CSCD 330 Network Programming Fall 2012

Size: px
Start display at page:

Download "CSCD 330 Network Programming Fall 2012"

Transcription

1 CSCD 330 Network Programming Fall 2012 Lecture 17 Link Layer Hardware and Protocols Who is this? Reading: Chapter 5 in text Some slides provided courtesy of J.F Kurose and K.W. Ross, All Rights Reserved, copyright

2 Robert (Bob) Metcalf Inventor of Ethernet Bob Metcalfe Helped build early Internet while still an undergraduate Invented Ethernet while at Xerox Palo Alto Research Center Founded 3Com Corp. Served as publisher at IDG's Infoworld Publishing Co. Wrote three books Since January 2001 has been a venture capitalist with Polaris Ventures Nice article on him if you want to read it 2

3 Introduction to Link Layer So far, Application Layer - applications interface to people Messages get delivered Transport Layer application to application Segments get delivered Network Layer destination to destination Datagrams get delivered Link Layer node to node delivery Frames are delivered 3

4 Link Layer Overview Main question at this layer How do I deliver packets or frames between two nodes in the network? Historical reasons look at other link layer schemes But, Ethernet is currently dominant technology Wireless another protocol Covered in a different chapter, in a different course and at a future time in a galaxy far away... 4

5 Link Layer 5.1 Introduction and services 5.1a NIC Cards 5.2 Error detection and correction 5.3Multiple access protocols 5.4 Link-layer Addressing 5.5 Ethernet 5

6 Link Layer - Introduction Link Layer Terms Both Hosts and routers Called nodes Communication channels connect adjacent nodes along communication path, links Wired links Wireless links Layer-2 packet is a frame encapsulates datagram Data-link layer responsible for transferring a frame from one node to adjacent node over a link 6

7 Link Layer Services The services offered by Link Layer are... Framing Link Access Reliable Delivery Flow Control Error Detection and Correction Half duplex and full duplex 7

8 Link Layer Services Framing Encapsulate datagram into frame, add header, trailer MAC (Media Access Control) addresses used in frame headers to identify source, destination Example: 00:13:02:BA:43:56 Reliable Delivery Between Adjacent Nodes Wireless links: higher error rates, Does more for reliability than wired Does compute errors Wired relies on upper layers to handle it Channel Access 8

9 Reliable Delivery Question on Reliability So, why would you need both link-level and transport layer reliability? Because dealing with reliability at two levels! Transport layer reliability For end-to-end delivery between two processes Link layer reliability For delivery between two nodes connected by a single link 9

10 Link Layer Services Continued Flow control Pacing between adjacent sending and receiving nodes 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 Half-duplex and full-duplex With half duplex, nodes at both ends of link can transmit, but not at same time 10

11 Link Layer Implementation Where is the link layer implemented? Hardware or software? Separate card or on chip? Mostly Implemented Hardware Network Interface Card (NIC) 11

12 Link Layer Implementation Alternative to actual NIC card... Built in to the motherboard

13 Where is the link layer implemented? In each host Link layer implemented in Network adaptor host schematic Network Interface Card (NIC) Ethernet card, PCMCI card, card Implements link and physical layers application transport network link link physical cpu memory controller physical host bus (e.g., PCI) Attaches to host s system buses Combination of hardware, software, firmware transmission network adapter card 13

14 Network Interface Cards (NIC) Basics A network interface card (NIC) Establishes link between computer and network, and manages link A NIC performs two crucial tasks: 1. Establishes and manages computer s network connection 2. Encodes and translates digital data into signals for outgoing messages, and Translates signals into digital computer data for incoming messages 14

15 Parallel vs. Serial Transmission NICs also manage transformation of network data s form Computer bus has series of parallel data lines (Parallel transmission) Signals traversing network media consist of a linear sequence of bits of data (serial transmission) NIC takes outgoing transmission in parallel form and recasts them into their serial equivalents For incoming messages, process reverses Converting between serial and parallel transmission, NIC has memory, to hold data temporarily 15

16 Parallel vs. Serial Transmission Bus width Bus width - number of parallel lines in a computer bus Industry Standard Architecture (ISA) bus 16-bit obsolete Peripheral Component Interconnect (PCI) bus 32- bit, 64-bit, faster 16

17 Network Interface Card Heart of card is a special purpose processor chip Does framing, link access, flow control and error detection Encryption too, for wireless Examples Intel 8254x controller implements Ethernet, Atheros AR5006 controller handles protocol Trend... Integrate adapters into motherboard, not separate cards anymore Particularly true for laptops and other small devices 17

18 Wireless Dongles However, newer devices implement wireless on a usb type dongle Can instantly add powerful wireless capability to any host g/n High Gain USB Wireless Long-Rang WiFi Network Adapter - Linksys Ultra RangePlus, b/g/a/n Dual-Band Wireless-N USB Network Adapter

19 Link Layer 5.1 Introduction and services 5.2 Error detection and correction - Later 5.3Multiple access protocols 5.4 Link-layer Addressing 5.5 Ethernet 19

20 Error Detection and Correction Transmission Error Causes Signal noise, attenuation or distortion Both on wired and wireless mediums See next slide...

21 Definitions What is Signal Attenuation? Loss of signal strength measured in decibels (db) Occurs for several reasons Range - both wireless and wired transmissions gradually dissipate in strength over longer distance Interference - on wireless networks, radio interference or physical obstructions like walls dampen communication signals Wire size - on wired networks, thinner wires suffer from higher (more) attenuation than thicker wires

22 Errors at Link Layer Two Ideas for Errors at Link Layer Error detection Parity checks, cyclic redundancy codes, checksum Error correction Send redundant information with frame When receiving frame incorrectly, receiver makes educated guess about the original frame

23 Error Detection Error Detection Lets Receiver Determine whether received message has been corrupted Checksum simplest method Checksum, function of message, gets appended to message Receiver uses same function to calculate checksum of received message and compare it with appended checksum

24 Internet Checksum Goal: Detect errors (e.g., flipped bits) in transmitted packet (note: used at transport layer only) Sender: Treat segment contents as sequence of 16-bit integers Checksum: addition (1 s complement sum) of segment contents Sender puts checksum value into UDP checksum field Receiver: Compute checksum of received segment Check if computed checksum equals checksum field value: NO - error detected YES - no error detected DataLink Layer 24

