光通信技术外文翻译(共11页)

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1、精选优质文档-倾情为你奉上外文文献阅读及翻译译文及原稿译文题目 以太网无源光网络 原稿题目 Passive optical network based on Ethernet 姓 名 吴腾 学 号 班 级 通信1204 专心-专注-专业以太网无源光网络 格伦克雷默 北京邮电大学出版社 2007 以太网无源光网络（Ethernet Passive Optical Network ， EPON） 是一种新型的光纤接入网技术，它采用点到多点结构、无源光纤传输，在以太网之上提供多种业务。它在物理层采用了PON技术，在链路层使用以太网协议，利用PON的拓扑结构实现了以太网的接入。因此，它综合了PON技术

2、和以太网技术的优点：低成本；高带宽；扩展性强，灵活快速的服务重组；与现有以太网的兼容性；方便的管理等等。由于EPON的众多优点，它越来越受到人们的青睐，即将成为宽带接入网一种最有效的通信方法。为了保证EPON网络能够稳定、高效、准确的运行，为EPON提供一个有效的网络管理系统显得尤为重要。 在网络管理领域，随着基于TCP/IP体系的网络管理技术的不断发展，SNMP已经成为事实上的标准。基于SNMP的EPON网络管理系统是指采用SNMP管理协议框架，对EPON网络实体的资源实现有效管理的系统。 SNMP的介绍SNMP（简单网络管理协议）是一种基于TCP/IP的网络管理协议，它使用UDP作为传输层

3、协议，能管理支持代理进程的网络设备。SNMP主要包括SMI（管理信息结构）、MIB（管理信息库）和SNMP协议几部分。SMI给出了管理对象定义的一般框架。MIB是设备所维护的全部被管理对象的结构集合。SNMP协议包括SNMP操作、SNMP信息的格式以及如何在应用程序和设备间交换消息。 SNMP采用代理/管理站模型进行网络管理。SNMP有5种消息类型，分别为Get-Request、Get-Response、Get-Next-Request、Set-Request和Trap。代理和管理站之间通过这几种消息报文进行相互通信，以获取网络设备的各种信息，从而控制网络设备的正常运行。EPON网管系统结构E

4、PON系统的管理对象为1个OLT（光线路终端）和32个ONU（光网络单元）。基于SNMP的EPON网管系统结构如图2所示。EMS网管系统安装在工作站，与OLT设备之间通过带外网管接口（F接口）相连。EMS网管系统和OLT、ONU设备之间采用SNMP协议进行通信，实现在EMS中对OLT、ONU的统一管理。通信的方式有2种：（1）轮询。管理站每隔一段时间对所有OLT和ONU代理站的MIB进行主动查询，各代理站返回被查询的结点值。（2）告警（trap）。当某些指定事件发生时，代理进程向管理站发送trap报文。管理站接收、显示告警事件，并做相应处理。 同时OLT设备和ONU设备具备本地Console接

5、口，可以实现本地操作管理维护。EPON网管系统的设计 EPON网管系统按照网管功能分为四大模块：配置管理、性能管理、故障管理和安全管理。1. 配置管理 配置管理主要是组织EPON网内运转所需要的资源和数据，构造和维护网络系统的配置，识别各网元，保证网元的基本配置，监控当前配置和按照具体情况改变配置，设置系统参数，收集并存储各参数，报告与基本配置值的偏差，启动和关闭资源等。 EPON配置管理包括系统初次启动时的配置管理和系统正常运行时的配置管理。 启动时，针对EPON网络，可自动或手动生成OLT、ONU设备拓扑图，显示当前网络中各OLT、ONU设备的状态。在网络拓扑图生成后，SNMP 管理进程采

6、用轮询的方式定期查询SNMP 代理进程，收集设备信息用于更新数据库，以实现配置信息的实时性。系统正常运行后，网管可根据需要随时手动设置其各项配置参数。如可以设置各OLT、ONU代理的标识信息和系统信息，启用、禁用某个端口，配置各端口的工作状态，配置网桥的工作参数，配置VLAN，重启设备等。还提供基于用户的动态带宽管理。2. 性能管理 性能管理功能对EPON网络性能进行监视、检测，采集相关性能统计数据，进行分析、诊断，从而为网络进一步规划与调整提供依据，以保证网络的业务质量。EPON的性能管理功能分为性能监测、性能管理控制和性能统计分析。性能监测是连续的收集OLT、ONU上与性能相关的数据，根据

7、性能数据确定网元的性能，从而掌握设备单元因不太频繁或间断的差错导致业务质量变差的性能情况。性能管理控制的目的是支持管理人员发出控制命令或网管软件自动发出控制命令，以改善OLT、ONU性能。它可以设置性能管理数据采集周期、设置性能监测数据存储过滤条件，并对门限值进行管理。性能统计分析是对收集到的性能数据做进一步的处理，以分析表或分析图的形式报告分析结果。如计算接口利用率、接口的输入错误率、接口输出错误率、吞吐率等。3. 故障管理 故障管理功能提供对EPON网络故障监测、故障定位，保护切换与恢复，并存储故障信息供以后查询。对来自硬件设备或路径结点的报警进行监控、报告和存储，对故障进行诊断、定位和处

8、理，是故障管理的重要工作。当监测到网络、设备故障或异常时，网管系统实时产生报警。一些故障、异常是由网管程序通过查询代理站MIB发现的，而另一些是代理站通过Trap通知管理站发现的。可以设置各种告警事件的告警等级。不同等级的告警事件采取不同的告警指示和处理措施。网管系统收到告警信息后，进行分析和提示，然后针对不同等级的告警，进行不同的处理。对于严重影响网络运行的故障，需要进行故障定位和测试。启动故障定位过程，试图从这些过程中获取相关信息。进行故障定位后，网管系统会尽快做出响应，采取故障修复措施，使EPON网络恢复正常。告警信息被存储到本地数据库。可以按照告警时间、告警设备、告警等级等关键字查询历

9、史告警信息。根据全部告警信息，进行告警统计分析，绘制出统计图表。4. 安全管理 安全管理功能通过访问操作控制策略等方法保证管理应用程序和管理信息不被非法访问和破坏。用户标识和鉴定，是网管系统提供的最外层的安全保护措施。网管用户在启动程序前必须输入用户名和登陆密码，系统在核实鉴定了用户身份以后才能提供网管系统的使用权。用户被分为3个等级，不同等级的用户设置不同的管理权限，第一级用户拥有最高管理权限，可以使用网管系统提供的所有功能；低级用户在设置参数、操作设备等权限上被限制；高级用户拥有低级用户的所有权限，并能对低级用户进行管理。系统还提供安全日志，登陆者的所有操作将被录入数据库，以便维护和检查使

10、用。EPON网管系统的实现EPON网管系统的实现包括管理站网管软件的实现和代理站软件的实现。1. 管理站网管软件的实现 管理站网管系统是为用户提供友好的交互式界面，利用SNMP协议对代理进程实现管理的控制实体。 通信模块的功能是按照SNMP协议，对网络中的代理站（OLT和ONU）发送、接收SNMP报文，从而获取或设置代理站中MIB库的相应信息。一方面，它将上层的操作、信息封装成对应的PDU（协议数据单元），向网络中发送。另一方面，它接收代理发给自己的PDU，并解析成上层可识别的信息，向上传递。对应于5种消息类型，SNMP有5种类型 数据采集、处理模块负责将采集的数据分析、处理、储存或者送往上层

11、。对各种采集到的数据，要按照配置、性能、故障几个模块的需求进行转换，向上传送。一些数据直接可以给上层显示使用；一些采集到的数据需要处理后，再送往上层显示。如通过访问接口MIB，可以得到每个接口在每个时刻的总流量。可以设置每隔一秒钟取一次值，然后计算秒间总流量差值，得到接口每秒钟的流量。有些数据暂时不需要显示，需要储存在数据库，供以后查询使用。 显示模块是面向用户的。它按照配置管理、性能管理、故障管理、安全管理几个模块分类，以图形化界面形式显示各项信息，并且提供人机接口，供配置使用。本系统是在Windows环境下，用VC+ 6.0开发出来的。 通信模块是利用Windows提供的API函数，封装成

12、一个SNMP类，来实现SNMP的各种操作。按照显示模块的需要，数据处理模块采用各种算法对采集到的数据进行分析处理。显示模块则以对话框、列表框、曲线图等形式，提供直观、方便的图形化界面，如图4所示。 2.代理站软件的实现SNMP在代理站的实现工作主要包括代理进程软件的实现和MIB的设计与组织。(1) 代理进程软件的实现代理进程软件实现SNMP协议，并管理MIB。它实际上是一个执行无限循环的守护进程，在循环中，它接收管理站的SNMP请求，然后进行相应的操作，并作出响应。同时，代理进程能够根据自身管理的MIB信息，主动向管理站发送陷阱报文（Trap），以通知管理站所管理的网络设备发生了异常事件，实现

