东南大学：《计算机网络体系结构》课程教学资源（课件讲稿）第七单元 特殊路由

特殊路由 组播的基本概念 组播地址管理 IGMP 内部组播路由协议 MBGP ●MSDP 移动路由 东南大学1

东南大学 1 特殊路由 • 组播的基本概念 • 组播地址管理 • IGMP • 内部组播路由协议 • MBGP • MSDP • 移动路由

组播的基本概念 为什么采用组播? 向多位接收者发送相同的信息 只在需要时进行包复制,提高带宽利用率 收件人地址未知 成员可以动态加入或退出 IP multicast-ena bled network 可以提供端一端组播服务的网络 主机可以向它所附接的路由器表达自己的群关系 路由器可以在彼此之间传递群关系,并按群关系 转发组播报文 东南大学2

东南大学 2 组播的基本概念 • 为什么采用组播？ –向多位接收者发送相同的信息 –只在需要时进行包复制，提高带宽利用率 –收件人地址未知 –成员可以动态加入或退出 • IP multicast-enabled network – 可以提供端－端组播服务的网络 – 主机可以向它所附接的路由器表达自己的群关系 – 路由器可以在彼此之间传递群关系，并按群关系 转发组播报文

单播/组播 组播的基本概念 单播 主机 路由器 组播 主机 路由器 东南大学3

东南大学 3 单播/组播 主机 路由器 单播 主机 路由器 组播 组播的基本概念

组播的基本概念 One-to-Many Applications A single host sending to two or more(n)receivers Scheduled audio/video(a/v) distribution: Lectures, presentations, meetings, or any other type of scheduled event Push media: News headlines, weather updates, sports scores, or other types of non-essential dynamic information File Distribution and Caching: Web site content, executable binaries, and other file-based updates sent to distributed end-user or replication/caching sites Announcements network time, multicast session schedules, random numbers, keys, configuration updates. or other types of information that are commonly useful 东南大学4

东南大学 4 One-to-Many Applications Many Applications • A single host sending to two or more (n) receivers – Scheduled audio/video (a/v) distribution: Lectures, presentations, meetings, or any other type of scheduled event. – Push media: News headlines, weather updates, sports scores, or other types of non-essential dynamic information. – File Distribution and Caching: Web site content, executable binaries, and other file-based updates sent to distributed end-user or replication/caching sites – Announcements: Network time, multicast session schedules, random numbers, keys, configuration updates, or other types of information that are commonly useful. 组播的基本概念

组播的基本概念 Many-to-Many Applications Any number of hosts sending to the same multicast group address, as well as receiving from it Multimedia Conferencing: Audio/video and whiteboard comprise the classic conference application. Synchronized resources: Shared distributed databases of any type(schedules, directories, traditional Information System databases, etc. Collaboration: Shared document editing Distributed Interactive Simulations Dis: Each object in a simulation multicasts descriptive information so all other objects can render the object, and interact as necessary. 东南大学5

东南大学 5 Many-to-Many Applications Many Applications • Any number of hosts sending to the same multicast group address, as well as receiving from it – Multimedia Conferencing: Audio/Video and whiteboard comprise the classic conference application. – Synchronized Resources: Shared distributed databases of any type (schedules, directories, traditional Information System databases, etc.) – Collaboration: Shared document editing. – Distributed Interactive Simulations [DIS]: Each object in a simulation multicasts descriptive information so all other objects can render the object, and interact as necessary. 组播的基本概念

组播的基本概念 Many-to-One Applications Any number of receivers sending data back to a( source)sender via unicast or multicast Resource Discovery: Service Location, for example, leverages ip multicast to enable something like a host anycasting service"Capability. Data Collection: the sensors might send updates in response to a request from the data collector. or send continuously at regular intervals, or send spontaneously when a pre-defined event occurs. Auctions: Theauctioneer"starts the bidding by describing whatever it is for sale (product or service), and receivers send their bids privately or publicly. 东南大学6

东南大学 6 Many-to-One Applications One Applications • Any number of receivers sending data back to a (source) sender via unicast or multicast – Resource Discovery: Service Location, for example, leverages IP Multicast to enable something like a "host anycasting service" Capability. – Data Collection: the sensors might send updates in response to a request from the data collector, or send continuously at regular intervals, or send spontaneously when a pre-defined event occurs. – Auctions: The "auctioneer" starts the bidding by describing whatever it is for sale (product or service), and receivers send their bids privately or publicly. 组播的基本概念

组播的基本概念 组播服务的支撑 Address management some assurances against"address collisions rovides Coordinated address allocation service that pi Hard-Coded, Advertised, Algorithmically derived Session management Making session descriptions available (via advertisements and explicit queries)within appropriate scopes, and also enabling registration of new sessions MMUSIC系列协议 The multiparty Multimedia Session Control) 东南大学7

东南大学 7 组播服务的支撑 组播服务的支撑 • Address Management – Coordinated address allocation service that provides some assurances against "address collisions". – Hard-Coded，Advertised，Algorithmically Derived • Session Management – Making session descriptions available (via advertisements and explicit queries) within appropriate scopes, and also enabling registration of new sessions – MMUSIC系列协议(The Multiparty MUltimedia SessIon Control ) 组播的基本概念

