Computer Networks. Wenzhong Li. Nanjing University
|
|
- Winifred Ross
- 5 years ago
- Views:
Transcription
1 Computer Networks Wenzhong Li Nanjing University 1
2 Chapter 2. Direct Link Networks Link Service and Framing Error Detection and Reliable Transmission HDLC, PPP, and SONET Token Ring Ethernet Bridges and Layer-2 switch Wireless Networks Network Performance 2
3 Network Performance
4 Delay Packets queue in switch buffers Packet arrival rate exceeds output link capacity Packet queues, wait for its turn 4
5 Four Sources of Packet Delay 1. Transmission R=link bandwidth (bps) L=packet length (bits) Time to send bits into link = L/R 2. Propagation d = length of physical link s = propagation speed in medium (~2x10 8 m/sec) Propagation delay = d/s 5
6 Four Sources of Packet Delay 3. Nodal processing Check bit errors Determine output link 4. Queuing Time waiting at output link for transmission Depending on congestion level of router 6
7 Magnitude of Different Delay Transmission delay Significant for low-speed links, now typically a few microseconds or less Propagation delay A few micro-seconds to hundreds of milliseconds Nodal processing delay Typically a few microseconds or less Queuing delay Depends on congestion, maybe seconds 7
8 Caravan Analogy Cars propagate at 100 km/hr Toll gate takes 12 sec to service car (nodal+trans) Car: packet; Caravan: packet flow Q: How long until caravan is lined up before 2nd toll gate? Time to push entire caravan through toll gate = 1210 = 120 sec Time for last car to propagate from 1st to 2nd toll gate: 100km/(100km/hr)= 1 hr Answer: 62 minutes Q: what about a single car? 8
9 Queuing Delay R=link bandwidth (bps) L=packet length (bits) =average packet arrival rate 流量强度 Traffic intensity = L/R Intensity ~ 0 : average queuing delay small Intensity 1 : delays become large, and huge Intensity 1 : average delay infinite 9
10 Real Internet Delays and Routes traceroute Provides delay measurement from source to router along endto-end Internet path towards destination Each intermediate router will return packets to sender Sender records time interval between transmission and reply 10
11 Real Internet Delays and Routes traceroute: gaia.cs.umass.edu to 11
12 Packet Loss Link in buffer of a router has finite capacity Packet arriving to full queue dropped (i.e. lost) Lost packet may be retransmitted by previous node, by source end system, or not at all 12
13 Throughput Throughput Rate (bits/unit per time) at which bits transferred between sender/receiver Instantaneous: rate at given point in time Average: rate over a period of time 13
14 Throughput Multiplexing Per-connection endto-end throughput: min(r c, R s, R/10) In practice: R s (or R) is often the bottleneck 14
15 Transmission time and Propagation time 1. Transmission R=link bandwidth (bps) L=packet length (bits) Time to send bits into link = L/R 2. Propagation d = length of physical link s = propagation speed in medium (~2x10 8 m/sec) Propagation delay = d/s 15
16 Network Performance Media Utilization Time used for frame transmission vs. time the shared media is occupied Time for frame transmission U total time for a frame Relative Propagation Time a a propagation time or transmission time length of the data path (in bits) length of a standard frame (in bits) 16
17 Different Networks Contention free Point-to-Point Link Ring LAN Random access ALOHA CSMA/CD 17
18 Point-to-Point Link with No ACK Large frame (a) transmission time = 1 propagation time = a<1 Small frame (b) transmission time = 1 propagation time = a>1 t 0 t 0 Define Start of transmission Start of transmission 1: normalized frame transmission time t 0 +a t 0 +1 a: end to end propagation delay t 0 +1 Start of reception t 0 +a End of transmission N: number of stations End of transmission Start of reception Q: Max Utilization U=? t 0 +1+a End of reception t 0 +1+a End of reception 18
