Subject: SRLG protection, LFAs and areas

From: Alia Atlas <[email-masked]>
Date: Mon, 02 May 2005 22:54:04 -0400

In considering the applicability statement for LFAs in regards to OSPF, it 
seems to me that a bit more detail/accuracy in describing SRLG protection 
is desirable.  Essentially, an alternate can only guarantee SRLG-protection 
for the area within which it is computed.  If an SRLG contains links from 
multiple areas, it is possible for traffic to leave one area (via the LFA) 
and then be forwarded across a path that includes the SRLG in the next 
area.  Of course, if the SRLG had actually failed, then the path in the 
next area would (hopefully) fail-over to the local alternate there.

I'm thinking of the following wording:  "Where SRLG protection is provided, 
it is in the context of the particular OSPF area or ISIS level, whose 
topology is used the SPF computations to compute the loop-free 
alternates.  If an SRLG contains links in multiple areas, then separate 
SRLG-protecting alternates
would be required in each area that is traversed by the affected
traffic."

Thoughts?  Is this useful or clear enough?

Thanks,
Alia

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From: Alex Zinin <[email-masked]>
Date: Wed, 25 May 2005 08:53:55 -0700

Alia,

  Catching up...
  
  I think putting something like this in the text would be useful.
  The only thing I would suggest is change "OSPF area or ISIS level"
  to "OSPF or IS-IS area".

-- 
Alex
http://www.psg.com/~zinin

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From: Alia Atlas <[email-masked]>
Date: Wed, 25 May 2005 17:22:19 -0400

Ok.  It'll be in the next version of the draft.

Alia