25 Error Detection Parity Checking Even Parity If you get odd number of bits including parity bit > A bit changed in transmission Single parity bit is an error detecting code, Not an error correcting code No way to determine which bit is corrupted Two-dimensional parity checks parity of both column and row, pinpoints error and allows for correction 25

26 Parity Checking Simplest Technique Single Bit Parity: Detect single bit errors Two Dimensional Bit Parity: Detect and correct single bit errors s Add a 1 Simple detection For Even Parity Number of 1 s in data + parity bit must be an Even number Can locate and correct errors 26

27 Parity Checking Comment Is a limit to parity schemes A parity bit only guaranteed to detect an odd number of bit errors One, three, five, and so forth If even number of bits (two, four, six and so on) are flipped, the parity bit appears to be correct, even though the data is corrupt This is for even parity Odd parity will have the reverse problem 27

28 Checksumming Cyclic Redundancy Check (CRC) Want algorithm detects some number of changed bits Ideally... implemented in hardware CRC Scheme CRC algorithms treat message as an enormous binary number, Divide it by another fixed binary number, Make remainder from this division the checksum Widely used in practice (Ethernet, WiFi, ATM) It has better powers of detection than bit parity or checksums uses entire number, handle more bit errors nice example below 28

29 Link Layer 5.1 Introduction and services 5.2 Error detection and correction 5.3 Multiple access protocols 5.4 Link-layer Addressing 5.5 Ethernet 29

30 Access Links and Protocols Two types of links Point-to-point PPP for dial-up access Point-to-Point link between Ethernet switch and host Broadcast (shared wire or medium) Old-fashioned Ethernet wireless LAN Satellite shared wire (e.g., shared RF cabled non-switch Ethernet) (e.g., WiFi) shared RF (satellite) humans at a cocktail party (shared air, acoustical) 30

31 Communication Between Nodes Point to Point Links These are dedicated channels between a node and switch or modem No need to share the link Broadcast Links Multiple sending and receiving nodes all connected to single broadcast channel Central problem at link layer How to share the link between nodes Must coordinate access between competing nodes Known as Multiple Access Problem

32 Multiple Access Problem Question is How do you fairly share the medium at the Link level? Everyone is connected to same network All want to send their data all the time. How do we fairly share the medium?

33 Multiple Access Protocols Idea is... can send and receive in both directions single shared broadcast channel Two or more simultaneous transmissions by nodes means interference Collision if node receives two or more signals at the same time gibberish, must retransmit, BAD! Multiple Access Protocol Distributed algorithm, determines how nodes share channel, i.e., determine when node can transmit Communication about channel sharing must use channel itself! No out-of-band channel for coordination 33

34 Multiple Access protocols Humans have following rules, speaking Give everyone a chance to speak Don t speak until you are spoken to Don t monopolize the conversation Raise your hand if you have a question Don t interrupt when someone is speaking Don t fall asleep when someone is talking Even in class! 34

35 Ideal Multiple Access Protocol Rules - Broadcast Channel, Rate = R bps 1. When one node wants to transmit, can send at full rate R 2. When M nodes want to transmit, each can send at average rate R/M... Fair 3. Fully decentralized No special node to coordinate transmissions No synchronization of clocks, slots 4. Simple In a perfect world... 35

36 Examine Following Strategies Look at each of the strategies and see how close each meets the IDEAL Multiple Access Channel properties...

37 Multiple Access Protocols: A Taxonomy Three broad classes: 1.Channel Partitioning Divide channel into smaller pieces Time slots, frequency, code division Allocate piece to node for exclusive use 2. Random Access Channel not divided, allow collisions Recover from collisions 3. Taking turns Nodes take turns, but nodes with more to send can take longer turns 37

38 Channel Partitioning

39 Channel Partitioning Protocols: TDMA TDMA: Time Division Multiple Access Access to channel in "rounds" Each station gets fixed length slot Length = packet transit time, in each round Whats the problem? Unused slots wasted Example: 6-station LAN, 1,3,4 have pkt, slots 2,5,6 idle 6-slot frame

40 TDMA: Time Division Multiple Access Analogy Take turns talking Fix each person a time slot All get a turn even when they have nothing to say Our class 5 slot limit Daryl, Jessica Alfredo Zieb Donny Talks Silent Talks Silent Talks Wasted two slots where others could have had useful things to say 40

41 Channel Partitioning Protocols: FDMA FDMA: frequency division multiple access Channel spectrum divided into frequency bands Each station assigned fixed frequency band Whats the problem? Some frequency bands are idle, limited to your band Example: 6-station LAN, 1,3,4 have pkt, frequency bands 2,5,6 idle FDM cable frequency bands time 41

42 Random Access Protocols

43 Broadcast Networks Data Link Layer Broadcast networks Single shared medium, simpler, no routing, Messages received by all stations, flat address When users try to transmit messages into medium, potential conflict MAC is needed to orchestrate the transmission from various users Old fashioned Ethernet LAN is a typical broadcast network Multiple Access Protocols allow sharing channel 43

44 Random Access Protocols When node has packet to send Transmit at full channel data rate R No a priori coordination among nodes Two or more transmitting nodes - collision Random access Medium Access Control (MAC) protocol specifies Key Problems How to detect collisions How to recover from collisions Examples Slotted ALOHA ALOHA CSMA, CSMA/CD, CSMA/CA 44

45 Aloha Protocol Simple protocol developed by Norman Abramson and colleagues at University of Hawaii, in 1968 Used low-cost amateur radio-like systems to create a computer network linking distributed campuses of the University Protocol allows every system to send a frame if its ready to send Based on a shared medium network This was basis for Ethernet!!!!

