广电IP城域网改造方案建议书.doc

广电IP城域网改造方案建议书广电IP城域网改造方案建议书 广电IP城域网改造方案建议书目录1项目概述11.1背景介绍11.2总体需求11.3项目目标21.4网络设计原则32技术介绍52.1MPLS/VPN52.2灵活QinQ技术63承载网整体方案建议13.1.1业务对承载网络的要求13.1.2整体网络拓扑图24设备推荐及特性介绍34.1核心路由交换机S850834.2汇聚交换机S5600104.3汇聚交换机S3900194.4接入交换机S2000265路由策略315.1 路由设计原则315.2 路由协议选择315.2.1 域间路由协议选择315.2.2 域内路由协议选择325.2.3 组播路由协议选择326宽带接入运营管理建议346.1 VLAN划分346.1.1 PUPSPV方式346.1.2 PUPV方式356.1.3 PSPV方式356.1.4 混合方式361 项目概述1.1 背景介绍目前广电行业正处于全国数字电视整体转换的历史时期，广电运营商除了传统广播电视业务的运营外，对数字电视、语音通信、宽带数据等多业务融合的有效支持，实现综合性全业务运营已成为业界普遍认同的趋势。国家“十一五规划”中明确提出了计算机网络、通信网络、广电网络实现“三网融合”的总体要求，近年来，下一代网络也一直是业界谈论的焦点。基于广电HFC 网络， 如何进行网络改造，顺利过渡到下一代有线电视网络（NGCN），逐步开展全新的数字电视业务以及丰富的增值业务，是广电行业面临的巨大挑战和历史机遇。另一方面，根据桐乡广电宽带城域网业务的发展和目前网络运营模式的发展趋势，现有的城域业务网的承载和接入能力已经不能满足当前市场的需求，急需进行改造和扩容。建设一个基于IP的高带宽、高可靠性、可运营管理、具备多种业务综合承载能力和扩展性的电信级IP网络，将成为桐乡广电开展全业务运营的关键。广电实现网络双向改造是其业务发展必须经过的技术门槛，实现网络双向改造的技术种类在一定时期内会并存，但最终的发展方向是IP的方向，以太接入网是最完善的接入方式，EPON是目前广电以太网建设的最佳起步方式；目前，华为是EPON技术的国内领先者。1.2 总体需求桐乡广电网络基本需求：根据桐乡市广电的实际情况，本次工程将升级中心机房的核心路由交换机(现有的是CISCO6509)，通过12条单模光纤连接12个镇、街道广电站的交换机（现有的是CISCO3550及CISCO2924），通过单模中距光纤连接到桐乡市区各个分前端机房汇聚层交换机，通过分前端机房再连接到小区机房接入层交换机。在中心机房设置一台核心路由交换机，与INTERNET、IPTV点播服务器连接。城区由4个分前端(分别为：体育路机房、梧桐广电站机房、银菊机房、传媒中心机房)组成，分别设置汇聚层交换机，小区机房放置接入层交换机。本期网络建设节点之间的距离小于10公里。1.3 项目目标桐乡城域网将根据桐乡广电台对数字电视网络建设的指导意见，充分参考杭州成熟的运营模式，建设一个高质量、高可靠性、高扩展性的多业务网络，网络设计坚持适度超前的原则，以满足未来几年桐乡广电对于业务的需求。桐乡业务初期规模虽小，但后期发展潜力大。在建网初期通过少量的投资和设备就可以提供完整的业务能力，并且随着业务的发展，在保护原有投资的情况下，可以对网络做平滑升级，直至万兆骨干城域网。网络建设的目标为1) 数字电视业务目标是整个城区4万电视用户的向数字电视平台( DVB )整体平移，同时城域网能够满足23万户增强型数字电视( VOD )用户的发展需要。初期目标为10000户增强型数字电视( VOD )用户。2) 家庭用户宽带上网业务在数字电视网络基础上发展宽带数据用户，包括企业专线、家庭宽带等以及相应的VoIP等增值业务。3) MPLS VPN业务 提供大客户的专网接入，重点是跨地区的专网业务。网络最终将分为三个层面：核心层、汇聚层、接入层。具体表现为以下的技术指标：A、核心层高性能、有效的数据转发；能够承载普通上网业务、广电内部DCN业务以及未来3G、NGN等业务；需要提供不同业务所需的QoS保证，以保证IPTV、NGN等应用对QOS的严格要求；电信级的稳定可靠性，具备自愈能力和快速的路由收敛；支持OSPF、ISIS、BGP，具备良好的路由转发处理能力，支持大容量路由表，支持 Differsrv/MPLS QOS，支持MPLS VPN、组播等协议；提供两个网络出口连接到两个ISP，实现城域网出口的备份；为各种增值业务和VPN提供单独的城域网出口；B、汇聚层支持千兆上行，每个县/区双归属到核心层，保障业务的不间断；为每个区/县提供两个连接到骨干网的出口，为普通业务和专线业务提供各自的出口，同时两个出口互相备份；在每个区/县的网络出口，部署QOS，通过业务感知、业务标识，实现不同用户或不同业务，分流到不同的业务平面，提供不同的服务质量保证；能够支持接入层用户灵活的接入方式，除了支持传统的以太网接入外，还支持EPON、WLAN等方式的接入；C、接入层为每个最终用户提供有足够的带宽，满足宽带上网和NGN等应用；具有IP、VLAN、MAC、PORT绑定；入户采用百兆速率；接入用户的二层隔离；限速功能，可以为不同的用户分配不同的带宽；可以实现特殊用户的VPN等需求。1.4 网络设计原则实事求是的原则。就是要求网络规划要从技术角度保障方案实施的可行性。一切从实际出发，实事求是。经济适用性的原则。要以市场为导向，如果建设太超前，原始投资就不能马上全部得到收益，因此在规划中需充分把握技术先进性与经济适用性的分寸，不能盲目追求功能的先进与完备高可靠性 合理选择设备、规划网络结构和路由部署，网络具备一定的冗余度和较强的故障自愈能力，保证网络稳定可靠运行。 高性能 设备处理能力、网络带宽及业务承载能力设计时应有余量，保证网络在高负荷或任何单点故障情况下仍具有较高的吞吐能力,不影响业务质量。 扩展性强 要求网络结构满足当前IP城域网发展的趋势，先实现网络的两个转发平面的逻辑分离，以后可以通过设备的增加和升级，使网络能够实现真正分离的两张物理网络，可以更好的承载Internet业务和增值业务。 多业务支持能力强 通过划分逻辑平面，使网络具备端到端的QoS保证能力，通过合理规划，能满足多业务承载的QoS要求。实现多种业务的安全隔离，避免相互干扰，充分保证各业务的安全性。 可运营可管理 网络应提供良好的业务管理和灵活的控制能力；实现集中监测、分权管理，实现统一的网络业务调度和管理，降低网络运营成本。 全网MPLS化 MPLS VPN是多业务承载的基石，NGN、3G、IPTV、Internet的统一承载需要通过划分不同的逻辑平面保障业务的安全性、QOS问题。2 技术介绍随着宽带业务的发展，人们越来越意识到网络的接入部分(最后1 km)存在严重的带宽“瓶颈”。接入部分两边目前都已跨入吉比特级以上的速率，如用户端广泛使用的PC其内部传送速率已达到千兆比特速率；而作为接入部分的另一头，城域网或国干网的每波长速率也已达到2.510 Gbps，它们都比接入部分高出至少3个数量级。随着三网合一的推行，突破接入网瓶颈变得越来越迫切，只有突破接入部分的带宽“瓶颈”，才能使整个网络有效发挥宽带的作用，真正推动各种业务的发展。下面对当前流行的几种网络技术进行简单的介绍。2.1 MPLS/VPNMPLS是多协议标签交换协议的简称。采用MPLS VPN技术可以把物理上单一的IP网络分解成逻辑上隔离的网络，并且每个VPN单独构成一个独立的地址空间，即VPN之间可以重用地址，在分配地址时不必考虑是否会与其他的VPN发生冲突，只需要考虑在本VPN之内不冲突即可，这样可以解决IP网络地址不足的问题，也方便网络的扩展和变更。MPLS VPN的网络构造由服务提供商来完成。在这种网络构造中，由服务提供商向用户提供VPN服务，用户感觉不到公共网络的存在，就好像拥有独立的网络资源一样。MPLS VPN网络中，有三种设备：CE、PE和P路由器，CE是用户直接与服务提供商相连的边缘设备，可以是路由器、交换机或者终端；PE是骨干网中的边缘设备，它直接与用户的CE相连；P 路由器是骨干网中不与CE直接相连的设备。P 路由器并也不知道有VPN的存在，仅仅负责骨干网内部的数据传输，但其必须能够支持MPLS协议，并使能该协议；PE位于服务提供商网络的边缘，所有的VPN的构建、连接和管理工作都是在PE上进行的。