19 Max Utilization for Point-to-Point Link Parameters and assumptions 1: normalized frame transmission time a: end to end propagation delay N: number of stations Each station has frames to transmit Total frame time=transmission delay + propagation delay: 1+a Max Utilization: U 1 1 a 19
20 Ring LAN Token is released at t 0 +1, and it will arrive the next station at t 0 +1+a/N (next transmission starts). End of the previous transmission at t 0 +1+a. t 0 t 0 +a t 0 +1 t 0 +1+a Define: T 1 : Average time to transmit a frame, i.e. T 1 = 1 (a) transmission time = 1, propagation time = a<1 t 0 t 0 +1 t 0 +a t 0 +1+a T 2 : Average time to pass the token after frame transmission N: number of stations Q: Max Utilization: U =? (b) transmission time = 1, propagation time = a>1 Token is released at t 0 +a, and it will arrive the next station at t 0 +a+a/n (next transmission starts). End of the previous transmission at t 0 +1+a. 20
21 Max Utilization for Ring LAN Define T 1 : Average time to transmit a frame, i.e. T 1 = 1 T 2 : Average time to pass the token after frame transmission Max Utilization: U = T 1 /(T 1 +T 2 ) 2 cases Case 1: a<1 (frame longer than ring) T 2 = time to pass token to the next station = a/n Case 2: a>1 (frame shorter than ring) T 2 = sender wait for frame returns after transmission = a 1+a/N 1 a 1 1 a/ N U 1 a 1 a a / N 21
22 Slotted ALOHA All frames have same size Time is uniformly slotted Nodes are synchronized Transmission begins at slot boundary Frames either miss or overlap totally operation: N nodes with many frames to send Each transmits in each slot with probability p until success Q: Max Utilization: U =? 22
23 Slotted ALOHA Suppose: N nodes with many frames to send, each transmits in slot with probability p Probability of successful transmission One node has success in a slot Any node has a success Maximize value of A (let A (p)=0) 23
24 Slotted ALOHA Efficiency Utilization if a slot is successfully used Since A is the rate of success slot Before data transmission, it takes a to detect collision; After transmission, it takes a to make sure the transmission of the last bit efficiency: long-run fraction of successful slots (many nodes, all with many frames to send) 24
25 Pure ALOHA Simpler but collision probability increases Frame sent at t 0 collides with other frames sent in [t 0 1, t 0 +1] Suppose: N nodes with many frames to send, each transmits in any time with probability p Q: Max Utilization: U =? 25
26 Pure ALOHA Efficiency Probability of successful transmission 26
27 CSMA/CD With CSMA, collision occupies medium for duration of transmission Colliding transmissions aborted once detected Stations listen whilst transmitting 1. If medium idle, transmit; otherwise, step 2 2. If busy, listen for idle, then transmit immediately 3. If collision detected, send jam signal then abort 4. After jam, wait random time then start from step 1 27
28 CSMA/CD Operation C ends transmission here A ends transmission here 28
29 CSMA/CD: Minimum Frame Size B: bandwidth L: length of the link V: propagation speed Size: size of a frame Collision occurs Propagation time: T a =L/v Transmission time for one frame: T b =Size/B In the worse case, collision detection takes 2T a. Frame1 L Collision detected Frame2 Minimum contention interval= 2T a Minimum frame size: If the transmission time of a frame is less than 2T a, it may not be able to detect collision if collision occurs. To assure collision detection, it must satisfies T b >=2T a Thus size/b>=2l/v, minimum frame size: size>=2*l*b/v