13、故障告警。通常，在开发过程中使用一些软件开发包可以大大缩短产品开发周期。ucd-snmp软件包是一个广泛使用的实现SNMP代理开发的免费软件包，它支持SNMP v1/v2c/v3，支持分布式代理的开发，支持MIB-II。它包括SNMP协议模块和MIB管理模块，实现了SNMP代理站的基本框架。 (2) EPON设备MIB的设计与组织OLT、ONU设备的MIB主要包括RFC1213定义的MIB-II、RFC1573定义的Interfaces MIB、RFC1493定义的Bridge MIB和根据EPON设备需要自定义的私有MIB。MIB-II包含了基于TCP/IP网络的基本网管信息，包括系统组、接

14、口组、IP组、ICMP组、UDP组、SNMP组等基本管理对象。通过MIB-II，我们可以获取OLT、ONU设备运行的基本网络信息，如系统信息、端口基本信息、IP、ICMP等类型数据包的统计等，对某些对象可以配置。Interfaces MIB是针对改善MIB-II中的接口组的不足和缺陷，发展而来的一个以定义网络接口管理对象为主的MIB。Bridge MIB是一个定义网桥管理对象的MIB，它包括一般网桥管理信息、生成树网桥管理信息和透明网桥管理信息。它主要对OLT设备中所具有的生成树网桥的设置、监测提供网络管理手段。自定义MIB是针对OLT、ONU特殊管理对象和特殊功能而定义的，主要包含各OLT、

15、ONU的特殊系统信息和带宽控制管理两部分。特殊系统信息包括硬件系统信息和软件系统信息。如我们的EPON系统上行是采用WDMA方式的，对于每个ONU端，对应于不同的上行波长。把波长信息加入每个ONU的自定义MIB中，这样通过网管系统就可以查询各ONU的波长相关信息了。带宽控制管理MIB是自定义MIB的一个重要部分，通过它，我们可以远程进行基于用户的带宽管理。 随着EPON的快速发展，为EPON设计和实现一个稳定高效和准确的网络管理系统具有重要的意义。本文结合EPON的特点，设计和实现了一个基于SNMP的EPON网络管理系统。目前，本系统已经基本完成，正在进行最后的测试工作。 Passive op

16、tical network based on Ethernet EPON Ethernet passive optical network is a new optical access network technology. It has a point to multipoint architecture and passive optical transmission, basing on Ethernet provides a variety of business. It uses the PON technology in the physical layer, the link

17、layer uses the Ethernet protocol, the use of the topology of the PON to achieve the Ethernet access. Therefore, it combines the advantages of PON technology and Ethernet Technology: low cost; high bandwidth; expansion of strong, fast and flexible service restructuring; compatibility with the existin

18、g Ethernet; convenient management and so on.Because of the many advantages of EPON, it is becoming more and more popular, and it will become one of the most effective communication methods for broadband access network. In order to ensure the stable, efficient and accurate operation of EPON network,

19、it is very important to provide an effective network management system for EPON. In the field of network management, with the development of network management technology based on TCP/IP system, SNMP has become the standard in fact. The EPON network management system based on SNMP is a system which

20、uses the SNMP management protocol framework and the EPON network entity to realize the effective management. InIntroduction of SNMP SNMP is a network management protocol based on TCP/IP, which uses UDP as the transport layer protocol, which can manage the network equipment supporting the agency proc

21、ess. SNMP mainly includes SMI , MIB and SNMP protocol. SMI gives the general framework of the management object definition. MIB is the structure of the entire managed object that is maintained by the device. The SNMP protocol includes SNMP operations, SNMP information format, and how to exchange mes

22、sages between applications and devices. The SNMP using the agent / management station model for network management. SNMP has 5 types of message types, Get-Request, Get-Next-Request, Set-Request, Trap and Get-Response. Between the agent and the management station, through the several messages to comm

23、unicate each other, in order to obtain a variety of network equipment information, so as to control the normal operation of network equipment.EPON network management system structure The management object of the EPON system is 1 OLT and 32 ONU . The structure of EPON network management system based

