Computer Networks Medium Access Control. Mostafa Salehi Fall 2008
|
|
- Marsha McGee
- 5 years ago
- Views:
Transcription
1 Computer Networks Medium Access Control Mostafa Salehi Fall
2 Outline Issues ALOHA Network Ethernet Token Ring Wireless 2
3 Main Issues Local Area Network (LAN) : Three or more machines are physically connected and communicating. Problems: How to connect them? Topology Sharing links How to address each machine? Addressing How to regulate accessing to the media? MAC (Media Access method or protocol) Collision! Different technology address each problem in different way
4 LAN Technologies Application Presentation Session Transport Network Link Physical The 7-layer OSI Model Telnet FTP SMTP IP TCP HTTP NNTP LAN-LINK TFTP UDP The 4-layer Internet Model Link layer can have two types of technologies; Point to point link like PPP where there are only 2 nodes. Broadcast link like Ethernet when there are more than nodes.
5 Data link sublayers Multiplexing Media Access (MAC) Error Detection Framing Our focus will be on MAC sublayer in this slide. The link is shared among different sender and receivers. Since every frame is simultaneously l accessed by different nodes; They are called multi access links. They are called broadcast links. (important) LAN because of limited area. We need some type of medium access rules to avoid collision
6 Ideal Multiple Access Protocol Broadcast channel of rate R bps 1. When one node wants to transmit, it can send at rate R. 2. When M nodes want to transmit, each can send at average rate R/M 3. Fully decentralized: no special node to coordinate transmissions no synchronization of clocks, slots 4. Simple
7 Goals of MAC Protocols MAC Protocols arbitrate access to a common shared channel among a population of nodes Goals: 1. Fair among users 2. High efficiency 3. Low delay 4. Fault tolerant 5. Easy to implement
8 Simple Random Complex Deterministic Examples of MAC Protocols Packet-Switched Radio Network Aloha Carrier Sense Multiple Access/Collision Detection Ethernet (IEEE 802.3) Token Passing Wireless Token Ring (IEEE 802.5) Fiber Distributed Data Interface (FDDI)
9 MAC Protocols Three broad classes: Channel Partitioning divide channel into smaller pieces (time slots, frequency, code) allocate piece to node for exclusive use Random Access channel not divided, allow collisions recover from collisions Taking turns Nodes take turns, but nodes with more to send can take longer turns Channel Reservation
10 Channel Partitioning: TDMA TDMA: time division multiple access access to channel in "rounds" each station gets fixed length slot (length = pkt trans time) in each round unused slots go idle example: 6-station LAN, 1,3,4 have pkt, slots 2,5,6 idle TDM (Time Division Multiplexing): channel divided into N time slots, one per user; inefficient with low duty cycle users and at light load
11 Channel Partitioning: FDMA FDMA: frequency division multiple access channel spectrum divided into frequency bands each station assigned fixed frequency band unused transmission time in frequency bands go idle example: 6-station LAN, 1,3,4 have pkt, frequency bands 2,5,6 idle frequency bands
12 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 MAC protocol specifies: how to detect collisions how to recover from collisions (e.g., via delayed retransmissions) Examples of random access MAC protocols: ALOHA slotted ALOHA 2008 CSMA, CSMA/CD, CSMA/CA 12
13 Central Node f0 f1 Implemented Aloha All nodes transmit on one freq. Central node relays packets on the other frequency If more than one node transmit at the same time Collision! If there is a collision, both nodes re-transmit packets
14 Pure (unslotted) ALOHA unslotted Aloha: simpler, no synchronization when frame first arrives transmit immediately collision probability increases: frame sent at ttt 0 collides with other frames sent in [t 0-1,t 1t+1]
15 Assumptions all frames have same size time is divided into equal size slots, time to transmit 1 frame nodes start to transmit frames only at beginning of slots nodes are synchronized if 2 or more nodes transmit in slot, all nodes detect collision Slotted ALOHA Operation when node obtains fresh frame, it transmits in next slot no collision, node can send new frame in next slot if collision, node retransmits frame in each subsequent slot with prob. p until success
16 Pros single active node can continuously transmit at full rate of channel highly decentralized: only slots in nodes need to be in sync simple Slotted ALOHA Cons collisions, wasting slots idle slots
17 Pure Aloha efficiency P(success by given node) = P(node transmits). P(no other node transmits in [t 0-1,t 0 ]. P(no other node transmits in [t 0,t 0 +1] = p. (1-p) N-1. (1-p) N-1 = p. (1-p) 2(N-1) choosing optimum p and then letting n -> infty... = 1/(2e) =
18 Slotted Aloha efficiency Efficiency is the long-run fraction of successful slots when there are many nodes, each with many frames to send Suppose N nodes with many frames to send, each transmits in slot with probability p prob that node 1 has success in a slot = p(1-p) N-1 prob that any node has a success = Np(1-p) N-1 For max efficiency with N nodes, find p* that maximizes Np(1-p) N-1 For many nodes, take limit of Np*(1-p*) N-1 as N goes to infinity, gives 1/e = 0.37 At best: channel used for useful transmissions 37% of time!
