QOS Questions

[jazzman20014]

Hi,

So I have been given the task of moving from an HP core switch (that is also the client switch) to a new 3750x switch stack. 

Everything is working but the requirement is to move the MPLS connection to the new Cisco whilst maintaining the QOS header tags so that the VoIP and video conferencing will still match up on the MPLS. 

What I know is that voice is DSCP 34 and video is IP precedence 5 (DSCP 101000)

That is where my understanding ends, is anyone able to shed some light on the configuration that is required for this to work.

Topology diagram is attached.

Thanks in advance.

[Mohamed Sobair]

Hi,

First, the recmmended Marking value for Voice is dscp 46 (IP Precedence 5) Expidite forwarding, and the recommended marking value for Video is (IP precednce 4).

For End to End QoS design, you need to make sure that your ISP, MPLS Provider preserve your marking across the MPLS cloud.

You also need to classify and mark as close to the source as possible on the Switches, trust Qos for Cisco Phones and set QoS for Video Conferencing,

You can mark based on Cos or ToS, however, the recommended marking approach is to mark based on DSCP values, and finally you need to trust those values on your uplinks toward Your provider Edge.

Let me kinow if this answers your question,

Regards,

Mohamed

[jazzman20014]

Hi,

Thanks for the reply and it does answer part of the question.

Where the confusion is setting in is that the current setup has the QOS enabled on the HP switch but nothing more configured.  So my logic is telling me that the voice packets are being tagged by the phones and the switch is just passing them through without molesting them in any way meaning that the WAN/MPLS can treat them as expected. 

It is probably worth noting that the phones are Alcatel-Lucent provided by Freedom and not Cisco, and I assume that it would be worth applying QOS on the core even through it is vastly over spec’d. 

Regards

Jazzman

[Mohamed Sobair]

Hi Jazzman,

Whether its Cisco or Non Cisco IP-Phones, it dosent make a difference. You need to trust the CoS value of the IP phones on the Switch (Trusted Boundary). The Switch will never forward the CoS set value by default unless you trust it.

For that , I also recommend you map your QoS value to a dscp recommended value based on the type of traffic and trust those values as well on the UPlink towards the Edge routers connected to the MPLS.

If you have Branch to Branch connectivity, then the MPLS MUST apply QoS to preserve your Marking and QoS across thier boundaries.

HTH

Mohamed

[Bert Gevers]

Hello Jazzman,

as I understand, you want the 3750X-stack to keep the QOS marking as is.

In order to achieve this, you can either:

- make sure that 'mls qos' is disabled.

OR

- if 'mls qos' is enabled, make sure that the correct trust state is configured on all the ports which are traversed.

The QOS configuration guide for the 3750X is very elaborate and can be found here:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750x_3560x/software/release/12.2_53_se/configuration/guide/swqos.html#wp1042819

HTH,

Bert