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1、,1,虚电路交换技术,Virtual Circuit Switching,,2,分组交换-Packet Switching,数据报交换通常在网络层中使用，而虚电路交换在数据链路层中使用,,3,报文交换-Datagram Approach,Each packet is treated independently from all others,,4,虚电路交换-Virtual Circuit Approach,发送方和接收方在传输数据之前需要建立一条连接（虚电路），通常分为： 交换式SVC(Switched Virtual Circuit) 永久式PVC(Permanent Virtual Ci
2、rcuit),,5,Example: VPs and VCs,,6,地址： VPI and VCI,,7,虚电路中的数据传输,三个阶段： 建立连接 传输分组 拆除连接 数据传输-交换机需要根据数据报中携带的虚电路信息完成输入/输出端口之间的交换,,8,交换,,9,连接的建立与拆除,分为交换式虚电路和永久式虚电路两种方式 永久式虚电路无连接建立和拆除的过程,,10,交换式虚电路-Switched Virtual Circuit-三大步骤,,11,永久式虚电路-Permanent Virtual Circuit,,12,ATM网络,设计思想-Design Goals 体系结构-ATM Archit
3、ecture ATM中的交换方式-Switching ATM中的交换结构-Switch Fabrics ATM中的层次结构ATM Layers ATM中的业务类型Service Classes ATM应用- Applications,,13,Path vs Route,,14,Dedicated vs Shared,,15,Message Switching,,16,混合网络通信,The variety of packet sizes makes traffic unpredictable,,17,信元网络,Cells are interleaved so that non suffers a
4、 long delay A cell network can handle real-time transmissions Network operation is more efficient and cheaper,,18,异步 TDM,ATM uses asynchronous TDM,,19,ATM 结构,,20,虚连接,TP (Transmission Path) VP (Virtual Path) VC (Virtual Circuit),,21,Example: VPs and VCs,,22,标志符: VPI and VCI,,23,VCI in UNI and NNI,,24
5、,信元,The basic data unit in an ATM network is called a cell,,25,SVC 连接建立,,26,VP 交换: Routing,,27,VP 交换: A Conceptual View,,28,VPC 交换: Routing,,29,VPC 交换: A Conceptual View,,30,交换结构,Crossbar switch Collision, n2 cross-points Knockout switch Distributors and queues, n2 cross-points Banyan switch Log2n s
6、tages with n/2 switches at each stage Batcher-Banyan switch No internal collision,,31,Crossbar Switch,,32,Knockout Switch,,33,Banyan Switch,,34,Banyan Switch: Example(1),,35,Banyan Switch: Example(2),,36,Batcher-Banyan Switch,,37,ATM 分层结构,,38,端点设备和交换机中的ATM Layers,,39,AAL (ATM 应用适配层),AAL protocols Ac
7、cept transmission from upper-layer services (e.g., packet data) Map them into fixed-sized ATM cells Data types Constant-bit-rate (CBR) data Variable-bit-rate (VBR) data Connection-oriented packet data Connectionless packet data,,40,AAL Types,,41,AAL Categories,AAL1 CBR data: video, voice, DS-3/E-1 A
8、AL2 VBR data AAL3 Connection-oriented data AAL4 Connectionless data AAL5 Point-to-point transmission without processing SEAL (Simple and Efficient Adaptation Layer),,42,AAL1,,43,AAL2,,44,,45,AAL5,,46,ATM 层,,47,,48,PT 域,,49,服务类型,,50,Service Classes & Network Capacity,,51,服务质量Quality of Service (QoS),
9、,52,QoS 参数,User-Related Attributes SCR(Sustained Cell Rate) PCR(Peak Cell Rate) MCR(Minimum Cell Rate) CVDT(Cell Variation Delay Tolerance) Network-Related Attributes CLR(Cell Loss Ratio) CTD(Cell Transfer Delay) CDV(Cell Delay Variation) CER(Cell Error Rate),,53,ATM 广域网,,54,ATM 局域网,Connectionless versus connection-oriented Physical addresses versus virtual connection identifiers Multicasting and broadcasting delivery,,55,LANE (LAN Emulation),,56,LEC, LES, and BUS,
