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Re: ISIS versus OSPF as IGP

  • From: fraanro <fraanro@arrakis.es>
  • Date: Tue, 13 Aug 2002 17:57:46 GMT
  • Cc: <mpls-ops@mplsrc.com>
  • Resent-Date: Tue, 13 Aug 2002 15:02:06 -0400
  • To: "alok" <alok.dube@apara.com>

inline

----- Mensaje Original -----
Remitente: "alok" <alok.dube@apara.com>
Fecha: Martes, Agosto 13, 2002 10:38 am
Asunto: [MPLS-OPS]: ISIS versus OSPF as IGP

> Hi,
> 
> what is the recommended IGP for an MPLS TE using RSVP? ISIS or OSPF?
> 
The only difference is that for TE updates, ISIS uses different 
different TLVs for each update, whereas OSPF may include more info in a 
single TLV object. 



> I always thought it was ISIS as the TLV extenstions support TE 
> across non
> IGP "best path" links too ..which is not yet done with OSPF with 
> opaqueLSAs...

What do you mean with that? With both ISIS and OSPF you can do TE based 
on constraints like bandwith request,link coloring, or even metric, 
that leads to paths not following the IGP best path.


> 
> am i right? any issues im overlooking etc?
> 
> I would also like to know, can ISIS be used in split 
> topologies...i mean
> like OSPF "area 0" ..does ISIS insist on only 1 "level-2"? or can 
> i have a
> non "hierarchial" topology with Level-2 between any 2 Level-1 
> areas and keep
> cascading?...there is nothing in the draft which seems to point to 
> that...

You can have TE inside a level 2 area, or inside a level 1 area, and 
depending on the specific implementation of TE (Cisco, Juniper, 
Riverstone, ...) you can/cannot do TE between areas, either OSPF or 
ISIS.


> rgds
> Alok
> 
> 
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