - frame:000023 - time:20.07 15:16:49.90 - length:12 ---------
> Dump:000  02 c3 0a 08                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 5 N(R) 4 P 0 
> Dump:004  08 01 ac 5a 08 02 80 d8                               ...Z....
> Q931: pd=Q.931/I.451, cr=0x2c (from destination), message=RELEASE COMPLETE: 
>      [cause: 88: Incompatible destination (Q.850) 
>           (location=user, std=CCITT)]
> 
> -- TE->NT - unit:0 - frame:000024 - time:20.07 15:16:49.90 - length:4 ----------
> Dump:000  02 c3 01 0c                                           ....
> Q921: SAP=0 (Call Control), R, TEI=97, S-Frame: RR N(R) 6 PF 0 
> 
> -- NT->TE - unit:0 - frame:000025 - time:20.07 15:16:50.73 - length:4 ----------
> Dump:000  02 a1 01 05                                           ....
> Q921: SAP=0 (Call Control), C, TEI=80, S-Frame: RR N(R) 2 PF 1 
> 
> -- NT->TE - unit:0 - frame:000026 - time:20.07 15:16:52.71 - length:40 ---------
> Dump:000  02 ff 03                                              ...
> Q921: SAP=0 (Call Control), C, TEI=127, U-Frame: UI PF 0 
> Dump:003  08 01 78 05 a1 04 02 88 90 18 01 89 6c 0b 21 81       ..x.........l.!.
> Dump:019  37 35 36 31 32 32 33 33 39 70 0a a1 33 30 32 34       756122339p..3024
> Dump:035  34 38 39 33 37                                        48937
> Q931: pd=Q.931/I.451, cr=0x78 (from origination), message=SETUP: 
>      [sending complete]
>      [bearer capability: 
>           cap=unrestricted digital information
>           std=CCITT
>           rate=64 kbit/s
>           mode=circuit]
>      [channel id: channel=B-1 (exclusive)]
>      [calling party number: 756122339 (type=national, plan=ISDN,
>           presentation allowed, screening user provided: verified & passed)]
>      [called party number: 302448937 (type=national, plan=ISDN)]
> 
> -- TE->NT - unit:0 - frame:000027 - time:20.07 15:16:52.75 - length:8 ----------
> Dump:000  00 c3 08 0c                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 4 N(R) 6 P 0 
> Dump:004  08 01 f8 07                                           ....
> Q931: pd=Q.931/I.451, cr=0x78 (from destination), message=CONNECT: 
> 
> -- NT->TE - unit:0 - frame:000028 - time:20.07 15:16:52.75 - length:4 ----------
> -- TE->NT - unit:0 - frame:000027 - time:20.07 15:16:52.75 - length:8 ----------
> Dump:000  00 c3 08 0c                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 4 N(R) 6 P 0 
> Dump:004  08 01 f8 07                                           ....
> Q931: pd=Q.931/I.451, cr=0x78 (from destination), message=CONNECT: 
> 
> -- NT->TE - unit:0 - frame:000028 - time:20.07 15:16:52.75 - length:4 ----------
> Dump:000  00 a1 01 06                                           ....
> Q921: SAP=0 (Call Control), R, TEI=80, S-Frame: RR N(R) 3 PF 0 
> 
> -- NT->TE - unit:0 - frame:000029 - time:20.07 15:16:52.76 - length:4 ----------
> Dump:000  00 c3 01 0a                                           ....
> Q921: SAP=0 (Call Control), R, TEI=97, S-Frame: RR N(R) 5 PF 0 
> 
> -- NT->TE - unit:0 - frame:000030 - time:20.07 15:16:52.82 - length:8 ----------
> Dump:000  02 c3 0c 0a                                           ....
> Q921: SAP=0 (Call Control), C, TEI=97, I-Frame: N(S) 6 N(R) 5 P 0 
> Dump:004  08 01 78 0f                                           ..x.
> Q931: pd=Q.931/I.451, cr=0x78 (from origination), message=CONNECT ACKNOWLEDGE: 
> 
> -- TE->NT - unit:0 - frame:000031 - time:20.07 15:16:52.82 - length:4 ----------
> Dump:000  02 c3 01 0e                                           ....
> Q921: SAP=0 (Call Control), R, TEI=97, S-Frame: RR N(R) 7 PF 0 
> 
> 

hellmuth
-- 
Hellmuth Michaelis                                    Tel   +49 40 559747-70
HCS Hanseatischer Computerservice GmbH                Fax   +49 40 559747-77
Oldesloer Strasse 97-99                               Mail  hm@hcs.de
22457 Hamburg                                         WWW   http://www.hcs.de

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