Network Working Group YL. Zhao Internet-Draft J. Zhang Intended status: Informational TT. Peng Expires: October 27, 2012 XS. Yu BUPT XP. Cao DJ. Wang XH. Fu ZTE Corporation April 25, 2012 PCEP Protocol Extension for spectrum utilization optimization in Flexi- Grid Networks draft-zhaoyl-pce-flexi-grid-pcep-ex-01 Abstract Flexi-grid networks overcomes the fixed grid channel of Wavelength Switched Optical Network(WSON) by flexible spectrum to allow non- uniform and dynamic allocation of spectrum based on the demand of the incoming services' LSP. Flexi-grid networks is an effective solution to solve the problem of efficient spectrum utilization. Because the client LSP needs to be assigned contiguous spectrum in flexi-grid networks, there will be two problems that would affect spectrum utilization, i.e. RSA and fragmentation. We introduce two kinds of methods which can improve the spectrum utilization further, and some related PCEP extensions are defined in this document. 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 October 27, 2012. Copyright Notice Zhao, et al. Expires October 27, 2012 [Page 1] Internet-Draft PCEP Extension April 2012 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 3. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3 4. RSA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Introduction of RSA . . . . . . . . . . . . . . . . . . . 4 4.2. Algorithms of RSA . . . . . . . . . . . . . . . . . . . . 4 4.3. RSA Schemes Selection . . . . . . . . . . . . . . . . . . 5 5. Defragmentation . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Motivation of Defragmentation . . . . . . . . . . . . . . 6 5.2. Definition of Defragmentation . . . . . . . . . . . . . . 6 5.3. Application Scene of Defragmentation . . . . . . . . . . . 6 6. PCEP Protocol Extension . . . . . . . . . . . . . . . . . . . 7 6.1. PCEP Protocol Extension for RSA . . . . . . . . . . . . . 7 6.2. PCEP Protocol Extension for Defragmentation . . . . . . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 8. Normative References . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Zhao, et al. Expires October 27, 2012 [Page 2] Internet-Draft PCEP Extension April 2012 1. Introduction Demand of traffic is increasing exponentially and already approaching the limit of single mode fiber capacity. At the same time, because of varying demand of trafficGBP[not]we need an efficient and agile utilization of the optical spectrum. ITU-T Study Group 15 introduce a new flexi-grid networks to enable dynamic allocation of spectrum resource. The flexi-grid networks is an effective solution to solve the problem of efficient spectrum resource utilization. The granularity of flexi-grid networks can be smaller and agile. i.e.(6.25GHz).In the flexi-grid networks, the appropriate size of spectrum is determined by the used modulation format.According to the client data rate request and physical constraints of the selected path,the appropriate size of spectrum is adaptively allocated to optical connections by assigning the appropriate number of contiguous spectrum from end-to-end.Before assigning the client request, we have to find suitable route and fit contiguous spectrum for it, and it is a complex process. So spectrum utilization is very important in RSA. While there are several algorithms for RSA, so flexi-grid networks require to extend PCEP protocol to support different algorithms seletion. Upon tearing down of connections, allocated spectrum are released for future requests. In a dynamic traffic scenario, this channel setup and tear down processes leads to fragmentation of spectral resources. Due to the fragmentation, the available spectrum divide into small noncontiguous spectral bands,the spectral effciency in the network is compromised. Therefore the probability of finding suffcient contiguous spectrum for a connection is decreased. We introduce Spectrum Fragments Cascading and Defragmentation to deal with fragmentation in flexi-grid networks. So PCEP protocol have to add some messages to support them. 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. Terminologies RSA: Routing and Spectrum Assignment Zhao, et al. Expires October 27, 2012 [Page 3] Internet-Draft PCEP Extension April 2012 WSON:Wavelength Switched Optical Network SFC:Spectrum Fragments Cascading 4. RSA 4.1. Introduction of RSA This part we focuses on the routing and spectrum assignment (RSA) problem. This problem can be partitioned into two subproblems - (1) routing and (2) wavelength assignment and each subproblem can be solved separately. Different from traditional WDM network, flexi- grid networks assign continuous spectrum for new arrival request. Static planning models used for flexi-grid networks to improve spectrum utilization. 