Network Working Group Iftekhar Hussain Abinder Dhillon Zhong Pan Marco Sosa Internet Draft Infinera Intended status: Standard Track July 25, 2011 Expires: January 2012 Generalized Label for Super-Channel Assignment on Flexible Grid draft-hussain-ccamp-super-channel-label-00.txt Abstract To enable scaling of existing transport systems to ultra high data rates of 1 Tbps and beyond, next generation systems providing super- channel switching capability are currently being developed. To allow efficient allocation of optical spectral bandwidth for such high bit rate systems, International Telecommunication Union Telecommunication Standardization Sector (ITU-T) is extending the G.694.1 grid standard (termed "Fixed-Grid") to include flexible grid (termed "Flex-Grid") support. This necessitates definition of new label format for the Flex-Grid. This document defines a super- channel label as a Super-Channel Identifier and an associated list of contiguous or non-contiguous set of 12.5 GHz slices representing optical spectrum of the super-channel. The label information can be encoded using a fixed length or variable length format. This label format can be used in GMPLS signaling and routing protocol to establish super-channel based optical label switched paths (LSPs). Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." Hussain Expires January 25, 2012 [Page 1] Internet-Draft Generalized Super-Channel Label July 2011 The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on January 25, 2012. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction...................................................2 2. Terminology....................................................5 3. Motivation for Super-Channel Label.............................5 3.1. Flex-Grid Slice Numbering.................................5 3.2. Super-Channel Label.......................................6 3.2.1. Super-Channel Label Encoding Format..................8 4. Security Considerations.......................................12 5. IANA Considerations...........................................12 6. References....................................................12 6.1. Normative References.....................................12 6.2. Informative References...................................12 7. Acknowledgments...............................................13 Appendix A. Super-Channel Label Format Example...................14 1. Introduction Future transport systems are expected to support service upgrades to data rates of 1 Tbps and beyond. To scale networks beyond 100Gbps, multi-carrier super-channels coupled with advanced multi-level Hussain Expires January 25, 2012 [Page 2] Internet-Draft Generalized Super-Channel Label July 2011 modulation formats and flexible channel spectrum bandwidth allocation schemes have become pivotal for future spectral efficient transport network architectures [1,2]. A super-channel represents an ultra high aggregate capacity channel containing multiple carriers which are co-routed through the network as a single entity from the source transceiver to the sink transceiver [3]. By multiplexing multiple carriers, modulating each carrier with multi-level advanced modulation formats (such as PM- QPSK, PM-8QAM, PM-16QAM), allocating an appropriate-sized flexible channel spectral bandwidth slot, and using a coherent receiver for detecting closely packed sub-carriers, a super-channel can support ultra high data rates in a spectrally efficient manner while maintaining required system reach. Figure 1 contrasts channel spectrum bandwidth allocation schemes for various bit rate optical paths on fixed-grid (G.694.1) and flex-grid. ITU-T fixed-grid permits allocation of channel spectrum bandwidth in "single" fixed- sized slots (e.g., 50GHz, 100GHz etc) independent of the channel bit rate. In contrast, a flex-grid can allocate "arbitrary" size channel spectral bandwidth as an integer multiple of 12.5 GHz fine granularity contiguous slices depending on channel bit rate. This means, a flex-grid can support multiple data rates channels (optical paths) in a spectrally efficient manner as it allocates appropriate- sized spectrum bandwidth slots, as opposed to fixed-sized slots. Hussain Expires January 25, 2012 [Page 3] Internet-Draft Generalized Super-Channel Label July 2011 ITU-T G.694.1 Center frequency (f) = 193.1 THz n=-3 n=-2 n=-1 n=0 n=+1 n=+2 ^ ^ ^ ^ ^ ^ ... | | | | | | ... | | | | | | | | | | | +--------+-------+-------+-------+-------+--- <-- --> <-- --> 50 GHz 50 GHz ^ ^ | n=-2 | n= +1 | | +------+ +------+ |50 GHz| |50 GHz| +------+ +------+ (10 Gbps channel) (40Gbps channel) (a fixed 50GHz chunk) (a fixed 50GHz chunk) (a) ^ ^ ^ ^ ^ ^ | | | | | + +| ... |-|-|-|-|-|-|-|-| |+|+|+|+|+|+|+|+|+|1|1| ... |8|7|6|5|4|3|2|1|0|1|2|3|4|5|6|7|8|9|0|1| ---+-------+-------+-------+-------+-------+--- ^ ^ ^ |<-- 200 GHz -->|<- ->| | | 50GHz | +-------------------------------+-------+ | 1 Tbps super-channel |100Gbps| | 16 slices of 12.5 GHz |Channel| | |4slices| +-------------------------------+-------+ (b) Figure 1 ITU-T (a) 50 GHz fixed-grid (G.694.1) (b) 12.5 GHz granular flex-grid Hussain Expires January 25, 2012 [Page 4] Internet-Draft Generalized Super-Channel Label July 2011 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT","SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 3. Motivation for Super-Channel Label [RFC3471] defines new forms of MPLS "label" for the optical domain that are collectively referred to as a "generalized label". [RFC6205] defines a standard wavelength label based on ITU-T fixed- grids ([G.694.1] and [G.694.2]) for use by Lambda-Switch-Capable (LSC) LSRs. A new label format for super-channels assignment on flex-grid is needed because the existing label formats (such as the waveband switching label defined in RFC3471 and the wavelength label defined in RFC6205) either lack necessary fields to carry required flex-grid related information (e.g., channel spacing) or do not allow signaling of arbitrary flexible-size optical spectral bandwidth in an efficient manner (e.g., in terms of integer multiple of fine granularity 12.5GHz slices). For example, o Waveband switching label format (defined in section 3.3.1 of RFC3471) lacks fields to carry necessary information to support flex-grid. o Wavelength label allows signaling of single fixed-size optical spectrum bandwidth slot only. o Wavelength label does not allow signaling of arbitrary flexible- size optical spectrum bandwidth needed for super-channels assignment on flex-grid. 3.1. Flex-Grid Slice Numbering Figure 2 (a) shows a 50 GHz ITU-T G.694.1 grid based on nominal central frequency (193.1 THz). In G.694.1, given a channel spacing (C.S) value and a value "n", the desired wavelength frequency can calculated as follows: Frequency (THz) = 193.1 THz + n * channel spacing (THz). Hussain Expires January 25, 2012 [Page 5] Internet-Draft Generalized Super-Channel Label July 2011 Where "n" is a two's-complement integer (i.e., positive, negative, or 0) and "channel spacing" can be 0.0125, 0.025, 0.05, or 0.1 THz. Figure 2 (b) shows a 12.5 GHz flex-grid with its nominal central frequency (193.1 THz) aligned with ITU-T G.694.1 nominal central frequency and with each 12.5 GHz slice represented by the "left- edge". Given the left edge frequency of a slice, one can calculate the value of n i.e., slice number as follows: Frequency (THz) = 193.1 THz + n * channel spacing (THz). Where "n" is a two's-complement integer (i.e., positive, negative, or 0) and "channel spacing" can be 0.0125 THz in this case. For example, slice number 0 is denoted by its left-edge frequency i.e., f= 193.1 THz, slice number 1 is represented by its left edge frequency of 193.1125 THz (193.1 THz + 0.0125 THz) and so on. 3.2. Super-Channel Label In order to setup an optical path manual or dynamically, we need a way to identify and reserve resources (i.e., signal optical spectral bandwidth for the super-channel) along the optical path. For this purpose, this document defines a super-channel label as consisting of a Super-Channel Identifier and an associated list of contiguous or non-contiguous set of 12.5 GHz slices representing arbitrary size optical spectrum of the super-channel (Note: in the future, slice granularity could be 6.25 GHz). Hussain Expires January 25, 2012 [Page 6] Internet-Draft Generalized Super-Channel Label July 2011 ITU-T G.694.1 Center frequency (f) = 193.1 THz n=-1 n=-1 n=0 n=+1 n=+2 ^ ^ ^ ^ ^ ... | | | | | ... | | | | | ---+-------+-------+-------+-------+--- <-- --> | 50 GHz | | (a) | | | ^ ^ ^ ^ ^ | | | | | ... |-|-|-|-|-|-|-|-| |+|+|+|+|+|+|+| ... |8|7|6|5|4|3|2|1|0|1|2|3|4|5|6|7| ---+-------+-------+-------+-------+--- ^ ^ | | | | +-----------------------+ | A super-channel with | | Spectral BW = 150 GHz | |(12 slices of 12.5 GHz)| | | | n_start= -7 | | n_end = +4 | | | | (see label encoding | | format for details) | +-----------------------+ (b) Figure 2 ITU-T (a) 50 GHz fixed-grid (G.694.1) (b) 12.5 GHs flex- grid with its nominal central frequency aligned with the ITU-T G.694.1 nominal central frequency Hussain Expires January 25, 2012 [Page 7] Internet-Draft Generalized