19 How to improve ALOHA Aloha is not efficient due to collisions. How to reduce collision and increase efficiency? Do not send any data if somebody else is already transmitting. Carrier Sense. While sending if you recognized somebody else is also transmitting, then, there is a collision. Please stop. Collision Detection
20 CSMA/CD Protocol All nodes transmit & receive on one channel Packets are of variable size. 1. Carrier Sense: Check if the line is idle before transmitting. 2. Collision Detection: If more than one node transmit. Collision! All nodes detect collision, wait for random delay. Goto 1. binary exponential backoff
21 CSMA/CD Network Size Restriction Node must be able to hear that there is a collision before its packet is transmitted completely. i.e. Packet Transmission Time > Round trip propagation time i.e. TRANSP > 2.PROP
22 Performance of CSMA/CD Assume time-slotted channel 1. Find : Probability that exactly one node transmits in a given slot, where: p = Prob{a node tries to transmit a packet in a time slot}, N = number of nodes N N 1 α( p) p(1 p) 1 dα N 1 = N(1 p) pn( N dp α max 36% 40% 1)(1 when : p) p N 2 = 1/ N
23 1-persistent CSMA CSMA Protocols Send frame whenever the channel is free if the channel is not free wait for a random time. More propagation delay results in less efficiency. Nonpersistent Sense the channel randomly. if the channel is not free wait for a random time. P-persistent Sense the channel at slot times. Whenever the channel is free send frame with p probability if the channel is not free wait for a random time
24 Persistent and Nonpersistent CSMA
25 CSMA with Collision Detection CSMA/CD can be in one of three states: contention, transmission, or idle
26 Collision-Free Protocols CSMA/CA N node sharing a single channel The basic bit-map protocol
27 CSMA/CA The binary countdown protocol. A dash indicates silence
28 Ethernet History developed by Xerox PARC in mid-1970s roots in Aloha packet-radio network standardized by Xerox, DEC, and Intel in 1978 similar to IEEE standard Uses CSMA/CD technique for Media access. Uses 10Mbps physical link originally and now extended to 100Mbps, Fast Ethernet, and recently to 1000Mbps, Gigabit Ethernet. Uses variable frame length, bytes
29 The Original Ethernet PROP TRANSP > 10Mb/s 2 PROP TRANSP l < = l / c = 1500 / µ s max = Packetsize m > 12µ s ( 12µ s) 10Mb / s = 120bits Thick copper coaxial cable In practice, minimum packet size = 512 bits. allows for extra time to detect collisions. allows for repeaters that can boost signal. Repeaters every 500m
30 The Original Ethernet Original picture drawn by Bob Metcalfe, inventor of Ethernet (1972 Xerox PARC) The Ethernet protocol is implemented in Contoroler (Adaptor)
31 Bytes: Ethernet Frame Format PreambleSFD e DA SA Type Data Pad CRC 1. Preamble: trains clock-recovery circuits 2. Start of Frame Delimiter: indicates start of frame 3. Destination Address: 48-bit globally unique address assigned by manufacturer. 1b: unicast/multicast 1b: local/global address 4. Type: Indicates protocol of encapsulated data (e.g. IP = 0x0800) 5. Pad: Zeroes used to ensure minimum frame length 6. Cyclic Redundancy Check: check sequence to detect bit errors
32 Ethernet Addresses Unique, 6 bytes or 48-bit address assigned to each adapter by manufacturer. An address with all 1s is a broadcast address. multicast: first bit is 1 In order to make the address unique, first 24 bits are assigned to manufacturers and the last 24 bits are assigned locally. Each adaptor accept the packet if the destination address is its own address, broadcast address or multicast to which this adaptor belongs
