基于EPON的DBA算法研究
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摘要
近年来,通信网的主干部分发生了巨大的变化,但在接入网部分却进展缓慢。由于光纤具有传输频带宽、容量大、抗干扰能力强等优点,非常适合作为高速、宽带业务的传输媒质。结合IP传输和无源光网络(PON)透明宽带传送能力优势的以太网无源光网络(EPON),被认为是实现未来宽带接入乃至最终实现FTTH(光纤到户)的主要手段。EPON中上行接入及动态带宽分配对提高系统的服务质量,改进EPON系统时延及以太网帧丢失率等性能指标有着重要的意义,是EPON系统的关键技术之一。目前,针对EPON的帧结构、带宽分配与性能分析以及如何实现服务质量(Qos)保证等问题正成为国内外的研究热点。
本论文主要对EPON上行发现过程和带宽动态分配技术进行了研究。本文首先介绍了接入网的发展现状和趋势、几种光接入网比较,然后阐明了EPON系统的结构和工作原理、协议层次结构和上下行传输帧结构,分析了EOPN的技术特点以及几项EPON的关键技术。对发现过程中的两种避免冲突的算法,通过仿真比较分析,得出在线路利用率变化不大的情况下,随机时延的算法在降低注册延迟更有优势。
本文在基于服务等级的带宽分配算法的基础上进行改进。该算法使用两层调度机制,将带宽分配分为光网络单元之间(Intra-ONU)和光网络单元内部(Inter-ONU)两层,在Intra-ONU层,光线路终端(OLT)负责分配给光网络单元(ONU)一个传输时隙。在Inter-ONU层,ONU将多种业务流分为不同的等级,对不同等级的数据给予不同等级的传输带宽。但该算法仍然存在等待时间和空闲时间的问题。改进后的算法通过对高优先级(EF)业务分配给除授权带宽外的额外带宽,以传送EF的空闲时间内到达的数据,降低EF业务的时延。并将ONU分为轻重负载,对于轻负载的ONU,收到报告帧(REPORT)后,直接进行带宽的分配,并计算剩余带宽。对于重负载的ONU, OLT等待收到所有的REPORT消息后,计算需要分配的带宽,并发送授权(GATE)消息到ONUs。为充分利用了空闲时间,需要在收到所有ONU的REPORT消息前,对一部分重负载的ONU进行授权,以提高了带宽利用率,降低了时延。
本文利用先进的网络仿真工具OPNET,建立了EPON网络上行信道介质访问控制(MAC)子层时分复用(TDMA)模型,在此仿真平台上对改进算法进行动态仿真。所有的仿真模型都是建立在有限状态机的基础上,通过与原来算法进行分析比较,该算法有效的提高带宽利用率,降低平均包延时。
In recent years, there are great changes in the backbone communication newtokrs, but little progress in the access newtork. The fiber has the advantages of broad banwdidth, huge capability, powerful interference rejection etc, which are greatly good for the transmission medium of high-speed broadband newtork. Thinking of the actuality of the IP network and the abiliy of EPON transport, EPON (Ethernet Passvae Optical Network) will be one of the main solutions to implement future broadband access newtork, even be the final technology to implement FTTH. Upstream access and dynamic bandwidth allocation which play an important role in raising the sevrice quality of EPON and reducing packet delay and packet loss rate, is one of key crucial technologies of EPON system. The structure of frame and bandwidth allocation algorihtm, performance analysis of EPON, and how to realize Qos guarantee are becoming domestic and international research hot spots.
The research is mainly focused on the dynamic bandwidth allocation schemes and finding process of EPON upsrteam channel. Firstly, this thesis introduces the development of the access network, makes some kinds of comparison with other optical access networks. Then, illuminating the strucutre of EPON system and transmission fame protocol, operation principle, finally, analyzing the characteristics and key techniques of EPON. According to simulation result, getting the conclusion that random delay has better time delay than random back off, with the little changing of bandwith utilization. Based on the bandwidth allocation algorihtm, which is supporting service level, an improving method is proposed. The algorithm uses two attemper mechanisms, in the Intra-ONU, the OLT assigns a transmission window to every ONU. In the Inter-ONU, Services are classified different priority levels. Transmission window is granted by different service. But there are sill wait time and idle time problem in the algorithm. The proposed algorithm resolved the wait time by reserving bandwith for EF service, resulting good time delay. About the idle time, OLT classified ONUs as heavy and light load. The light ONUs are granted as soon as OLT receives REPORT message, and OLT calculates the surplus bandwith at the same time. The heavy ONUs are granted after all REPORT messages are arrived. In order to solve the idle time, some heavy ONUs should be granted before all REPORT message arrive.
