implementing QoS

I remember a QoS example in a document/tutorial, which was like this:

40% Priority
60% Best Effort

..and in addition there was following table:

TOS/EXP          Class of service          Customer TOS/DSCP
     0                  Best Effort              0
     2               Advanced Class         AF30, 31, 32, 33, 40, 41, 42, 43
     5                Priority Class             EF

As I understand, Best Effort is DSCP value of 000000 and EF(Expedited Forwarding) has a value of 101110. In addition, I generally understand the idea of Assured Forwarding classes, but how to implement those in a router? How to set up such QoS?

In addition, am I correct, that DSCP value is checked only by routers?

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Comments

networker050184

This should help you get what you are looking for.

Implementing Quality of Service Policies with DSCP [QoS Packet Marking] - Cisco Systems

burbankmarc

That gives you a good starter read. But if you want to do QoS right I'd look into some of these too:

RFC2581 - TCP Congestion Control
Voice Over IP - Per Call Bandwidth Consumption - Cisco Systems
Bridging the gap between 3550 and 3560 QoS: Part I | CCIE Blog

And, a video:

https://learningnetwork.cisco.com/docs/DOC-1368

There's more too, but that's all i felt like digging up.

Forsaken_GA

the thing to not get caught up on is that the EF/AF stuff are only guidelines. the router doesnt default to prioritizing EF above an AF class, for example, you have to set that up. I could set traffic marked as BE to go into the priority queue and let EF suffer as class-default traffic. You can mark the traffic all you want, but it's not going to do anything but flip some bits in the header. If you want it to mean something, you have to actually act on the traffic