33 The 10Mb/s Ethernet Standard IEEE Different physical layer options Ethernet MAC Protocol 10Base-5 10Base-2 10Base-T 10Base-F physical layer 10: 10Mbs Base: baseband 5: 500 Meter 10Base-5: Original Ethernet: large thick coaxial cable. 10Base-2: Thin coaxial cable version. 10Base-T: Voice-grade unshielded twisted-pair Category-3 telephone cable. 10Base-F: Two optical fibers in a single cable
34 Ethernet Cabling Three kinds of Ethernet cabling. (a) 10Base5, (b) 10Base2, (c) 10Base-T
35 Cable topologies (a) Linear, (b) Spine, (c) Tree, (d) Segmented
36 Transmit Algorithm If line is idle send immediately upper bound message size of 1500 bytes must wait 9.6us between back-to-back frames If line is busy wait until idle and transmit immediately called 1-persistent
37 Algorithm (cont) If collision jam for 32 bits, then stop transmitting frame (minimum frame is 64 bytes (header + 46 bytes of data)) delay and try again 1st time: 0 or 51.2us 2nd time: 0, 51.2, or 102.4us 3rd time51.2, 102.4, or 153.6us nth time: k x 51.2us, for randomly selected k=0..2 n -1 give up after several tries (usually 16) exponential backoff
38 Increasing the data rate Increasing the data rate create the following Problem: E.g. CSMA/CD at 100Mb/s over 1500m of cable: TRANSP > 2PROP PROP = 1500 / = 6µ s TRANSP > 12µ s Packetsize 1200bits To overcome this two techniques used: Cable length limited to 100m: 8 PROP = 200 / Packetsize 160bits Increase the minimum packet length
39 4-32 plug-in line card Switched Ethernet 1-8 connector for each line card
40 Ethernet Switch Router Ethernet Switch/Bridge If only one computer per port, no collisions can take place (each cable is now a self-contained point-to-point Ethernet link). Capacity is increased: the switch can forward multiple frames to different computers at the same time. An Ethernet switch must contain buffers to hold frames during times of congestion
41 Ethernet Hub Extending LANs Combinations of Hub, switch and router Broadcasts by Hub is sensed by switch Ethernet Switch/Bridge Router
42 IEEE 802.2: Logical Link Control (a) Position of LLC. (b) Protocol formats
43 Wireless LAN (a) Hidden station problem (C B) (b) Exposed station problem (C D)
44 Collision Avoidance in Wireless MACA RTS (request to send) CTS (clear to send) (a) A sending an RTS to B. (b) B responding with a CTS to A
45 The MAC Sublayer Protocol The use of virtual channel sensing using CSMA/CA
46 Local Internetworking A configuration with four LANs and two bridges
47 Backward Learning Flooding algorithm for the first run If source LAN is the same as Destination LAN discard frame If source LAN as Destination LAN are different transmit to Destination LAN If Destination LAN is unknown use flooding algorithm
48 Spanning Tree Bridges Two parallel transparent bridges
49 Spanning Tree Bridges (a) Interconnected LANs. (b) A spanning tree covering the LANs. The dotted lines are not part of the spanning tree
50 Repeaters, Hubs, Bridges, Switches, Routers and Gateways
51 Repeaters, Hubs, Bridges, Switches, Routers and Gateways
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 informationTopics. 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 information1-1. 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 informationThe 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 informationOutline. 