24、on SNMP is shown in Figure 2.EMS network management system is installed on the workstation, and the OLT device is connected with the F interface. EMS network management system and OLT, ONU devices using SNMP protocol to communicate, to achieve the unified management of ONU and OLT in EMS. There are

25、2 ways of communication:(1) polling. Management station every time to all OLT and ONU proxy MIB to carry out the active query, each agent to return the query node value. (2) alarm (trap). When certain events occur, the broker sends a trap message to the management station. Management station to rece

26、ive, display the alarm event, and do the appropriate processing. At the same time, the OLT equipment and ONU equipment with the local Console interface, can realize the local operation management and maintenance.Design of EPON network management systemEPON network management system is divided into f

27、our major modules: configuration management, performance management, fault management and security management.1 configuration management Configuration management is mainly within the organization of EPON network operation needed resources and data, construction and maintenance of network system conf

28、iguration, each network element identification, basic configuration to ensure network, monitoring the current configuration and in accordance with the specific circumstances change the configuration, the system parameter setting, to collect and store the parameters, report and basic configuration va

29、lue deviation, start and close the resource etc. At the start of the EPON network, can be automatically or manually generated OLT, ONU device topology, showing the current network in the ONU, OLT device status. After the network topology map is generated, the SNMP management process uses the polling

30、 method to query the SNMP proxy process regularly, and collects the equipment information to update the database, in order to realize the configuration information. After the normal operation of the system, the network management can manually set up the configuration parameters according to the need

31、. If we can set the OLT, ONU agent identification information and information systems to enable, disable a port, and configure the port, the working parameters of the bridge configuration, VLAN configuration, reboot the device. Also provides user based dynamic bandwidth management.2 performance mana

32、gement The functions of performance management of EPON network performance for monitoring, detecting and related performance statistics data acquisition, analysis, diagnosis, so as to network further planning and to provide references for the adjustment, in order to ensure the service quality of the

33、 network. Performance management function of EPON is divided into performance monitoring, performance management control and performance analysis. Performance monitoring is a continuous collection of OLT and ONU and performance related data, according to the performance data to determine network per

34、formance, so as to grasp the equipment unit business quality becomes poor performance caused from the less frequent or constant error. The purpose of the performance management control is to support the management personnel to issue control commands or network management software to automatically is

35、sue control commands to improve the performance of ONU and OLT. It can set up the performance management data collection period, set up the performance monitoring data storage filtering condition, and the threshold value is managed. Performance statistics analysis is a collection of performance data

36、 to do further processing, in order to analyze the table or analysis of the results of the report analysis. Such as the calculation of the use of the interface, the interface of the input error rate, interface output error rate, throughput, etc.3 fault management Fault management function provides t

37、he EPON network fault monitoring, fault location, protection switching and recovery, and storage of fault information for future inquiries. To monitor, report and store the alarm from the hardware device or path node, and fault diagnosis, location and processing. It is an important work of fault man

38、agement. When monitoring network, equipment malfunction or abnormal, the network management system can produce the alarm in real time. Some failures and exceptions are found by the network management program through the query agent station MIB, while others are found by the Trap notification managem

39、ent station. You can set up a variety of alarm alarm level. Different levels of alarm events to take different alarm instructions and treatment measures. After receiving the alarm information, the network management system is analyzed and prompted, and then the different levels of alarm, different p

40、rocessing. Fault location and testing are required for the serious impact of network operation. Start the fault location process, and try to get the relevant information from these processes. After the fault location, the network management system will respond quickly, take the fault repair measures

41、, so that the EPON network to resume normal. Alarm information is stored to the local database. Can be in accordance with the alarm time, alarm equipment, alarm level, and other key words query historical alarm information. According to all the alarm information, alarm statistics analysis, draw a st

42、atistical chart.4 security management Security management functions such as access control policies to ensure that management applications and management information is not illegal access and destruction. User identification and authentication is the most external security measures provided by the n

43、etwork management system. Network users must enter the user name and password before starting the program. The system can provide the right to use the network management system after verification and identification. User is divided into three levels, different levels of users set different managemen

44、t authority, the first level user has the highest administrative authority, you can use management system to provide all of the functions; low-level users in the permission of the parameter setting and operating equipment is limited; advanced users have low-level user all the permissions, and can ca

45、rry on the management to the low-level user.The system also provides a security log, all of the operator will be entered into the database, so as to maintain and check the use.Implementation of EPON network management system The realization of EPON network management system includes the realization