30 CSMA/CD (p-persistent): Max Utilization Contention Slots Frame Frame Frame Frame Contention Interval Idle Contention slots end in a collision Contention interval is a sequence of contention slots Length of a slot in contention interval is 2a (in worst case it takes 2a time to detect contention) Assume p-persistent: The probability that a station attempts to transmit in a slot is p Q: Max Utilization: U =? 30
31 Max Utilization for CSMA/CD (1) Let A be the probability that some station can successfully transmit in a slot, then: N A p 1 1 p Np 1 p 1 N 1 N1 In above formula, A is maximized when p=1/n, thus: A 1 1 N N 1 31
32 Max Utilization for CSMA/CD (2) Probability of a contention interval with j slots Prob[ j unsuccessful attempts] Prob[1 successful attempt] A 1 A j The expected number of slots in a contention interval is then calculated as (Geometric distribution, mean=(1-p)/p): j1 ja 1 A j 1 A A 32
33 Max Utilization for CSMA/CD (3) Maximum Utilization U Frame time Frame time+propagation time+average contention interval A 2 A 1 a 2a 1 a A A Let N, A = (1 1/N) N 1 = 1/e (e=2.718) U A 1 a 1 2e 1 a a A 33
34 Summary 网络性能指标 网络时延 丢包 吞吐量概念 四种时延 : 处理 排队 传输 传播 传输媒介利用率分析 Point-to-point link Ring LAN ALOHA, Slotted ALOHA CSMA/CD ( p-persistent )
35 Homework 第 5 章 :R4, R6, R8, R10, P1, P11, P18, P19
end systems, access networks, links circuit switching, packet switching, network structure
Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge end systems, access networks, links 1.3 Network core circuit switching, packet switching, network structure 1.4 Delay, loss and throughput
More informationFour sources of packet delay
Outline q Major Internet components q Network architecture and protocols q Switching strategies q Internet protocol stack, history q to network performance Four sources of packet delay q 1. nodal processing:
More informationComputer Networks & Security 2016/2017
Computer Networks & Security 2016/2017 Protocol Layering (02) Dr. Tanir Ozcelebi Courtesy: Kurose & Ross TU/e Computer Science Security and Embedded Networked Systems Your typical lunch Slide 2 What is
More informationChapter 1. Computer Networks and the Internet
Chapter 1 Computer Networks and the Internet Internet traffic What s the Internet? (hardware) PC server wireless laptop cellular handheld wired links millions of connected computing devices: hosts = end
More informationComputer Networking Introduction
Computer Networking Introduction Halgurd S. Maghdid Software Engineering Department Koya University-Koya, Kurdistan-Iraq Lecture No.2 Chapter 1: roadmap 1.1 what is the Inter? 1.2 work edge end systems,
More informationChapter 1 Introduction
Chapter 1 Introduction 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 animations;
More informationCS 4390 Computer Networks
CS 4390 Computer Networks UT D application transport network data link physical Session 04 Packet Switching dapted from Computer Networking a Top-Down pproach 1996-2012 by J.F Kurose and K.W. Ross, ll
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 5.4: Multiple Access Protocols Dr. Nghi Tran (ECE-University of Akron) ECE 4450:427/527
More informationRandom Access. 1. Aloha. 2. Slotted Aloha 3. CSMA 4. CSMA/CD
Random Access 1. Aloha 2. Slotted Aloha 3. CSMA 4. CSMA/CD Background Communication medium B No Collision collision A C Modern Local Area Networks (LANs) operate as follows Users are connected to communication
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 informationLast Lecture. Nuts-and-bolts description of the Internet. ! The topology. ! The communication links. ! The core. ! The edge
Last Lecture Nuts-and-bolts description of the Internet! The topology! The core! The edge! The communication links SUNY AT BUFFALO; CSE489/589 MODERN NETWORKING CONCEPTS; Fall 2010; INSTRUCTOR: HUNG Q.