4.2. Algorithms of RSA There are several spectrum assignment algorithms. (1)Random Fit (RF) This scheme first searches the space of wavelengths to determine the set of all spectrum that are available on the required route. Among the available wavelengths, one is chosen randomly. (2)First-Fit (FF) In this scheme, all spectrum is numbered.When searching for available spectrum, a lower numbered spectrum is considered before a higher- numbered spectrum.The first available spectrum is then selected. Compared to Random spectrum assignment, the computation cost of this scheme is lower because there is no need to search the entire spectrum space for each route. (3)Least-Used (LU)/SPREAD LU selects the spectrum that is the least used in the network, thereby attempting to balance the load among all the spectrum. The performance of LU is worse than Random, while also introducing additional communication overhead (e.g., global information is required to compute the least-used spectrum). (4)Most-Used (MU)/PACK MU is the opposite of LU in that it attempts to select the most-used spectrum in the network. The communication overhead, storage, and Zhao, et al. Expires October 27, 2012 [Page 4] Internet-Draft PCEP Extension April 2012 computation cost are all similar to those in LU.MU also slightly outperforms FF, doing a better job of packing connections into fewer wavelengths and conserving the spare capacity of less-used wavelengths. (5)Min-Product (MP) MU is the opposite of LU works. In a single fiber network, MP becomes FF. The goal of MP is to pack wavelengths into fibers, thereby minimizing the number of fibers in the network. (6)Least-Loaded (LL) The LL heuristic, like MP, is also designed for multi-fiber networks. This heuristic selects the spectrum that has the largest residual capacity on the most loaded link along route. (7)MAX-SUM (MS) MS was proposed for multi-fiber networks but it can also be applied to the single-fiber case.MS considers all possible paths in the network and attempts to maximize the remaining path capacities after lightpath establishment. (8)Relative Capacity Loss (RCL) RCL is based on MS. RCL chooses spectrum to minimize the relative capacity loss. RCL is based on the observation that minimizing total capacity loss sometimes does not lead to the best choice of spectrum. (9)Spectrum Reservation (Rsv) In Rsv, a given spectrum on a specified link is reserved for a traffic stream, usually a multihop stream. This scheme reduces the blocking for multihop traffic,while increasing the blocking for connections that traverse only one fiber link (single-hop traffic). (10)Protecting Threshold (Thr) In Thr, a single-hop connection is assigned spectrum only if the number of idle spectrum on the link is at or above a given threshold. 4.3. RSA Schemes Selection There are several spectrum assignment algorithms , we have to choose one of them for use in flexi-grid networks. Diffrent RSA schemes selected according to diffrent network condition. The PCEP protocol need to extend a bit that provide different Schemes to choose. Zhao, et al. Expires October 27, 2012 [Page 5] Internet-Draft PCEP Extension April 2012 5. Defragmentation 5.1. Motivation of Defragmentation New arrival of requests are then either forced to utilize more spectrum in the network or blocked in spite of suffcient spectrum being available. Additionally, as the network evolves, a current optimal routing scheme might no longer provide the optimal spectral utilization over time. There is an increasing demand from the network operators to be able to periodically recon?gure the network and return it to its optimal state, so that the network can operate more effciently. 5.2. Definition of Defragmentation There is an operation defined as network defragmentation to solve above problem. Reducing the blocking by consolidating the available network resources, this operation will also enable better network maintenance and more effcient network restoration and bandwidth adjustment. 5.3. Application Scene of Defragmentation The process of defragmentation: (1) select which LSP to defragmentation, interrupt it, (2) choose forward spectrum in original route or new route, (3) move the LSP on possible spectrum. An example of defragentation is as following: A,B,C are client LSPs on link l, l1 is Original statement of link l,l2 is statement of link l after defragementation. +-------------+ +----+ +---------+ l1: | A | | B | | C | +-------------+----------+----+-----+---------+-- +-------------+----+-----------+ l2: | A | B | C | +-------------+----+-----------+----- we first focus on the problem of the time-point when should defragmentation be operated. So far, two new concepts proposed to solve this problem. One concept is Utilization Entropy that represents the level of resource fragmentation in an optical network proposed by Fujitsu Labs of America; the other concept is Spectrum Compactness that represents the spectrum distribution state in a link or in the network proposed by State key Laboratory of Information Zhao, et al. Expires October 27, 2012 [Page 6] Internet-Draft PCEP Extension April 2012 Photonics and Optical Communications of Beijing University of Posts and Telecommunications. These two methods both related to threshold, it necessary to set threshold, when reaching threshold triggered defragmentation. PCEP protocol should include these information. we consider the methods of defragmentation. At present, there are two methods for defragmentation. First is change route of client LSP means the spectrum of this LSP in new route is ahead than the spectrum in original route. Second is the LSP move forward directly in original route. Defragmentation has to interrupt the traffic; the application scene is leisure network. When the network is busy, defragmentation lead to the increase of interrupt traffic demands. Before defragmentation for the network, we have to do static programming for existing traffic demand in the network. We hope the defragmentation result reach or approach the static programming. Maybe some network has requirement of interrupting rate or defragmentation time and so on, we should provide corresponding information to meet above requirements. 