Re: [CCAMP] Adding composite labels to flexi-grid
malcolm.betts@zte.com.cn Thu, 19 June 2014 10:11 UTC
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Subject: Re: [CCAMP] Adding composite labels to flexi-grid
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Hi Adrian, I have some concerns about using the term VCAT in the context of a media channel. The media is flat and has no structure so if the "concatenated" media channels are adjacent, we have a larger media channel. If (as I think you intend) the media channels are not adjacent then you have a set of media channels. Another way of looking at this (and please don't over extend the analogy) is water and pipe. The water is the optical signal and the media channel is the pipe. This draft is addressing the management of pipes. The concept of VCAT only applies to digital streams, it cannot be applied to the media layer layer. This concept of a group (or set) of media channels may be useful in the future after SG15 have completed the work on OTN B100G where the possibility of inverse multiplexing a 400G OTN digital stream into two (or four) digital streams which are then modulated onto two (or four) optical signals that use two (or four) independent media channels is under consideration and managing these independent media channels as a set would be useful. However, this is still under discussion in SG15. Regards, Malcolm "Adrian Farrel" <adrian@olddog.co.uk> Sent by: "CCAMP" <ccamp-bounces@ietf.org> 17/06/2014 08:55 AM Please respond to adrian@olddog.co.uk To <ccamp@ietf.org>, cc Subject [CCAMP] Adding composite labels to flexi-grid Hi, Ramon and I have worked up some text to go in draft-ietf-ccamp-flexigrid-lambda-label to describe composite labels. There is not a huge amount to say *in*this*document* partly because we have lots of running code about how to do VCAT in a number of technologies, and partly because this document describes the label format, not the signaling, routing, or usage. Would like your comments and plan to post before the Toronto cut-off. We can return to the debate in Toronto if it needs f2f time. BTW, as an aside, this is deliberately not intended to discuss the "super channel". At this stage, super-channel is not something that the ITU-T recognises as a data plane concept (although I know a number of companies are interested in this and will work in that area). Iftekhar has a strong interest in describing GMPLS labels and processing for super channels, and has indicated that he is willing to be an anchor for this work in the IETF. Thanks, Adrian ==== New section 2.1. Virtual Concatenation It is possible to construct an end-to-end connection by "concatenating" more than one flexi-grid slot. The mechanism used is similar to virtual concatenation (VCAT) familiar in time-division multiplexing (TDM) and optical transport networks (OTN). The concatenated slots could potentially be contiguous or non-contiguous (as allowed by the definitions of the data plane) and could be signaled as a single LSP or constructed from a group of LSPs. For more details, refer to Section 4.3. === New section 4.3. Virtual Concatenation Virtual concatenation is already supported in GMPLS for TDM and OTN [RFC4606], [RFC6344], [RFC7139]. The mechanism used for flexigrid is similar. To signal an LSP that uses multiple flexi-grid slots a "compound label" is constructed. That is, the LABEL object is constructed from a concatenation of the 64-bit Flexi-Grid Labels shown in Figure 1. The number of elements in the label can be determined from the length of the LABEL object. The resulting LABEL object is shown in Figure 2 including the object header that is not normally shown in diagrammatic representations of RSVP-TE objects. Note that r is the count of component labels, and this is backward compatible with the label shown in Figure 1 where the value of r is 1. The order of component labels MUST be presented in increasing order of the value n. Implementations MUST NOT infer anything about the encoding of a signal into the set of slots represented by a compound label from the label itself. Information about the encoding MAY be handled in other fields in signaling messages or through an out of band system, but such considerations are out of the scope of this document. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Object Length (4 + 8r) | Class-Num (16)| C-Type (2) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Grid | C.S. | Identifier | n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | m | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Grid | C.S. | Identifier | n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | m | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2 : A Compound Label for Virtual Concatenation Note that specific rules must be applied as follows: - Grid MUST show "ITU-T Flex" value 3 in each component label. - C.S. MUST have the same value in each component label. - Identifier in each component label may identify different physical equipment. - Values of n and m in each component label define the slots that are concatenated. At the time of writing [G.694.1] only supports the concatenation of adjacent slots (i.e., without intervening unused slots that could be used for other purposes) of identical width (same value of m), and the component slots must be in increasing order of frequency (i.e., increasing order of the value n). The mechanism defined here MUST NOT be used for other forms of concatenation unless and until those forms of concatenation are defined and documented in Recommendations published by the ITU-T. Note further that while the mechanism described here naturally means that all component channels are corouted, a composite channel can also be achieved by constructing individual LSPs from single flexi- grid slots and managing those LSPs as a Virtual Concatenation Group (VCG). A mechanism for achieving this for TDM is described in [RFC6344], but is out of scope for discussion in this document because the labels used are normal, single slot labels and require no additional definitions. _______________________________________________ CCAMP mailing list CCAMP@ietf.org https://www.ietf.org/mailman/listinfo/ccamp -------------------------------------------------------- ZTE Information Security Notice: The information contained in this mail (and any attachment transmitted herewith) is privileged and confidential and is intended for the exclusive use of the addressee(s). If you are not an intended recipient, any disclosure, reproduction, distribution or other dissemination or use of the information contained is strictly prohibited. If you have received this mail in error, please delete it and notify us immediately.
- [CCAMP] Adding composite labels to flexi-grid Adrian Farrel
- Re: [CCAMP] Adding composite labels to flexi-grid malcolm.betts
- Re: [CCAMP] Adding composite labels to flexi-grid Adrian Farrel
- Re: [CCAMP] Adding composite labels to flexi-grid Varma, Eve L (Eve)
- Re: [CCAMP] Adding composite labels to flexi-grid Adrian Farrel