More informationChapter 6 Medium Access Control Protocols and Local Area Networks
Chapter 6 Medium Access Control Protocols and Local Area Networks Part I: Medium Access Control Part II: Local Area Networks CSE 3213, Winter 2010 Instructor: Foroohar Foroozan Chapter Overview Broadcast
More informationLANs. Local Area Networks. via the Media Access Control (MAC) SubLayer. Networks: Local Area Networks
LANs Local Area Networks via the Media Access Control (MAC) SubLayer 1 Local Area Networks Aloha Slotted Aloha CSMA (non-persistent, 1-persistent, p-persistent) CSMA/CD Ethernet Token Ring 2 Network Layer
More informationCSCE 463/612 Networks and Distributed Processing Spring 2018
CSCE 463/612 Networks and Distributed Processing Spring 2018 Introduction II Dmitri Loguinov Texas A& University January 25, 2018 Original slides copyright 1996-2004 J.F Kurose and K.W. Ross 1 Chapter
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 informationECE453 Introduction to Computer Networks. Broadcast vs. PPP. Delay. Lecture 7 Multiple Access Control (I)
ECE453 Introduction to Computer Networks Lecture 7 Multiple Access Control (I) 1 Broadcast vs. PPP Broadcast channel = multiaccess channel = random access channel Broadcast LAN Satellite network PPP WAN
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 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 informationComputer Networks Chapter 1: Introduction. Introduction
Computer Networks Chapter 1: Introduction CSC 249 January 25, 2018 Introduction What is the Inter? Define work edge: hosts,, physical media Define the work core & Inter structure First glimpse at the layers
More informationCSC 401 Data and Computer Communications Networks
CSC 401 Data and Computer Communications Networks Computer Networks and The Internet Sec 1.4-1.5 Prof. Lina Battestilli Outline Computer Networks and the Internet (Ch 1) 1.1 What is the Internet? 1.2 network
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 informationCS 716: Introduction to communication networks. - 9 th class; 19 th Aug Instructor: Sridhar Iyer IIT Bombay
CS 716: Introduction to communication networks - 9 th class; 19 th Aug 2011 Instructor: Sridhar Iyer IIT Bombay Contention-based MAC: ALOHA Users transmit whenever they have data to send Collisions occur,
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 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 informationProblem Set Name the 7 OSI layers and give the corresponding functionalities for each layer.
Problem Set 1 1. Why do we use layering in computer networks? 2. Name the 7 OSI layers and give the corresponding functionalities for each layer. 3. Compare the network performance of the 3 Multiple Access
More informationEITF25 Internet Techniques and Applications L4: Network Access. Stefan Höst
EITF25 Internet Techniques and Applications L4: Network Access Stefan Höst Repetition The link layer protocol should make sure that the data is correctly transmitted over the physical link using error
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 informationRandom Assignment Protocols
Random Assignment Protocols Random assignment strategies attempt to reduce problem occur in fixed assignment strategy by eliminating pre allocation of bandwidth to communicating nodes. Random assignment
More informationCSMA/CD (Collision Detection)
CSMA/CD (Collision Detection) CD (collision detection): easy in wired LANs: measure signal strengths, compare transmitted, received signals difficult in wireless LANs: received signal strength overwhelmed
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 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 informationCollege of Computer and Information Sciences Department of Computer Engineering CEN444 Computer Networks Midterm 2 Exam Second Semester 1434/1435
College of Computer and Information Sciences Department of Computer Engineering CEN444 Computer Networks Midterm 2 Exam Second Semester 1434/1435 Student Name ID Time Allowed: 2.0 Hours. Closed Book, Closed
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 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 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 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 informationComputer Networks. Wenzhong Li. Nanjing University
Computer Networks Wenzhong Li Nanjing University 1 Chapter 2. Direct Link Networks Link Service and Framing Error Detection and Reliable Transmission HDLC, PPP, and SONET Token Ring Ethernet Bridges and
More informationComputer Networks and the Internet. CMPS 4750/6750: Computer Networks
Computer Networks and the Inter CMPS 4750/6750: Computer Networks Outline What Is the Inter? Access Networks Packet Switching and Circuit Switching A closer look at delay, loss, and throughput Interconnection