Super-Channel Label July 2011 3.2.1. Super-Channel Label Encoding Format This section describes two options (option A and B) for encoding super-channel label by making extensions to waveband switching label[RFC3471] and wavelength label [RFC6205] formats. o Option A: Encode super-channel label as a first slice number of the grid (denoted as "n_start of Grid") plus the entire list of slices in the grid as a Bitmap 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Super-Channel Id (16-bit) |Grid | C.S. | Reserved (9-bit)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | n_start of Grid (16-bit) |Num of Slices in Grid (16-bit) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Bitmap Word #1(first set of 32 slices from the left most edge) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Bitmap Word #2 (next set of 32 contiguous slice numbers) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Bitmap Word #N(last set of 32 contiguous slice numbers) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Where: Super-Channel Id: 16 bits Hussain Expires January 25, 2012 [Page 8] Internet-Draft Generalized Super-Channel Label July 2011 This field represents a logical identifier for a super-channel. To disambiguate waveband switching and super-channel label applications, we propose to rename the Waveband Identifier (32- bit) as a super-channel Identifier (16-bit). Grid: 3 bits This field indicates the Grid type. The value for Grid should be set to xx (to be assigned by IANA) for the ITU-T flex-grid based on ongoing [G.694.1] standard flex-grid extensions. +----------------+---------+ | Grid | Value | +----------------+---------+ | Reserved | 0 | +----------------+---------+ |ITU-T DWDM | 1 | +----------------+---------+ |ITU-T CWDM | 2 | +----------------+---------+ |ITU-T Flex-Grid | xx (TBD)| +----------------+---------+ |Future use | 3 - 7 | +----------------+---------+ C.S. (channel spacing): 4 bits This field should be set to a value of 4 to indicate 12.5 GHz in both labels. ITU-T G694.1 has currently defined following DWDM channel spacing. +----------+---------+ |C.S. (GHz)| Value | +----------+---------+ | Reserved | 0 | +----------+---------+ | 100 | 1 | +----------+---------+ | 50 | 2 | +----------+---------+ | 25 | 3 | +----------+---------+ | 12.5 | 4 | +----------+---------+ |Future use| 5 - 15 | +----------+---------+ Hussain Expires January 25, 2012 [Page 9] Internet-Draft Generalized Super-Channel Label July 2011 n_start of Grid: 16-bit This field indicates the first slice number in Grid for the band being referenced (i.e., the start of the or the left most edge of the Grid). Num of Slices in Grid: 16-bit This field represents the total number of slices in the band. The value in this field determines the number of 32-bitmap words required for the grid. Bit map (Word): 32-bit Each bit in the 32-bitmap word represents a particular slice with a value of 1 or 0 to indicate whether for that slice reservation is required (1) or not (0). Bit position zero in the first word represents the first slice in the band (Grid) and corresponds to the value indicated in the "n_start of Grid" field. o Option B: Encode super-channel label as a list of start and end slice numbers corresponding to N groups of contiguous slices with each group denoted by its starting and ending slice number (e.g., "n_start_1" and "n_end_1" represent contiguous slices in group#1, "n_start 2" and "n_end 2" in group#2, ..., "n_start N" and "n_end N" in group#N). 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Super-Channel Id (16-bit) |Grid | C.S. | Reserved (9-bit)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved (16-bit) | Number of Entries(16-bit) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |n_start_1(contiguous group #1) | n_end_1(contiguous group #1) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Hussain Expires January 25, 2012 [Page 10] Internet-Draft Generalized Super-Channel Label July 2011 |n_start_2(contiguous group #2) | n_end_2(contiguous group #2) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |n_start_N (contiguous group #N) | n_end_N (contiguous group#N | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Where: Super-Channel Id, Grid, and C.S fields are same as described earlier in option A. Number of Entries: 16-bit This field represents the number of 32-bit entries in the super-channel label (i.e., number of groups with contiguous slices). For example, in the case of a super-channel with contiguous optical spectrum, this field should have a value of 1 (indicating one group of contiguous