The solution is quite simple: "Flow Labels MUST not be used in an MPLS-TP environment." Luca On 08/16/11 21:46, Alexander Vainshtein wrote: > Pablo, > Sorry, but I think you're wrong. Only T-PE can insert the flow label > (because only T=PE can be "flow-aware"). S-PE simply performs swap on > PW label. > > Regards, > Sasha > > ------------------------------------------------------------------------ > *From:* Pablo Frank [pabloisnot@xxxxxxxxx] > *Sent:* Wednesday, August 17, 2011 12:17 AM > *To:* Alexander Vainshtein > *Cc:* ietf@xxxxxxxx; mpls@xxxxxxxx; Vladimir Kleiner; Idan Kaspit; > Mishael Wexler; pwe3; Oren Gal; John Shirron; Rotem Cohen > *Subject:* Re: [PWE3] IETF Last Call comment on draft-ietf-pwe3-gal-in-pw > > I think it's okay because as the PW crosses the ECMP-enabled IP/MPLS > domain in the middle segment, you're no longer in an MPLS-TP > environment and so the GAL is not required to be BOS. During that > middle segment, the PW flow label would be placed below the GAL and > above the GACh. It gets removed when it hits the S-PE that switches > you back into the MPLS-TP environment. In other words, whether you're > in an MPLS-TP environment is determined segment by segment in a MS-PW. > > Pablo > > On Tue, Aug 16, 2011 at 1:02 PM, Alexander Vainshtein > <Alexander.Vainshtein@xxxxxxxxxxx > <mailto:Alexander.Vainshtein@xxxxxxxxxxx>> wrote: > > Hi all, > After having sent out my comments I've noticed that the specific > example to illustrate the need to combine GAL and "flow label" was > inaccurate. > > A more relevant example would look like following (I do not > include a diagram, but it can be easily provided if necessary) > > 1. A MS-PW: > * Starts at an S-PE that resides at the edge of an MPLS-TP > domain (no ECMP) > * Crosses this domain and enters an IP/MPLS domain with ECMP > enabled using a T-PE that resides at the age of these two > domains > * Leaves this domain and enters a 2nd MPLS-TP domain (using > the 2nd T-PE) > * Terminates on another S-PE at the edge of the 2nd MPLS-TP > domain > 2. The operator intends to improve traffic distribution in the > IP/MPLS domain, hence he enables insertion and discard of > "flow labels" at the two S-PEs. Note that: > * This does not violate the MPLS-TP restriction on ECMP: > ECMP does not happen in he MPLS-TP domains > * T-PEs do not even have to be aware of flow labels > 3. The operator also intends to operate some end-to-end OAM for > this MS-PW using "GAL-in-PW". This results in a conflict since > both GAL and "flow label" are defined (in the corresponding > drafts) as bottom of stack. > > > > IMHO this describes a realistic scenario where the two drafts are > in controversy. > > Regards, > Sasha > ------------------------------------------------------------------------ > *From:* mpls-bounces@xxxxxxxx <mailto:mpls-bounces@xxxxxxxx> > [mpls-bounces@xxxxxxxx <mailto:mpls-bounces@xxxxxxxx>] On Behalf > Of Alexander Vainshtein [Alexander.Vainshtein@xxxxxxxxxxx > <mailto:Alexander.Vainshtein@xxxxxxxxxxx>] > *Sent:* Tuesday, August 16, 2011 4:26 PM > *To:* ietf@xxxxxxxx <mailto:ietf@xxxxxxxx> > *Cc:* mpls@xxxxxxxx <mailto:mpls@xxxxxxxx>; Vladimir Kleiner; Idan > Kaspit; Mishael Wexler; pwe3; Oren Gal; John Shirron; Rotem Cohen > *Subject:* [mpls] IETF Last Call comment on draft-ietf-pwe3-gal-in-pw > > Hi all, > > > > I would like to raise the following issue with regard to > draft-ietf-pwe3-gal-in-pw > <http://datatracker.ietf.org/doc/draft-ietf-pwe3-mpls-tp-gal-in-pw/?include_text=1>: > controversy vs. draft-ietf-pwe3-fat-pw > <http://datatracker.ietf.org/doc/draft-ietf-pwe3-fat-pw/?include_text=1> > with regard to bottom-of-stack position. > > > > As stated in the Introduction, this draft removes the restriction > imposed by RFC 5586 on usage of Generic Associated Channel Label > (GAL) in PWs. The corresponding text Section 4.2 