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 informationChapter 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 informationCMPE 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 informationChapter 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 informationData 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 informationCS 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 informationCSC 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 informationHigh 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 informationMultiple 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 informationEE 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 informationLecture 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 informationCSC 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 informationChapter 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 informationLink 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 informationLecture 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 informationCS 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 informationCS 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 informationELEC / COMP 177 Fall Some slides from Kurose and Ross, Computer Networking, 5 th Edition
ELEC / COMP 177 Fall 2011 Some slides from Kurose and Ross, Computer Networking, 5 th Edition Project #2 Due Thursday, Nov 10 th By midnight Homework #5 Due Thursday, Nov 17 th Later this semester: Homework
More informationLecture 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 informationLink 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 informationRedes 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 informationChapter 4. The Medium Access Control Sublayer
Chapter 4 The Medium Access Control Sublayer The Channel Allocation Problem Static Channel Allocation in LANs and MANs Dynamic Channel Allocation in LANs and MANs Dynamic Channel Allocation in LANs and
More informationLecture 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 informationLinks 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 informationPhysical 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 informationComputer 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 informationMultiple Access Channels
Multiple Access Channels Some Queuing Theory MAC: Aloha, ethernet Exponential backoff & friends LANs: Local Area Networks Goal: extend benefits of simple connection as far as possible Means: Share medium
More informationLecture 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 informationBroadcast 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 informationCSE 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 informationChapter 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 informationComputer Networking Lecture 5 Data link Layer Access Control. Based on slides by Peter Steenkiste Copyright, Carnegie Mellon
15-441 Computer Networking Lecture 5 Data link Layer Access Control Based on slides by Peter Steenkiste Copyright, Carnegie Mellon 2007-12 1 Datalink Functions Framing: encapsulating a network layer datagram
More informationChapter 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 informationLink 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 informationCCM 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 informationLecture 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 informationtransferring 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 informationChapter 4. The Medium Access Control Sublayer. Points and Questions to Consider. Multiple Access Protocols. The Channel Allocation Problem.
Dynamic Channel Allocation in LANs and MANs Chapter 4 The Medium Access Control Sublayer 1. Station Model. 2. Single Channel Assumption. 3. Collision Assumption. 4. (a) Continuous Time. (b) Slotted Time.
More informationMULTIPLE 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 informationCSE 461: Multiple Access Networks. This Lecture
CSE 461: Multiple Access Networks This Lecture Key Focus: How do multiple parties share a wire? This is the Medium Access Control (MAC) portion of the Link Layer Randomized access protocols: 1. Aloha 2.
