Subject: Re: [Isis-wg] I-D ACTION:draft-ietf-isis-wg-multi-topology-00.txt

From: Tony Przygienda <[email-masked]>
Date: Wed, 28 Feb 2001 21:30:10 -0800

Serge Maskalik wrote:

>      Tony et al.,
>
>    Outside of the protocol-based VPN (limited amount), the
>   benefits of having multiple parallel IGP topologies is
>   not obvious to me. Even the VPNs are questionable. Can
>   you explain why someone would want a different topology
>   for and in-band management network? Are there NSPs asking
>   for this functionality?
>
>         - Serge

yepp, some of the functionality has been requested by ISPs since
a while and the draft is somehow a generalization of the problem.
Look @ the section describing different topology numbers and their
uses.

And as we say "you can run only very limited amount of VPNs" that
way ...

        -- tony

_______________________________________________
Isis-wg mailing list  -  [email-masked]
http://external.juniper.net/mailman/listinfo/isis-wg

---

From: Naiming Shen <[email-masked]>
Date: Thu, 01 Mar 2001 00:01:25 -0800

Serge,

 ]   Outside of the protocol-based VPN (limited amount), the 
 ]  benefits of having multiple parallel IGP topologies is 
 ]  not obvious to me. Even the VPNs are questionable. Can 
 ]  you explain why someone would want a different topology 
 ]  for and in-band management network?

In the case of applying M-ISIS in in-band management, "different topology"
probably means they share the same set of routers in the network, and
they may use different set of links each topology.

Using a simple example to illustrate this will be all the routers are 
connected using ATM links; between some pair of routers, there are 1 or 
2 VCs dedicated for in-band management use. The "normal" VCs are 
configured with high BW using UBR, the in-band management VCs are
configured with low BW using CBR. One ISIS topology only "sees" the UBR 
data links, the other only "sees" the CBR links. They use seperate routing 
tables.
The in-band management topology now has more protection from the general
routing problems, it can use it's own private address space, it can
use different QoS mechanisms and different ACLs on the links with less
concern of performance, it can also set different IGP costs on the links
independent of data traffic reqirements on other links.

In real life, you can replace the above CBR VCs example with dedicated T1s,
channelized bandwidths, etc.

 ]Are there NSPs asking for this functionality? 
 ]
 ] 	- Serge 

- Naiming