Hi Lars,
Master and slave ports of a BC can have different, distinct encapsulations (mappings) as long as PTP message information are preserved. As such, LER can receive PTP messages with IP mapping, and, by implementing BC function, could send the same PTP messages over an LSP with some MPLS encapsulation and receiving LER can transmit with Ethernet mapping. In this draft, the original encap tends to be preserved over the LSP with assumption that LER is either an ordinary or a boundary clock. Actually LER in this draft might be PTP unaware, thus not providing any timing assistance but only MPLS transport, with the risk to impair the quality of the timing distribution. One key point, I guess for all LSRs between two LERs (assuming OC or BC), is either to use the same encapsulation to keep the timestamp point unique or to define an unique timestamp point for their residence time measurement. The first option should be fine for most intra-carrier cases (except, e.g., when adding a label for FRR tunnel) when the second option could allow adding extra label e.g., for FRR or CSC in inter-carrier cases. Thanks, Laurent From: [email protected] [mailto:[email protected]] On Behalf Of Lars Ellegaard Sent: mardi 29 novembre 2011 22:27 To: Greg Mirsky Cc: [email protected] Subject: Re: [TICTOC] FW: I-D Action: draft-ietf-tictoc-1588overmpls-02.txt Hi Greg You are of course right. My point is merely that if the PTP frame arrives at the MPLS network encapsulated in Ethernet (for example) the other end (PTP application) would expect the same encapsulation. I suppose that in princple the Ethernet header could be stripped, the PTP frame carried in G-Ach, and then a new, identical Ethernet header added again? Rgds Lars From: Greg Mirsky [mailto:[email protected]] Sent: 29 November 2011 22:15 To: Lars Ellegaard Cc: Ron Cohen; [email protected] Subject: Re: [TICTOC] FW: I-D Action: draft-ietf-tictoc-1588overmpls-02.txt Hi Lars, I think that non-MPLS portions are outside of scope for 1588 Over MPLS document. Regards, Greg On Tue, Nov 29, 2011 at 1:12 PM, Lars Ellegaard <[email protected]> wrote: And there are cases where MPLS transport is only a part of the e2e path From: [email protected] [mailto:[email protected]] On Behalf Of Greg Mirsky Sent: 29 November 2011 22:09 To: Ron Cohen Cc: [email protected] Subject: Re: [TICTOC] FW: I-D Action: draft-ietf-tictoc-1588overmpls-02.txt Dear Ron, need to point that only IP and MPLS payload can be carried over MPLS natively, directly. Any other payload, including Ethernet, would require PW. Perhaps PTP can be carried over G-ACh? Regards, Greg On Tue, Nov 29, 2011 at 1:00 PM, Ron Cohen <[email protected]> wrote: If the encapsulation was directly over MPLS, i.e. no Ethernet / IP layers in between MPLS and PTP, there were no layers to violate.... On Tue, Nov 29, 2011 at 8:35 PM, Anthony Magee <[email protected]> wrote: Hi Yaakov, The layer violation issue is something which I believe needs further discussion. If a higher layer entity is placed inside a device and is used to act as the Transparent Clock i.e. calculating residence time and modifying the correction field in the layer with which that higher layer entity is associated, one could use an identifier such as a label, or a multicast Destination address in order to address that higher layer entity, allowing it to make the change without it being a layer violation. Then on the transmit side, there is nothing specifically incorrect in a device modifying the Source Address of the packet sent from a Transparent Clock within the scope of IEEE 1588 and this would be needed in order to indicate that the device has effectively created a new packet - however, the function of the node is still that of a Transparent Clock. So as long as the various standards are observed and the modifying devices update the packets in a standards compliant manner, I don't see that such a Transparent Clock would constitute a layer violation. Anthony -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Yaakov Stein Sent: 26 November 2011 20:25 To: [email protected]; Shahram Davari Cc: '[email protected]' Subject: Re: [TICTOC] FW: I-D Action: draft-ietf-tictoc-1588overmpls-02.txt Shahram and Stewart If we need intermediate MPLS nodes to perform special processing on 1588oMPLS packets there are several methods to lower the processing requirements. Of course, DPI could be performed to go below the MPLS and IP headers as Shahram said, but as Stewart pointed out this would be prohibitively expensive. Two