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 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 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 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 informationChapter I: Introduction
Chapter I: Introduction UG3 Computer Communications & Networks (COMN) Myungjin Lee myungjin.lee@ed.ac.uk Slides copyright of Kurose and Ross The work core mesh of interconnected routers packet-switching:
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 informationMultiple 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 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 informationComputer 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 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 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 informationCS 3516: Advanced Computer Networks
Welcome to CS 3516: Advanced Computer Networks Prof. Yanhua Li Time: 9:00am 9:50am M, T, R, and F Location: Fuller 320 Fall 2017 A-term 1 Some slides are originally from the course materials of the textbook
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 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 informationPacket-switching: store-and-forward
Packet-switching: store-and-forward L R R R Takes L/R seconds to transmit (push out) packet of L bits on to link or R bps Entire packet must arrive at router before it can be transmitted on next link:
More informationData Link Layer: Collisions
Data Link Layer: Collisions 1 Multiple Access Data Link layer divided into two sublayers. The upper sublayer is responsible for datalink control, The lower sublayer is responsible for resolving access
More informationInternetworking Technology -
Internetworking Technology - Chapter 1 Computer Networks and the Internet (Cont.) Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Network access and physical media 1.5
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 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 informationCSC 4900 Computer Networks: Introduction
CSC 4900 Computer Networks: Introduction Professor Henry Carter Fall 2017 Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Delay & loss in packet-switched networks 1.5
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 informationCOS 140: Foundations of Computer Science
COS 140: Foundations of C S Network Protocol Family Fall 2017 Copyright c 2002 2017 UMaine School of Computing and Information S 1 / 25 Homework Homework Slides, book Chapter 24 on line Homework: All exercises
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 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 informationCommunication and Networks. Problems
Electrical and Information Technology Communication and Networks Problems Link Layer 2016 Problems 1. Consider a network applying a slotted Aloha access system. The assumption for this is that all nodes
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 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 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 informationData Link Layer -2- Network Access
EITF25 Internet: Technology and Applications Data Link Layer -2- Network Access 2015, Lecture 03 Kaan Bür Previously on EITF25 Logical Link Control Sublayer Flow control Send data Wait for ACK Error control
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 informationChapter 6 Medium Access Control Protocols and Local Area Networks
Chapter 6 Medium Access Control Protocols and Local Area Networks Part I: Medium Access Control Part II: Local Area Networks Chapter Overview Broadcast Networks All information sent to all users No routing
More informationLecture 2 Communication services The Trasport Layer. Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it
Lecture 2 Communication services The Trasport Layer Antonio Cianfrani DIET Department Networking Group netlab.uniroma1.it The structure edge: applications and hosts core: routers of s access s, media:
More informationInternet Architecture & Performance. What s the Internet: nuts and bolts view
Internet Architecture & Performance Internet, Connection, Protocols, Performance measurements What s the Internet: nuts and bolts view millions of connected computing devices: hosts, end systems pc s workstations,
More informationData and Computer Communications
Data and Computer Communications Chapter 16 High Speed LANs Eighth Edition by William Stallings Why High Speed LANs? speed and power of PCs has risen graphics-intensive applications and GUIs see LANs as
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 informationMultiple Access (1) Required reading: Garcia 6.1, 6.2.1, CSE 3213, Fall 2010 Instructor: N. Vlajic
1 Multiple Access (1) Required reading: Garcia 6.1, 6.2.1, 6.2.2 CSE 3213, Fall 2010 Instructor: N. Vlajic Multiple Access Communications 2 Broadcast Networks aka multiple access networks multiple sending
More informationData Link Layer -2- Network Access
