RE: mls Qos

I think the horse has been properly beaten. It's already a long thread, so if I'm repeating anything it won't be anything new :) The default behavior is that QoS is disabled, so as Evan said all traffic from any port can have any marking that it likes. This isn't the end of the world, but it requires that your voice routers crack the packets further to properly mark and then queue them, then you're looking at least three packet remarks to classify voice bearer, signaling and then remarking default to ... default.

As Darby pointed out a long time ago (and sort of swayed away from), there is the SRND (I haven't read it a long time), but I'm pretty sure it says to mark at the endpoints and setup proper trust boundaries. So, while in the hands of the "wrong admin" someone might turn on QoS and then forget to trust ports / trunks / uplinks, Cisco has taken measures to prevent this with products like CNA and the basic built in web server. If CLI is scary, people have options like global macros and smartports (aka interface macros).

Tracking down improper marking and trust boundaries should be completed way before implementing voice. I think it would negligent to have some setting up your QoS who doesn't have a clue.

In short, I think you're right on Evan.

-ryan

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of Evan Weston
Sent: Sunday, July 26, 2009 9:37 PM
To: 'Darby Weaver'; 'CCIE Groupstudy'
Subject: RE: mls Qos

Basic CCNP principle here, I can't believe what Im reading.

Set your trust boundary as close to the endpoints as possible. No mls qos =
no trust boundary, you trust everything.

Leaving mls qos turned off on an access switch because it will break things
is just sloppy admin.

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
Darby Weaver
Sent: Monday, 27 July 2009 11:19 AM
To: CCIE Groupstudy
Subject: Re: mls Qos

Again, let me refer you to the SRND by Cisco for further review of the
subject:

http://www.cisco.com/univercd/cc/td/doc/solution/esm/qossrnd.pdf

A lot of classes explain it, but not everyone makes it that class and if
they did let's face it QoS is a lot of material to cover in the the time
usually given to it.

Now if you actually have to work on a topic like video conferencing and
video streaming there is a white paper I strongly recommend reading...

http://www.cisco.com/en/US/solutions/collateral/ns340/ns394/ns158/ns280/net_
design_guidance09186a00800d67f6.pdf

http://www.cisco.com/en/US/docs/video/cuvc/design/guides/srnd/vidpref.html

Blogs and organic groups at http://www.ccie.net
Received on Sun Jul 26 2009 - 22:13:38 ART