of RFC 5586 states: > > In MPLS-TP, the GAL MUST be used with packets on a G-ACh on LSPs, > Concatenated Segments of LSPs, and with Sections, and MUST NOT be > used with PWs. It MUST always be at the bottom of the label stack > (i.e., S bit set to 1). > > > > draft-ietf-pwe3-gal-in-pw proposed to replace the original text in > RFC 5586 with the following > > > > In MPLS-TP, the GAL MUST be used with packets on a G-ACh on LSPs, > Concatenated Segments of LSPs, and with Sections, and MAY be used > with PWs. It MUST always be at the bottom of the label stack > (i.e., S bit set to 1). > > > > I.e., while removing this restriction of 5586, it does not modify > its requirement for the GAL being always at the bottom of the > label stack. > > > > At the same draft-ietf-pwe3-fat-pw (currently also in the IESG > review) reserves the bottom of the PW stack for the PW flow > labels, e.g., in Section 1.1: > > > > This document describes a method of adding an additional label > stack entry (LSE) at the bottom of stack in order to facilitate > the load balancing of the flows within a PW over the available > ECMPs. > > > > One could argue that draft-ietf-pwe3-gal-in-pw only applies to > MPLS-TP pseudowires, and that MPLS-TP does not use ECMP. IMHO and > FWIW, > > such an argument, were it presented, would be highly problematic, > because: > > > > 1. RFC 5960 (which defines the MPLS-TP data plane) did not > define any differences between the PW data plane in IP/MPLS and > MPLS-TP. > > 2. One of the most popular scenarios for using multi-segment > pseudowires is the case when an edge-to-edge service emulation > crosses multiple IP/MPLS and MPLS-TP domains. In these scenarios, > the flow label of draft-ietf-pwe3-fat-pw (inserted by a flow-aware > T-PE at the edge of an IP/MPLS domain) would potentially compete > with GAL (inserted by a T-PE at the edge of an MPLS-TP domain, > e.g., for relying a PW status message that it has received over a > Targeted LDP session from the IP/MPLS domain to a static PW status > message to cross the MPLS-TP domain) for the bottom-of-stack > position. > > > > The issue I am raising Is not new. It has been actively discussed > on the PWE3 mailing list with regard to adoption of > draft-nadeau-pwe3-vccv-2 as a WG document, with arguments for > both the flow label and GAL taking the bottom-of-the-stack > position. But, to the best of my understanding, consensus on this > issue has not been reached. > > > > Hopefully this comment will be useful. > > > > Regards, > > Sasha > > > > This e-mail message is intended for the recipient only and > contains information which is CONFIDENTIAL and which may be > proprietary to ECI Telecom. If you have received this transmission > in error, please inform us by e-mail, phone or fax, and then > delete the original and all copies thereof. > > This e-mail message is intended for the recipient only and > contains information which is CONFIDENTIAL and which may be > proprietary to ECI Telecom. If you have received this transmission > in error, please inform us by e-mail, phone or fax, and then > delete the original and all copies thereof. > > > _______________________________________________ > pwe3 mailing list > pwe3@xxxxxxxx <mailto:pwe3@xxxxxxxx> > https://www.ietf.org/mailman/listinfo/pwe3 > > > This e-mail message is intended for the recipient only and contains > information which is CONFIDENTIAL and which may be proprietary to ECI > Telecom. If you have received this transmission in error, please > inform us by e-mail, phone or fax, and then delete the original and > all copies thereof. > > > > _______________________________________________ > Ietf mailing list > Ietf@xxxxxxxx > https://www.ietf.org/mailman/listinfo/ietf _______________________________________________ Ietf mailing list Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf