Network Working Group Qilei Wang Internet-Draft Xihua Fu Intended status: Standards Track ZTE Corporation Expires: January 17, 2013 Jul 16, 2012 OSPF extensions for support spectrum sub-band allocation draft-wang-ccamp-flexigrid-wavelength-range-ospf-01.txt Abstract This document addresses the requirements and routing protocol extension of spectrum sub-bandallocation in order to help reduce non- linear effect and raise spectrum utilization rate in the process of path computation. 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). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on January 17, 2013. Copyright Notice Copyright (c) 2012 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. Qilei Wang & Xihua Fu Expires January 17, 2013 [Page 1] Internet-Draft spectrum sub-band allocation Jul 2012 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions used in this document . . . . . . . . . . . . . . . 4 3. Overview of the Solution . . . . . . . . . . . . . . . . . . . 4 4. Extension of routing protocol . . . . . . . . . . . . . . . . . 5 4.1. Relationship with WSON . . . . . . . . . . . . . . . . . . 6 4.2. Extensions of OSPF Protocol to Support Spectrum Group Allocation . . . . . . . . . . . . . . . . . . . . . . . . 6 4.2.1. Spectrum sub-band Allocation by Bitrates . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 6. IANA considerations . . . . . . . . . . . . . . . . . . . . . . 8 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.1. Normative References . . . . . . . . . . . . . . . . . . . 8 7.2. Informative References . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Qilei Wang & Xihua Fu Expires January 17, 2013 [Page 2] Internet-Draft spectrum sub-band allocation Jul 2012 1. Introduction Two kinds of DWDM application is described in the newest version of [G.694.1], one is fixed grid, and the other is flexible grid. Fixed grid is the traditional DWDM application with fixed channel slot width (e.g., 50GHz) which has been deployed in large scale in the network. In current DWDM systems with different bit rates, completely freedom and indiscriminate positioning of various channels with respect to each other is likely to lead to dramatically impaired system performance due to XPM (Cross-phased Modulation) effect. The XPM effects are quite important for WDM systems because the phase of each optical channel depends on the bit patterns of all other channels. For example, if we mix 10Gbit/s NRZ modulated channels with 100Gbit/s xPSK modulated channels indiscriminately, XPM would have a detrimental effect on the 100Gbit/s signal if this are caused by 10Gbit/s signal; Complex modulation formats (e.g., 16QAM) would be used to modulate signal beyond 100Gbit/s (e.g., 400Gbit/s, 1Tbit/s), while QAM modulation format experiences both intensity and phase modulation, a QAM signal may affect another QAM signal due to XPM effect. In current DWDM system with different bit rates, general advice is to group the channels with the same bit rates into the same spectrum sub-band to avoid the detrimental XPM effect. The flexible grid technology is also a DWDM application which is different from fixed grid application. Flexible grid is a kind of new DWDM application with different channel slot width (e.g., 50GHz, 87.5GHz etc). Signals with different bit rates may occupy different slot widths and use different modulation format. Grouping of signals with the same bit rates into the same spectrum may also be a better choice than completely freedom positioning. Frequently setup and release of flexible grid optical channels which occupy different slot widths would result in the spectrum fragments that can't be used anymore, and this will cause the decline of spectrum utilization rate. Global Concurrent Optimization (GCO), which combines with the implementation of the stateful PCE, can be used for defragmentation and raise spectrum utilization rate. But it's complicated to apply the GCO in current network, because this will involve a large scale of resources and computation. Another method that can be used is to group the channels with the same bit rates into the same spectrum sub-band and this is also a feasible solution to help raise spectrum utilization rate. According to the previous description, grouping of channels with the same bit rates maybe a good choice to reduce the XPM effect and raise Qilei Wang & Xihua Fu Expires January 17, 2013 [Page 3] Internet-Draft spectrum sub-band allocation Jul 2012 spectrum utilization rate, especially in network with different slot widths. So in order to take the grouping into consideration during the path computation, a sub-band spectrum of the available spectrum SHOULD be allocated in advance and this spectrum allocation information SHOULD be known by path computation element when compute the path. This document mainly addresses the routing protocol extension to support the advertisement of the spectrum allocation information. Policy may be used by operator when split spectrum supported on a link into several sub-bands. One spectrum sub-band can only be used for path (optical channel) setup with specific attributes, for example, with specific bitrates and/or modulation format. 2. Conventions used in this document 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 [RFC2119]. 