Subject: merging of guaranteed service and controlled load reservations

From: Paul WHITE <[email-masked]>
Date: Tue, 28 Apr 1998 12:08:36 +0100

Hello folks,

In RFC2210, "The use of RSVP with intserv" it says

"      NOTE: In RSVP Version 1, all receivers within a session are
      required to choose the same QoS control service.  This restriction
      is imposed by the difficulty of merging reservations requesting
      different QoS control services, and the current lack of a general
      service replacement mechanism.  The restriction may be eliminated
      in the future."

I assume this restriction is in place to prevent scenario 1) below

guaranteed service reservation R, Tspec= p1, b1, r1, m, M
controlled load service reservation Tspec=p2, b2, r2, m, M

scenario 1
----------
Assuming p2>p1, b2>b1, r2>r1 then merging these 2 reservations(worst case) is 
non-trivial

scenario 2
----------
p2<=p1, b2<=b1, r2<=r1 then merging is very easy and the merged reservation 
will be simply
	guaranteed service reservation( R, Tspec= p1, b1, r1, m, M )

It is my understanding then  that in a situation where scenario 2 would always 
be the case then merging of controlled-load and guaranteed service would not 
be a problem. However we disallow merging to prevent scenarios such as 
scenario 1)

Can anyone confirm this please?

Cheers,

Paul.

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From: Roch Guerin <[email-masked]>
Date: Tue, 28 Apr 98 10:39:25 -0400

Paul,

Merging reservations from different services is in general complicated 
because of the difficulty in constructing a proper "ordering" among
reservations.  The example you give (scenario 2) is one such instance,
but there are many others, and it is not simple task to cover all possible
cases.  Back in 96, Lee Breslau and Scott Shenker wrote a draft entitled
"A Proposal for Accommodating Heterogeneity", that dealt with some of
these issues but more from the perspective of heterogeneous support of
different services on network links, and how to deal with this to 
satisfy specific end-to-end service guarantees.  It is a somewhat different 
perspective even if it shares some of the basic issues faced when merging
reservations from heterogeneous services.  I believe that Lee Breslau
([email-masked]) may have done some subsequent work on this latter 
aspect. 

Hope this helps.

Roch