In this paper, EPON newtork model is established by using advanced newtork simulation tool OPNET to simulate MPCP(multipul point control protocol), which is based on TDMA. Our proposed scheme is simulated by using this model. All the emulations are based on the finite state machine model. Comparing with original algorithm, bandwith and time delay have made a great progress.
本论文主要对EPON上行发现过程和带宽动态分配技术进行了研究。本文首先介绍了接入网的发展现状和趋势、几种光接入网比较,然后阐明了EPON系统的结构和工作原理、协议层次结构和上下行传输帧结构,分析了EOPN的技术特点以及几项EPON的关键技术。对发现过程中的两种避免冲突的算法,通过仿真比较分析,得出在线路利用率变化不大的情况下,随机时延的算法在降低注册延迟更有优势。
本文在基于服务等级的带宽分配算法的基础上进行改进。该算法使用两层调度机制,将带宽分配分为光网络单元之间(Intra-ONU)和光网络单元内部(Inter-ONU)两层,在Intra-ONU层,光线路终端(OLT)负责分配给光网络单元(ONU)一个传输时隙。在Inter-ONU层,ONU将多种业务流分为不同的等级,对不同等级的数据给予不同等级的传输带宽。但该算法仍然存在等待时间和空闲时间的问题。改进后的算法通过对高优先级(EF)业务分配给除授权带宽外的额外带宽,以传送EF的空闲时间内到达的数据,降低EF业务的时延。并将ONU分为轻重负载,对于轻负载的ONU,收到报告帧(REPORT)后,直接进行带宽的分配,并计算剩余带宽。对于重负载的ONU, OLT等待收到所有的REPORT消息后,计算需要分配的带宽,并发送授权(GATE)消息到ONUs。为充分利用了空闲时间,需要在收到所有ONU的REPORT消息前,对一部分重负载的ONU进行授权,以提高了带宽利用率,降低了时延。
本文利用先进的网络仿真工具OPNET,建立了EPON网络上行信道介质访问控制(MAC)子层时分复用(TDMA)模型,在此仿真平台上对改进算法进行动态仿真。所有的仿真模型都是建立在有限状态机的基础上,通过与原来算法进行分析比较,该算法有效的提高带宽利用率,降低平均包延时。
In recent years, there are great changes in the backbone communication newtokrs, but little progress in the access newtork. The fiber has the advantages of broad banwdidth, huge capability, powerful interference rejection etc, which are greatly good for the transmission medium of high-speed broadband newtork. Thinking of the actuality of the IP network and the abiliy of EPON transport, EPON (Ethernet Passvae Optical Network) will be one of the main solutions to implement future broadband access newtork, even be the final technology to implement FTTH. Upstream access and dynamic bandwidth allocation which play an important role in raising the sevrice quality of EPON and reducing packet delay and packet loss rate, is one of key crucial technologies of EPON system. The structure of frame and bandwidth allocation algorihtm, performance analysis of EPON, and how to realize Qos guarantee are becoming domestic and international research hot spots.
The research is mainly focused on the dynamic bandwidth allocation schemes and finding process of EPON upsrteam channel. Firstly, this thesis introduces the development of the access network, makes some kinds of comparison with other optical access networks. Then, illuminating the strucutre of EPON system and transmission fame protocol, operation principle, finally, analyzing the characteristics and key techniques of EPON. According to simulation result, getting the conclusion that random delay has better time delay than random back off, with the little changing of bandwith utilization. Based on the bandwidth allocation algorihtm, which is supporting service level, an improving method is proposed. The algorithm uses two attemper mechanisms, in the Intra-ONU, the OLT assigns a transmission window to every ONU. In the Inter-ONU, Services are classified different priority levels. Transmission window is granted by different service. But there are sill wait time and idle time problem in the algorithm. The proposed algorithm resolved the wait time by reserving bandwith for EF service, resulting good time delay. About the idle time, OLT classified ONUs as heavy and light load. The light ONUs are granted as soon as OLT receives REPORT message, and OLT calculates the surplus bandwith at the same time. The heavy ONUs are granted after all REPORT messages are arrived. In order to solve the idle time, some heavy ONUs should be granted before all REPORT message arrive.