MPLS，不是特指某一种业务或应用，而是一种标准化的路由与交换技术平台，可以支持各种高层协议与业务，MPLS报文交换和转发是基于标签的。IP包在进入MPLS网络时，入口的路由器分析IP包的内容并且为这些IP包选择合适的标签，然后所有MPLS网络中节点都是依据这个简短标签来作为转发依据。MPLS 结合了IP的灵活连接和可扩展性，以及ATM的可靠传输和QOS。标签交换的工作流程如下：由LDP（标签分发协议）和传统路由协议（OSPF等）在LSR中建立路由表和标签映射表。 在MPLS入口处的LER接收IP包，完成第三层功能，并给IP包加上标签；在MPLS出口处的LER将分组中的标签去掉后继续进行转发。LSR不再对分组进行第三层处理，只是根据分组上的标签通过交换单元进行转发。MPLS-VPN即采用MPLS技术，在公共IP网络上构建企业IP专网，实现数据、语音、图像多业务宽带连接，并结合差别服务、流量工程等相关技术，为用户提供高质量的服务。MPLS-VPN能够在提供原有VPN网络所有功能的同时，提供强有力的QoS能力，具有可靠性高、安全性高、扩展能力强、控制策略灵活以及管理能力强大等特点。基于MPLS 的VPN具有以下优势。MPLS VPN 提供一个可快速部署实施增值IP业务的平台，包括内部网、外部网、 话音、多媒体及网络商务。MPLS VPN 通过限制VPN 路由信息的传播仅在VPN成员内部，可提供与第二层VPN 相同的私密性及安全性。MPLS VPNs扩展性好，每个服务提供商可以设定数十万VPN， 每个VPN 可有数千个现场。MPLS VPNs 提供与用户内部网的无缝集成。2.2 灵活QinQ技术QinQ实现方式一种是基于端口的QinQ，一种是基于流分类的灵活QinQ。基于端口的QinQ的实现机理如下：当该设备端口接收到报文，无论报文是否带有VLAN Tag，交换机都会为该报文打上本端口缺省VLAN的VLAN Tag。这样，如果接收到的是已经带有VLAN Tag的报文，该报文就成为双Tag的报文；如果接收到的是untagged的报文，该报文就成为带有端口缺省VLAN Tag的报文。由于基于端口的QinQ比较容易实现，所以业界主流厂家的三层交换机都支持。基于端口的QinQ的缺点是外层Vlan Tag封装方式死板，不能根据业务种类选择外层Vlan Tag封装的方式，从而很难有效支持多业务的灵活运营。基于流分类的灵活QinQ实现机理如下：基于流的QinQ特性（Selected QinQ），可灵活根据流分类的结果选择是否打外层VLAN tag、打上何种外层VLAN tag：如根据用户Vlan tag、MAC地址、IP协议、源地址、目的地址、优先级、或应用程序的端口号等信息实施灵活QinQ特性。借助上述流分类方法，实际实现了根据不同用户、不同业务、不同优先级等对报文进行外层VLAN tag封装，对多种业务实施不同承载的方案57opinion about, and statement of, the theme. Moral inferences drawn from most stories: Moral inferences may be drawn from most stories, no doubt, even when an author does not intend his/her story to be read this way. In “A Clean, Well-Lighted Place”, we feel that Hemingway is indirectly giving us advice for properly regarding and sympathizing the lonely, the uncertain, and the old. But obviously the story does not set forth a lesson that we are supposed to put into practice. We can say for sure that “A Clean, Well-Lighted Place” contains several themes and other statements could be made to take in Hemingways view of love, of communication between people, of dignity. Great stories, like great symphonies, frequently have more than one theme. When we say that the title of Pride and Prejudice conveys the theme of the novel or that Uncle Toms Cabin and The Grapes of Wrath treat the themes of slavery and migratory labor respectively, this is to use theme in a larger and more abstract sense than it is in our discussion of Hemingways “A Clean, Well-Lighted Place.” In this larger sense it is relatively easy to say that Mark Twains Huckleberry Finn, Updikes A & P, and Faulkners Barn Burning concern the theme of “initiation into maturity.” Such general descriptions of theme can be useful, especially if we want to sort a large number of stories and novels into rough categories, but the fact that they are similar in theme does not mean that they mean the same thing. The attitude towards the theme may be very different: the tone of treatment may be, for example, either comic or tragic, straightforward or ironic. The writers vision of life is the special underlying fact of a story, and a theme, abstractly stated, is not the same thing as a vision of life. And we suggest anyway that, in the beginning, you look for whatever truth or insight you think the writer of a story intends to reveal. Try to state a theme in a sentence. By doing so, we will find ourselves looking closely at the story. Kennedy and Gioia make a helpful suggestion to consider the following points when we think about the theme of a story:Look back once more at the title of the story. What does it indicate in relation to the whole story?Does the main character