Path: utzoo!attcan!uunet!samsung!uakari.primate.wisc.edu!sdd.hp.com!usc!wuarchive!julius.cs.uiuc.edu!apple!bionet!hayes.ims.alaska.edu!accuvax.nwu.edu!nucsrl!telecom-request
From: goldstein@delni.enet.dec.com (Fred R. Goldstein)
Newsgroups: comp.dcom.telecom
Subject: Re: ISDN Frame Relay Service
Message-ID: <14445@accuvax.nwu.edu>
Date: 6 Nov 90 21:13:29 GMT
Sender: news@accuvax.nwu.edu
Organization: Digital Equipment Corp., Littleton MA USA
Lines: 40
Approved: Telecom@eecs.nwu.edu
X-Submissions-To: telecom@eecs.nwu.edu
X-Administrivia-To: telecom-request@eecs.nwu.edu
X-Telecom-Digest: Volume 10, Issue 797, Message 5 of 10


In article <14396@accuvax.nwu.edu>, zweig@cs.uiuc.edu (Johnny Zweig)
writes...

>I was talking to Van Jacobson last week and he described a service his
>local telco is going to offer real soon now in which the customer sets
>up virtual calls using the D-channel and then dumps HDLC frames onto
>the B-channel and they get routed by the CO switch. Zounds! This
>sounds really neat -- the functionality of IP coming right out of the
>funny-looking ISDN jack on the wall.  

>Does anyone know more about this service?  I am mostly interested in
>how reliable the frame delivery would be, whether frames would be
>delivered in order, whether one could set up calls to the same
>destination over both B-channels in a PRI (to crank out 128kbps to a
>single other machine) and that sort of thing.

Frame Relay Service is, as you say, based upon using the D channel to
set up calls and the B channel (OR the D channel, on a low priority
basis) to send the bearer frames.  The bearer frame uses the "Core
Aspects of LAPD" protocol (ANSI T1.6ca, partially through balloting,
and also a subset of CCITT draft Q.922), which has an HDLC flag, CRC,
and LAPD address, but NO HDLC control info.  (That's payload, in a
higher layer.)

It does not guarantee frame delivery, but what frames it delivers
should be in order (under normal circumstances).  Two separate B
channels would normally be two separate packet streams, though a 128
kbps access to the packet handler (bit-synchronized) isn't
inconceivable for the future.  Private FR switches, of course, can
have faster accesses; you can also theoretically use ISDN H channels
(384 kbps, 1.472 and 1.536 Mbps).

We spent _years_ working on this at ANSI T1S1...


Fred R. Goldstein              Digital Equipment Corp., Littleton MA
goldstein@delni.enet.dec.com   voice: +1 508 486 7388
 Do you think anyone else on the planet would share my opinions, let
 alone a multi-billion dollar corporation?