[Isis-wg] IS-IS Extensions for Traffic Engineering

[Grant Mills]

Henk,

thanks for the reply.

>   Thank you.
>  One of the reasons that we didn't put this in our draft is that
>  the I/E metric bit is implemented wrongly in our IOS implementation.
>  No customer ever really complained about it. So it seems the I/E
>  metric bit is not used at all. At least not by our customers.

I'm glad you said that. ;-) We have a Cisco metrics mode which we can turn on if we wish to interoperate properly with Cisco ISIS.
And turn it off to work the Digital/ISO way. ;-)

>   So why do you want to see the difference between internal prefixes
>  and external prefixes ? It doesn't matter for route selection.
>  So I assume you want to use this to prevent "redistribution
>  feedback" when doing mutual redistributing with another IGP
>  at two or more places ? Or do you have another reason ?

True route selection is not the issue. As you say it is useful when injecting foreign routes from another IGP, e.g. OSPF, BGP, etc
and have those routes tagged at a different route priority or effected by targeted route policies than the ISIS routes. 
 
>   draft-ietf-isis-traffic-01 allows us to specify sub-TLVs for
>  IP prefixes. One thing we plan to do is define a sub-TLV to
>  tag or color IP prefixes. Those tags/colors can be used to
>  distinquish between internal and external routes. Then you
>  can use those tags/colors to control redistribution. We could
>  even define one or more "well-known colors", like well-known
>  BGP communities like no-advertise, etc.

When do you plan to publish the sub-TLV options. I assume this sub-TLV is similar to the one that appears in the extended IS
reachability TLV?

Cheers,

Grant.

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Grant Mills,                            Tel:   +44 (1252) 360013
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