Dear Sasha, I think I disagree with your assessment of applicability of Section GAL to PTP.propagation throughout MPLS-TP network. If we set performance (delay, jitter, and latency introduced by an MPLS-TP node that is end-point of a Section) aside for now, I don't see what precludes a PTP packet from being forwarded (both unicast and multicast) over DCN. Yes, the performance hit might be prohibitive but with enough thrust ...
Regards, Greg On Mon, Jul 19, 2010 at 8:06 AM, Alexander Vainshtein <[email protected]> wrote: > Tal, > > I think that we are in full agreement regarding a single-label GAL-only > stack: > > It allows the LSRs to modify PTP packets (as TC must do), but it does not > support forwarding (unicast and multicast). Hence it is useless. > > IMO GAL/G-ACH are a clear dead end in this discussion. > > > > If you have been following this list, I’ve suggested allocating a new > reserved label which, at the top of the stack, would indicate PTP packets. > > IMHO this is the only method that would somehow accommodate TC (which is a > layer violation, of course) without completely breaking MPLS data plane. > > However, this approach did not gain support on the list. > > > > “PTP FEC” IMO is also a dead end. E.g., you would not be able such popular > recovery techniques as Facility FRR for this FEC, etc. > > > > At the same time, if TC support is not required, there is no need to invent > any special encapsulation of PTP over MPLS. All the rest of the use cases > can be easily accommodated with PTP/UDP/IP/MPLS without inventing new > wheels. > > > > My 2c, > > Sasha > > > > From: Tal Mizrahi [mailto:[email protected]] > Sent: Monday, July 19, 2010 5:55 PM > To: Alexander Vainshtein > Cc: [email protected] > Subject: Re: [TICTOC] FW: 1588 over MPLS draft > > > > Hi Sasha, all, > > > > A couple of comments: > > 1. Generally, regarding using GAL+ACH: according to RFC 5586: “LSRs MUST NOT > modify the G-ACh message, the ACH or the GAL towards the targeted > destination”. However, a PTP capable LSR that functions as a TC must modify > the packet (including the correctionField and the UDP checksum). This means > that if an LSR functions as a TC, either (a) the functionality in RFC 5586 > must be enhanced to allow modification, or (b) the LSR terminates all > incoming PTP messages, and then re-generates them, which may burden the > control plane. > > 2. Sasha, regarding your option 1 below: if each packet has a label stack > with 1 label (GAL), it raises the question how to distinguish between > single-target and multi-target PTP packets. PTP calls for both multicast > frames (e.g.), and unicast (e.g. Delay_Req). > > > > That’s not to say I am against using the GAL, but it needs some further > refinement. > > > > Tal. > > > > > > > > > > > > > > -----Original Message----- > > > > Yaakov and all, > > Please note that GAL and, by implication, the ACH header are only looked at > by > > an LSTR if GAL happens to be the top label in the stack (either because it > has > > been the top label in originally received packet, or because all the labels > > above it have been popped by this LSR). > > > > This leaves two options IMO: > > 1. You carry PTP directly across physical links using labeled packets that > > have a label stack of depth 1 containing GAL. > > In this case you can probably do want you want with the PTP packets' > > payload, (e.g., support TC), but you need some new mechanism for > forwarding > > PTP packets along a multi-hop path. > > > > 2. You can carry PTP across any LSP using GAL at the bottom of the label > stack. > > In this case only the tail end of the LSP will be PTP-aware, i.e., TC > will > > not be supported with this option. > > > > I suggest taking a look at > http://datatracker.ietf.org/doc/draft-ietf-mpls-tp-data-plane for details > > regarding MPLS (and MPLS-TP) data plane. > > > > Regards, > > Sasha > > > > -----Original Message----- > > From: tictoc-bounces at ietf.org [mailto:tictoc-bounces at ietf.org] On > Behalf Of Yaakov Stein > > Sent: Monday, July 19, 2010 12:06 PM > > To: Mikael Abrahamsson > > Cc: tictoc at ietf.org > > Subject: Re: [TICTOC] FW: 1588 over MPLS draft > > > > No. Not a new Ethertype - we are talking about MPLS NOT Ethernet. > > > > There is a protocol type (it's actually called a "channel type") > > in the Ach control word. See RFC 4385. > > Right now only a few are defined (raw BFD, IPv4, IPv6). > > > > > > Y(J)S > > > > -----Original Message----- > > From: Mikael Abrahamsson [mailto:swmike at swm.pp.se] > > Sent: Monday, July 19, 2010 09:48 > > To: Yaakov Stein > > Cc: stbryant at cisco.com; tictoc at ietf.org > > Subject: Re: [TICTOC] FW: 1588 over MPLS draft > > > > On Sun, 18 Jul 2010, Yaakov Stein wrote: > > > >> 1) define a new protocol type (plenty of openings in THAT registry!) > > > > New protocol type on what level? Ethernet, so this would involve a new > > ethertype? > > > > If routers generally can look that far into the packet on the correct > > forwarding level (I doubt it though) then that would be the least > > intrusive, but having LSRs look for ethertype within MPLS labeled packets > > sounds kind of advanced to do that early in the receive path? > > > > Why not do it more like an MPLS L3 VPN terminated/routed by all > > involved&&aware routers, then it would signal special labels to its > > neighbours that would be local significance only? But now we're talking > > handling it like a tree and that would involve routing protocols as > > well... Basically this would be like multicast IP and could leverage all > > the multicast MPLS standards out there. > > > > -- > > Mikael Abrahamsson email: swmike at swm.pp.se > > _______________________________________________ > > TICTOC mailing list > > TICTOC at ietf.org > > https://www.ietf.org/mailman/listinfo/tictoc > > > > _______________________________________________ > TICTOC mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/tictoc > > _______________________________________________ TICTOC mailing list [email protected] https://www.ietf.org/mailman/listinfo/tictoc
