Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!hplabs!hpl-opus!hpccc!leinwand
From: leinwand@hpccc.HP.COM (Allan Leinwand)
Newsgroups: comp.dcom.sys.cisco
Subject: Re: Switched T1 with ciscos?
Message-ID: <14050003@hpccc.HP.COM>
Date: 26 Jul 90 16:28:35 GMT
References: <23828@boulder.Colorado.EDU>
Organization: HP Corp Computing & Services
Lines: 49

> / hpccc:comp.dcom.sys.cisco / tjs@uh.msc.umn.edu (Tim Salo) /  3:47 pm  Jul 23, 1990 /
>    !--------!  56k line (up all the time)         !--------!
>    !        !-------------------------------------!        !
>    ! router !  switched T1 (up only when needed)  !        !
>    !        !-------------------------------------!        !
>    !--------!                                     !--------!
> 
> Has anyone tried this?

Yes.  Here at HP we have code that given the above situation will 'turn up' 
the interface on the router as needed.  Our setup involves a 56Kb line
which is always in use and a Switched 56 circuit which is only called
when needed.  Basically the setup requires one interface on the router
administratively down with the other active.  When the code decides to
turn on the downed interface, this raises DTR and the Switched 56 modem
automatically dials the call.

We dial the Switched 56 call when we see a high error rate
on the original 56Kb, or perhaps the utilization exceeds a user defined
threshold.  The code allows the user select the error rate and/or utilization
threshold which must be seen on the original circuit before the Switched 
56 line takes affect.  The code also sends mail informing the network 
operators about the new circuit in place and the reason it was activated.

In guessing the next question:  I don't know if I can give the code out.  Right
now it works *real* good on HP-UX :-)  If there is significant interest, 
perhaps we can arrange something.

> 
> Will IGRP handle the addition and deletion of the T1 line gracefully?  (Will
> the 56k line be used at all when the T1 line is active?)

I would think that the 56Kb in your situation will not be used unless
load on the T-1 becomes significant.  Also, it depends on the minimum 
bandwidth on the path to the destination.  

In our scenario the additional 56Kb (or whatever speed) is handled by IGRP
nicely.

Thanks,

Allan Leinwand
Hewlett-Packard
Corporate Telecommunications
Network Solutions Engineering
(415)-424-3738
allan@hpcta.corp.hp.com

"I'm going to hell in a bucket, but at least I'm enjoying the ride"