46 ALOHA Topology Broadcast medium with multiple stations Aloha Protocol When station has data, it transmits immediately Does not check if channel is busy Receivers ACK all packets No ACK = collision Wait a random time and retransmit 46

47 Pure ALOHA In pure ALOHA, frames are transmitted at completely arbitrary times.

48 48 Aloha, Simple but Radical Previous attempts all partitioned channel TDMA, FDMA, etc. Aloha optimized common case A few senders Dealt with collisions through retries

49 49 Trade-off Compared to TDMA In TDMA, you always have to wait your turn Delay proportional to number of sites In Aloha, can send immediately Aloha gives much lower delays, at the price of lower utilization (as we will see)

50 Slotted ALOHA Improvement on Aloha Assumptions All frames same size Time divided into equal size slots Time to transmit 1 frame Nodes transmit only at slot beginning Nodes are now synchronized If 2 or more nodes transmit in slot, all nodes detect collision 50

51 Slotted ALOHA Operation When node obtains fresh frame, transmits in next slot If no collision, node can send new frame in next slot If collision, node retransmits frame in each subsequent slot with probability p until success Probability is key and is between 0 and 1

52 Slotted ALOHA Probability is key Probability p means each node independently tosses a coin, heads or tails P says how likely it is node gets a head Node transmits under this event (1-p) is the probability of getting tail on a coin Means node skips a slot and tosses again in next slot 52

53 Slotted Aloha C collision E empty S - Success

54 Slotted ALOHA C collision E empty S - Success Pros Single active node can continuously transmit at full rate of channel Highly decentralized: Slots in nodes need to be in sync Simple Takes 9 slots Cons Collisions, wasting slots Idle slots Nodes may be able to detect collision in less than time to transmit packet Clock synchronization 54

55 Slotted Aloha efficiency Whats the Efficiency of Aloha? Efficiency : long-run fraction of successful slots (many nodes, all with many frames to send) Suppose: N nodes with many frames to send, each transmits in slot with probability p Probability that given node has success in a slot = p(1- p) N-1 Prob that any node has a success = Np(1-p) N-1 Max efficiency: find p* that maximizes, successful nodes Np(1-p) N-1 For many nodes, take limit of Np*(1-p*) N-1 as N goes to infinity, gives: Max efficiency = 1/e =.37 At best: channel used for useful transmissions 37% of time!! 55

56 Slotted ALOHA Throughput versus offered traffic for ALOHA systems.

57 57 CSMA (Carrier Sense Multiple Access) Max throughput achievable by slotted ALOHA is CSMA improved throughput compared to Aloha protocols. Big Improvement... Listen before you speak! Listens to the channel before transmitting a packet (avoid avoidable collisions)

58 Assumptions with CSMA Networks 1. Constant length packets 2. No errors, except those caused by collisions 3. Each host can sense the transmissions of all other hosts 4. The propagation delay is small compared to the transmission time 58

59 CSMA (Carrier Sense Multiple Access ) CSMA: Listen before transmit: If channel sensed idle Transmit entire frame If channel sensed busy Defer transmission Human analogy: Don t interrupt others! 59

60 CSMA collisions spatial layout of nodes Collisions can still occur: propagation delay means two nodes may not hear each other s transmission Collision: entire packet transmission time wasted 60

61 CSMA/CD (Collision Detection) CSMA/CD: Carrier sensing, deferral as in CSMA Collisions detected within short time Colliding transmissions aborted, reduces channel wastage Collision Detection Easy in wired LANs Measure signal strengths, compare transmitted and received signals Difficult in wireless LANs: received signal strength overwhelmed by local transmission strength 61

62 CSMA/CD collision detection 62

63 63 CSMA/CD Sense the channel If idle, transmit immediately If busy, wait until the channel becomes idle Collision detection Abort a transmission immediately if a collision is detected Try again later after waiting a random amount of time Will revisit this later when we describe Ethernet...

64 Taking Turns 64

65 Taking Turns MAC protocols Polling: Master node invites slave nodes to transmit in turn Typically used with dumb slave devices Bluetooth uses polling Concerns: Polling overhead Latency Single point of failure (master) data slaves data poll master 65

66 Token Passing Protocols Token Ring protocol was developed by IBM mid-1980s Access method involves token-passing In Token Ring, computers are connected so that signal travels around the network from one computer to another in a logical ring A single electronic token moves around ring from one computer to the next If computer does not have information to transmit, it simply passes the token on to the next workstation If computer wishes to transmit and receives an empty token, it attaches data to the token

67 Token Passing Protocols Token Ring protocol requires a star-wired ring using twisted pair or fiber optic cable It operates, transmission speeds of 4 Mbps or 16 Mbps Due to the increasing popularity of Ethernet, Use of Token Ring in decreased dramatically

68 Taking Turns MAC protocols Token passing: Control token passed from one node to next sequentially. Token message Concerns: Token overhead Latency Single point of failure (token) (nothing to send) T T data 68

69 Summary of Protocols Channel partitioning, by time, frequency or code Time Division, Frequency Division Random access (dynamic), ALOHA, S-ALOHA, CSMA, CSMA/CD Carrier sensing: easy in some technologies (wire), hard in others (wireless) CSMA/CD used in Ethernet CSMA/CA used in Taking turns Polling from central site, token passing Bluetooth, FDDI, IBM Token Ring 69

70 End No Lab this week. Take-home Final will be put up on Wednesday 70

CSCD 330 Network Programming

CSCD 330 Network Programming CSCD 330 Network Programming Spring 2018 Lecture 17 Link Layer Hardware and Protocols Who is this? Reading: Chapter 5 in text Some slides provided courtesy of J.F Kurose and K.W. Ross, All Rights Reserved,

More information

Chapter 5 Link Layer and LANs

Chapter 5 Link Layer and LANs Chapter 5 Link Layer and LANs Computer Networking: A Top Down Approach 4 th edition. Jim Kurose, Keith Ross Addison-Wesley, July 2007. All material copyright 1996-2007 J.F Kurose and K.W. Ross, All Rights

More information

CS 455/555 Intro to Networks and Communications. Link Layer

CS 455/555 Intro to Networks and Communications. Link Layer CS 455/555 Intro to Networks and Communications Link Layer Dr. Michele Weigle Department of Computer Science Old Dominion University mweigle@cs.odu.edu http://www.cs.odu.edu/~mweigle/cs455-s13 1 Link Layer

More information

The Link Layer and LANs. Chapter 6: Link layer and LANs

The Link Layer and LANs. Chapter 6: Link layer and LANs The Link Layer and LANs EECS3214 2018-03-14 4-1 Chapter 6: Link layer and LANs our goals: understand principles behind link layer services: error detection, correction sharing a broadcast channel: multiple

More information

Chapter 5: Link layer

Chapter 5: Link layer Chapter 5: Link layer our goals: v understand principles behind link layer services: error detection, correction sharing a broadcast channel: multiple access link layer addressing local area networks:

More information

CMPE 150/L : Introduction to Computer Networks. Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 16

CMPE 150/L : Introduction to Computer Networks. Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 16 CMPE 150/L : Introduction to Computer Networks Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 16 1 Final project demo Please do the demo next week to the TAs. So basically you may need