46、of the management station network management software and the realization of the proxy software.1 management station network management software Management station network management system is to provide users with a friendly interactive interface, the use of SNMP protocol to achieve the management

47、of the agent process control entities. In The function of the communication module is to transmit and receive SNMP packets according to SNMP protocol, which can obtain or set up the corresponding information of the MIB Library in the ONU. On the one hand, it will be the upper operation, the informat

48、ion is encapsulated into the corresponding PDU (protocol data unit), to send to the network. On the other hand, it receives the PDU that the proxy sends to its own, and is resolved into the upper layer which can be identified by the information that is transmitted to the. SNMP has 5 types, correspon

49、ding to the 5 message types The data acquisition, processing module is responsible for data collection, analysis processing, storage or sent to the upper. On the various data collected, according to the configuration, performance, failure of the needs of several modules to convert, to send. Some of

50、the data can be displayed directly to the upper level; some of the collected data need to be processed, and then sent to the upper display. The total flow rate at each moment can be obtained by accessing the interface MIB. You can set a value every second to take a second, and then calculate the tot

51、al flow difference between seconds, get the flow of the interface per second. Some data is not required for the time being, the need to be stored in the database for future use. Display module is for the user. According to the configuration management, performance management, fault management, secur

52、ity management of several modules to display information, and to provide a graphical interface for the use of human machine interface. This system is developed by VC+ 6 in Windows environment. Communication module is the use of API to provide the Windows function, packaged into a SNMP class, to achi

53、eve a variety of SNMP operation. According to the needs of the display module, data processing module uses various algorithms to analyze and process the data collected. Display module in the form of dialog box, list box, graph, etc., to provide intuitive and convenient graphical interface, as shown

54、in figure 4. In2 proxy software implementation The implementation of SNMP in the proxy station mainly includes the implementation of the proxy process software and the design and organization of MIB.(1) implementation of the agent process software The SNMP protocol is implemented with the MIB protoc

55、ol, and the management is implemented. It is actually a process of executing an infinite loop, in the loop, it receives the SNMP request of the management station, and then performs the corresponding operation, and makes the response. At the same time, the process agent can according to their own ma

56、nagement MIB information, take the initiative to the management station to send trap message (TRAP), to inform the management station management network equipment occurred abnormal events, and to realize the fault alarm. In general, in the development process using a number of software development p

57、ackage can greatly shorten the product development cycle. Ucd-snmp software package is a widely used SNMP agent to achieve the development of free software packages, which supports v1/v2c/v3 SNMP, support for the development of distributed agents, support MIB-II. It includes SNMP protocol module and

58、 MIB management module, and realizes the basic framework of SNMP proxy. In(2) the design and organization of EPON MIB ONU, OLT device MIB mainly includes the definition of MIB-II RFC1213, RFC1573 Interfaces MIB, RFC1493 definition of MIB Bridge and EPON devices based on the need to customize the pri

59、vate MIB. MIB-II contains the basic network management information based on TCP/IP network, including system group, interface group, IP group, ICMP group, UDP group, SNMP group, etc. Through mib-ii, we can obtain the OLT, ONU equipment operation of the basic network information, such as system infor

60、mation, basic information of port, IP, ICMP, packet types of statistics, for certain objects can be configured. MIB MIB is a Interfaces based on the definition of network interface management for improving the deficiencies and defects of the interface group in MIB-II. Bridge MIB is a definition of b

61、ridge management object in the MIB. It includes general bridge management information, generates tree bridge management information and transparent bridge management information. It mainly provides network management tools, set up monitoring to the OLT equipment in the spanning tree bridge. The cust

62、om MIB is defined by the OLT, ONU special management object and the special function, which mainly includes two parts: the OLT, ONU, the special system information and the bandwidth control management. Information of special system includes hardware system and software system. Such as our EPON syste

63、m uplink is the use of WDMA, for each ONU terminal, corresponding to different upstream wavelength. The wavelength information of each MIB is added to each ONU, so that the wavelength of the ONU can be queried by the network management system. Bandwidth control management MIB is an important part of

64、 the custom MIB, through which we can remotely carry on the user based bandwidth management. In With the rapid development of EPON, the design and implementation of a stable and efficient and accurate network management system is of great significance for EPON. This paper designs and implements a EPON based SNMP network management system based on EPON. At present, the system has been basically completed, an