From: Arun Arumuganainar (aarumuga@hotmail.com)
Date: Thu Aug 18 2005 - 04:47:03 GMT-3
Hi ,
> What I have not being able to understand is how my set MPLS EXP bits will
be
> carried to the other PEs ?
> Will I need to apply any service policy to carry MPLS EXP bits from PE to
> the other ?
>
By default . DSCP or IP Prec or Dot1Q COS will be automatically copied to
MPLS EXP !!! No configuration is needed for doing this .
However if you want to change behavior you will have create policy map and
apply it on the input or output interface using service policy command .
There are two set command available for use in your policy map !!!
a) set mpls exp topmost : This will set exp for topmost label .
b) set mpls exp imposition : This will set exp bits in the entire label
stack .
Also it will be interesting to understand how various MPLS operations
affects your exp values . Basically there are four variants of MPLS
operations .
1) Label Imposition : This happens in IP-MPLS boundaries . Default : DSCP
/IP Prec is copied . The behavior can be changes using set commands in a
policy map
2) Label Swap : This happens in MPLS to MPLS path . Here incoming label is
swapped with outgoing label . Default : EXP bit of incoming label is copied
to outgoing label's EXP . This behavior can be changed using set commands
discussed above
3)POP operation in Label Stack : Incoming packet has stack of labels and top
most label will be poped( Removed ) . Exp bit on topmost label will be
copied to topmost label( next-level label ) on the outgoing interface . This
behavior can be changed using set commands discussed above .
4) PHP POP operation : Incoming packet has a single label and Label will be
removed as we forward the Packet . Here EXP will be fully lost . By default
it is not copied on to DSCP or IP-Prec back !!!
This is a special case where in end to end QoS policies implementation based
on exp is not possible . However you can work around this situation via two
methods.
a) Signaling explicit null between PHP LSR and Egress LSR . When explicit
nul is done then PHP-POP( case 4) operation will be changed to Label Swap
( case 2) Hence Problem can be worked around ,
b) Use policy map to mark discard class( one discard class for each exp
values ) in the incoming interface of PHP router and use policies based on
Discard class on the output interface !!!
Based on your need you can employ any of the techniques for achieving the
QoS in MPLS VPN environment .
Hope this helps .
Thanks and Regards
Arun
----- Original Message -----
From: "Zahid Hassan" <zhassan@gmx.net>
To: "C&S GroupStudy" <comserv@groupstudy.com>; "R&S CCIE GroupStudy"
<ccielab@groupstudy.com>
Sent: Thursday, August 18, 2005 3:54 AM
Subject: QOS for MPLS VPNs
> Dear All,
>
>
> I would be really grateful if someone could suggest or
> propose any config for implementing QOS for MPLS VPNs.
>
> I have the following scenario:
>
> CE1 -->PE1-->PE2-->CE2
>
> I understand that it is possible to mark and match DSCP and MPLS EXP bits
as
> follows:
>
> DSCP (CE1)-->EXP(PE1)--->EXP(PE2)--->DSCP(CE2)
>
> I am being able to match DSCP bits from CE on PE and apply whatever
policing
> required.
> I can also set MPLS EXP bits on PE according to matched DSCP bits from CE.
>
> What I have not being able to understand is how my set MPLS EXP bits will
be
> carried to the other PEs ?
> Will I need to apply any service policy to carry MPLS EXP bits from PE to
> the other ?
>
>
> Regards,
>
> Zahid
>
> _____________________________________________________________________
> Subscription information: http://www.groupstudy.com/list/comserv.html
This archive was generated by hypermail 2.1.4 : Sun Sep 04 2005 - 17:01:19 GMT-3