网络层介绍.ppt

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 work 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.
网络层
1.   服务和协议
⑴ 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. Services and Protocols
(1). 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) works in the process.
⑵ (IGMP, Group Management Protocol)
组管理协议(IGMP) 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) Group Management Protocol (IGMP)
Group Management protocol (IGMP) is a protocol for managing multicasting groups. It is used by conferencing applications to join and leave particular multicast group.
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.
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 ponent. 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,altho