RE: [chat] Re: [SLUG] Answer + Disappointment

[Jill Rowling <Rowling@xxxxxxxxxx>]

I had a similar experience at Scitec. We were designing 2Mbit/s E1 modems
which had to implement all the Siemens CLEP stuff which telephone exchanges
use, plus they had a control function which was a local extension to the
protocol.
Under normal circumstances, the user never needed to worry about the local
extension because it never got through the telephone exchanges (indeed, the
protocol specifically forbids this sequence from appearing in the data
stream).
But there's always a catch. One customer (who should remain nameless) wanted
to use the modems in a private network, ie not going through a telephone
exchange.
Using their own nonstandard protocol.
And yes, you guessed it, the magic sequence came up... about once or twice a
month.
"But you said they were clear channel modems"
"Well, yes, as clear as E1 is supposed to be..."

The moral of the story is this:
If it's a clear channel modem, then the customer is allowed to transmit
anything.
If services are allowed, then all participants need to adhere to the
standard.
Non-adherents will cause problems, a bit like driving up the wrong side of
the road (yes you can physically do it but no you should not).

Regards,

Jill.


-- 
Jill Rowling, Snr Des. Eng. & Unix System Administrator
Eng. Systems Dept, Aristocrat Technologies Australia
3rd Floor, 77 Dunning Ave Rosebery NSW 2018
Phone: (02) 9697-4484 Fax: (02) 9663-1412 Email: rowling@xxxxxxxxxx
 


> -----Original Message-----
> From: Jamie Wilkinson [mailto:jaq@xxxxxxxxxxxxxx]
> Sent: Tuesday, 11 September 2001 12:05
> To: slug-chat@xxxxxxxxxxx
> Subject: Re: [chat] Re: [SLUG] Answer + Disappointment
> 
> 
> This one time, at band camp, Crossfire wrote:
> >One of people's favourite little tricks used to be sending the hangup
> >sequence with a dial command after it in a ICMP echo request, which
> >would then be echo'd by the host's IP stack, and would hit the modem,
> >which would then execute the commands.  Lets just say its 
> not nice. :)
> 
> I got a similar one done to me late one night by a friend.  
> He pinged me
> with the triple + and then ATM3 (I think, my hayes factoids 
> are a little
> rotten) which turned the modem volume up high.  The bastard 
> didn't even
> switch it back out of control mode afterwards!  Needless to 
> say, I had a
> stalled modem screaming at top volume in the middle of the night.
> 
> -- 
> jaq@xxxxxxxxxxxxxx                        
> http://spacepants.org/jaq.gpg
> <Balial> This port may thing it's fortified, butt I seem to 
> be mounting
> a pretty good assault
> 
> -- 
> SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/
> More Info: http://lists.slug.org.au/listinfo/slug-chat
> 


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