In this paper, EPON newtork model is established by using advanced newtork simulation tool OPNET to simulate MPCP(multipul point control protocol), which is based on TDMA. Our proposed scheme is simulated by using this model. All the emulations are based on the finite state machine model. Comparing with original algorithm, bandwith and time delay have made a great progress.
引文
[1]李征,王晓宁,金添,接入网与接入技术,北京：清华大学出版社,2003：25-31页
[2]余景文,EPON技术最新发展探讨,通信世界,2005(18)：36-37页
[3]胡春琳,三种宽带无源光接入网技术比较,光通信研究,2004,(5)：27-29页
[4]EPON和GPON成本比较.http://www.eetchina.com,2007
[5]黄晓燕,雷维礼.IEEE 802.3ah标准与以太接入网.通信与信息技术.2004：8页
[6]中国电子设计技术网.http://www.ednchina.com,2008
[7]Pesavento, Ethemet Passive Optical Network (E-PON) architecture for broadband access, Optical network Magazine.2003:41-43P
[8]Ethernet in the First Mile, Point to Multipoint, Ethernet Passive Optical Network (EPON) Tutorial, EFM IEEE 802.3 Stuy Group,2008
[9]陈强.EPON系统的研究与实现.http://www.wanfangdata.com.cn,2007
[10]BroardLight, FlexLight. ITU-TG. 984 GPON vs. IEEE 802.3ah EPON. www.broadlight.com,2008
[11]郭巍,刘冬等.面向FTTH的EPON系统应用与管理.通信世界.2005,10：28页
[12]Hyun-Su KO, Sub Han, Man-Seop Lee, et al,1.25Gb/s burst-mode optical receiver for the Ethernet PON using 0.35um CMOS, The 6th International Conferene on Advanced Communication Technology,2004, (2):877-880P
[13]陈雪,孙曙和等.基于以太网的无源光网络.北京：北京邮电大学出版社,2007：58-51页
[14]Inter Operability Laboratory. Discovery Process for EPON. http://www.iol.unh.edu,2008
[15]Michael P.McGarry, Martin Maier, Martin Reisslein. Ethernet PONs:A Survey of Dynamic Bandwidth Allocation (DBA) Algorithms.2008
[16]Edward Beili. Ethernet PON (EPON) Protocol. http://grouper.ieee.org,2007
[17]谢永锋,张家树.EPON的OAM协议原理与设计方案.光通信技术.2005,10：41-45页
[18]黄晓燕,雷维礼.IEEE 802.3ah标准与以太接入网.通信与信息技术.2004,8：24-26页
[19]Metro Ethernet Forum. Ethernet in the First Mile Operations, Administration and Maintenance (OAM)-A Tutorial. www.metroethernetforum.org,2007
[20]原荣,宽带光接入网.北京：电子工业出版社.2003,8：99-108页
[21]邓羽,孙曙和等.MS-EPON系统的安全性分析与保证.http://www.gwtt.com,2007
[22]李江涛,陈雪等,EPON MAC控制层实现动态带宽分配策略的研究,电信科学,2002,7：35-38页
[23]G Kramer and B.Mukherjee, "Ethernet PON:design and analysis of an optical access network," Photonic Network Commun.2001,3(3):307-319P
[24]G Kramer, PASAVENTOG Interleaved polling with adaptive cycle time (IPACT):a dynamic bandwidth distribution scheme in an optical access network. Photonic Network Commun,2002,4(1):89-107P
[25]K.Rege et al. Qos management in trunk and branch switched ethernet networks. IEEE Commun. Mag,2002,40:30-36P
[26]M.Ma, Y.Zhu, T. H. Cheng. A bandwidth guaranteed polling MAC protocol for Ethernet passive optical networks. Proc.IEEEINFOCOM, San Francisco, CA, Mar-Apr 2003:22-31P
[27]G Kramer, B. Mukherjee, S. Dixit, Y. Ye, R. Hirth. Supporting differentiated classes of service in Ethernet passive optical networks. J. Opt. Networks. 2002：280-298P
[28]陈敏,OPNET网络仿真,北京：清华大学出版社,2004：68-49页
