Subject: Multi-level Aggregration

From: Michael Menth <[email-masked]>
Date: Wed, 10 Jan 2001 19:45:41 +0100

Hello,

I have a question / suggestion to section 1.4.9 
(Multi-level Aggregration) of draft-ietf-issll-rsvp-aggr-02.txt.

The draft allows only for aggregation of rsvp sessions of the same 
aggregation level:

E2E RSVP reservations are considered to be at aggregation level 0
and level n+1 aggregations consist of level n reservations. This, 
however, implicitly implies in its realization, that a level n+1
aggregation may consist *** only *** of level n reservations. 
Hence, level n and level m reservations (n <> m) can not be merged
into the same aggregate although it might be useful under some
circumstances since the level of aggregation does not necessarily
denote the size of the aggregate.

What do you think of the following definition:

We count how often aggregation has been performed on a 
reservation, thus getting the "aggregation depth". Instead of the 
aggregation level, we record the aggregation depth in the router 
alert option field. 
When a reservation is established, its aggregation depth is 0. 
The following aggregators examine the RSVP control message and 
increase the reservation depth. If the resulting value is 1, the 
protocol number is swapped from RSVP to RSVP-E2E-IGNORE. 
In the same way, the following deaggregators decrease that value. 
If the resulting value is 0, the E2E-RSVP-IGNORE is swapped back 
to RSVP.

Doing so, an aggregation region is no longer restricted to carry
only aggregates of only one common level but it may carry 
aggregates of different depths. The benefit of this approach is 
clearly the higher flexibility for building aggregates. The 
drawback is that RSVP-E2E-IGNORE messages must not only be 
examined at the deaggregator but also at the aggregator. 

However, if this is a major drawback, then it is a weakness of 
the whole concept anyway since all RSVP messages of all (even 
recursively) aggregated reservations must be investigated at the 
deaggregators.

Are there other considerations why the "aggregation level"
approach is taken instead of an "aggregation depth" approach?

Kind regards, 

   Michael

-- 
Dipl.-Inform. Michael Menth
University of Wuerzburg, Institute of Computer Science
Am Hubland, D-97074 Wuerzburg, Germany, room A212
phone: (+49)-931/888-6644, fax: (+49)-931/888-6632
mailto:[email-masked]
http://www-info3.informatik.uni-wuerzburg.de/~menth