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Re: [PWE3] draft-bryant-pwe3-packet-pw-02.txt

It depends what you mean by optimize.

Say you have 100 PWs and 2 protocols
If you optimize for minimum number of unique labels by separating the functions, as per the draft, this takes 102 labels
If you optimize for number of labels in the stack, which is what you are requesting, you need 200 unique labels. 

- Stewart




HENDERICKX Wim wrote:

This is correct but could we not optimize this special mapping ?

-----Original Message-----
From: Andrew G. Malis [mailto:amalis at gmail.com] Sent: maandag 16 november 2009 15:39 
To: HENDERICKX Wim
Cc: stbryant at cisco.com; pwe3 at ietf.org
Subject: Re: [PWE3] draft-bryant-pwe3-packet-pw-02.txt

Wim,

It's still more efficient on the wire than a simulated Ethernet PW,
because you would have one less label (the protocol identifier), but
would add the Ethernet MAC header instead.

Cheers,
Andy

On Mon, Nov 16, 2009 at 9:03 AM, HENDERICKX Wim
<wim.henderickx at alcatel-lucent.be> wrote:

Ok good, this is what I thought, the client LSP exist in the "client
packet Network layer".

Don't you think this is a huge stack for such a function. You could have
4-6 LBL(s) + CW (optionally). I understand this proposal re-uses
existing functions defined in MPLS, but there are lot's of optimizations
possible here -> we could combine FAT LBL, PID LBL, CW potentially.

-----Original Message-----
From: Stewart Bryant [mailto:stbryant at cisco.com]
Sent: maandag 16 november 2009 14:49
To: HENDERICKX Wim
Cc: pwe3 at ietf.org
Subject: Re: [PWE3] draft-bryant-pwe3-packet-pw-02.txt


WH> what I meant is this:

            --------                       --------
   PE1-----|        |                     |        | --- PE3
           |  LSR   |------- PKT PW ------|  LSR   |
           |        |                     |        |
   PE2-----|        |                     |        |---- PE4
            --------                       --------

Assume PE1 has a LSP to PE3 and PE2 has an LSP to PE4, how is this
distinguished on the PKT PW ?



SB> I am not sure what you have drawn there, but it is not what is

shown

in  the draft. The pkt pw run between the PEs and is carried over the
LSPs. PWs are distinguished from each other at the PE via the PW

label.

WH> What I tried to draw is PE(s) attached to the device (drawn with

the

box) which is performing the LSR function on a PKT PW to another

device

(drawn with the box) which attaching PE(s).

The question is if I have multiple LSPs from different PE(s) through

the

PKT PW how are the distinguished. Do I need a separate PID LBL, a
separate PW, etc such that the LSR can make the correct LBL mappings.



Wim

Think of the PW as a point to point link between a pair of PEs. The PE
chooses what traffic to sent over a given PW. The PE then pushes an MPLS

label to identify the destination. The mid-point LSRs have no clue what
is being carried over the LSP. The egress PE unwraps that packet and
figures out what the payload is.

RFC3985 applies to pkt pw as it does to any other PW.

- Stewart



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