[29]王文博,张金文,OPNET Modeler与网络仿真,北京：人民邮电出版社,2003：35-50页
[30]张剑,基于OPNET仿真建模方法研究.武汉理工大学硕士论文,2005：9-11页
[31]罗万明,林闯,阎保平,一种支持多媒体通信Qos的拥塞控制机制,电子学报,2000,25(11)：48-52页
[32]黄勇军,肖晓军.以太无源光网络(EPON)技术应用和标准化.电信科学.2002,11：52-56页
[33]沈丽,汪敏,基于OpnetModler的EPON建模和带宽分配算法仿真研究.光通信技术.2007,2：31-33页
[34]Wenfeng Chen, Montuno D, Y, Felske, K, Enhanced EPON auto-discovery for fast network and service recovery, Electrical and Computer Engineering, 2004,3:1683-1687P
[35]J.Zheng and H.T.Mouftah, "Media access control for Ethernet passive optical network", IEEE Communications Magazine,2005,23(40):145-150P
[36]G. Kramer. On configuring logical links in EPON.2005:31-40P
[37]McGarry, M.P.Maier, M., and Reisslein.Ethernet PONs:a survey of dynamic bandwidth allocation (DBA) algorithms. IEEE Commun.2004,42 (8): 8-15P
[38]B.Lannoo, L.Verslegers, D.Colle, M.Pickavet, M.Gagnaire, P. Demeester, "Analytical Model for the IPACT Dynamic Bandwidth Allocation Algorithm for EPONs", Journal of Optical Networking,2007,6(6):677-688P
[39]C.G Park, D.H.Han, B.Kim, Packet Delay Analysis of Dynamic Bandwidth Allocation Scheme in an Ethernet PON.2005:13-15P
[40]Su-il Choi, Jae-dooHuh. Dynamic Bandwidth Allocation Algorithm for Multimedia Services over Ethernet PONs. ETRI Journal, December 2002, 24(6):466-468P
[41]戚世杰,邹君妮,李迎春等,EPON系统的Qos管理方案,光通信研究,2005,10(1)：26-28页
[42]Chadi M.Assi, Yinghua ye, Sudhir Dixit, et al. Dynamic bandwidth allocation for quality-of-service over Ethernet PONs. IEEE Journal on Selected Areas in Communications. Nov.2003,13(9):1467-1477P
[43]S.Bhatia, D.Garbuzov, R.Bartos, Analysis of the Gated IPACT Scheme for EPONs. Proceedings of ICC 2006:35-42P
[2]余景文,EPON技术最新发展探讨,通信世界,2005(18)：36-37页
[3]胡春琳,三种宽带无源光接入网技术比较,光通信研究,2004,(5)：27-29页
[4]EPON和GPON成本比较.http://www.eetchina.com,2007
[5]黄晓燕,雷维礼.IEEE 802.3ah标准与以太接入网.通信与信息技术.2004：8页
[6]中国电子设计技术网.http://www.ednchina.com,2008
[7]Pesavento, Ethemet Passive Optical Network (E-PON) architecture for broadband access, Optical network Magazine.2003:41-43P
[8]Ethernet in the First Mile, Point to Multipoint, Ethernet Passive Optical Network (EPON) Tutorial, EFM IEEE 802.3 Stuy Group,2008
[9]陈强.EPON系统的研究与实现.http://www.wanfangdata.com.cn,2007
[10]BroardLight, FlexLight. ITU-TG. 984 GPON vs. IEEE 802.3ah EPON. www.broadlight.com,2008
[11]郭巍,刘冬等.面向FTTH的EPON系统应用与管理.通信世界.2005,10：28页
[12]Hyun-Su KO, Sub Han, Man-Seop Lee, et al,1.25Gb/s burst-mode optical receiver for the Ethernet PON using 0.35um CMOS, The 6th International Conferene on Advanced Communication Technology,2004, (2):877-880P
[13]陈雪,孙曙和等.基于以太网的无源光网络.北京：北京邮电大学出版社,2007：58-51页
[14]Inter Operability Laboratory. Discovery Process for EPON. http://www.iol.unh.edu,2008
[15]Michael P.McGarry, Martin Maier, Martin Reisslein. Ethernet PONs:A Survey of Dynamic Bandwidth Allocation (DBA) Algorithms.2008
[16]Edward Beili. Ethernet PON (EPON) Protocol. http://grouper.ieee.org,2007
