现代通信网络 ppt课件

Virtual Circuit Network: MPLS
通信业务网(Service Network)：分类：
Switched Network：【通信交换网络】
Node Switching （节点交换 ）
• A node (switch) in a circuit switching network
• Generally on demand • Handle and acknowledge requests • Determine if destination is free • construct path
Maintain connection Disconnect
现代通信网络 Modern Telecommunication Network
Lecture 3 (CS)电路交换与软交换
北邮软件学院：陈候武
Chenhouwu@email.buptsse.cn 电话：
Communication Networks 【通信网络的分类】
Communication Network
Analog line
Central Office
Central Office
Digital Trunks 数字中继
PSTN: Public Circuit Switched Network
CS: Components 【网络组成】
• Subscriber 【用户：电话】
Devices attached to network
必须具有智能以对呼叫进行选路
Circuit Switching - Applications
• Inefficient
Channel capacity dedicated for duration of connection If no data, capacity wasted
• Set up (connection) takes time • Once connected, transfer is transparent • Developed for voice traffic (phone: 电话网)
Circuit Switching Concepts
• Digital Switch 【数字交换】
Provide transparent signal path between devices
• Network Interface 【网络接口】 • Control Unit 【控制单元】
Establish connections
Switched Communication
Network
Broadcast Communication
Network 广播，电视，卫星
Circuit-Switched (CS) - 电话
Packet Switch (PS) - 分组交换
Datagram Network: Internet: IP因特网
CS:Circuit Switch 电路交换
【Overview】
CS: Circuit Switching 【电路交换】
• Dedicated communication path between two stations 【专用/独享的通信通道】
• Three phases 【呼叫建立：3个阶段】
Some redundant connecห้องสมุดไป่ตู้ions 【冗余连接 】are desirable for reliability
• Two different switching technologies Circuit switching 【电路交换】 Packet switching 【分组交换】
incoming links
Node
outgoing links
Nodes 【交换节点】
• Nodes may connect to other nodes only, or to stations and other nodes
• Node to node links usually multiplexed 【复用】 • Network is usually partially connected
Establish Transfer Disconnect
• Must have switching capacity and channel capacity to establish connection
• Must have intelligence to work out routing
• Trunks 【中继线】
Branches between exchanges Multiplexed 【复用】
Legacy Digital Circuit Switch
Centralized Intelligence
Proprietary Code
Proprietary service deployment
Very expensive
SS7 Network
Switch Controller
Line
Trunk
Card
Card
Next Switch
Line Card
Trunk Card
Next Switch
Line Card
Trunk Card
Next Switch
Circuit Switch Elements 【电路交换组成】
• Subscriber line 【用户连线】
Local Loop 【本地环路】 Subscriber loop 【用户环路】 Connection to network Few km up to few tens of km
• Exchange / Switch 【交换机】
Switching centers End office - supports subscribers
CS：PSTN – 网络结构
PSTN – Public Switched Telephone Network Uses digital trunks between Central Office switches (CO) Uses analog line from phones to CO