More information

CSC 4900 Computer Networks: The Link Layer

CSC 4900 Computer Networks: The Link Layer CSC 4900 Computer Networks: The Link Layer Professor Henry Carter Fall 2017 Last Time We talked about intra-as routing protocols: Which routing algorithm is used in RIP? OSPF? What techniques allow OSPF

More information

Data Link Layer: Multi Access Protocols

Data Link Layer: Multi Access Protocols Digital Communication in the Modern World Data Link Layer: Multi Access Protocols http://www.cs.huji.ac.il/~com1 com1@cs.huji.ac.il Some of the slides have been borrowed from: Computer Networking: A Top

More information

ECE 4450:427/527 - Computer Networks Spring 2017

ECE 4450:427/527 - Computer Networks Spring 2017 ECE 4450:427/527 - Computer Networks Spring 2017 Dr. Nghi Tran Department of Electrical & Computer Engineering Lecture 5.4: Multiple Access Protocols Dr. Nghi Tran (ECE-University of Akron) ECE 4450:427/527

More information

CSC 401 Data and Computer Communications Networks

CSC 401 Data and Computer Communications Networks CSC 401 Data and Computer Communications Networks Link Layer: Intro, Errors, Multiple Access Sec 6.1, 6.2, 6.3 Prof. Lina Battestilli Fall 2017 Chapter 6: Link layer Goals: understand principles behind

More information

Outline. Introduction to Networked Embedded Systems - Embedded systems Networked embedded systems Embedded Internet - Network properties

Outline. Introduction to Networked Embedded Systems - Embedded systems Networked embedded systems Embedded Internet - Network properties Outline Introduction to Networked Embedded Systems - Embedded systems Networked embedded systems Embedded Internet - Network properties Layered Network Architectures - OSI framework descriptions of layers

More information

Lecture 8 Link Layer: functionality, error detection, media access algorithm

Lecture 8 Link Layer: functionality, error detection, media access algorithm Lecture 8 Link Layer: functionality, error detection, media access algorithm From Kurose & Ross Book slightly modified by Romaric Duvignau duvignau@chalmers.se Thanks and enjoy! JFK/KWR All material copyright

More information

Chapter 5 Link Layer. Computer Networking: A Top Down Approach. 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012

Chapter 5 Link Layer. Computer Networking: A Top Down Approach. 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Chapter 5 Link Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and can

More information

Lecture 19. Principles behind data link layer services Framing Multiple access protocols

Lecture 19. Principles behind data link layer services Framing Multiple access protocols Link Layer Lecture 19 Principles behind data link layer services Framing Multiple access protocols ALOHA *The slides are adapted from ppt slides (in substantially unaltered form) available from Computer

More information

Topics. Link Layer Services (more) Link Layer Services LECTURE 5 MULTIPLE ACCESS AND LOCAL AREA NETWORKS. flow control: error detection:

Topics. Link Layer Services (more) Link Layer Services LECTURE 5 MULTIPLE ACCESS AND LOCAL AREA NETWORKS. flow control: error detection: 1 Topics 2 LECTURE 5 MULTIPLE ACCESS AND LOCAL AREA NETWORKS Multiple access: CSMA/CD, CSMA/CA, token passing, channelization LAN: characteristics, i basic principles i Protocol architecture Topologies

More information

Link Layer and LANs 안상현서울시립대학교컴퓨터 통계학과.

Link Layer and LANs 안상현서울시립대학교컴퓨터 통계학과. Link Layer and LANs 안상현서울시립대학교컴퓨터 통계학과 ahn@venus.uos.ac.kr Data Link Layer Goals: understand principles behind data link layer services: error detection, correction sharing a broadcast channel: multiple

More information

CS 43: Computer Networks. 27: Media Access Contd. December 3, 2018

CS 43: Computer Networks. 27: Media Access Contd. December 3, 2018 CS 43: Computer Networks 27: Media Access Contd. December 3, 2018 Last Class The link layer provides lots of functionality: addressing, framing, media access, error checking could be used independently

More information

Links. CS125 - mylinks 1 1/22/14

Links. CS125 - mylinks 1 1/22/14 Links 1 Goals of Today s Lecture Link-layer services Encoding, framing, and error detection Error correction and flow control Sharing a shared media Channel partitioning Taking turns Random access Shared

More information

CS 43: Computer Networks Media Access. Kevin Webb Swarthmore College November 30, 2017

CS 43: Computer Networks Media Access. Kevin Webb Swarthmore College November 30, 2017 CS 43: Computer Networks Media Access Kevin Webb Swarthmore College November 30, 2017 Multiple Access Links & Protocols Two classes of links : point-to-point dial-up access link between Ethernet switch,

More information

1-1. Switching Networks (Fall 2010) EE 586 Communication and. November 8, Lecture 30

1-1. Switching Networks (Fall 2010) EE 586 Communication and. November 8, Lecture 30 EE 586 Communication and Switching Networks (Fall 2010) Lecture 30 November 8, 2010 1-1 Announcements Quiz on Wednesday Next Monday hands-on training on Contiki OS Bring your laptop 4-2 Multiple Access

More information

CC451 Computer Networks

CC451 Computer Networks CC451 Computer Networks Lecture 9 Link Layer 5: DataLink Layer 5-1 Chapter 5 Link Layer and LANs A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students,

More information

Lecture 6. Data Link Layer (cont d) Data Link Layer 1-1

Lecture 6. Data Link Layer (cont d) Data Link Layer 1-1 Lecture 6 Data Link Layer (cont d) Data Link Layer 1-1 Agenda Continue the Data Link Layer Multiple Access Links and Protocols Addressing Data Link Layer 1-2 Multiple Access Links and Protocols Two types

More information

Links Reading: Chapter 2. Goals of Todayʼs Lecture. Message, Segment, Packet, and Frame

Links Reading: Chapter 2. Goals of Todayʼs Lecture. Message, Segment, Packet, and Frame Links Reading: Chapter 2 CS 375: Computer Networks Thomas Bressoud 1 Goals of Todayʼs Lecture Link-layer services Encoding, framing, and error detection Error correction and flow control Sharing a shared

More information

Computer Networks. Today. Principles of datalink layer services Multiple access links Adresavimas, ARP LANs Wireless LANs VU MIF CS 1/48 2/48

Computer Networks. Today. Principles of datalink layer services Multiple access links Adresavimas, ARP LANs Wireless LANs VU MIF CS 1/48 2/48 Computer Networks VU MIF CS 1/48 Today Principles of datalink layer services Multiple access links Adresavimas, ARP LANs Wireless LANs 2/48 1 Link layer: introduction terminology: hosts and routers: nodes

