哈工大刘晓峰计算网络课件第五章.pdf

Chapter 5: The Data Link Layer Our goals:  understand principles behind data link layer services:  error detection, correction  sharing a broadcast channel: multiple access  link layer addressing  reliable data transfer, flow control: done!  instantiation and implementation of various link layer technologies 哈工大计算机学院 李全龙 Computer Networks 5: The Data link Layer 1 Link Layer  5.1 Introduction and  5.6 Hubs and switches services  5.7 PPP  5.2 Error detection  5.8 Link Virtualization: and correction ATM and MPLS  5.3Multiple access protocols  5.4 Link-Layer Addressing  5.5 Ethernet 哈工大计算机学院 李全龙 Computer Networks 5: The Data link Layer 2 Link Layer: Introduction “link” Some terminology:  hosts and routers are nodes  communication channels that connect adjacent nodes along communication path are links  wired links  wireless links  LANs  layer-2 packet is a frame, encapsulates datagram data-link layer has responsibility of transferring datagram from one node to adjacent node over a link 哈工大计算机学院 李全龙 Computer Networks 5: The Data link Layer 3 Link layer: context  Datagram transferred transportation analogy by different link  trip from Princeton to protocols over Lausanne  limo: Princeton to JFK different links:  plane: JFK to Geneva  e.g., Ethernet on first  train: Geneva to Lausanne link, frame relay on  tourist = datagram intermediate li