6. PCEP Protocol Extension 6.1. PCEP Protocol Extension for RSA The PCEP protocol need to be extended to support the Algorithms choosing of RSA. PCReq need to adding RAEO-list information. This information include "Algorithm Id", which stand for the number of different algorithms, and "Pri" that means priority of these algorithms. ::= [] [] [] [] [[]] [] [] Zhao, et al. Expires October 27, 2012 [Page 7] Internet-Draft PCEP Extension April 2012 [] defined as follows: 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-Class | OT |Res|P|I| Object Length (bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Algorithm Id | Pri | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ [] defined as follows: 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-Class | OT |Res|P|I| Object Length (bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Algorithm Id | Pri | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Zhao, et al. Expires October 27, 2012 [Page 8] Internet-Draft PCEP Extension April 2012 ::= [] [] [] NO-PATH: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Nature of Issue|C| Flags | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: NO-PATH Object Format NI - Nature of Issue (8 bits): The NI field is used to report the nature of the issue that led to a negative reply. Two values are currently defined: 0: No path satisfying the set of constraints could be found 1: PCE chain broken 2: No path satisfying the Continuous spectrum 6.2. PCEP Protocol Extension for Defragmentation The presence of defragmentation in Flexi-Grid Networks has an impact on the information that needs to be transferred by the control plane and the PCE. Defragmentation has to interrupt the traffic and move it to another spectrum or route. The PCEP protocol needs to be extended two messages to support defragmentation, including information of original route/spectrum and present route/spectrum, when to stop defragmentation, the selection of methods and the limit of corresponding factors and so on. Here is Spectrum Defragmentation Request Message and Spectrum Defragmentation Reply Message. "Target Clutter Value" stand for the threshold of defragmentation. "R" means whether the network MUST make it."Id 1" is number of defragmentation methods, "Id 2" is number of methods to trigger defragmentation, "L" means limit of interrupting rate or defragmentation time. ::= [LSPA Object] [] Zhao, et al. Expires October 27, 2012 [Page 9] Internet-Draft PCEP Extension April 2012 Spectrum Defragmentation Reply Message ::= [LSPA Object] [] Spectrum Defragmentation Reply Message SDTO: Spectrum Defragmentation Target Object defined as follows: 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-Class | OT |Res|P|I| Object Length (bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | L |Id1|Id2|R| Pri | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Target Clutter Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ::=
where Center Frequence is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Center Frequence | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Center Frequence: The requested bandwidth is encoded in 32 bits, expressed in bytes per second. Zhao, et al. Expires October 27, 2012 [Page 10] Internet-Draft PCEP Extension April 2012 7. Security Considerations TBD. 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFC's to Indicate Requirement Levels", RFC 2119, March 1997. [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. Authors' Addresses Yongli Zhao BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8613811761857 Email: yonglizhao@bupt.edu.cn URI: http://www.bupt.edu.cn/ Jie Zhang BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8613911060930 Email: lgr24@bupt.edu.cn URI: http://www.bupt.edu.cn/ Zhao, et al. Expires October 27, 2012 [Page 11] Internet-Draft PCEP Extension April 2012 Tiantian Peng BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8615116984347 Email: tt871228@163.com URI: http://www.bupt.edu.cn/ Xiaosong Yu BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8613811731723 Email: yu.xiaosong@qq.com URI: http://www.bupt.edu.cn/ Xuping Cao ZTE Corporation No.16,Huayuan Road,Haidian District Beijing 100191 P.R.China Phone: +8615801379189 Email: cao.xuping@zte.com.cn URI: http://www.zte.com.cn/ Dajiang Wang ZTE Corporation No.16,Huayuan Road,Haidian District Beijing 100191 P.R.China Phone: +8613811795408 Email: wang.dajiang@zte.com.cn URI: http://www.zte.com.cn/ Zhao, et al. Expires October 27, 2012 [Page 12] Internet-Draft PCEP Extension April 2012 Xihua Fu ZTE Corporation West District,ZTE Plaza,No.10,Tangyan South Road,Gaoxin District Xi'an 710065 P.R.China Phone: +8613798412242 Email: fu.xihua@zte.com.cn URI: http://www.zte.com.cn/ Zhao, et al. Expires October 27, 2012 [Page 13]