slices). n_start_i (i=1,2,...N): 16 bits n_end_i (i=1,2,...N): 16 bits A super-channel with contiguous or non-contiguous optical spectrum can be represented by N groups of slices where two adjacent groups can be contiguous or non-contiguous however each group contains contiguous slices. Each group is denoted by n_start_i (which indicates the lowest or starting 12.5 GHz slice number of the group) and n_end_i (which indicates the highest or ending 12.5 GHz slice number of the group). "n_start_i" and "n_end_i" are two's-complement integer that can take either a positive, negative, or zero value. Hussain Expires January 25, 2012 [Page 11] Internet-Draft Generalized Super-Channel Label July 2011 Both options allow efficient encoding of super-channel label with contiguous and non-contiguous slices. Option A yields a fixed length format while option B a variable length format. Option A is relatively simpler, more flexible, however, might be less compact than option B for encoding super-channel with contiguous optical spectrum. In contrast, option B provides a very compact representation for super-channels with contiguous optical spectrum, however, might be less flexible in encoding super-channels with arbitrary non-contiguous set of slices. 4. Security Considerations 5. IANA Considerations IANA needs to assign a new Grid field value to represent ITU-T Flex- Grid. 6. References 6.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003. [RFC6205] Otani, T., Ed., "Generalized Labels for Lambda-Switch- Capable (LSC) Label Switching Routers", RFC 6205, March 2011. [RFC6163] Lee, Y., Ed., "Framework for GMPLS and Path Computation Element (PCE) Control of Wavelength Switched Optical Networks (WSONs)", RFC 6163, April 2011 6.2. Informative References [1] Gringeri, S., Basch, B. Shukla,V. Egorov, R. and Tiejun J. Xia, "Flexible Architectures for Optical Transport Nodes and Networks", IEEE Communications Magazine, July 2010, pp. 40-50 Hussain Expires January 25, 2012 [Page 12] Internet-Draft Generalized Super-Channel Label July 2011 [2] M. Jinno et. al., "Spectrum-Efficient and Scalable Elastic Optical Path Network: Architecture, Benefits and Enabling Technologies", IEEE Comm. Mag., Nov. 2009, pp. 66-73. [3] S. Chandrasekhar and X. Liu, "Terabit Super-Channels for High Spectral Efficiency Transmission",in Proc. ECOC 2010, paper Tu.3.C.5, Torino (Italy), September 2010. [4] ITU-T Recommendation G.694.1, "Spectral grids for WDM applications: DWDM frequency grid", June 2002 [5] [4] "Finisar to Demonstrate Flexgrid(TM) WSS Technology at ECOC 2010", press release. 7. Acknowledgments Hussain Expires January 25, 2012 [Page 13] Internet-Draft Generalized Super-Channel Label July 2011 Appendix A. Super-Channel Label Format Example Suppose node A and Node Z are super-channel switching capable and node A receives a request for establishing a 1 Tbps optical LSP from itself to node Z. Assume the super-channel requires a "contiguous" spectral bandwidth of 200 GHz with left-edge frequency of 191.475 THz for the left-most 12.5 GHz slice and left-edge frequency of 191.6625 THz for the right-most slice. This means n_start = (191.475 - 193.1)/0.0125 = -130 and n_end = (191.6625 - 193.1)/0.0125 = -115 (i.e. we need 16 slices of 12.5 GHz starting from slice number -130 and ending at slice number -115). Node A signals the LSP via a Path message including a super-channel label format encoding option B defined in section 3.3: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Super-Channel Id (16-bit) |Grid | C.S. | Reserved (9-bit)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved (16-bit) | Number of Entries(16-bit) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |n_start_1 (contiguous group #1) | n_end_1(contiguous group #1) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Where: Super-Channel Id = 1 : super-channel number 1 Number of Entries: 1 Grid = xx : ITU-T Flex-Grid C.S. = 4 : 12.5 GHz slices n_start_1 = -130 : left-most 12.5 GHz slice number for group 1 n_end_1 = -115 : Right-most 12.5 GHz slice number for group 1 Hussain Expires January 25, 2012 [Page 14] Internet-Draft Generalized Super-Channel Label July 2011 Authors' Addresses Iftekhar Hussain Infinera 140 Caspian Ct., Sunnyvale, CA 94089 Email: ihussain@infinera.com Abinder Dhillon Infinera 140 Caspian Ct., Sunnyvale, CA 94089 Email: adhillon@infinera.com Zhong Pan Infinera 140 Caspian Ct., Sunnyvale, CA 94089 Email: zpan@infinera.com Marco Sosa Infinera 140 Caspian Ct., Sunnyvale, CA 94089 Email: msosa@infinera.com Hussain Expires January 25, 2012 [Page 15]