More informationData 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 informationReminder: 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 informationCC451 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 informationMaster 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 informationChapter 4: The Medium Access Layer
Chapter 4: The Medium Access Layer Computer Networks Maccabe Computer Science Department The University of New Mexico September 2002 Medium Access Layer Point-to-point versus broadcast networks Broadcast
More informationLinks. 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 informationThe Medium Access Control Sublayer
The Medium Access Control Sublayer Chapter 4 Channel Allocation Problem Static channel allocation Assumptions for dynamic Assumptions for Dynamic Channel Allocation 1. Independent traffic 2. Single channel
More informationChapter 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 informationChapter 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 informationAdaptors 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 informationRaj Jain. The Ohio State University Columbus, OH
Columbus, OH 43210 Jain@CIS.Ohio-State.Edu http://www.cis.ohio-state.edu/~jain/ 3-1 Overview ISO/OSI Reference Model TCP/IP Reference Model Differences between ISO and TCP Ethernet/IEEE 802.3 LANs Interconnecting
More informationEthernet. Introduction. CSE 3213 Fall 2011
Ethernet CSE 3213 Fall 2011 19 October 2011 1 Introduction Rapid changes in technology designs Broader use of LANs New schemes for high-speed LANs High-speed LAN technologies: Fast and gigabit Ethernet
More informationCMPE 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 informationReview. Error Detection: CRC Multiple access protocols. LAN addresses and ARP Ethernet. Slotted ALOHA CSMA/CD
Review Error Detection: CRC Multiple access protocols Slotted ALOHA CSMA/CD LAN addresses and ARP Ethernet Some slides are in courtesy of J. Kurose and K. Ross Overview Ethernet Hubs, bridges, and switches
More informationLecture 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 informationProtocols for Multiaccess Networks
Protocols for Multiaccess Networks Hosts broadcast packets When a collision occurs, all transmitted packets are lost Lost packets have to be retransmitted => Need Multiaccess Protocol Model - Slotted Aloha
More informationChapter 12 Multiple Access 12.1
Chapter 12 Multiple Access 12.1 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 12.2 Figure 12.1 Data link layer divided into two functionality-oriented sublayers
More informationChapter 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 informationMedium Access Control Sublayer
Wireless (WLAN) Medium Access Control Sublayer Mahalingam Mississippi State University, MS October 20, 2014 Outline Medium Access Protocols Wireless (WLAN) 1 Medium Access Protocols ALOHA Slotted ALOHA
More informationChapter 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 informationCOS 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 informationModule 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 informationLink 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 informationMedium 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 informationData Link Layer, Part 5. Medium Access Control
CS 455 Medium Access Control, Page 1 Data Link Layer, Part 5 Medium Access Control These slides are created by Dr. Yih Huang of George Mason University. Students registered in Dr. Huang s courses at GMU
More informationSC250 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 informationPart3. Local Area Networks (LAN)
Part3 Local Area Networks (LAN) LAN Characteristics Small geographical area Relatively high data rate Single management Topologies Bus, star, ring Specifications at physical and data link layer mostly
More informationGoals 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 informationAccess Technologies! Fabio Martignon
Access Technologies! Fabio Martignon 1 LAN Ethernet - IEEE 802.3 Broadcast Bus Capacity=10 Mb/s Xerox-Intel-Digital inventors Standardized at the beginning of the 80s as IEEE 802.3 Big Success and Several
More informationCOMP/ELEC 429/556 Introduction to Computer Networks
COMP/ELEC 429/556 Introduction to Computer Networks Broadcast network access control Some slides used with permissions from Edward W. Knightly, T. S. Eugene Ng, Ion Stoica, Hui Zhang T. S. Eugene Ng eugeneng
More informationDirect Link Networks (II)
Direct Link Networks (II) Computer Networking Lecture 03 HKU SPACE Community College January 30, 2012 HKU SPACE CC CN Lecture 03 1/25 Outline Reliable Link Service Stop-and-Wait Sliding Window Media Access
More informationEthernet. Typical Setup. Names. Operations. Operations Switch: No Collisions EECS 122. Hub: Single Collision Domain
Overview Physical Layer MAC Bridged VLAN Link Aggregation XON/XOFF 802.11 Summary Overview Typical Setup Names Operations Perspective TOC TOC Overview Typical Setup Names Structure [rate][modulation][media
More informationNetworking Technologies and Applications