组播的基本概念 组播服务的支 共享学习:如果发现了丢包现象,接收者启动 个随机的定时器。如果在定时内收到其它接 收者的丢包报告,就停止定时器并且不发送丢 Heterogeneous包报告,否则就发无包报告发送者通过 Sending to recei决定是否调整数据发送速率 bandwidth capacity ncy characteristics, and network cop on requires feed back to monitor receir performance Shared Learning, Local recovery Reliable data delivery E d by all re( 本地恢复:一些接收者被定义为本地转发点,它 可以在收到本地的丢包报告后重发数据包,或者将 Si接收到的数据重新编码为速率较低的数据,再向低 速信道转发。 东南大学8

东南大学 8 组播服务的支撑 组播服务的支撑 • Heterogeneous Receiver Support – Sending to receivers with a wide variety of bandwidth capacities, latency characteristics, and network congestion requires feedback to monitor receiver performance. – Shared Learning，Local Recovery • Reliable Data Delivery – Ensuring that all data sent is received by all receivers – Similar mechanisms as above 组播的基本概念 共享学习：如果发现了丢包现象，接收者启动 一个随机的定时器。如果在定时内收到其它接 收者的丢包报告，就停止定时器并且不发送丢 包报告，否则就发送丢包报告。发送者通过 RTP/RTCP协议了解接收者总体的丢包率，以 决定是否调整数据发送速率。 本地恢复：一些接收者被定义为本地转发点，它们 可以在收到本地的丢包报告后重发数据包，或者将 接收到的数据重新编码为速率较低的数据，再向低 速信道转发

组播的基本概念 组播服务的支撑 Security Ensuring content privacy among dynamic multicast group memberships, and limiting senders 对发送者、接收者和内容访问的限制;对接收内容的验 证;对接收者的隐私保护;防火墙的穿越,对发送者的 标识验证,成员关系的撤销 Synchronized Play-Out Allow multiple receivers to replay" data received in synchronized fashion required:所有系统时钟必须同步,数据流必须分帧并 带时标,要考虑多媒体硬件回放的时延。 东南大学9

东南大学 9 组播服务的支撑 组播服务的支撑 • Security – Ensuring content privacy among dynamic multicast group memberships, and limiting senders – 对发送者、接收者和内容访问的限制； 对发送者、接收者和内容访问的限制；对接收内容的验 对接收内容的验 证；对接收者的隐私保护 对接收者的隐私保护 对接收者的隐私保护；防火墙的穿越，对发送者的 标识验证，成员关系的撤销 成员关系的撤销 • Synchronized Play-Out – Allow multiple receivers to "replay" data received in synchronized fashion – required：所有系统时钟必须同步 ：所有系统时钟必须同步 所有系统时钟必须同步，数据流必须分帧并 数据流必须分帧并 带时标，要考虑多媒体硬件回放的时延。 要考虑多媒体硬件回放的时延。 组播的基本概念

组播的基本概念 IP的组播通信机制 IP的组播通信机制是对于正常传输功能的扩展,即不 是一个主机使用一个IP地址,而是多个主机(一个群) 使用一个IP地址(群地址)。 IP的组播报文也采用尽力而为的传输方式,也可能发 生丢失和错序。组播通信机制可降低网络负载,因为 它仅在两个接收者不能共享下一条链路时才进行报文 复制,即对一个组播通信而言,相同的报文不会在 个链路上传输两次。 ·组播通信同样分为组播路由和组播转发。与正常IP转 发不同的是,组播通信的终点数是可变化的,因此组 播路由器根据源点来判定转发方向。如果根据报文的 TT来判定转发要求(在T允许的情况下要不断地转 发),这就有可能形成转发回路和组播转发风暴。 东南大学10

东南大学 10 组播的基本概念 IP的组播通信机制 • IP的组播通信机制是对于正常传输功能的扩展，即不 是一个主机使用一个 IP地址，而是多个主机（一个群） 使用一个 IP地址（群地址）。 • IP的组播报文也采用尽力而为的传输方式，也可能发 生丢失和错序。组播通信机制可 。组播通信机制可 。组播通信机制可 。组播通信机制可降低网络负载，因为 它仅在两个接收者不能共享 个接收者不能共享 个接收者不能共享 个接收者不能共享下一条链路时才进行报文 复制，即对一个组播通信而言，相同的报文不会在一 个链路上传输两次。 • 组播通信同样分为组播路由和组播转发。与正常IP转 发不同的是，组播通信的 发不同的是，组播通信的 发不同的是，组播通信的 发不同的是，组播通信的终点数是可变化的，因此组 播路由器根据源点来判定转发方向。如果 定转发方向。如果 定转发方向。如果 定转发方向。如果根据报文的 TTL来判定转发要求（在TTL允许的情况下要不断地转 发），这就有可能形成转发回路和组播转发 成转发回路和组播转发 成转发回路和组播转发 成转发回路和组播转发风暴