Cell Relay Archive

["Jimmie McKeown" <ahit@tinet.ie>]

-----Original Message-----
From: Vikas_Kaushik <vkaushik@duettech.com>
To: cell-relay@cell.ucs.indiana.edu <cell-relay@cell.ucs.indiana.edu>
Date: 27 April 1998 22:15
Subject: CR: Re: QoS versus CoS


>
>Mike Vogeleer wrote:
>> Can anyone explain me (in general + some simple examples) the difference
>> between QoS and CoS (class of service). Is the term 'CoS' ever really
>> used?
>
>
>QoS is "QUALITY" of service.  QoS Specifications are based on the "quality"
aspects of the contract, viz jitter in cell transfer delay (CDV), end to end
transit delay in the network and cell loss ratio, cell misinsertion rate.
>
>Class of service instead is a specification (by the application) of the
application's expectation (regarding quality) from the network for a given
type of traffic.  Specifying a desired CoS implies defining many other
parameters BESIDES QoS.  These may include traffic shape and burstiness and
feedback mechanism for congestion control.
>
>Specifying QoS requirements for an application is not suggestive enough of
the type of traffic that shall be expected, but specifying a CoS does hint
at the "quality" of service expected of the network.
>
>Putting it simply:-
>
> Specifying only QoS means "This is what I expect from network."
>
> Specfying CoS means "This is what I expect from the network if this is how
my traffic looks like.".