Addressing Mode Usually address refers to single system or port - Individual or unicast(单播) address Address can refer to more than one entity or port Multiple simultaneous recipients for data Broadcast for all entities within domain Multicast for specific subset of entities 176
21/76 Addressing Mode • Usually address refers to single system or port - Individual or unicast （单播） address • Address can refer to more than one entity or port - Multiple simultaneous recipients for data - Broadcast for all entities within domain - Multicast for specific subset of entities
Multiplexing Multiple connections into single system(多个连 接进入一个系统) E.g. frame relay, can have multiple data link connections terminating in single end system Connections multiplexed over single physical interface Can also be accomplished via port names Also permit multiple simultaneous connections E.g. multiple TCP connections to given system OEach connection on different pair of ports
22/76 Multiplexing • Multiple connections into single system（多个连 接进入一个系统） - E.g. frame relay, can have multiple data link connections terminating in single end system - Connections multiplexed over single physical interface • Can also be accomplished via port names - Also permit multiple simultaneous connections - E.g. multiple TCP connections to given system oEach connection on different pair of ports
Multiplexing Between Levels Upward or inward multiplexing(上行复用) Multiple higher-level connections share single lower level connection oMore efficient use of lower-level service oProvides several higher-level connections where only single lower-level connection exists Downward multiplexing, or splitting(下行/分裂) Higher-level connection built on top of multiple lower level connections Traffic on higher connection divided among lower connections rEliability, performance, or efficiency.(可以提高可靠性、性 能或效率) 2376
23/76 Multiplexing Between Levels • Upward or inward multiplexing(上行/内复用) - Multiple higher-level connections share single lowerlevel connection oMore efficient use of lower-level service oProvides several higher-level connections where only single lower-level connection exists • Downward multiplexing, or splitting(下行/分裂) - Higher-level connection built on top of multiple lowerlevel connections - Traffic on higher connection divided among lower connections oReliability, performance, or efficiency.（可以提高可靠性、性 能或效率）
Transmission services Protocol may provide additional services to entities g Priority Connection basis On message basis OE.g. terminate-connection request Quality of service E.g. minimum throughput or maximum delay threshold Security Security mechanisms, restricting access These services depend on underlying transmission system and lower-level entities 24/76
24/76 Transmission Services • Protocol may provide additional services to entities • E.g.: • Priority - Connection basis - On message basis oE.g. terminate-connection request • Quality of service - E.g. minimum throughput or maximum delay threshold • Security - Security mechanisms, restricting access • These services depend on underlying transmission system and lower-level entities
互联网与因特网 互连在一起的网络要进行通信,会遇到许多问题需要解 决,如: 不同的寻址方案 不同的最大分组长度 不同的网络接入机制 不同的超时控制 不同的差错恢复方法 不同的状态报告方法 不同的路由选择技术 不同的用户接入控制 不同的服务(面向连接服务和无连接服务) 不同的管理与控制方式 2576
25/76 • 互连在一起的网络要进行通信，会遇到许多问题需要解 决，如： - 不同的寻址方案 - 不同的最大分组长度 - 不同的网络接入机制 - 不同的超时控制 - 不同的差错恢复方法 - 不同的状态报告方法 - 不同的路由选择技术 - 不同的用户接入控制 - 不同的服务（面向连接服务和无连接服务） - 不同的管理与控制方式 互联网与因特网