Subject: RE: [Isis-wg] Protocols Supported field in pseudonode LSP

From: Jeff Learman <[email-masked]>
Date: Mon, 26 Nov 2001 16:05:24 -0500

At 03:43 PM 11/26/2001, Jeff Parker wrote:
>> As I understand it, in networks that follow
>> the deployment rules, there is no need to check the 
>> protocols-supported option in LSPs when running SPF.  
>> Checking it is an optimization: if an LSP doesn't 
>> support IP, then there's no need to look for IP
>> addressing info in the LSP, because it won't be there.
>> 
>> Jeff [L]
>
>Jeff -
>        I thought this was an issue, due to transitive
>closure.  You don't have any IP addresses, but you 
>present an attractive route to a router that does
>have IP addresses.  If I don't check your protocols
>supported, I might use you on a path.  Since
>you don't forward IP packets, we have a black hole
>if all routers ignore protocol supported in SPF, or 
>a routing loop if some check and some do not.  

But this only happens in networks that don't follow the deployment rules.
SO: Do people follow the rules?

Are the rules really correct, if all routers in the subdomain check the
protocols supported option?  I think they could be relaxed to "sufficient
connectivity" for each protocol within each subdomain.

Regards,
Jeff

>- jeff parker  

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From: Dave Katz <[email-masked]>
Date: Mon, 26 Nov 2001 14:52:11 -0800 (PST)

I guess this begs the question, are there any OSI-only routers out there?
There are the goofy ADMs, I suppose

There are plenty of IP-only routers running ISIS, which leads one to 
believe that mixed networks are extremely rare.
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From: Jeff Learman <[email-masked]>
Date: Mon, 26 Nov 2001 18:11:00 -0500

Dave,

SONET network management uses OSI with ISIS, and are planning (last I
heard) to use integrated IP & OSI networks using RFC 1195.  For more
information, please contact T1.X1.

But we better work out these rules anyway, because IPV6 will raise
them yet again.

Regards,
Jeff

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From: Tony Przygienda <[email-masked]>
Date: Mon, 26 Nov 2001 14:23:50 -0800

> There are the goofy ADMs, I suppose

Well, the "goofy" ADMs still generate serious amounts of money so anybody
on this list runs some danger to possibly working on a goofy ADM one of these
days. So no point in ticking the TDM folks off ;-)

> believe that mixed networks are extremely rare.

with GMPLS and IP generally vying to control TDM networks and possibly
toasters in the future, I would say it is thinkable ....

My take on the protocols-supported field: If you have to stick something in,
stick the superset of all protocols supported by all the routers on the LAN.
This is
because a pseudo-node is not 'belonging' to the DIS, it is representation of
the
LAN as a shared resource by a chosen member ...

In this way, anybody checking for the field in pseudo-node will be happy and it

will not hurt anybody who doesn't  ...

    thanks

    -- tony