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RE: Re: label values

  • From: "Alexander Schlager" <Alex@Tatonka.at>
  • Date: Fri, 28 Sep 2001 23:50:55 +0200
  • Importance: Normal
  • Resent-Date: Fri, 28 Sep 2001 20:16:51 -0400
  • To: <mpls-ops@mplsrc.com>
  • X-OriginalArrivalTime: 28 Sep 2001 21:50:51.0509 (UTC) FILETIME=[A41A1A50:01C14867]

hi,
i?d like to add some notes on packet classification:

once a packet gets classified at the ingress there is no way for
reclassification as the packet travels along it?s LSP
(so far i know - pls. correct me if i am wrong)

practicaly spoken a FEC per default is created per IGP prefix, for BGP
routes there is no FEC creation, a BGP route gets mapped into the same FEC
as its next-hop (learned via IGP) was mapped to.

when using MPLS applications like VPN, TE and QoS we could also talk about
classification of packets into special FECs
- map a packet to a FEC to be forwarded/routed "against" a specific VRF
- map a packet to a FEC to be forwarded/routed "against" a specific LSP
tunnel
- map a packet to a FEC to be treated referent to specific QoS
specifications
...

pls. be aware that all of this represents my understanding of the cisco
implementation - would be nice to gain some infos about other vendors
implemtations !

thx

alex



-----Original Message-----
From: Hemant P. Kelkar [mailto:hemant@cyberspace.org]
Sent: Donnerstag, 27. September 2001 18:33
To: adithya@sasken.com
Cc: krishnakanth.rao@mail.cominsights.com; mpls-ops@mplsrc.com;
mpls@UU.NET
Subject: re: Re: label values


Hi Aditya,

Before classification, the 5 tuple Source IP + Destination IP + Service +
Source Port + Destination Port or  the tuple Source IP + Destination IP
determines the flow.
After classification since the flow is denoted by the label assigned,
there is no further need of classification.

--
Hemant

Date: Thu, 27 Sep 2001 21:41:24 +0530
From: Adithya Bhat <adithya@sasken.com>
To: Hemant P. Kelkar <hemant@cyberspace.org>
Cc: krishnakanth.rao@mail.cominsights.com, mpls-ops@mplsrc.com,
mpls@UU.NET
Subject: Re: label values

Hi Hemant,

Once a label is assigned to a set of packets, the label effectively
defines
the "flow" through the LSP,
So will it not be better to say that, packets will be classified based on
the
Labels ??

-Adithya


"Hemant P. Kelkar" wrote:

> Hi Krishnakanth,
> Label values are of local significance only , limited significance
between
> the neighbour routers (LSRs). Hence, there may be same label values on
two
> different LSPs in the MPLS Domain.
> Packets are classified into different FECs using a flow classifier e.g.
> same source/destination IP addresses, and service types. (TCP port
> numbers).
>
> --
> Hemant

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