[17]谢永锋,张家树.EPON的OAM协议原理与设计方案.光通信技术.2005,10：41-45页
[18]黄晓燕,雷维礼.IEEE 802.3ah标准与以太接入网.通信与信息技术.2004,8：24-26页
[19]Metro Ethernet Forum. Ethernet in the First Mile Operations, Administration and Maintenance (OAM)-A Tutorial. www.metroethernetforum.org,2007
[20]原荣,宽带光接入网.北京：电子工业出版社.2003,8：99-108页
[21]邓羽,孙曙和等.MS-EPON系统的安全性分析与保证.http://www.gwtt.com,2007
[22]李江涛,陈雪等,EPON MAC控制层实现动态带宽分配策略的研究,电信科学,2002,7：35-38页
[23]G Kramer and B.Mukherjee, "Ethernet PON:design and analysis of an optical access network," Photonic Network Commun.2001,3(3):307-319P
[24]G Kramer, PASAVENTOG Interleaved polling with adaptive cycle time (IPACT):a dynamic bandwidth distribution scheme in an optical access network. Photonic Network Commun,2002,4(1):89-107P
[25]K.Rege et al. Qos management in trunk and branch switched ethernet networks. IEEE Commun. Mag,2002,40:30-36P
[26]M.Ma, Y.Zhu, T. H. Cheng. A bandwidth guaranteed polling MAC protocol for Ethernet passive optical networks. Proc.IEEEINFOCOM, San Francisco, CA, Mar-Apr 2003:22-31P
[27]G Kramer, B. Mukherjee, S. Dixit, Y. Ye, R. Hirth. Supporting differentiated classes of service in Ethernet passive optical networks. J. Opt. Networks. 2002：280-298P
[28]陈敏,OPNET网络仿真,北京：清华大学出版社,2004：68-49页
[29]王文博,张金文,OPNET Modeler与网络仿真,北京：人民邮电出版社,2003：35-50页
[30]张剑,基于OPNET仿真建模方法研究.武汉理工大学硕士论文,2005：9-11页
[31]罗万明,林闯,阎保平,一种支持多媒体通信Qos的拥塞控制机制,电子学报,2000,25(11)：48-52页
[32]黄勇军,肖晓军.以太无源光网络(EPON)技术应用和标准化.电信科学.2002,11：52-56页
[33]沈丽,汪敏,基于OpnetModler的EPON建模和带宽分配算法仿真研究.光通信技术.2007,2：31-33页
[34]Wenfeng Chen, Montuno D, Y, Felske, K, Enhanced EPON auto-discovery for fast network and service recovery, Electrical and Computer Engineering, 2004,3:1683-1687P
[35]J.Zheng and H.T.Mouftah, "Media access control for Ethernet passive optical network", IEEE Communications Magazine,2005,23(40):145-150P
[36]G. Kramer. On configuring logical links in EPON.2005:31-40P
[37]McGarry, M.P.Maier, M., and Reisslein.Ethernet PONs:a survey of dynamic bandwidth allocation (DBA) algorithms. IEEE Commun.2004,42 (8): 8-15P
[38]B.Lannoo, L.Verslegers, D.Colle, M.Pickavet, M.Gagnaire, P. Demeester, "Analytical Model for the IPACT Dynamic Bandwidth Allocation Algorithm for EPONs", Journal of Optical Networking,2007,6(6):677-688P
[39]C.G Park, D.H.Han, B.Kim, Packet Delay Analysis of Dynamic Bandwidth Allocation Scheme in an Ethernet PON.2005:13-15P
[40]Su-il Choi, Jae-dooHuh. Dynamic Bandwidth Allocation Algorithm for Multimedia Services over Ethernet PONs. ETRI Journal, December 2002, 24(6):466-468P
[41]戚世杰,邹君妮,李迎春等,EPON系统的Qos管理方案,光通信研究,2005,10(1)：26-28页
[42]Chadi M.Assi, Yinghua ye, Sudhir Dixit, et al. Dynamic bandwidth allocation for quality-of-service over Ethernet PONs. IEEE Journal on Selected Areas in Communications. Nov.2003,13(9):1467-1477P
[43]S.Bhatia, D.Garbuzov, R.Bartos, Analysis of the Gated IPACT Scheme for EPONs. Proceedings of ICC 2006:35-42P