Subject: Re: [PWE3] WG Last Call for draft-ietf-pwe3-fat-pw-03

From: Yong Lucy <[email-masked]>
Date: Wed, 01 Sep 2010 12:24:22 -0500

Comments:

Regarding PW label space, PW with flow label SHOULD use platform based label
space, not interface based label space in order to support ECMP at ingress
PE.

Regarding Text: Thus a PE sending a FL Sub-TLV with T = 1 and receiving a FL
Sub-TLV

   with R = 1 MUST include a flow label in the PW packet.  Under all

   other combinations of FL Sub-TLV signaling a PE MUST NOT include a

   flow label in the PW packet.

Suggested Text: Thus a PE sending a FL Sub-TLV with T = 1 and receiving a FL
Sub-TLV with R = 1 MUST include a flow label in the PW packet; A PE sending
a Flow Label Flag with R=1 and receiving a Flow Label Flag with T=1, PE MUST
strip off both PW label and flow label on packets before forwarding them to
CEs.  Under all other combinations of FL Sub-TLV signaling a PE MUST NOT
include a flow label in the PW packet.

Some statement about QoS and DSCP aspect is necessary when applying it to
DiffServ enabled domain. 

Regards,

Lucy

 

> -----Original Message-----

> From: [email-masked] [mailto:[email-masked]] On Behalf Of

> Stewart Bryant

> Sent: Friday, August 27, 2010 3:32 AM

> To: Ben Niven-Jenkins

> Cc: AISSAOUI Mustapha; KOMPELLA Vach; [email-masked]

> Subject: Re: [PWE3] WG Last Call for draft-ietf-pwe3-fat-pw-03

>   On 09/08/2010 17:43, Ben Niven-Jenkins wrote:

> > Stewart,

> > Apologies for the delay in responding, please see inline my comments.

> > On 5 Jul 2010, at 19:08, Stewart Bryant wrote:

> >> The signaling text that I am suggesting we use is:

> >> =========

> >> 4.  Signaling the Presence of the Flow Label

> >>     When using the signalling procedures in [RFC4447], a Pseudowire

> >>     Interface Parameter Flow Label Sub-TLV (FL Sub-TLV) type is used to

> >>     synchronise the flow label states between the ingress and egress

> PEs.

> >>     The absence of a FL Sub-TLV indicates that the PE is unable process

> >>     flow labels.  A PE that is using PW signalling and that does not

> send

> >>     a FL Sub-TLV MUST NOT include a flow label in the PW packet.  A PE

> >>     that is using PW signalling and which does not receive a FL Sub-TLV

> >>     from its peer MUST NOT include a flow label in the PW packet.  This

> >>     preserves backwards compatibility with existing PW specifications.

> >>     A PE that wishes to send a flow label in a PW packet includes in

> its

> >>     label mapping message a FL Sub-TLV with T = 1 (see Section 4.1).

> > Should this be "MUST include" or "SHOULD include"?

> >>     A PE that is able to receive a flow label includes in its label

> >>     mapping message a FL Sub-TLV with R = 1 (see Section 4.1).

> > Should this also be "MUST include" or "SHOULD include"?

> In both cases it is a MUST - apologies for the informal language.

> Stewart

> _______________________________________________

> pwe3 mailing list

> [email-masked]

> https://www.ietf.org/mailman/listinfo/pwe3

---

From: [email-masked]
Date: Thu, 2 Sep 2010 19:21:26 +0800

Hi Lucy,
I don't think we should do any restriction on flow label label space. IMO, 
the flow label can use any label space it want, the only requirement is 
using different flow label for different flow within one PW.

BR
Lizhong

> ------------------------------
> 
> Message: 4
> Date: Wed, 01 Sep 2010 12:24:22 -0500
> From: Yong Lucy <[email-masked]>
> To: [email-masked], 'Ben Niven-Jenkins' <[email-masked]>
> Cc: [email-masked]
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From: Yong Lucy <[email-masked]>
Date: Thu, 02 Sep 2010 14:57:25 -0500

It seems previous message lost somewhere. Send again.

Lucy

  _____  

From: Yong Lucy [mailto:[email-masked]] 
Sent: Thursday, September 02, 2010 12:02 PM
To: [email-masked]'
Cc: [email-masked]'
Subject: RE: [PWE3] WG Last Call for draft-ietf-pwe3-fat-pw-03

Stewart,

Thanks for the response. In fact, my comments were based on -04 text.

Lucy

  _____  

From: Stewart Bryant [mailto:[email-masked]] 
Sent: Thursday, September 02, 2010 10:11 AM
To: Yong Lucy
Cc: [email-masked]
Subject: Re: [PWE3] WG Last Call for draft-ietf-pwe3-fat-pw-03

Lucy,

I think that it is my fault in constructing a reply to -03, but we are
actually on -04

On 02/09/2010 15:25, Yong Lucy wrote: 

Comments:

RFC3985 is (regrettably) silent on the subject, but RFC4447 specifically
states that the platform label space needs to be used. The PPLS needs to be
used to cope with IGP reroute and, in the case of an MPLS-TE core,
protection switching. 

Since there is a higher order requirement for the use of PPLS it does not
need to be stated here.

[LY] You are right.

This is already covered in Section 3:

"The forwarder at the egress PE uses the pseudowire label to identify the
pseudowire. From the context associated with the pseudowire label, the
egress PE can determine whether a flow label is present. If a flow label is
present, the label is discarded."

[LY] I see and agree.

 If forwarder at the egress PE can determine whether a flow label is present
or not, then forwarder at the ingress PE may choose inserting or not
inserting flow label. "Thus a PE sending a FL Sub-TLV with T = 1 and
receiving a FL Sub-TLV with R = 1 MUST include a flow label in the PW
packet;"  "MUST" is not necessary. "SHOULD" is enough.. 

What is the problem that you wish to see addressed here? The TC bits will
not be examined until after the PW label has been popped. Are you suggesting
that the egress queue may be chosen on the basis of the FL TC bits? 

Something like: "The ingress PE MAY set the TC bits in the FL to indicate to
the egress PE the relative priority of the flow with respect to other flows
delivered to the egress interface?"

[LY] Not really. This is not the behavior we expect, right? Something like:
PW with flow label can apply to a Diff-Serv enabled domain. DiffServ
[RFC3270] specifies per hop based Diff-Serv forwarding that uses TC bits of
the top label on label stack. Since flow label is always pushed in or popped
out with PW label together, the flow label is never appear on the top of
label stack. Thus, Diff-Serv forwarder does not exam TC bits on flow label;
Diff-Serv behavior is the same whether flow label is used or not.

Lucy

Stewart