Subject: Re: [Isis-wg] Choice of encapsulation on ATM

From: Dave Katz <[email-masked]>
Date: Tue, 31 Oct 2000 22:06:18 -0800 (PST)

We support NLPID and SNAP by configuration.  It's got to be the same as
the IP encapsulation, of course.

Henk's very fine NLPID hack (treating 0x40-0x4f as IP, and 0x83 as ISIS)
means that VCMUX could be used as well (taking most of the wind out of
the sails of ISIS-over-IP).

I suspect that most folks use SNAP encaps as it is the default (and the
cell tax has already been paid for the small packets in any case.)

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   Date: Tue, 31 Oct 2000 17:50:35 -0800

   Hi,

   We've been brushing off 3Com's old IS-IS implementation, making it
   support IPv6, and have noticed that it was never (in our system)
   made to run over ATM, so we're doing that too.  The problem is that
   in RFC1483 it describes two encapsulations for OSI packets over
   ATM - the LLC encapsulation FE-FE-03 and the NLPID encapsulation,
   which for IS-IS would simply be the IS-IS frame (NLPID is the first
   octet, er, byte).

   So, which of these encapsulations ever got used?  I know that CLNP
   was quite dead by the time everybody was implementing ATM (the reason
   I don't already know the answer), but IS-IS was certainly used over ATM
   to support IPv4 routing ala RFC1195.

   Does anybody out there know?  Do we need to do both?  Is there any reason
   one might be preferred?

   Thanks,

   Cyndi

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From: Rick Han <[email-masked]>
Date: Fri, 10 Nov 2000 15:34:58 +0000

Hi, I have a question about TLV-135 (described in
draft-ietf-isis-traffic-02.txt). How does TLV-135 indicate the metric
type (internal/external)? Is there a bit in the 4-byte metric field
reserved for metric-type?

Thanks

Rick

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From: stefano previdi <[email-masked]>
Date: Fri, 10 Nov 2000 16:50:05 +0100

At 16:34 10/11/2000, Rick Han wrote:
>type (internal/external)?

it doesn't.

If you refer to the use of I/E bit in draft-ietf-isis-domain-wide, 
keep in mind that we have the up/down bit for that.

> Is there a bit in the 4-byte metric field

no. 

Note that to my knowledge thare are no implementations that really use 
I/E bit in TLV-128/130. Therefore the interest of having similar bit 
in TLV-135 was quite limited....

s.