MPLS QoS

[dknov]

Hi,

I have two questions:

1. Can anyone put in plain words the differences between E-LSP and L-LSP and what would be a valid application of each?

2. Is it correct that when poping labels the EXP value is not copied to a revealed label by default (as opposed to push and swap) and you need to use qos-group to make LSR "remember" the EXP value so it can apply it to a new label.

Thanks,

David

[mheusinger]

Hi,

I would assume the post

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Service%20Providers&topic=MPLS&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.1ddae096

should pretty much answer your first question.

For the second question the answer is: yes, this is true. On selected platforms you can use "mpls propagate-cos" to achieve the copying from EXP to DSCP.

Hope this helps! Please rate all posts.

Regards, Martin

[dknov]

Hi Martin,

What would EXP to DSCP copying achieve? Is that applicable to label poping in MPLS core?

David

[mheusinger]

exp to dscp copying is useful in case you have the "uniform mode" of QoS, where any changes in exp bits should be reflected in changes in DSCP.

[maher]

Martin,

Sorry to hijack the thred.

May I know on selected platform can use "mpls propagate-cos" - is that a command supported in most MPLS IOS or maybe global configuration? Try to dig out the command but couldn't find. :)

cheers.

maher

[mheusinger]

Hi Maher,

I found it here:

http://www.cisco.com/en/US/products/hw/routers/ps368/products_configuration_guide_chapter09186a0080699326.html#wp1350305

Hope this helps.

[dknov]

Hi,

There is much info on that command. It would seem that it simplifies Uniform tunnel mode configuration by allowing to avoid "set ip dscp" policy-map statements on egress PE towards the customer.

With this command EXP value is automatically copied into IPP field of outbound (untagged) packet.

David