Re: [mpls] [PWE3] ELI as a reserved label
Curtis Villamizar <curtis@occnc.com> Mon, 02 August 2010 13:50 UTC
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To: Shane Amante <shane@castlepoint.net>
From: Curtis Villamizar <curtis@occnc.com>
In-reply-to: Your message of "Fri, 30 Jul 2010 17:31:23 +0200." <6F8F5330-91F8-456F-BFDC-FF5735CFDD9E@castlepoint.net>
Date: Mon, 02 Aug 2010 09:50:29 -0400
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Cc: mpls@ietf.org, pwe3@ietf.org
Subject: Re: [mpls] [PWE3] ELI as a reserved label
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In message <6F8F5330-91F8-456F-BFDC-FF5735CFDD9E@castlepoint.net> Shane Amante writes: > > Curtis, > > On Jul 30, 2010, at 14:02 GMT+02:00, Curtis Villamizar wrote: > > In message <0DEFA7EF-8DC4-4EF2-ABDF-0404FC32B992@castlepoint.net> > > Shane Amante writes: > >> On Jul 30, 2010, at 11:06 GMT+02:00, Curtis Villamizar wrote: > > [--snip--] > > >>> 3. Providing a means to carry indication of large flow as described > >>> in draft-yong-pwe3-enhance-ecmp-lfat-01.txt and > >>> draft-yong-pwe3-lfc-fat-pw-01.txt without changing the use of TC > >>> in a forwarding LSP label. > >> > >> I'm unclear how a single, reserved label would be a means of signaling > >> a large vs. small flow. How can a single label represent two states > >> (large vs. small flow)? > > > > That's the slightly ugly part. If ELI carries a TTL=0 then it can't > > be used to forward and among those that discussed this (in one of the > > "hallway sessions" near the registration desk) it was not seen as too > > horribly ugly if TC meaned something else in the ELI label stack entry > > only. > > > > Lucy has a different way to do multipath and this is an enabler. If > > your LSRs don't use it, then it does no harm as long as the hashed > > entropy value is there too. > > Understood. > > I would note that in draft-kompella-mpls-entropy-label-01 it is NOT envisioned that there will be a "standalone ELI" in all cases. Specifically, in the case where application labels are in use, (e.g.: 2547 VPN's, 6PE, etc.), the application label itself is intended to serve the purpose of an ELI, indicating that the label that immediately follows the application label is an entropy-label, i.e.: > > +----------------+ > | Tunnel Label | > +----------------+ > | App. Label | > +----------------+ > | Entropy Label | > +----------------+ > > In these cases, there wouldn't be a reserved label used for a ELI in the label stack. Thus, I'm not sure you can count on the LFC-bit *only* being set in entropy-labels that are immediately preceded by a reserved ELI label. > > So, with respect to LFC, IMO it's: > a) orthogonal to the discussion of whether or not a reserved label for the ELI is absolutely _required_ or just nice-to-have; and, > b) the MPLS WG needs to weigh in with a definitive answer on whether changing the semantics of the MPLS TC is appropriate to accommodate end-users who desire LFC. > > -shane This doesn't work in the following cases: 1. P2MP (multiple egress, therefore multiple ELI values). 2. Label stack depth is limited in order to accommodate MPLS-TP (midpoints must know to look past the ELI to include the entropy label in the hash). Since Lucy's large flow work needed TC, using TTL=0, and reserving one TC bit for large flow seemed to do no harm. I spoke to Stewart and Kireeti about this at IETF. Perhaps either or both of them could weigh in on this topic on the list. Curtis
- Re: [mpls] [PWE3] ELI as a reserved label Shane Amante
- Re: [mpls] ELI as a reserved label Shane Amante
- Re: [mpls] [PWE3] ELI as a reserved label Curtis Villamizar
- [mpls] ELI as a reserved label Curtis Villamizar
- Re: [mpls] [PWE3] ELI as a reserved label Shane Amante
- Re: [mpls] [PWE3] ELI as a reserved label Curtis Villamizar
- Re: [mpls] [PWE3] ELI as a reserved label Curtis Villamizar
- Re: [mpls] [PWE3] ELI as a reserved label Greg Mirsky
- Re: [mpls] [PWE3] ELI as a reserved label John E Drake
- Re: [mpls] [PWE3] ELI as a reserved label Curtis Villamizar
- Re: [mpls] [PWE3] ELI as a reserved label Curtis Villamizar
- Re: [mpls] [PWE3] ELI as a reserved label John E Drake
- Re: [mpls] [PWE3] ELI as a reserved label Curtis Villamizar
- Re: [mpls] [PWE3] ELI as a reserved label John E Drake
- Re: [mpls] [PWE3] ELI as a reserved label Curtis Villamizar
- Re: [mpls] [PWE3] ELI as a reserved label Yong Lucy
- Re: [mpls] [PWE3] ELI as a reserved label David Allan I
- Re: [mpls] [PWE3] ELI as a reserved label John E Drake
- [mpls] ELI and EL in P2MP (Re: [PWE3] ELI as a re… Curtis Villamizar
- Re: [mpls] [PWE3] ELI as a reserved label Curtis Villamizar
- Re: [mpls] ELI and EL in P2MP (Re: [PWE3] ELI as … Curtis Villamizar
- Re: [mpls] ELI and EL in P2MP (Re: [PWE3] ELI as … David Allan I
- Re: [mpls] [PWE3] ELI as a reserved label Kireeti Kompella
- Re: [mpls] [PWE3] ELI as a reserved label Kireeti Kompella
- Re: [mpls] [PWE3] ELI as a reserved label Curtis Villamizar
- Re: [mpls] [PWE3] ELI as a reserved label Yong Lucy
- Re: [mpls] [PWE3] ELI as a reserved label John E Drake
- Re: [mpls] [PWE3] ELI as a reserved label John E Drake
- Re: [mpls] [PWE3] ELI as a reserved label Yong Lucy
- [mpls] draft-ietf-mpls-entropy-label-01 Sami Boutros