计算机网络 胥正川( XU Zhengchuan) 管理学院信息管理与信息系统系 办公室:思源楼708室,电话:25011237 Email:zexu@fudan.edu.cn
1 计算机网络 胥正川（XU Zhengchuan） 管理学院 信息管理与信息系统系 办公室：思源楼708室，电话：25011237 Email: zcxu@fudan.edu.cn
First Chapter Topics Covered
First Chapter Topics Covered
Network Elements: Recap Applications( the only element that users care about) Computers Clients Never talk about an Servers innovation"reducing cost, increasing speed, etc · Switches and routers without specifying Transmission lines Which element is cheaper or faster Trunk lines Access Lines For example, multiplexing Messages(Frames) only reduces the cost of trunk lines: other Wireless access points costs are not decreased
3 Network Elements: Recap • Applications (the only element that users care about) • Computers – Clients – Servers • Switches and Routers • Transmission Lines – Trunk lines – Access Lines • Messages (Frames) • Wireless Access Points Never talk about an innovation “reducing cost,” “increasing speed,” etc. without specifying which element is cheaper or faster. For example, multiplexing only reduces the cost of trunk lines; other costs are not decreased
Recap: LANs and WANs LANs transmit data within corporate sites WANS transmit data between corporate sites · Each lan or wan is a single network WAN LAN coSts are low and speeds are high WaN coSts are high and speeds are lower
4 Recap: LANs and WANs • LANs transmit data within corporate sites • WANs transmit data between corporate sites • Each LAN or WAN is a single network • LAN costs are low and speeds are high • WAN costs are high and speeds are lower WAN
Recap: Internets Most firms have multiple LANs and WANs They must create internets An internet is a collection of networks connected by routers so that any application on any host on any single network can communicate with any application on any other host on any other network in the internet Application Application LAN WAN LAN Router Router 5
5 LAN WAN LAN Recap: Internets • Most firms have multiple LANs and WANs. • They must create internets – An internet is a collection of networks connected by routers so that any application on any host on any single network can communicate with any application on any other host on any other network in the internet. Application Application Router Router