Networking Technologies and Applications Rolland Vida BME TMIT September 23, 2016 Aloha Advantages: Different size packets No need for synchronization Simple operation If low upstream traffic, the solution
More informationComputer Networks. Medium Access Sublayer (Part I)
Computer Networks Medium Access Sublayer (Part I) Topics Introduction Multiple Access Protocols Ethernet Wireless LAN Protocols Bridges Misc (brief) High-Speed LANs Satellite Networks Introduction Remember,
More informationOutline: Connecting Many Computers
Outline: Connecting Many Computers Last lecture: sending data between two computers This lecture: link-level network protocols (from last lecture) sending data among many computers 1 Review: A simple point-to-point
More informationSummary 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 informationECE 4450:427/527 - Computer Networks Spring 2017
ECE 4450:427/527 - Computer Networks Spring 2017 Dr. Nghi Tran Department of Electrical & Computer Engineering Lecture 5.5: Ethernet Dr. Nghi Tran (ECE-University of Akron) ECE 4450:427/527 Computer Networks
More informationComputer 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 informationLink Layer: Retransmissions
Link Layer: Retransmissions Context on Reliability Where in the stack should we place reliability functions? Application Transport Network Link Physical CSE 461 University of Washington 2 Context on Reliability
More informationData and Computer Communications. Chapter 11 Local Area Network
Data and Computer Communications Chapter 11 Local Area Network LAN Topologies Refers to the way in which the stations attached to the network are interconnected Bus Topology Used with multipoint medium
More informationJaringan Komputer. Broadcast Network. Outline. MAC (Medium Access Control) Channel Allocation Problem. Dynamic Channel Allocation
Broadcast Network Jaringan Komputer Medium Access Control Sublayer 2 network categories: point-to-point connections broadcast channels Key issue in broadcast network: how to determine who gets to use the
More informationLAN PROTOCOLS. Beulah A AP/CSE
LAN PROTOCOLS Beulah A AP/CSE IEEE STANDARDS In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards to enable intercommunication among equipment from a variety
More informationLink 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 informationInternet Architecture and Protocol
Internet Architecture and Protocol Set# 03 Local Area Networks Delivered By: Engr Tahir Niazi Layer Reference to Protocol Application Presentation Session Application FTP, Telnet, SMTP, HTTP, SNMP.. Transport
More informationMessage, 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 informationRMIT 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 informationMedium 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 informationMedium Access Control. CSCI370 Lecture 5 Michael Hutt New York Institute of Technology
Medium Access Control CSCI370 Lecture 5 Michael Hutt New York Institute of Technology The Data Link Layer Logical Link Control (LLC) IEEE 802.2 Standard RFC 1042 Provides three service options Unreliable
More informationData Link Layer, Part 3 Medium Access Control. Preface
Data Link Layer, Part 3 Medium Access Control These slides are created by Dr. Yih Huang of George Mason University. Students registered in Dr. Huang's courses at GMU can make a single machine-readable
More informationLocal 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 informationCHAPTER 7 MAC LAYER PROTOCOLS. Dr. Bhargavi Goswami Associate Professor & Head Department of Computer Science Garden City College
CHAPTER 7 MAC LAYER PROTOCOLS Dr. Bhargavi Goswami Associate Professor & Head Department of Computer Science Garden City College MEDIUM ACCESS CONTROL - MAC PROTOCOLS When the two stations transmit data
More informationHousekeeping. Fall /5 CptS/EE 555 1
Housekeeping Lab access HW turn-in Jin? Class preparation for next time: look at the section on CRCs 2.4.3. Be prepared to explain how/why the shift register implements the CRC Skip Token Rings section
More informationThe random access methods we study in this chapter have evolved from a very interesting protocol known as ALOHA, which used a very simple procedure
Multiple Accesses When nodes or stations are connected and use a common link, called a multipoint or broadcast link, we need a multiple-access protocol to coordinate access to the link. The problem of
More informationChapter 8 LAN Topologies
Chapter 8 LAN Topologies Point-to-Point Networks In a Point-to-Point network, each wire connects exactly two computers Point To Point Link Machine A Machine B Figure 1: Each line connects two machines
More informationCIS 551 / TCOM 401 Computer and Network Security. Spring 2007 Lecture 7
CIS 551 / TCOM 401 Computer and Network Security Spring 2007 Lecture 7 Announcements Reminder: Project 1 is due on Thursday. 2/1/07 CIS/TCOM 551 2 Network Architecture General blueprints that guide the
More informationContention Protocols and Networks
4/13/2005 314 Lecture Contention Protocols and Networks 1 Contention Protocols and Networks Contention Protocols CSMA/CD Network Topologies Ethernet 4/13/2005 314 Lecture Contention Protocols and Networks
More information