Nexus 7000 QoS process

[senguu]

Hi everyone,

I am working on implementing QoS on large campus network.

I don't have much experience with Nexus and implementing QoS on it is somewhat confusing.

Despite doing alot of research online and watching videos... I hope someone can give me some advice and clarification.

We have a pair of Nexus 7000 (N7K-SUP2, N7K-F248XP-25E) running in the core network.

We have catalyst switches (4500x, 3650, 2900) for the distribution and access layers.

Based on what I gathered;

- Nexus trust marking by default and has queuing classes already set. We can adjust it if needed.

- Nexus uses COS markings. If it received DSCP marking it will map accordingly to COS equivalent.

If I am correct, then out of the box the Nexus shouldn't really need much configuration at all and should already prioritize based on it's default DSCP to COS marking. Traffic would already be marked by our distribution/access layers. The only thing that we probably need to adjust is the bandwidth requirements of each queue and the drop thresholds.

When I issue the command "show queuing interface et3/4"... The below to me indicates that it has CoS assigned to the queues.

Egress Queuing for Ethernet3/4 [System]
-------------------------------------------
Template: 4Q8E (2 Ingress Buffers)
-----------------------------------------------------------------------------
     Queue                     Group   Bandwidth% PrioLevel Shape%   CoSMap
-----------------------------------------------------------------------------
1p3q1t-8e-out-pq1                 0          -      High      -        5-7
1p3q1t-8e-out-q2                  1         33         -      -        3-4
1p3q1t-8e-out-q3                  2         33         -      -          2
1p3q1t-8e-out-q-default           3         33         -      -        0-1


Ingress Queuing for Ethernet3/4 [System]
-------------------------------------------
Trust: Trusted
DSCP to Ingress Queue : Disabled
------------------------------------------------------------
      Queue                   Group Qlimit% IVL      CoSMap
------------------------------------------------------------
2q4t-8e-in-q-default              1      90   0         0-4
2q4t-8e-in-q1                     0      10   5         5-7

I hope someone can help clarify. Thanks!!!

[sbhadrav@cisco.com]

You use classification to partition traffic into classes. You classify the traffic based on the port characteristics (class of service [CoS] field) or the packet header fields that include IP precedence, Differentiated Services Code Point (DSCP), Layer 2 to Layer 4 parameters, and the packet length.

The values used to classify traffic are called match criteria. When you define a traffic class, you can specify multiple match criteria, you can choose to not match on a particular criterion, or you can determine the traffic class by matching any or all criteria

Traffic that fails to match any class is assigned to a default class of traffic called class-default.