QOS on LAN

[mohammedrafiq]

Hi,

We would like to configure COS/QOS in our LAN as shown in diagram attached.

My question is where is the best way to apply all QOS classification/marking , setting and  apply policy map  in our LAN for Voice/video and data.

We are planning on core 6500 switch but not sure how the router will let pass our setting to MPLS cloud to our ISP to honor.

Do we all request to configure on WAN router ( provided by ISP ) or 6500 Core switch,  to keep all control under our management?

Regards,

[Francesco Molino]

Hi

Marking traffic should be done on closest equipment from where the traffic is initiated, it means, you need to tag packets on access switches.

However, in order to make the QoS consitency, you should validate that marked traffic keeps DSCP/COS value until it's forwarded to WAN links. It means, that on Core switch, firewall and WAN, the DSCP/COS value should be trusted.

Afterwards, as you have MPLS cloud with your ISP, you shouldn't be a big deal to validate with them with QoS possibility they offer in order to prioritize your traffic. Depending on that, you may tag packets differently on access switches or you can add a policy-map (Your ISP will do it) to re-mark traffic to match their QoS policy.

All these steps are for 1 way traffic. The return traffic should be marked as well from the beginning. But let's suppose that your ISP isn't offering you QoS features. On your WAN router (from WAN to LAN), you should have policy-map that will classify and mark your traffic back.

In this scenario, you will have QoS priorization within your LAN but not on your WAN. That's why, specially for Voice, Video and other business important traffic, you should involve your ISP in order to have a policy from 1 end to the other end.

Hope this's clarifying your point.

Let me know.

Thanks

[mohammedrafiq]

Hi supportlan,

If I clearly understand, We can just say on our access, core switch and firewall to just trust the COS/DSCP value ( do not alter it ) which is marked by devices ( IP Phones and VC devices) and send to WAN router where we can use MQC to tag traffic and forwarded to MPLS?

Please clarify.

[Francesco Molino · Accepted solution]

Yes

If devices are tagging, you just have to trust it otherwise you need to tag it at the access switch. 

For WAN, you have to check with your ISP otherwise you need to put a policy for the return traffic in order to mark it again.

You can use multiple tool like wireshark to view if your traffic is marked when he pass through the mpls. For the MQC policy, only your provider can tell it. Normally you should have something on your mpls. 

[Joseph W. Doherty]

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Posting

Older Cisco switches, if QoS enabled, often needed to be configured to trust ingress marking, otherwise, by default, they erase them.

New Cisco switches, behave much like Cisco routers, in that they implicitly pass QoS markings, by default.  However, such newer Cisco switches often have some default QoS treatment for different marking, while routers generally don't treat marked packets differently (again by default).

The "best" way to mark (and verify usage) is generally considered as close to the source (including at the source) as possible.  However, QoS is to serve you needs, so you can do it where ever it's needed.  For example, at major bottlenecks, such a going from a LAN to WAN.

ISPs (Internet service providers) generally never support QoS.  SPs (service providers) might support some form of QoS.  What they might support, what they might charge, what options they support, all would need to be discussed with your SP.  SPs using MPLS often provide some kind of QoS (optional) treatment.  (BTW, MPLS provided QoS is often/generally not at rich as a Cisco WAN router might provide.)

ISPs and SPs, generally will pass L3 ToS markings, unchanged.  However, you may need to use L3 ToS markings, in a specific way, to obtain whatever QoS treatment your SP provides.