Subject: RE: [Diffserv] why 4 AF classes?

From: Shahram Davari <[email-masked]>
Date: Fri, 8 Oct 1999 09:53:29 -0700

Hi ,
 
See comments below:
 
Regards,
Saharam Davari
PMC-Sierra Inc.

-----Original Message-----
From: xizheng shi [mailto:[email-masked]]
Sent: Thursday, October 07, 1999 11:40 PM
To: [email-masked]
Subject: [Diffserv] why 4 AF classes?

Hello, diffservers
 
Can anyone enlighten me about following maybe naive questions:
Q1: Why do we need exactly 4 AF classes in AF PHB rather than 1, 2 or even
5...
 
At begining there was a priority relationship between the 4 AF classes, but
it was removed in the final RFC. As I remember, Brian and others have
suggested to reduce it to only 1 AF class (when it moves to draft
statndard), because simply all are the same.
 
For time being 4 AF classes are recommended, but not enforced.
 
Q2: Why "DS node MUST NOT aggregate two or more AF classes together"? 
I am not sure the meaning of aggregate, does it mean putting them into one
queue or something else?

Thanks in advance.
 
Aggregation means treating them the same in the traffic manager. One aspect
of aggregation is sending them into one queue. If you aggregate two AF
classes then they become one AF class, and you loose your class
differentiation.
 
Xizheng Shi
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