More information

Chapter 6 The Link Layer and LANs

Chapter 6 The Link Layer and LANs Chapter 6 The Link Layer and LANs A note on the use of these Powerpoint slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the

More information

Chapter V: Link Layer

Chapter V: Link Layer Chapter V: Link Layer UG3 Computer Communications & Networks (COMN) Myungjin Lee myungjin.lee@ed.ac.uk Slides copyright of Kurose and Ross Link layer services framing, link access: encapsulate datagram

More information

Lecture 8 The Data Link Layer part I. Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it

Lecture 8 The Data Link Layer part I. Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it Lecture 8 The Data Link Layer part I Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it Link Layer: setting the context two physically connected devices: host-router, router-router,

More information

Link layer, LANs: outline. Chapter 5-1 Link Layer. Link layer: introduction. Link layer services

Link layer, LANs: outline. Chapter 5-1 Link Layer. Link layer: introduction. Link layer services Chapter 5 Link Layer Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Link layer, LANs: outline 5.1 introduction, services 5.2 error detection, correction

More information

Chapter 5 Link Layer and LANs

Chapter 5 Link Layer and LANs Chapter 5 Link Layer and LANs A note on the use of these ppt slides: All material copyright 1996-2007 J.F Kurose and K.W. Ross, All Rights Reserved Computer Networking: A Top Down Approach 4 th edition.

More information

Goals of Today s Lecture. Adaptors Communicating

Goals of Today s Lecture. Adaptors Communicating Goals of Today s Lecture EE 122: Link Layer Ion Stoica TAs: Junda Liu, DK Moon, David Zats http://inst.eecs.berkeley.edu/~ee122/ (Materials with thanks to Vern Paxson, Jennifer Rexford, and colleagues

More information

Lecture 6 The Data Link Layer. Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it

Lecture 6 The Data Link Layer. Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it Lecture 6 The Data Link Layer Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it Link Layer: setting the context two physically connected devices: host-router, router-router, host-host,

More information

CMPE 150: Introduction to Computer Networks

CMPE 150: Introduction to Computer Networks CMPE 150: Introduction to Computer Networks Katia Obraczka Computer Engineering UCSC Baskin Engineering Lecture 18 Project Deliverables: Project demo. Code (documented). Demo schedule: Judith: Monday 03.18

More information

Module 10 Data Link Layer CS655! 10-1!

Module 10 Data Link Layer CS655! 10-1! Module 10 Data Link Layer CS655! 10-1! Please note: Most of these slides come from this book. Note their copyright notice below! A note on the use of these ppt slides: We re making these slides freely

More information

Message, Segment, Packet, and Frame Link-layer services Encoding, framing, error detection, transmission control Error correction and flow control

Message, Segment, Packet, and Frame Link-layer services Encoding, framing, error detection, transmission control Error correction and flow control Links EE 122: Intro to Communication Networks Fall 2007 (WF 4-5:30 in Cory 277) Vern Paxson TAs: Lisa Fowler, Daniel Killebrew & Jorge Ortiz http://inst.eecs.berkeley.edu/~ee122/ Announcements Homework

More information

Adaptors Communicating. Link Layer: Introduction. Parity Checking. Error Detection. Multiple Access Links and Protocols

Adaptors Communicating. Link Layer: Introduction. Parity Checking. Error Detection. Multiple Access Links and Protocols Link Layer: Introduction daptors ommunicating Terminology: hosts and routers are nodes communication channels that connect adjacent nodes along communication path are links wired links wireless links LNs

More information

transferring datagram from one node data-link layer has responsibility of to adjacent node over a link 5-1 TDTS06 Computer networks

transferring datagram from one node data-link layer has responsibility of to adjacent node over a link 5-1 TDTS06 Computer networks TDTS06 Computer networks Lecture 7: The link layer I Link Layer: Introduction Some terminology: hosts and routers are nodes communication channels that connect adjacent nodes along communication path are

More information

Data Link Layer: Overview, operations

Data Link Layer: Overview, operations Data Link Layer: Overview, operations Chapter 3 1 Outlines 1. Data Link Layer Functions. Data Link Services 3. Framing 4. Error Detection/Correction. Flow Control 6. Medium Access 1 1. Data Link Layer

More information

Multiple Access Links and Protocols

Multiple Access Links and Protocols Multiple Access Links and Protocols Two types of links : point-to-point PPP for dial-up access point-to-point link between Ethernet switch and host broadcast (shared wire or medium) old-fashioned Ethernet

More information

CS 3516: Computer Networks

CS 3516: Computer Networks Welcome to CS 3516: Computer Networks Prof. Yanhua Li Time: 9:00am 9:50am M, T, R, and F Location: AK219 Fall 2018 A-term 1 Some slides are originally from the course materials of the textbook Computer

More information

Link Layer and LANs. CMPS 4750/6750: Computer Networks

Link Layer and LANs. CMPS 4750/6750: Computer Networks Link Layer and LANs CMPS 4750/6750: Computer Networks 1 Outline overview (6.1) multiple access (6.3) link addressing: ARP (6.4.1) a day in the life of a web request (6.7) 2 Link layer: introduction terminology:

More information

Lecture 5 The Data Link Layer. Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it

Lecture 5 The Data Link Layer. Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it Lecture 5 The Data Link Layer Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it Link Layer: setting the context two physically connected devices: host-router, router-router, host-host,

More information

Physical Layer. Medium Access Links and Protocols. Point-to-Point protocols. Modems: Signaling. Modems Signaling. Srinidhi Varadarajan

Physical Layer. Medium Access Links and Protocols. Point-to-Point protocols. Modems: Signaling. Modems Signaling. Srinidhi Varadarajan P Physical Layer Srinidhi Varadarajan Medium Access Links and Protocols Three types of links : point-to-point (single wire, e.g. PPP, SLIP) broadcast (shared wire or medium; e.g, Ethernet, Wavelan, etc.)

More information

Broadcast Links, Addressing and Media Access Control. Link Layer B. Link and Physical Layers. MAC Addresses

Broadcast Links, Addressing and Media Access Control. Link Layer B. Link and Physical Layers. MAC Addresses roadcast Links, ddressing and Media ccess Control Message M C Message M Link Layer In a broadcast, there are two additional issues that must be resolved How do the nodes agree on who gets to use the next?