EITF25 Internet: Technology and Applications Data Link Layer -2- Network Access 2013, Lecture 03 Kaan Bür, Stefan Höst Previously on EITF25 Logical Link Control Sublayer Flow control Send data Wait for
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 informationMultiple Access. Data Communications and Networking
Multiple Access In the previous part we discussed data link control, a mechanism which provides a link with reliable communication. In the protocols we described, we assumed that there is an available
More informationData Communications. Automatic Repeat Request Medium Access Control
Data Communications Automatic Repeat Request Medium Access Control Handling Error Cases Automatic Repeat request(arq), also known as Automatic Repeat Query, is an error-control method ARQ uses acknowledgements
More informationECEN 5032 Data Networks Medium Access Control Sublayer
ECEN 5032 Data Networks Medium Access Control Sublayer Peter Mathys mathys@colorado.edu University of Colorado, Boulder c 1996 2005, P. Mathys p.1/35 Overview (Sub)networks can be divided into two categories:
More informationECE 358 MAC Examples. Xuemin (Sherman) Shen Office: EIT 4155 Phone: x
ECE 358 MAC Examples Xuemin (Sherman) Shen Office: EIT 4155 Phone: x 32691 Email: xshen@bbcr.uwaterloo.ca Problem 1. Consider the following Aloha systems. (a) A group of N users share a 56 kbps pure Aloha
More informationNetworks Homework # 2
ISLAMIC UNIVERSITY OF GAZA COMPUTER ENGINEERING DEPARTMENT Networks Homework # 2 INSTRUCTIONS: 1. Show your work (i.e., how you derived your answer or the reason behind your thinking) in addition to your
More informationCOMPUTER NETWORKS - Local area networks
Local area networks Telecommunication Networks Group firstname.lastname@polito.it http://www.telematica.polito.it/ COMPUTER NETWORKS LANs - 1 Copyright Quest opera è protetta dalla licenza Creative Commons
More informationLocal area networks. Copyright
Local area networks Telecommunication Networks Group firstname.lastname@polito.it http://www.telematica.polito.it/ COMPUTER NETWORKS LANs - 1 Copyright Quest opera è protetta dalla licenza Creative Commons
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 informationHomework 1 50 points. Quantitative Comparison of Packet Switching and Circuit Switching 20 points Consider the two scenarios below:
Homework 1 50 points Quantitative Comparison of Packet Switching and Circuit Switching 20 points Consider the two scenarios below: A circuit-switching scenario in which Ncs users, each requiring a bandwidth
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 informationCPSC 441 Tutorial-19. Department of Computer Science University of Calgary
CPSC 441 Tutorial-19 Department of Computer Science University of Calgary Problem-1 Consider n nodes that use the slotted CSMA/ CD with binary exponential back-off to access a shared broadcast channel.
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 informationLANs Local Area Networks LANs provide an efficient network solution : To support a large number of stations Over moderately high speed
Local Area Networks LANs provide an efficient network solution : To support a large number of stations Over moderately high speed With relatively small bit errors Multiaccess Protocols Communication among
More informationPower Laws in ALOHA Systems
Power Laws in ALOHA Systems E6083: lecture 7 Prof. Predrag R. Jelenković Dept. of Electrical Engineering Columbia University, NY 10027, USA predrag@ee.columbia.edu February 28, 2007 Jelenković (Columbia
More informationCHAPTER 15 LOCAL AREA NETWORKS ANSWERS TO QUESTIONS
CHAPTER 15 LOCAL AREA NETWORKS ANSWERS TO QUESTIONS 15.1 Computer room networks require very high data rates and usually are concerned with transfer of large blocks of data. 15.2 Backend LAN: Backend networks
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 informationMedium Access Control
Medium Access Control Fundamental Problem N nodes in vicinity want to transmit (to, say, N other nodes). How to do this interference free? Interference free means SINR Otherwise, we say that packets collide.
More informationEP2210 FEP3210 Performance analysis of Communication networks. Topic 2 Medium access control (or multiple access protocols)
EP2210 FEP3210 Performance analysis of Communication networks Topic 2 Medium access control (or multiple access protocols) 1 Medium access control Lecture material: R. Rom, M. idi, Multiple access protocols,
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 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 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 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 informationCOMMUNICATION NETWORKS NETW 501
COMMUNICATION NETWORKS NETW 501 TUTORIAL 6 Presented by: Eng. Hana Hesham Eng. Mohamed Atef Data Link Layer Data Link Layer is split into 2 sublayers which are the Logical Link Control (LLC) and the Medium
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 information