From: David Porta (David.Porta003@msd.govt.nz)
Date: Sat Nov 15 2003 - 20:12:18 GMT-3
Hi Michael,
I would think that you are correct about DSCP CS5 and IP Precedence 5 being
the same thing, because a DSCP based network will understand CS5 = Critical
priority, while an IP Precedence network will read the first 3 bits of the
DSCP CS5 value and understand that it is IP Precedence 5 (critical)
Hence the reason why DSCP is backward compatible with IP Precedence.
I would think that what we need to be careful about is that when traffic
from an IP Precedence based network goes into a DSCP based network, that we
have the appropriate policies in place to convert the IP Precedence value
into the appropriate DSCP value (CS5 or EF).
And the same goes for all the AF values, since essentially one IP precedence
value has 4 different possible DSCP values per class (3 AF values + 1 CS
value).
What do you think?
Cheers,
Dave
Michael Snyder wrote:
> I've been reading the new Cisco Press DQOS book. I highly recommend it.
> It's basically a tutorial on each of cisco's queuing tools.
>
> Anyway, it directly links Precedence and DCSP because of the overlapping
> bit fields used in the packet.
>
> Taking this concept a bit farer; my question is can you use DCSP CS5
> and Precedence 5 interchangeably?
>
> I can envision a lab question stating all voice traffic (via dial peer)
> in the network should be marked with a DCSP value of 40.
>
> Could you image the possible time wasted trying to mark the voice
> traffic via dcsp, when a simple precedence command could do it.
>
>
> Thanks for Your Time,
>
> Michael
>
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