More information

Medium Access Control

Medium Access Control Medium Access Control All material copyright 1996-2009 J.F Kurose and K.W. Ross, All Rights Reserved 5: DataLink Layer 5-1 Link Layer Introduction and services Multiple access protocols Ethernet Wireless

More information

Adaptors Communicating. Link Layer: Introduction. Parity Checking. Error Detection. Multiple Access Links and Protocols

Adaptors Communicating. Link Layer: Introduction. Parity Checking. Error Detection. Multiple Access Links and Protocols Link Layer: Introduction daptors ommunicating hosts and routers are nodes links connect nodes wired links wireless links layer-2 packet is a frame, encapsulates datagram datagram controller sending host

More information

Master Course Computer Networks IN2097

Master Course Computer Networks IN2097 Chair for Network Architectures and Services Prof. Carle Department for Computer Science TU München Master Course Computer Networks IN2097 Prof. Dr.-Ing. Georg Carle Christian Grothoff, Ph.D. Dr. Nils

More information

Link Layer and Ethernet

Link Layer and Ethernet Link Layer and Ethernet 14-740: Fundamentals of Computer Networks Bill Nace Material from Computer Networking: A Top Down Approach, 6 th edition. J.F. Kurose and K.W. Ross traceroute Data Link Layer Multiple

More information

Link Layer and Ethernet

Link Layer and Ethernet Link Layer and Ethernet 14-740: Fundamentals of Computer Networks Bill Nace Material from Computer Networking: A Top Down Approach, 6 th edition. J.F. Kurose and K.W. Ross traceroute Data Link Layer Multiple

More information

Chapter V: Link Layer

Chapter V: Link Layer Chapter V: Link Layer UG3 Computer Communications & Networks (COMN) Myungjin Lee myungjin.lee@ed.ac.uk Slides copyright of Kurose and Ross Link layer: introduction terminology: hosts and routers: nodes

More information

MULTIPLE ACCESS PROTOCOLS 2. 1

MULTIPLE ACCESS PROTOCOLS 2. 1 MULTIPLE ACCESS PROTOCOLS AND WIFI 1 MULTIPLE ACCESS PROTOCOLS 2. 1 MULTIPLE ACCESS LINKS, PROTOCOLS Two types of links : point-to-point broadcast (shared wire or medium) POINT-TO-POINT PPP for dial-up

More information

Chapter 4 Network Layer

Chapter 4 Network Layer Chapter 4 Network Layer Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Slides adopted from original ones provided by the textbook authors. Network

More information

Master Course Computer Networks IN2097

Master Course Computer Networks IN2097 Chair for Network Architectures and Services Prof. Carle Department for Computer Science TU München Master Course Computer Networks IN2097 Prof. Dr.-Ing. Georg Carle Christian Grothoff, Ph.D. Chair for

More information

Chapter 6: Link layer and LANs. Link layer, LANs: outline. Link layer: introduction. Link layer: context. Link layer services (more)

Chapter 6: Link layer and LANs. Link layer, LANs: outline. Link layer: introduction. Link layer: context. Link layer services (more) Chapter 6: Link layer and LANs our goals: understand principles behind layer services: error detection, sharing a broadcast channel: multiple access layer addressing local area networks: ernet, VLANs instantiation,

More information

Computer Networks Medium Access Control. Mostafa Salehi Fall 2008

Computer Networks Medium Access Control. Mostafa Salehi Fall 2008 Computer Networks Medium Access Control Mostafa Salehi Fall 2008 2008 1 Outline Issues ALOHA Network Ethernet Token Ring Wireless 2 Main Issues Local Area Network (LAN) : Three or more machines are physically

More information

Chapter 5 Link Layer. Computer Networking: A Top Down Approach. 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012

Chapter 5 Link Layer. Computer Networking: A Top Down Approach. 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Chapter 5 Link Layer Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 All material copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved

More information

Redes de Computadores. Medium Access Control

Redes de Computadores. Medium Access Control Redes de Computadores Medium Access Control Manuel P. Ricardo Faculdade de Engenharia da Universidade do Porto 1 » How to control the access of computers to a communication medium?» What is the ideal Medium

More information

Chapter 5: DataLink Layer

Chapter 5: DataLink Layer Chapter 5: DataLink Layer Course on Computer Communication and Networks, CTH/GU The slides are adaptation of the slides made available by the authors of the course s main textbook Slides with darker background

More information

High Level View. EE 122: Ethernet and Random Access protocols. Medium Access Protocols

High Level View. EE 122: Ethernet and Random Access protocols. Medium Access Protocols High Level View EE 122: Ethernet and 802.11 Ion Stoica September 18, 2002 Goal: share a communication medium among multiple hosts connected to it Problem: arbitrate between connected hosts Solution goals:

More information

Link Layer: Introduction. Chapter 5 Link Layer & LANS. Link layer: context. Link Layer Services

Link Layer: Introduction. Chapter 5 Link Layer & LANS. Link layer: context. Link Layer Services Chapter 5 Link Layer & LNS Link Layer: Introduction Some terminology: hosts and routers are nodes communication channels that connect adjacent nodes along communication path are links wired links wireless

More information

Module 4 Data Link Layer CS655! 4-1!

Module 4 Data Link Layer CS655! 4-1! Module 4 Data Link Layer CS655! 4-1! Please note: Most of these slides come from this book. Note their copyright notice below! A note on the use of these ppt slides: We re making these slides freely available

More information

Link Layer and LANs. Our Goals. Link Layer

Link Layer and LANs. Our Goals. Link Layer Link Layer and LANs Instructor: Anirban Mahanti Office: ICT 745 Email: mahanti@cpsc.ucalgary.ca Class Location: ICT 121 Lectures: MWF 12:00 12:50 hours Notes derived from Computer Networking: A Top Down

More information

SC250 Computer Networking I. Link Layer. Prof. Matthias Grossglauser LCA/I&C.