in any way change in the story? Does this character arrive at any eventual realization or understanding? Are you left with any realization or understanding after finishing reading the story?Does the author (through the narrator) make any general observations about life or human nature? Do the characters make any (Caution: Characters now and again will utter opinions with which the reader is not necessarily supposed to agree.)Does the story contain any especially curious objects, mysterious flat characters, significant animals, repeated names, special allusions, or whatever, that hint towards meanings larger than such things ordinarily have? In literary stories, such symbols or metaphors may point to central themes.When we have worked our statement of theme, have we cast our statement into general language, not just given a plot summary? Does our statement hold true for the story as a whole, not just part of it?Chapter Four Setting“Once upon a time there lived a king named Midas in Phrygia. He loved gold more than anything else but his little daughter.” This is the opening sentences of “Golden Touch”, which introduces the time, place, and the usual mentality of the character. What is setting?An event occurs and a character exists in a particular time and place. This particular time and place is referred to as setting. A setting is the background against which a character is depicted or an event narrated. Its purpose is to provide an imaginary link between what happens in the novel and what the reader takes to be reality. Like some other elements, setting is not peculiar to the novel. The reader finds it serving the same purpose in different genres. The traditional way to tell a story reveals much about setting.Usually, a setting consists of time and place. It can also mean circumstances such as Midass mentality. A setting may be detailed or sketchy. It depends on the novelists purpose of writing and his idea of works of art. A setting may or may not be symbolic. Generally, a setting is more concerned with the physical aspects. Setting is closely related with exposition in that they both help to make possible the events in the novel. In fact, an exposition must have a setting. But setting goes along with every event in the novel whereas exposition is only the initiating action.1. The elements making up a settingBy the setting of a story, we simply mean its place and time, the physical, and sometimes spiritual, background against which the action of a narrative takes place. Every a story as short as the one at the beginning of the introduction must be set in a certain place and time: we have an “old, shuttered house” and the present tense suggests time (though the present tense indicates much more than time itself in the story). The elements making up a setting are generally: (1) the actual geographical location, its topography, scenery, and such physical arrangements as the location of the windows and doors in a room; (2) the occupations and daily manner of living of the characters; (3) the time or period in which the action takes place, for example, the late eighteenth century in history or winter of the year; (4) the general environment of the characters, for example, religious, mental, moral, social, and emotional conditions through which characters in the story move. (Holman and Harman, A Handbook to literature, 1986) But often, in an effective story, setting may figure as more than mere background. It can make things happen. It can