Understanding CoS

[nix-patheon]

Hi all. I'm having a bit of trouble understanding CoS markings and I would appreciate some help.

As it stands we have 1xE1 MPLS WAN link and CoS bandwidth allocations (which are currently set logically). I would like to classify further traffic (without the expense of increasing the bandwidth) and I have been given the option of a logical change (adding to the class map) or marking LAN traffic. From my understanding, won't the CoS markings be removed from the 802.1q header once traffic has passed through a switch, which makes the CoS markings only locally significant and won't have any affect on WAN traffic? Can I add further interesting traffic to my current allocations?

Your replies are always very much appreciated.

[Jeff Van Houten]

Use class-maps to classify traffic. Then use a policy- map to both mark dscp values and apply bandwidth allocations. Then apply outbound to your wan interface.

Sent from Cisco Technical Support iPad App

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

From my understanding, won't the CoS markings be removed from the 802.1q header once traffic has passed through a switch, which makes the CoS markings only locally significant and won't have any affect on WAN traffic?

Maybe CoS marking will be removed, maybe not; depends on switch configuration.  Biggest issue with L2 CoS, requires VLAN tag.

If platforms support L3 ToS DSCP, best to use it.  Many Cisco devices can mark/remark L3 ToS; many can use L2 CoS marking to help decided on L3 ToS marking.

Unless MPLS vendor is referencing MPLS exp-bits, usually when they reference CoS, it's actually L3 ToS.