SC250 Computer Networking I. Link Layer. Prof. Matthias Grossglauser LCA/I&C. SC250 Computer Networking I Link Layer Prof. Matthias Grossglauser LCA/I&C http://lcawww.epfl.ch 1 Objectives Understand principles behind data link layer services: sharing a broadcast channel: multiple

More information

Chapter 5 Link Layer and LANs

Chapter 5 Link Layer and LANs Chapter 5 Link Layer and LANs A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you can add, modify, and

More information

EE 122: Ethernet and

EE 122: Ethernet and EE 122: Ethernet and 802.11 Ion Stoica September 18, 2002 (* this talk is based in part on the on-line slides of J. Kurose & K. Rose) High Level View Goal: share a communication medium among multiple hosts

More information

Links. Error Detection. Link Layer. Multiple access protocols. Nodes Links Frame. Shared channel Problem: collisions How nodes share a channel

Links. Error Detection. Link Layer. Multiple access protocols. Nodes Links Frame. Shared channel Problem: collisions How nodes share a channel Link Layer Error Detection Nodes Links Frame R yclic Redundancy hecksum Parity its More about this in exercise! Data Link Layer -1 Data Link Layer -2 Links Two types of links : point-to-point broadcast

More information

Computer Network Fundamentals Spring Week 3 MAC Layer Andreas Terzis

Computer Network Fundamentals Spring Week 3 MAC Layer Andreas Terzis Computer Network Fundamentals Spring 2008 Week 3 MAC Layer Andreas Terzis Outline MAC Protocols MAC Protocol Examples Channel Partitioning TDMA/FDMA Token Ring Random Access Protocols Aloha and Slotted

More information

Links. COS 461: Computer Networks Spring Mike Freedman h?p://

Links. COS 461: Computer Networks Spring Mike Freedman h?p:// Links COS 461: Computer Networks Spring 2011 Mike Freedman h?p://www.cs.princeton.edu/courses/archive/spring11/cos461/ 2 Link layer protocols Outline Encoding, framing, error detecjon MulJple access links:

More information

Link Layer: Introduction. Chapter 5 Link Layer & LANS. Link layer: context. Link Layer Services

Link Layer: Introduction. Chapter 5 Link Layer & LANS. Link layer: context. Link Layer Services Chapter 5 Link Layer & LANS Link Layer: Introduction Some terminology: hosts and routers are nodes communication channels that connect adjacent nodes along communication path are links wired links wireless

More information

Chapter 5 Link Layer. Computer Networking: A Top Down Approach. 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012

Chapter 5 Link Layer. Computer Networking: A Top Down Approach. 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Chapter 5 Link Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and can

More information

Principles behind data link layer services

Principles behind data link layer services Data link layer Goals: Principles behind data link layer services Error detection, correction Sharing a broadcast channel: Multiple access Link layer addressing Reliable data transfer, flow control: Done!

More information

CSE 461: Multiple Access. Homework: Chapter 2, problems 1, 8, 12, 18, 23, 24, 35, 43, 46, and 58

CSE 461: Multiple Access. Homework: Chapter 2, problems 1, 8, 12, 18, 23, 24, 35, 43, 46, and 58 CSE 461: Multiple Access Homework: Chapter 2, problems 1, 8, 12, 18, 23, 24, 35, 43, 46, and 58 Next Topic Key Focus: How do multiple parties share a wire? This is the Medium Access Control (MAC) portion

More information

Medium Access Control

Medium Access Control Medium Access Control Mark Handley UCL Computer Science CS 3035/GZ01 Context: OSI Layer 2, S&K Link Layer email WWW phone...! SMTP HTTP RTP...! TCP UDP!! IP!! ethernet PPP! CSMA async sonet...! copper

More information

Goal and Outline. Computer Networking. What Do We Need? Today s Story Lecture 3: Packet Switched Networks Peter Steenkiste

Goal and Outline. Computer Networking. What Do We Need? Today s Story Lecture 3: Packet Switched Networks Peter Steenkiste Goal and Outline 15-441 15-641 Computer Networking Lecture 3: Packet Switched Networks Peter Steenkiste Fall 2016 www.cs.cmu.edu/~prs/15 441 F16 Goal: gain a basic understanding of how you can build a

More information

Links Reading: Chapter 2

Links Reading: Chapter 2 Links Reading: Chapter 2 COS 461: Computer Networks Spring 2009 (MW 1:30 2:50 in COS 105) Mike Freedman hgp://www.cs.princeton.edu/courses/archive/spring09/cos461/ 1 Goals of Today s Lecture Link layer

More information

Getting Connected (Chapter 2 Part 4) Networking CS 3470, Section 1 Sarah Diesburg

Getting Connected (Chapter 2 Part 4) Networking CS 3470, Section 1 Sarah Diesburg Getting Connected (Chapter 2 Part 4) Networking CS 3470, Section 1 Sarah Diesburg Five Problems Encoding/decoding Framing Error Detection Error Correction Media Access Five Problems Encoding/decoding Framing

More information

CSCI Computer Networks Spring 2017

CSCI Computer Networks Spring 2017 source: computer-networks-webdesign.com CSCI 6760 - Computer Networks Spring 2017 Instructor: Prof. Roberto Perdisci perdisci@cs.uga.edu These slides are adapted from the textbook slides by J.F. Kurose

More information

ECE 158A: Lecture 13. Fall 2015

ECE 158A: Lecture 13. Fall 2015 ECE 158A: Lecture 13 Fall 2015 Random Access and Ethernet! Random Access! Basic idea: Exploit statistical multiplexing Do not avoid collisions, just recover from them When a node has packet to send Transmit

More information

CSCI Computer Networks Fall 2016

CSCI Computer Networks Fall 2016 source: computer-networks-webdesign.com CSCI 4760 - Computer Networks Fall 2016 Instructor: Prof. Roberto Perdisci perdisci@cs.uga.edu These slides are adapted from the textbook slides by J.F. Kurose and

More information

CCM 4300 Lecture 5 Computer Networks, Wireless and Mobile Communications. Dr Shahedur Rahman. Room: T115

CCM 4300 Lecture 5 Computer Networks, Wireless and Mobile Communications. Dr Shahedur Rahman. Room: T115 CCM 4300 Lecture 5 Computer Networks, Wireless and Mobile Communications Dr Shahedur Rahman s.rahman@mdx.ac.uk Room: T115 1 Recap of Last Session Described the physical layer Analogue and Digital signal

More information

Link Layer: Introduction. Chapter 5 Link Layer & LANS. Link layer: context. Link Layer Services

Link Layer: Introduction. Chapter 5 Link Layer & LANS. Link layer: context. Link Layer Services Chapter 5 Link Layer & LNS Link Layer: Introduction Some terminology: hosts and routers are nodes communication channels that connect adjacent nodes along communication path are links wired links wireless

More information

Lecture 6 - Link layer. Lecture 5 Review. Link Layer. Introduction, Services. Notes. Notes. Notes. Notes. Networks and Security. Jacob Aae Mikkelsen

Lecture 6 - Link layer. Lecture 5 Review. Link Layer. Introduction, Services. Notes. Notes. Notes. Notes. Networks and Security. Jacob Aae Mikkelsen Lecture 6 - Link layer Networks and Security Jacob Aae Mikkelsen IMADA October 21, 2013 October 21, 2013 1 / 91 Lecture 5 Review Explain in short the following abbreviations, and the concept behind it.