3. Overview of the Solution In current DWDM system with different bit rates, general advice is to group the channels with the same bit rates and modulation format into the same spectrum sub-band to avoid the detrimental XPM effect. As signals of the same bitrates usually use the same modulation format on a specific link, this document mainly pays attention to grouping of channels with the same bitrates. Figure 1 shows an example, in which part of the spectrum frequency slots (i.e., the left sub-band) are allocated to 10 Gbit/s channels while another part of the frequency slots (i.e., the right sub-band) are allocated to 100 Gbit/s channels. Currently an NRZ modulation format is employed for 10 Gbit/s channels, while 40 Gbit/s and/or 100 Gbit/s channels are mostly phase-modulated (e.g. xPSK) signals. As noted above it is common practice to keep an appropriate guard band between channels with different bit rates and/or modulation format to minimize nonlinear effects induced signal degradations and to group channels with the same bit rate and modulation format. 10G OCh 50GHz 10G OCh 50GHz +---+---+---+---+---+ +---+---+---+---+---+ | | | | | | guard band | | | | | | __|___|___|___|___|___|____________|___|___|___|___|___|____ 193.025 197.025 193.075 196.975 Qilei Wang & Xihua Fu Expires January 17, 2013 [Page 4] Internet-Draft spectrum sub-band allocation Jul 2012 Figure 1: Group of Channels [Notes: According to the simulation results about grouped spectrum allocation and ungrouped spectrum allocation for 100Gbit/s and 400Gbit/s transmissions are carried. A grouped spectrum allocation only resulted in a small improvement (about 0.2 and 0.5 dB) compared to ungrouped spectrum allocation for 100G and 400G data transmissions respectively. The penalty induced by mixed QPSK and 16QAM signals seems to be much smaller than in a QPSK and NRZ hybrid system. This may be explained by the similar spectrum of the QPSK and 16QAM formats for the same baud rate. These results seem to indicate that systems operated with only phase modulated signals may show significantly lower impairments compared to systems operated with a mix of NRZ and phase modulated signals.] [Note: we are not sure if grouping of channels with the same bit rate is needed in future. According to the discussion in ITU-T, a part of the experts express that: we should use grouping of channels with the same bit rate in the short term, however, in the long term, it may be forced to use indiscriminate positioning of the spectrum.] Some other advantages are also brought if operator split available spectrum into several sub-bands and one spectrum sub-band can only be used for optical channel setup with the same bit rate. A spectrum sub-band which can only be used for optical channel setup with the same bit rate will help reduce fragments. Channels in the same spectrum group sub-band with the same bitrates looks almost like fixed grid technology with the same slot width, and they won't generate fragments in the process of path setup and release. It may also be convenient for operator to manage the network if the operator groups the optical channel with the same bit rate. When control plane uses path computation element to setup an end-to- end path through the DWDM network, spectrum available information and restriction information (e.g., spectrum partition information) should be taken into consideration in order to compute a suitable end-to-end path. The spectrum sub-band information needs to be advertised by routing protocol in order to help the path computation. Section 4 describes the extension of OSPF routing protocol to advertise these spectrum sub-band information in order to help path computation. 4. Extension of routing protocol Qilei Wang & Xihua Fu Expires January 17, 2013 [Page 5] Internet-Draft spectrum sub-band allocation Jul 2012 4.1. Relationship with WSON WSON related work can be re-used in this document to advertise the spectrum group information. This Section addresses the routing extension work of the features which is describe in the previous section base on the current WSON work in IETF CCAMP Group. In the document [draft-ietf-ccamp-general-constraint-encode], a new link sub-TLV called Port Label Restrictions sub-TLV is defined. Descriptions about Port Label Restrictions sub-TLV in the draft [draft-ietf-ccamp-gmpls-general-constraints-ospf-te] are introduced here: "Port label restrictions describe the label restrictions that the network element (node) and link may impose on a port. These restrictions represent what labels may or may not be used on a link and are intended to be relatively static. More dynamic information is contained in the information on available labels. Port label restrictions are specified relative to the port in general or to a specific connectivity matrix for increased modeling flexibility" and "For example, Port Label Restrictions describes the wavelength restrictions that the link and various optical devices such as OXCs, ROADMs, and waveband multiplexers may impose on a port in WSON". According to the previous description, the restrictions information carried in the port label restriction sub-TLV are used to represent what wavelength/spectrum may or may not be used on a link and are relatively static. The spectrum group allocation information described in this document can be regarded as label restrictions