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DSCP, COS, and QOS

Hello,

 

What is DSCP and QOS and how is used with switches, phones, etc.  Also, what does it mean by DSCP trust boundaries can I have an example of this?

Thanks,

3 REPLIES
Cisco Employee

http://en.wikipedia.org/wiki

http://en.wikipedia.org/wiki/Differentiated_services_code_point

http://en.wikipedia.org/wiki/Quality_of_service

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/srnd/collab10/collab10/netstruc.html

HTH

java

if this helps, please rate

www.cisco.com/go/pdi
Cisco Employee

Hi,Just to give you an idea

Hi,

Just to give you an idea QOS is used to prioritize the network traffic.

We use COS to Prioritize traffic in Layer 2 frames & DSCP to Prioritize traffic in Layer 3 frames.

 

Refer the below document for brief understanding and configuration assistance:

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_55_se/configuration/guide/3750xscg/swqos.html#wp1020443

 

 

Regards,

Venkatesh.

Super Bronze

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Posting

DSCP is a way of marking packets so they may easily identified for different service level treatments.

QoS is the overall "bucket" that encompasses providing different service level treatments.

Basically some traffic, such as packets from VoIP phones have their packets marked differently so those packets might be treated better, when there's resource contention, on switches (and routers).

As different DSCP marking might be used for different service levels, the issue of trust arises.  I.e. is a marking that denotes better treatment "trusted" to be legitimate.  A trust boundary defines demarcation of a range, within a network, that a DSCP marking is assumed to be valid.

QoS isn't really complex, but it's very broad subject.  You need to know much to understand how it all fits together.

Cisco has some nice information on QoS, you might start with documents off this page: http://www.cisco.com/c/en/us/solutions/enterprise/design-zone-application-performance/landing_cVideo.html

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