ntanaka@ARAGORN.GANDALF.CS.CMU.EDU (Nobuyoshi Tanaka) (06/26/89)
Two weeks ago, I asked net people about implementation of IP over
LAPB. I have had several responses via e-mails. I will post here the
summary. Thanks to all responders!
--Nobu
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Question:
I am interested in how to implement IP over LAPB (or HDLC). Are
there any references, any public domain implementations or any
pointers to comercial products.
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satz@cisco.com:
cisco Systems supports IP and multiple protocols over LAPB. The router
product has two kinds of LAPB for serial lines. One is plain LAPB (DTE or
DCE) where IP packets are put in the data field of IFRAMEs. The other is
what we call Multi-LAPB where the first 16 bits of the IFRAME contain a
packet type. Ethernet packet types are used to identify protocols.
Multi-LAPB can be either DTE or DCE too. [almes@rice.edu also told me
the pointer to satz.--Nobu]
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From: Drew Daniel Perkins <ddp+@andrew.cmu.edu>:
I am the Chairman of the IETF Working Group which is standardizing this.
We hope to have an RFC out by the end of the summer. What are you up
to?
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From: nowicki@Sun.COM (Bill Nowicki):
You do not need the retransmission part of HDLC. We use the framing
part for our point-to-point links because most serial chips can do this
in hardware, including the CRC. We sell a software product called
SunLink Inter-Network Router that implements it, but the protocol is
open, and can run on the Sun CPU ports up to 56Kbps, (such as is done
on Sun.COM!) or through higher-speed optional hardware like the Sun MCP.
The reference I have for the protocol (could be old) is:
"Synchronous Point-to-Point Protocol",
Xerox System Integration Standard XSIS 158412, December 1984.
US Mail address: Telephone:
Xerox Corporation (408) 737-4652
475 Oakmead Parkway
Sunnyvale, CA 94086
Attn: Xerox Systems Institute
MS: SVHQ 4
______________________________________________________________________
From: mahan@ncsa.uiuc.edu (Kurt Mahan):
There is an RFC (930? I can't remember off the top of my head ) that
describes it. [I'm not sure. RFC930 is not.--Nobu]
I did it already here at NCSA ( for a project we are working on.. )..
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From: Nick Felisiak <nick@spider.co.uk>
Just for fun, I set this up a few weeks ago here at Spider. By way of
background, we've developed X.25 and TCP for V.3 streams, so I had ready
access to all the bits.
I had two hosts with synchronous boards, set up one as a DTE and one as
a DCE, wrote a glue module, based on or SLIP driver, which took the
bottom end of IP and fed it into the HDLC driver. Since HDLC is frame
oriented, there was no need for the escape mechanisms which SLIP needs.
Unfortunately, the source is all commercial, so I can't just send it all to
you (and I bet you want to run it on a BSD machine, right :-)), but just to say
it works, and isn't that much work if you have the right code already around.
--