prompt characters to act, bring them to realizations, or cause them to reveal their innermost natures, as we shall see in John Cheevers short story “The Swimmer”.First, as we have said, the idea of setting includes the physical environment of a story: a region, a landscape, a city, a village, a street, a housea particular place or a series of places where a story occurs. (Where a story takes place is sometimes called its locale.) Places in fiction not only provide a location for an action or an event of the story but also provoke feelings in us. A sight of a green field dotted with fluttering daffodils affects us very differently from a sight of a dingy alley, a tropical jungle, or a small house crowded with furniture. In addition to a sense of beauty or ugliness, we usually build up certain associations when we put ourselves in such a scene. We are depressed by a dingy alley, not only because it is ugly, but because it may arouse a feeling, perhaps sometimes unconsciously, of poverty, misery, violence, viciousness, and the struggles of human beings who have to live under such conditions. A tropical jungle, for example, in Joseph Conrads Heart of Darkness, might involve a complicated analysis: the pleasure of the colours and forms of vegetation, the discomfort of humidity, heat, and insects, a sense of mystery, horror, etc. The popularity of Sir Walter Scotts “Waverley” novels is due in part to their evocation of a romantic mood of Scotland. The English novelist Graham Greene apparently needed to visit a fresh scene in order to write a fresh novel. His ability to encapsulate the essence of an exotic setting in a single book is exemplified in The Heart of the Matter; his contemporary Evelyn Waugh stated that the West Africa of that book replaced the true remembered West Africa of his own experience. Such power is not uncommon: the Yorkshire moors have been romanticized because Emily Bronte wrote of them in Wuthering Heights, and literary tourists have visited Stoke-on-Trent in northern England because it comprises the “Five Towns” of Arnold Bennets novels of the early twentieth century. Thus, a readers reaction to a place is not merely based upon the way it looks, but upon the potentialities of action suggested by it. Places matter greatly to many writers. For instance, the French novelist Balzac, before writing a story set in a town, he would go and visit that town, select a few lanes and houses, and describes them in detail, down to their very smells. In his view the place in which an event occurs was of equal moment with the event itself, and it has a part to play. Another example is Thomas Hardy, under whom the presentation of setting assumes an unusual importance. His “Wessex” villages cast intangibly such as spell upon the villagers that once they leave their hometowns they will inevitably suffer from disasters, and the farther they are away from their hometowns, the more, terrible their disasters will be. For example, in the Tess of the DUrbervilles, the Vale of Blakemore was the place where Tess was born and her life was to unfold. Every contour of the surrounding hills was as personal to her as that of her relatives faces; she loved the place and was loved in the place. The vale, far from the madding crowd of the civilized city, was as serene and pure as the inhabitants. Tess, imbued deeply with the natural hue of the vale and bound closely to this world of simplicity and seclusion, experienced her own delight and happiness though