Subject: hop count vs real metrics LFA analysis

From: Pierre Francois <[email-masked]>
Date: Wed, 05 Dec 2007 14:22:41 -0800

Hi,

To illustrate the discussion in rtgarea about the importance of
using the configured link metrics vs using hop count when looking at LFA 
coverage,
here's a comparison of LFA's coverage, considering the percentage of 
links that are fully covered by LFAs in various topologies.

It shows the coverage with configured metrics vs. coverage with hop count.
ISPs A,  D, and E are national ISPs. ISPs B and C are Tier-1 ISPs
Note that the results for ISPE have *not* been swapped.

ISPA : 46% vs 12%
ISPB : 50% vs 40%
ISPC :  66% vs 46%
ISPD : 31% vs 21%
ISPE : 7% vs  46%

Regards,

Pierre.

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From: dimitri papadimitriou <[email-masked]>
Date: Sat, 08 Dec 2007 15:04:19 +0100

thanks for the data (q: what characterizes ISPE vs the other cases)?

would it be also possible for the speaker to send the slides / makes the 
slides presented available ?

-d.
Pierre Francois wrote:
> .

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From: Michael Menth <[email-masked]>
Date: Wed, 12 Dec 2007 16:02:15 +0100

Hi Pierre,

thanks for this note. Just to explain the difference of the analyses to 
the list:
* Pierre's numbers tell how many links can be fully protected by LFAs. A 
link is fully protected if ALL destinations carried over that link can 
be protected by some  LFA, no matter which type, and the protecting LFAs 
do not need to be the same for the protected destinations (?).
* TR432 ( http://www3.informatik.uni-wuerzburg.de/TR/tr432.pdf ) shows 
how many destinations can be protected at a node by which kind of LFA 
when a certain protection level is required. Increased resilience 
requirements reduce the set of applicable LFA types.

In any case, the existence of LFAs is very sensitive to the topology and 
to the link metrics. Certainly, an analysis of the existence of 
different LFA types in operational networks with real link metrics would 
be interesting. I hope that our national grant will be extended such 
that we can have a deeper look at that issue. In this case, we would 
appreciate interest and willingness of network operators to cooperate 
with us on this area.

Pierre, I hope we'll soon find some time to work together on some ideas 
that we sketched out in Vancouver. It was great talking to you.

Regards,

    Michael

Pierre Francois wrote:
> using the configured link metrics vs using hop count when looking at 
> LFA coverage,

-- 
Dr. Michael Menth, Assistant Professor
University of Wuerzburg, Institute of Computer Science
Am Hubland, D-97074 Wuerzburg, Germany, room B206
phone: (+49)-931/888-6644, fax: (+49)-931/888-6632
mailto:[email-masked]
http://www3.informatik.uni-wuerzburg.de/research/ngn