methods have been proposed. The method of the present draft is to use the standard encapsulations (after ensuring that 1588 is supported) and to inform the intermediate nodes that the particular label value being used is special. For this special label value the node has been informed of what to do, e.g., has the offset of a TC. Any use of TC is necessarily a layer violation (after all, the timestamp is a layer-0 entity and we are placing it in a layer 2 or higher field), but correcting a field inside 1588 in UDP in IP in MPLS is not really that much worse than correcting on in 1588 in UDP in IP in Ethernet. The alternative method that I proposed is to invent a completely new timestamping mechanism. This has the advantage of being applicable to all MPLS packets (and thus can solve other problems), but requires inventing yet another timing distribution protocol. I know that Stewart succeeded in inventing a new packet loss and delay measurement protocol for TP, but I didn't gauge support in TICTOC for something new here. Y(J)S -----Original Message----- From: Stewart Bryant [mailto:[email protected]] Sent: Thursday, November 24, 2011 19:30 To: Shahram Davari Cc: '[email protected]'; '[email protected]' Subject: Re: [TICTOC] FW: I-D Action: draft-ietf-tictoc-1588overmpls-02.txt Shahram I will ponder the answer to this question, but will note that you have not addressed my second question which relates to whether there is MPLS WG buy-in for this proposal. - Stewart On 24/11/2011 16:34, Shahram Davari wrote: > Hi Stewart, > > The parsing required by the draft is not complex and almost all MPLS routers have support it already. The idea was to reuse existing data plane mechanisms and not invent a new one. This I believe is in the spirit of IETF to reuse existing mechanisms. > > I don't believe adding a shim makes the design simpler. You still need to detect that such shim exists and for that you need parsing that doesn't even exist today. > > > This draft has been implemented by vendors, so we have a working code and I believe we also have rough consensus. > > Thanks > Shahram > > > > ----- Original Message ----- > From: Stewart Bryant [mailto:[email protected]] > Sent: Thursday, November 24, 2011 07:58 AM > To: [email protected]<[email protected]> > Cc: [email protected]<[email protected]>; > [email protected]<[email protected]> > Subject: Re: [TICTOC] FW: I-D Action: > draft-ietf-tictoc-1588overmpls-02.txt > > Can we wind back to my original points here which have not addressed. > > Why are is the WG proposing a design that needs such complex parsing, > against the ethos of MPLS, when a simpler design would be more > universally applicable? > > Does the WG have any input to suggest that the design will survive a > review by MPLS/PWE3 WG and then by IESG? > > - Stewart > > > On 22/11/2011 09:12, Stewart Bryant wrote: >> Speaking as an individual here, I really have a hard time >> understanding why it is necessary to have quite the egregious layer >> violation that this draft uses. >> >> The idea of having an LSP type that is dedicated to tracking the time >> of passage through the network is a good idea. However MPLS is >> completely geared to the concept that only the LSP endpoints know how >> to resolve the payload type. >> >> The function that you require could be achieved by including a shim >> that contains the time compensation information and adjust the >> payload on egress from the LSP. That would be rather more consistent >> with the MPLS architecture. >> >> I have not seen a request for review by the MPLS or PWE3 WGs and I >> would suggest that you request that sooner rather than later since it >> is inevitable that the draft will be sent there later in it's life, >> and if they do not subscribe to your mode of operation the draft is >> unlikely to progress. >> >> I would also suggest that you discuss the extent of layer violation >> with your AD to make sure he is confident that this draft will pass >> IESG review. >> >> - Stewart >> >> >> _______________________________________________ >> TICTOC mailing list >> [email protected] >> https://www.ietf.org/mailman/listinfo/tictoc >> > -- For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/index.html _______________________________________________ TICTOC mailing list [email protected] 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 CONFIDENTIALITY NOTICE: This e-mail message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. 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