Subject: FW: Qry on Guaranteed service

From: sivakumarg <[email-masked]>
Date: Thu, 05 Jun 97 20:39:00 PDT

Hi,

I have a doubt reg. Guaranteed delay service. Assume a router
with two interfaces R1 and R2. Guaranteed service is being
provided on R2. R1 caters to best effort traffic.
Further assume that host H1 connected on interface R2 requests
guaranteed service. The router determines, based on the current
traffic conditions that this service can be provided and accepts
the request. Suppose after the acceptance, traffic on R1
increases dramatically and router does not have enough
computational resources to provide the guaranteed service (host
H1 conforms to its advertised traffic spec's) how should
this situation be handled?

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From: John Wroclawski <[email-masked]>
Date: Thu, 5 Jun 1997 16:55:46 -0400

Hi,

If you accept a flow for guaranteed service, you have offered a guarantee.
Presumably here the router would throw away traffic on R1 so that it could
meet its commitment to the guaranteed service traffic.

If the router is designed in a way which makes this impossible - for
example, there is no way to manage shared computational resources so that
the guaranteed flows get what they need - then it just can't implement a
high-quality guaranteed service.

Your question actually raises the easy case - I think you would simply
limit your poll rate for R1 to make sure that R2 got enough CPU. A harder
case is if the flood of best-effort traffic is also arriving on R2 - in
that case you need at least enough CPU and input b/w to look at all of the
packets so that you can find the guaranteed-service ones.