Subject: RE: [Isis-wg] Wide Metric

From: "Nurit Sprecher" <[email-masked]>
Date: Tue, 1 Feb 2005 12:46:23 +0200

But if you want to use the link from B to D for non-TE advertisement
using the wide metric, you have to use the extended TLV without the TE
sub TLV. In such a case the value of the Wide metric is used also for
the TE metric, and the link is considered as TE link.
I think combining these two mechanisms (wide and TE) is too confusing.

_____________________________________________
From: hemanthbs [mailto:[email-masked]] 
Sent: Tuesday, February 01, 2005 10:14 AM
To: 'Marc Binderberger'
Cc: Nurit Sprecher; [email-masked]
Subject: RE: [Isis-wg] Wide Metric

Hi Marc,

>> [...] This mandatory requirement does not
>> allow advertising a non-TE link. If for example, an IS supports TE on
>> some links but non-TE only on other links, this mandatory requirement
>> causes that even the Non-TE links will be considered in the CSPF
>> calculation. [...]
>
> The above concern may be answered as below, I guess.
> In an implementation where in the TE links are considered based on the
> following condition. "TE should be enabled for the ISIS process and 
> MPLS
> TE should be enabled on the interface"
> i.e for TE computation only those links be will be considered, for
> which MPLS TE is enabled on the interface and TE is enabled for that
> ISIS process running on that interface.

Hemanth, but how does a distance router _know_ what interfaces are 
enabled if not IS-IS is signaling this?

How does the IS-IS process running on A know that B's interface to C 
allows TE while the interface to D doesn't ?

   A--(te)--B--(te)--C
            |        |
            |       (te)
            |        |
            D--------E
Every ISIS process on a router will maintain a separate database for the
TE information. The TE advertisements made will also be little different
from the normal LSPs. With such a condition,
Router B's TE advertisements would advertise a link to C but not to D.
Hence when Router A processes this TE LSP, it would know that Router B
has a TE link only to C and not to D. From this information Router A can
build its own TE database, which it can use to build the TE link and
network information. Finally this TE link and network information is
given to CSPF.

-Hemanth.

(please switch on your fixed font ;-)

Or is there the implicit condition that all routers must be "TE-aware" 
and you simply put a very high TE metric on the links you don't want?

Or trial & error? (wasn't it named "cut back"? The RSVP will tell 
finally that a link is not TE/RSVP enabled).

What am I missing? :-)

Regards, Marc
--
Marc Binderberger    <[email-masked]>
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