From: Ahmed Mustafa (ahmed.mustafa@sbcglobal.net)
Date: Tue May 11 2004 - 00:20:07 GMT-3
Yasser,
After enabling "MLS QOS TRUST COS" command on a switch, you are only
instructing a switch to trust the COS value coming from the IP Phone only.
However, if the IP Phone is extended to a PC then it is a different case.
Remember, the command, "SWITCHPORT PRIOIRITY EXTEND" command is for the
traffic coming from the extenstion and most of the time it is a data
traffic.
Here is what I believe
If the requirement is that switch should maintain the COS values are coming
from both IP Phone and the PC, then I would do
mls qos
interface fas 0/x
mls qos trus cos-------------------> voice traffic will be trusted by the
switch. Default IP Precedence value will be 5
switchport priority extended trust-----------------> data traffic will be
trusted by the switch. Note: if this command is not enabled, then by
default IP phone will
rewrite the PC's COS ro zero.
If the requirement is that the switch should rewrite the COS of PC to 3
then
switchport priority extended cos 3
If the requirement is that switch should change the Precendence value to 6
for voice traffic, then
mls qos cos override
mls qos cos 6
----- Original Message -----
From: "Yasser Aly" <blackyeyes00@hotmail.com>
To: <ccielab@groupstudy.com>
Sent: Monday, May 10, 2004 2:38 PM
Subject: End-to-End Switch QoS
> Hello,
>
> Scenario is as follows: VLAN 4 is configured on many ports on the
switch.
> One of the ports is connected to a server providing multicast feeds with a
> CoS value of 4.
>
> Required:
>
> 1) Maintain multicast feed CoS value received at this port as it enters
the
> switch block.
>
> 2) Other ports that belongs to VLAN 4 should be marked with a CoS value of
1
> to avoid getting any better treatment.
>
> Solution Provided:
> ---------------
> mls qos
> !
> int f0/4 ( Where the server is connected )
> mls qos trust cos
> !
> int f0/8 ( Other port belongs to VLAN 4 )
> mls qos cos 1
> mls qos cos override
> -----------------
>
> My questions:
>
> 1) Will there be a difference if I used switchport priority extend cos 1
> instead of using mls qos cos 1 + mls qos cos override on other
ports
> that belongs to this VLAN other than the server port ?
>
> 2) If the scenario has 2 switches and this VLAN has ports on both
switches,
> will there be any configuration needed to the trunk ports to maintain the
> CoS value or I just need to care about the entry point and that's it ?
What
> are the guarantees that the CoS values will be maintained between both
> switches ?
>
> 3) Finally, on the port having the server. Is it possible to assign two
> differnt CoS values on the same port ( One for the mcast feed, and other
for
> the rest of traffic ) ?
>
> Your feedback is highly appreciated.
>
> Yasser
>
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