Hi Manav, See my comments in line. Thanks Lizhong
Manav Bhatia <[email protected]> wrote on 2011-01-27 11:59:38: > Hi Lizhong, > > > > > > > You can only ensure that 1588aware LSRs will not do ECMP on PTP > > > LSPs. What if we have a non-1588aware LSR in the path? > > [Lizhong] All the LSRs and LERs along PTP LSP MUST be 1588aware, right? > > In an ideal world Yes, all routers would be 1588aware. However, this > being far from an ideal world, you can always have some LSRs that are > not draft-ietf-tictoc-1588overmpls aware. You will note that this draft > also has some text on the non 1588aware LSRs. These LSRs could be doing > ECMP and without an entropy label, may cause PTP messages to be load > distributed across different paths. [Lizhong] then in section 13, it is said: "This capability MUST then be taken into account during path computation to prefer nodes that advertise themselves as 1588-aware, so that the PTP LSPs can be properly handled." How to understand "prefer nodes"? If there is a shortest path with some non 1588aware LSRs, and a less optimal path with all 1588aware LSRs, which path the ingress LER should take? > > > > > >The head end > > > when setting up the RSVP path would know this (by inspecting the IS- > > > IS or OSPF TE info) and could in such cases make use of the Entropy > > > label to ensure that all PTP packets follow the same path. > > [Lizhong] How to use entropy label to ensure all PTP packets follow the > > same path? > > Using an entropy label will ensure that all PTP packets in one direction > follow the same path. [Lizhong] since control word is required for 1588 over PW encapsulation, if without entropy label, all PTP packets in one direction will also follow the same path. > > > If there is entropy label, it is possible that the forward > > and reverse path would be different. > > Since LSPs are unidirectional there is no guarantee that the two paths > would be symmetrical. So this really is an issue orthogonal to the use > of entropy labels for carrying PTP traffic. > > We should probably add some text in the draft that says that the two > paths must be symmetrical. [Lizhong] If there is a boundled interface between two LSRs, the control plane will only see one logical interface. Then it is still possible the forward and reverse path be different at the physical level in ECMP case. > > Cheers, Manav > > > > > >This is > > > one scenario where i think we may want to use Entropy labels. > > > > > > Cheers, Manav > > > > > > From: [email protected] [mailto:[email protected]] > > > Sent: Tuesday, January 18, 2011 6.03 PM > > > To: Bhatia, Manav (Manav) > > > Cc: [email protected] > > > Subject: Re: [TICTOC] Transporting PTP messages (1588) over MPLS Networks > > > > > > > > Hi Manav, > > > In section 8 ECMP, since it is said PTP LSPs and PWs MUST NOT be > > > subject to ECMP, why in section 5.2 the encapsulation of figure 2 > > > has entroy label? I am a bit confused. > > > > > > Regards > > > Lizhong > > > > > > > > > > ---------------------------------------------------------------------- > > > > > > > > Message: 1 > > > > Date: Sat, 15 Jan 2011 16:25:59 +0530 > > > > From: "Bhatia, Manav (Manav)" <[email protected]> > > > > Subject: [TICTOC] Transporting PTP messages (1588) over MPLS Networks > > > > To: "[email protected]" <[email protected]> > > > > Message-ID: > > > > <[email protected]. > > > > alcatel-lucent.com> > > > > > > > > Content-Type: text/plain; charset="us-ascii" > > > > > > > > Hi, > > > > > > > > We have posted a revised version of draft-davari- > > > > tictoc-1588overmpls-01 and would appreciate a feedback from the WG. > > > > > > > > The draft is available here: > > > > http://www.ietf.org/id/draft-davari-tictoc-1588overmpls-01.txt > > > > > > > > Cheers, Manav > > > > > > > > -- > > > > Manav Bhatia, > > > > IP Division, Alcatel-Lucent, > > > > Bangalore - India > > > > > > > > > > > > > > > -------------------------------------------------------- > > > ZTE Information Security Notice: The information contained in this > > > mail is solely property of the sender's organization. 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