ECE/CS 372 Introduction to Computer Networks Lecture 1: Chapter 5 The Data Link Layer with goald understand principles behind data link layer services, instantiation and implementation of various link layer technologies. | 5: DataLink Layer 5a- 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 Overview: link layer services error detection, correction multiple access protocols and LANs link layer addressing, ARP specific link layer technologies: Ethernet hibs, bridges, switches IEEE LANs PPP ATM 5: DataLink Layer 5a- Link Layer: setting the context 5: DataLink Layer 5a- Link Layer: setting the context two physically connected devices: host-router, router-router, host-host unit of data: frame application transport network link physical network link physical M M M M H t H t H n H t H n H l M H t H n H l frame phys. link data link protocol adapter card 5: DataLink Layer 5a- Link Layer Services Framing, link access: encapsulate datagram into frame, adding header, trailer implement channel access if shared medium, ‘physical addresses’ used in frame headers to identify source, dest different from IP address! Reliable delivery between two physically connected devices: we learned how to do this already (chapter 3)! seldom used on low bit error link (fiber, some twisted pair) wireless links: high error rates Q: why both link-level and end-end reliability? 5: DataLink Layer 5a- Link Layer Services (more) Flow Control: pacing between sender and receivers Error Detection: errors caused by signal attenuation, noise. receiver detects presence of errors: signals sender for retransmission or drops frame Error Correction: receiver identifies and corrects bit error(s) without resorting to retransmission 5: DataLink Layer 5a- Link Layer: Implementation implemented in “adapter” ., PCMCIA card, Ethernet card typically includes: RAM, DSP chips, host bus interface, and link interface application transport network link . | 5: DataLink Layer 5a- 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 Overview: link layer services error detection, correction multiple access protocols and LANs link layer addressing, ARP specific link layer technologies: Ethernet hibs, bridges, switches IEEE LANs PPP ATM 5: DataLink Layer 5a- Link Layer: setting the context 5: DataLink Layer 5a- Link Layer: setting the context two physically connected devices: host-router, router-router, host-host unit of data: frame application transport network link physical network link physical M M M M H t H t H n H t H n H l M H t H n H l frame phys. link data link protocol adapter card 5: DataLink Layer 5a- Link Layer Services Framing, link access: encapsulate .
