Subject: [Diffserv] A Question on Admission Control

From: Jay Wang <[email-masked]>
Date: Tue, 15 Aug 2000 14:54:31 -0700

Hi All,
 
In conducting connection admission control for a DS network, before
considering
an end-to-end scenario, suppose one of the admission criteria is the
bandwidth 
availability of the ingress edge node, in which packets enter the node from
a 
line card and exit the node through a trunk card (before entering the
backbone).
So to consider whether we may accept a new connection or service, we need to
check both the ingress line card and the egress (trunk) card of the edge
node. The cards
are interconnected by a switch fabric.  For switched traffic like MPLS, the
path from the 
ingress card to the egress card may be determined a priori.  However, for
routed traffic 
the path is determined only dynamically.  So the question is how do we
handle the bandwidth 
accounting for the egress cards if the traffic placed on it is not
deterministic at the connection 
setup time, unless routed traffic is placed as best effort always?
 
Although one may say the accounting could be done on a usage (hence
measurement) basis.  
This however shifts the philosophy.  Besides, usage based bandwidth
management does not
appear to be appropriate for EF traffic anyway (on the other hand, maybe EF
traffic should be 
always explicitly routed?)
 
Any one who has thoughts on this or aware of any prior work that addressed
this issue?
 
Thanks.
 
- Jay Wang

---

From: "C. Chen" <[email-masked]>
Date: Tue, 15 Aug 2000 17:29:37 -0500

Mr. Wang,

In ATM PNNI, the issue you brought up is well addressed in CAC mechanism
residing in the switch. It requires a quick and not so accurate
algorithm (called G-CAC) for source node to calculate the equivalent
bandwidth for source routing determination and a more accurate CAC is
needed in each ATM switch to verify in real-time the bandwidth
availability on the node which is member of source routed path
determined by source node. May be  similar mechanisms are needed for
MPLS source routing as you have suggested.

Cheng C. Chen

Jay Wang wrote:

>  Hi All,In conducting connection admission control for a DS network,
> before consideringan end-to-end scenario, suppose one of the admission
> criteria is the bandwidth availability of the ingress edge node, in
> which packets enter the node from a line card and exit the node
> through a trunk card (before entering the backbone).So to consider
> whether we may accept a new connection or service, we need tocheck
> both the ingress line card and the egress (trunk) card of the edge
> node. The cardsare interconnected by a switch fabric.  For switched
> traffic like MPLS, the path from the ingress card to the egress card
> may be determined a priori.  However, for routed traffic the path is
> determined only dynamically.  So the question is how do we handle the
> bandwidth accounting for the egress cards if the traffic placed on it
> is not deterministic at the connection setup time, unless routed
> traffic is placed as best effort always?Although one may say the
> accounting could be done on a usage (hence measurement) basis. This
> however shifts the philosophy.  Besides, usage based bandwidth
> management does notappear to be appropriate for EF traffic anyway (on
> the other hand, maybe EF traffic should be always explicitly
> routed?)Any one who has thoughts on this or aware of any prior work
> that addressed this issue?Thanks.- Jay Wang

_______________________________________________
diffserv mailing list
[email-masked]
http://www1.ietf.org/mailman/listinfo/diffserv
Archive: http://www-nrg.ee.lbl.gov/diff-serv-arch/

---

From: Brian E Carpenter <[email-masked]>
Date: Wed, 16 Aug 2000 09:21:26 -0500

This topic belongs on the diffserv-interest list.

[email-masked]

Send "subscribe diffserv-interest" to [email-masked]

There's also an implementation list; see  http://www.tip.csiro.au/dsimplementation

  Brian Carpenter
  diffserv co-chair