多媒体传输网络层的需求是高带宽

1、多媒体传输网络层的需求是高带宽、多点发送、资源保管和QoS 保证，有支持数据流有新路由协议，及支持集成式效力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-

2、capacity routers with support of intergated services.网络层1 Internet效力和协议 Internet 协议IPIP提供从源端点到目的端点之间的非可靠的数据文传输，在处置过程中能够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 pa

3、ssing through one or more gateways (routers) and networks in the process. Internet IGMP，Internet Group Management ProtocolInternet 组管理协议IGMP是用于管理Internet 多点发送组的协议。它可让会议运用参与和分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 I

4、nternet multicasting groups. It is used by conferencing applications to join and leave particular multicast group.根本的效力是让源发送数据包给多点发送组的一切成员。它不保证数据发送能到达组中的任一目的或一切目的。 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

5、 or all targets in the group.Resource reSerVation Protocol RSVP RSVP 协议用于传输保管资源，并在中间节点保管形状。它没有数据传输组件。RSVP音讯以IP数据报文的方式发送，路由器保管“软形状，由周期性保管音讯进展刷新。假设没有刷新音讯，那么路由器在某一时间之后保管。RSVP is a protocol which transfers reservations and keeps a stare at the intermediate nodes. It does not have a data transfer compone

6、nt. 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.1 Stream 协议，版本2ST-IIST-II提供基于流模型的面向衔接的、性能得到期保证的数据传输效力。虽然也可建立双向衔接。但普通以单

7、向衔接方式建立发送者与几个接纳者之间的衔接。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 ca

8、n be setup. ST-II 是原ST协议的扩展FOR79。它由两个组件组成：ST控制音讯协议SCMP，它支持可靠的面向非衔接的协议音讯的传输；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 a

9、nd the ST protocol itself, which is an unreliable transport for the data. ST-II 在衔接建立时提供资源保管，资源保管来本人于源。用流阐明发送SCMP音讯。它以数据包大小、数据位率描画流需求QoS。假设目的接纳呼叫，那么前往最终的流阐明给源。11.3.3节详细阐明资源保管机制。 ST-II provides a resource reservation during the connection setup. The reservations originated from the source.It sends a

10、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.ST-

11、II 非常适宜于多媒体传输，由于它从发送者到接纳者沿路都进展资源保管。ST-II is suitable for multimedia transmission because of its resource reservation along the path between the sender and receiver.1 实时Internet协议(RTIP) Tenet机制中运用RTIP实时 Internet协议效力。RTIP提供面向衔接的、保证性能的、非可靠的数据包发送。就像IP在 Internet 协议本栈中占有的位置那样VZ91。1. Real-Time Internet Pro

12、tocol (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. 效力质量的数由国际规范化组织ISO经过QoS Quality of Service这一术语来定义。QoS确定了网络效力质量的优劣，QoS 有一组参数来标定。 Basic ConceptsParameterizat

13、ion 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. T

14、here are several important issues which need to be considered with respect to QoS.根本概念1 QoS分层传统的QoS在通讯系统工程的网络层中定义，经过把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 induc

15、ing QoS into transport services.2，效力对象各种效力在不同的对象如媒体源、媒体信息接纳点、衔接和虚拟线路等上，因此，在QoS的描画集中在处置传输层/网络衔接的效力上。2. Service ObjectsServices 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 standa