her family was poor. It was, to some extent, her departure from her native place that led to her tragedy. In The Return of the Native, the atmosphere of Egdon Heath prevails over the whole book; as an environment, it absorbs some and repels others of the characters: those who are absorbed achieve a somber integration with it, but those who are repelled and rebel suffer disaster.Sometimes an environment serves as more than a mere place to set the story. Often, it is inextricably entangled with the protagonist, and even carries strong symbolic meanings. Cathy as an image of the feminine personality, for example, in Emily Brontes Wuthering Heights, is not supposed to possess the “wilderness” characteristic of masculinity and symbolized by the locales of Heathcliff and Wuthering Heights. In some fiction, setting is closely bound with theme. In The Scarlet Letter, even small details afford powerful hints at the theme of the story. At the start of the story, the narrator describes a colonial jailhouse: Before this ugly edifice, and between it and the wheeltrack of the street, was a grass-plot, much overgrown with burdock, pigweed, apple-peru, and such unsightly vegetation, which evidently found something congenial in the soil that had so early borne the black flower of civilized society, a prison. But, on one side of the portal, and rooted almost at the threshold, was a wild rosebush, covered, in this month of June, with its delicate gems, which might be imagined to offer their fragrance and fragile beauty to the prisoner as he went in, and to the condemned criminal as he came forth to his doom, in token that the deep heart of Nature could pity and be kind to him.Apparently, the author makes a contrast between the ugly jailhouse with a tangled grass-plot overgrown with burdock and pigweed and something as beautiful as a wild rose. As the story unfolds, he will further suggest that secret sin and a pretty child may go together like a pigweed and wild roses. In this artfully crafted novel, setting is intimately blended with characters, symbolism, and theme.In addition to place, setting may crucially involve the time of the storycentury, year, or even specific hour. It may matter greatly that a story takes places in the morning or at noon. The medieval background informs us differently from the twentieth century. Kennedy and Gioia note that in The Scarlet Letter, the nineteenth-century author Nathaniel Hawthrone, utilizes a long introduction and a vivid description of the scene at a prison door to inform us that the events in the story took place in the Puritan community of Boston of the earlier seventeenth century. This setting, to which Hawthorne pays so much attention, together with our schemata concerning Puritan practice, helps us understand what happens in the novel. We can understand to some extent the agitation in the town when a woman is accused of adultery, for adultery was a flagrant defiance of church for the God-fearing New England Puritan community, and an illegitimate child was evidence of sin. Without information about the seventeenth-century Puritan background, a reader today may be perplexed at the novel. The fact that the story in Hawthornes novel took place in a time remote from our own leads us to expect different attitudes and customs of the characters, is strongly suggestive of the whole society, which is crucial to an essential understanding of The Scarlet Letter as a whole.Besides place and time, setting may also include the