which are imposed by network element (node) on a port, and the network element include various optical devices such as OXCs, ROADMs and waveband multiplexers and so on. These spectrum sub-bands restrictions represent the spectrum allocation information and a spectrum sub-band can only be used for channels setup with specific bitrates and/or modulation format. This restriction is relative static and can be carried in Port Label Restrictions sub-TLV. 4.2. Extensions of OSPF Protocol to Support Spectrum Group Allocation Spectrum sub-band allocation information should be known by path computation element if operators want to compute an end-to-end optical channel path. As described in the previous section, Port Label Restrictions sub-TLV can be used to carry this spectrum sub- band allocation restriction information. Figure 1 is the format of Port Label Restrictions sub-TLV which is described in [draft-ietf-ccamp-general-constraint-encode] and definition of the parameters included in this sub-TLV can be found in this document. Qilei Wang & Xihua Fu Expires January 17, 2013 [Page 6] Internet-Draft spectrum sub-band allocation Jul 2012 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MatrixID |RestrictionType| Reserved/Parameter | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | : Additional Restriction Parameters per RestrictionType : | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Port Label Restrictions sub-TLV 4.2.1. Spectrum sub-band Allocation by Bitrates As described in section 3, channels on a single fiber with the same bitrates usually use the same modulation format, especially when the equipments come from one vendor. So here operator can split spectrum into several spectrum sub-bands by bitrates. In this section, OSPF protocol is extended to cover the spectrum sub-bands allocation information by bitrates. The spectrum sub-bands allocation information by bitrates is needed in the process of path computation if an end-to-end path needs to be computed by path computation element and this information SHOULD be advertised by routing protocols. Figure 3 gives a new kinds of Port Label Restrictions sub-TLV which mainly extent the Additional Restriction Parameters field to cover the spectrum sub-bands allocation information. The parameters in the Additional Restriction Parameters field include Bit Rate which indicates the bitrates of the specific spectrum sub-bands and spectrum boundaries information of the sub-band. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MatrixID |RestrictionType| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bit Rate | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ : Spectrum Sub-band Range : +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3 Qilei Wang & Xihua Fu Expires January 17, 2013 [Page 7] Internet-Draft spectrum sub-band allocation Jul 2012 Definition of MatrixID and RestrictionType field can be found in the document [draft-ietf-ccamp-general-constraint-encode]. Value of RestrictionType needs to be assigned by IANA. [Note: As several routing documents exist in the CCAMP and the label_set object encoding is not determined, this document use "spectrum sub-band range" to represent spectrum allocation information temporarily.] "Bit Rate" field indicates the bitrates of the specific spectrum sub- band. In some situation, modulation format information may also be needed to help allocation wavelength range, as signals with the same bitrates on a single fiber can use different modulation format. In this case, modulation formats information is needed to be carried in Port Label Restrictions sub-TLV. Wavelength that is supported by subsystems can be partitioned to service traditional fixed grid technology. 5. Security Considerations TBD 6. IANA considerations TBD. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC6163] Lee, Y., Bernstein, G., and W. Imajuku, "Framework for GMPLS and Path Computation Element (PCE) Control of Wavelength Switched Optical Networks (WSONs)", RFC 6163, April 2011. 7.2. Informative References [G.694.1 v1] International Telecommunications Union, "Draft revised G.694.1 version 1.3". Qilei Wang & Xihua Fu Expires January 17, 2013 [Page 8] Internet-Draft spectrum sub-band allocation Jul 2012 [WD6-12] International Telecommunications Union, "Discussion on progressing Q.6/15's work on DWDM applications using flexible grid". [flexible-grid-ospf-ext] Fatai Zhang, Xiaobing Zi, Ramon Casellas, O. Gonzalez de Dios, and D. Ceccarelli, "GMPLS OSPF-TE Extensions in support of Flexible-Grid in DWDM Networks", draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt . [flexigrid-lambda-label] D. King, A. Farrel, Y. Li, F. Zhang, and R. Casellas, "Generalized Labels for the Flexi-Grid in Lambda-Switch- Capable (LSC) Label Switching Routers", draft-farrkingel-ccamp-flexigrid-lambda-label-01.txt . [super-channel-label] Iftekhar Hussain, Abinder Dhillon, Zhong Pan, Marco Sosa and Bert Basch, Steve Liu, Andrew G. Malis, "Generalized Label for Super-Channel Assignment on Flexible Grid", draft-hussain-ccamp-super-channel-label-02.txt . Authors' Addresses Qilei Wang ZTE Corporation Email: wang.qilei@zte.com.cn Xihua Fu ZTE Corporation ZTE Plaza, No.10, Tangyan South Road, Gaoxin District Xi'an 210012 P.R.China Email: fu.xihua@zte.com.cn Qilei Wang & Xihua Fu Expires January 17, 2013 [Page 9]