From: Scott Morris (swm@emanon.com)
Date: Wed Apr 16 2003 - 13:19:47 GMT-3
Mathematically (all AF/EF stuf aside), it works out where:
DSCP 0-7 = IP Prec 0
DSCP 8-15 = IP Prec 1
DSCP 16-23 = IP Prec 2
DSCP 24-31 = IP Prec 3
DSCP 32-39 = IP Prec 4
DSCP 40-47 = IP Prec 5
DSCP 48-53 = IP Prec 6
DSCP 54-63 = IP Prec 7
Furthermore:
AF11 = DSCP 10
AF12 = DSCP 12
AF13 = DSCP 14
AF21 = DSCP 18
AF22 = DSCP 20
AF23 = DSCP 22
AF31 = DSCP 26
AF32 = DSCP 28
AF33 = DSCP 30
AF41 = DSCP 34
AF42 = DSCP 36
AF43 = DSCP 38
EF = DSCP 46
Be careful, this level of understanding only comes from being bored. :)
But it's interesting to look at the correlations from the intent behind
DSCP and the "new-fangled" stuff that is really only a rehash of the
bits that have been around forever! It's all just semantics anyway.
But hopefully that helps your idea of "aggregating" the dscp values.
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Scott M. Livingston
Sent: Wednesday, April 16, 2003 10:06 AM
To: 'Mark Miller'; ccielab@groupstudy.com
Subject: RE: Aggregating DSCP values
Mark,
Thank you for the insight! Basically, I have a task (from a gentleman's
Mock lab) that wants me to mark certain DSCP values. I interpreted one
of the tasks to combine values 28-32, but maybe I interpreted that
wrong.?
In any event you have been a tremendous help here; looks like I need to
spend more time w/ DSCP.
Thank you!
scott
-----Original Message-----
From: Mark Miller [mailto:markmiller@alltel.net]
Sent: Tuesday, April 15, 2003 8:04 PM
To: Scott M. Livingston; ccielab@groupstudy.com
Subject: Re: Aggregating DSCP values
Scott,
I'm not sure what you're asking here, but I'll give it my best shot at
answering this question.
DSCP values are categorized into four 'Assured forwarding Classes, and
one 'Expedited forwarding' class.
Class 1 = AF11, AF12, AF13 -- maps to ip prec. 1
Class 2 = AF 21, AF22,AF23 -- maps to ip prec 2
Class 3 = AF31, AF32, AF33 -- maps to ip prec 3
Class 4 = AF41, AF42, AF43 -- maps to ip prec 4
Expedited Forwarding (EF) -- maps to ip prec 5
The bit values for all of these assured forwarding (AF) can
be 'summarized' into a specific class (Class 1, Class2, etc.).
Now I'm not really sure about what you mean by "aggregate DSCP levels",
but if you look at these bit values, that's how these
different AF levels are put into different Classes.
For example....
AF21 010010
AF22 010100
AF23 010110
These AF values are in Class2. The first three bits are the same to map
to ip prec of 2, and are defined as the class selector code..... 010 =2,
or Class 2. The last three bits define a prefered drop
preference. AF23 will get dropped before AF22, etc.
I may be WAY OFF here, but if I were asked to "aggregate" some dscp
values, I would guess you were being asked to specify what class (Class
1, Class 2, etc) to put all of them in.
In your example, however, you could not put these in one class because a
value of 32 moves into the Class 4 space.
I hope this helps. If I'm way off in left field from what you were
asking please disregard and have a nice day.
Mark :-)
----- Original Message -----
From: "Scott M. Livingston" <scottl@sprinthosting.net>
To: <ccielab@groupstudy.com>
Sent: Tuesday, April 15, 2003 4:20 PM
Subject: Aggregating DSCP values
> I am going to keep digging at it, but I am stumped now. I believe I
> understand how to aggregate precedence levels, but I am clueless on
how
> to aggregate DSCP values. Is there a way to do this? I have browsed
some
> url's and looked at the two RFC's, but nothing is jumping out at me
yet.
> Guess I have to dig a little deeper.
>
> Let us say there is a task to group DSCP 28 through 32. How would one
do
> this without having to create 5 ACL's for each value?
>
> Thank You,
> scott
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