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多媒体传输网络层的需求是高带宽、多点发送、资源保留和 QoS 保证，有支持数据流有新路由协议，及支持集成式服务的新高容量路由的前提条件。

网络层. 多媒体传输网络层的需求是高带宽、多点发送、资源保留和 QoS 保证，有支持数据流有新路由协议，及支持集成式服务的新高容量路由的前提条件。

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多媒体传输网络层的需求是高带宽、多点发送、资源保留和 QoS 保证，有支持数据流有新路由协议，及支持集成式服务的新高容量路由的前提条件。

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  1. 网络层 • 多媒体传输网络层的需求是高带宽、多点发送、资源保留和QoS 保证，有支持数据流有新路由协议，及支持集成式服务的新高容量路由的前提条件。 • The requirements on the network layer for multimedia transmission are a provision of high bandwidth, multicasting, resource reservation and QoS guarantees, new routing protocols with support for streaming capabilities and new higher-capacity routers with support of intergated services.

  2. 1．Internet服务和协议 • ⑴ Internet 协议（IP） • IP提供从源端点到目标端点之间的非可靠的数据文传输，在处理过程中可能经过一个或几个网关（路由器）和网络。 • 1. Internet Services and Protocols • (1). Internet Protocol (IP) • IP provides for the unreliable carriage of data grams from source host to destination hosts, possibly passing through one or more gateways (routers) and networks in the process.

  3. ⑵ Internet （IGMP，Internet Group Management Protocol） • Internet 组管理协议（IGMP）是用于管理Internet 多点发送组的协议。它可让会议应用加入和离开特定的多点发送组。 • (2) Internet Group Management Protocol (IGMP) • Internet Group Management protocol (IGMP) is a protocol for managing Internet multicasting groups. It is used by conferencing applications to join and leave particular multicast group.

  4. 基本的服务是让源发送数据包给多点发送组的所有成员。它不保证数据发送能到达组中的任一目标或所有目标。基本的服务是让源发送数据包给多点发送组的所有成员。它不保证数据发送能到达组中的任一目标或所有目标。 • The basic service permits a source to send datagrams to all members of a multicast group. These are no guarantees of the delivery to any or all targets in the group.

  5. ⑶Resource reSerVation Protocol （RSVP） • RSVP 协议用于传输保留资源，并在中间节点保留状态。它没有数据传输组件。RSVP消息以IP数据报文的形式发送，路由器保留“软状态”，由周期性保留消息进行刷新。如果没有刷新消息，则路由器在某一时间之后保留。 • RSVP is a protocol which transfers reservations and keeps a stare at the intermediate nodes. It does not have a data transfer component. RSVP messages are sent as IP datagrams, and the router keeps “soft state”, which is refreshed by periodic reservation messages. In the absence of the refresh messages, the routers delete the reservation after a certain timeout.

  6. 1 Stream 协议，版本2（ST-II） • ST-II提供基于流模型的面向连接的、性能得到期保证的数据传输服务。尽管也可建立双向连接。但一般以单向连接方式建立发送者与几个接收者之间的连接。 • 1. Stream protocol, Version 2(ST-II) • ST-II provides a connection-oriented, guaranteed service for data transport based on the stream model [Top90]. The connections between the sender and several receivers are setup as uni-directional connections,although also duplex connections can be setup.

  7. ST-II 是原ST协议的扩展[FOR79]。它由两个组件组成：ST控制消息协议（SCMP），它支持可靠的面向非连接的协议消息的传输；另一组件是ST协议本身，它支持非可靠的数据传输。 • ST-II is an extension of the original ST protocol [For79]. It consists of two components: the ST Control Message Protocol (SCMP), which is a reliable, connectionless transport for the protocol messages and the ST protocol itself, which is an unreliable transport for the data.

  8. ST-II 在连接建立时提供资源保留，资源保留来自己于源。用流说明发送SCMP消息。它以数据包大小、数据位率描述流需求（QoS）。如果目标接收呼叫，则返回最终的流说明给源。11.3.3节详细说明资源保留机制。 • ST-II provides a resource reservation during the connection setup. The reservations originated from the source.It sends a SCMP message with a flow specification, which describes the stream requirements (QoS) in terms of packet size, data rate, etc. If the destination accepts the call, it returns the final flow specification to the source. The resource reservation scheme is presented in more detail in Section 11.3.3.

  9. ST-II 非常适合于多媒体传输，因为它从发送者到接收者沿路都进行资源保留。 • ST-II is suitable for multimedia transmission because of its resourcereservation along the path between the sender and receiver.

  10. 1．实时Internet协议(RTIP) • Tenet机制中使用RTIP（实时 Internet协议）服务。RTIP提供面向连接的、保证性能的、非可靠的数据包发送。就像IP在 Internet 协议本栈中占有的地位那样[VZ91]。 • 1. Real-Time Internet Protocol (RTIP) • In the Tenet scheme, the services of RTIP (Real-Time Internet Protocol) are used. RTIP provides for connection-oriented, performance-guaranteed, unreliable delivery of packets [VZ91].

  11. 基本概念 服务质量的数由国际标准化组织（ISO）通过QoS （Quality of Service）这一术语来定义。QoS确定了网络服务质量的优劣，QoS 有一组参数来标定。 Basic Concepts • Parameterization of the services is defined in ISO (International Standard Organization) standards through the notion of Quality of Service(QoS) .The ISO standard defines QoS as a concept for specifying how “good” the offered networking services are. QoS can be characterized by a number of specific parameters. There are several important issues which need to be considered with respect to QoS.

  12. 1．QoS分层 • 传统的QoS在通信系统工程的网络层中定义，通过把QoS概念要引入到传输层，可加强对QoS的控制。 • 1. QoS Layering • Traditional QoS (ISO standards) was provided by the network layer of the communication system.An enhancement of QoS was achieved through inducing QoS into transport services.

  13. 2，服务对象 • 各种服务在不同的对象（如媒体源、媒体信息接收点、连接和虚拟线路等）上，因此，在QoS的描述集中在处理传输层/网络连接的服务上。 • 2. Service Objects • Services are performed on different objects, for example, media sources,media sinks, connections and Virtual Circuits (VCs), hence the QoS parameterization specifies these service objects. In ISO standards, the QoS description is meant to be for services, processing a transport/network connection.

  14. 在Telnet协议组中，服务操作在分组交换网的实时通道上进行[FV90]。在Telnet协议组中，服务操作在分组交换网的实时通道上进行[FV90]。 • In Tenet protocol suite, the services operate over a “real-time” channel of a packet switched network [FV90].

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