More information

Reminder: Datalink Functions Computer Networking. Datalink Architectures

Reminder: Datalink Functions Computer Networking. Datalink Architectures Reminder: Datalink Functions 15-441 15 441 15-641 Computer Networking Lecture 5 Media Access Control Peter Steenkiste Fall 2015 www.cs.cmu.edu/~prs/15-441-f15 Framing: encapsulating a network layer datagram

More information

Principles behind data link layer services:

Principles behind data link layer services: Data link layer Goals: Principles behind data link layer services: Error detection, correction Sharing a broadcast channel: Multiple access Link layer addressing Reliable data transfer, flow control Example

More information

Principles behind data link layer services:

Principles behind data link layer services: Data link layer Goals: Principles behind data link layer services: Error detection, correction Sharing a broadcast channel: Multiple access Link layer addressing Reliable data transfer, flow control Example

More information

Chapter 5: The Data Link Layer

Chapter 5: The Data Link Layer Chapter 5: The Data Link Layer Our goals: principles behind data link layer services: error detection, correction sharing a broadcast channel: multiple access link layer addressing reliable data transfer,

More information

CS 3640: Introduction to Networks and Their Applications

CS 3640: Introduction to Networks and Their Applications CS 3640: Introduction to Networks and Their Applications Fall 2018, Lecture 7: The Link Layer II Medium Access Control Protocols Instructor: Rishab Nithyanand Teaching Assistant: Md. Kowsar Hossain 1 You

More information

CARRIER SENSE MULTIPLE ACCESS (CSMA):

CARRIER SENSE MULTIPLE ACCESS (CSMA): Lecture Handout Computer Networks Lecture No. 8 CARRIER SENSE MULTIPLE ACCESS (CSMA): There is no central control management when computers transmit on Ethernet. For this purpose the Ethernet employs CSMA

More information

CS 3640: Introduction to Networks and Their Applications

CS 3640: Introduction to Networks and Their Applications CS 3640: Introduction to Networks and Their Applications Fall 2018, Lecture 5: The Link Layer I Errors and medium access Instructor: Rishab Nithyanand Teaching Assistant: Md. Kowsar Hossain 1 You should

More information

Introduction to Computer Networks. 03 Data Link Layer Introduction

Introduction to Computer Networks. 03 Data Link Layer Introduction Introduction to Computer Networks 03 Data Link Layer Introduction Link Layer 1 Introduction and services 2 Link Layer Services 2.1 Framing 2.2 Error detection and correction 2.3 Flow Control 2.4 Multiple

More information

Chapter 5 Link Layer. Computer Networking: A Top Down Approach. 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012

Chapter 5 Link Layer. Computer Networking: A Top Down Approach. 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Chapter 5 Link Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and can

More information

Lecture 9: Bridging. CSE 123: Computer Networks Alex C. Snoeren

Lecture 9: Bridging. CSE 123: Computer Networks Alex C. Snoeren Lecture 9: Bridging CSE 123: Computer Networks Alex C. Snoeren Lecture 9 Overview Finishing up media access Ethernet Contention-free methods (rings) Moving beyond one wire Link technologies have limits

More information

CSC 8560 Computer Networks: Link Layer

CSC 8560 Computer Networks: Link Layer CSC 8560 Computer Networks: Link Layer Professor Henry Carter Fall 2017 Last Time We talked about intra-as routing protocols: Which routing algorithm is used in RIP? OSPF? What techniques allow OSPF to

More information

Multiple Access Protocols

Multiple Access Protocols Multiple Access Protocols Computer Networks Lecture 2 http://goo.gl/pze5o8 Multiple Access to a Shared Channel The medium (or its sub-channel) may be shared by multiple stations (dynamic allocation) just

More information

Medium Access Protocols

Medium Access Protocols Medium Access Protocols Summary of MAC protocols What do you do with a shared media? Channel Partitioning, by time, frequency or code Time Division,Code Division, Frequency Division Random partitioning

More information

RMIT University. Data Communication and Net-Centric Computing COSC 1111/2061/1110. Lecture 8. Medium Access Control Methods & LAN

RMIT University. Data Communication and Net-Centric Computing COSC 1111/2061/1110. Lecture 8. Medium Access Control Methods & LAN RMIT University Data Communication and Net-Centric Computing COSC 1111/2061/1110 Medium Access Control Methods & LAN Technology Slide 1 Lecture Overview During this lecture, we will Look at several Multiple

More information

Local Area Networks (LANs) SMU CSE 5344 /

Local Area Networks (LANs) SMU CSE 5344 / Local Area Networks (LANs) SMU CSE 5344 / 7344 1 LAN/MAN Technology Factors Topology Transmission Medium Medium Access Control Techniques SMU CSE 5344 / 7344 2 Topologies Topology: the shape of a communication

More information

Your Future?! Links and LANs! Regrading of Homework! Other Announcements! Goals of Todayʼs Lecture! Link-Layer Services!

Your Future?! Links and LANs! Regrading of Homework! Other Announcements! Goals of Todayʼs Lecture! Link-Layer Services! Your Future?! Who is planning to go to grad school (in CS)? Links and LANs! Who is interested in research possibilities? EE 122: Intro to Communication Networks Fall 2010 (MW 4-5:30 in 101 Barker) Scott

More information

COS 140: Foundations of Computer Science

COS 140: Foundations of Computer Science COS 140: Foundations of Computer Science ALOHA Network Protocol Family Fall 2017 Homework 2 Introduction 3 Network Protocols.......................................................... 3 Problem.................................................................

More information

Chapter 6 The Data Link layer

Chapter 6 The Data Link layer Chapter 6 The Data Link layer 6.1 introduction, services 6.2 error detection, correction 6.3 multiple access protocols 6.4 LANs addressing, ARP Ethernet layer-2 switches VLANS 6.5 link virtualization:

More information

Summary of MAC protocols

Summary of MAC protocols Summary of MAC protocols What do you do with a shared media? Channel Partitioning, by time, frequency or code Time Division, Code Division, Frequency Division Random partitioning (dynamic) ALOHA, S-ALOHA,

More information