ECE 428 Computer Networks and Security

Save this PDF as:
 WORD  PNG  TXT  JPG

Size: px
Start display at page:

Download "ECE 428 Computer Networks and Security"

Transcription

1 ECE 428 Computer Networks and Security 1

2 Instructor: Sagar Naik About the Instructor Office: EIT 4174, ECE Dept. Other courses that I teach ECE 355: Software Engineering ECE 453/CS 447/ SE 465: Software Testing and QA ECE 454: Distributed and Network-Centric Computing ECE 750-4: Protocols, Software, and Issues in Mobile Comp. Research interest: Computer networks, mobile computing, wireless communication, network-based applications Book: Software Testing and QA (Wiley, August 2008) 2

3 Objective #1 Course Outline Fundamentals of transporting messages from one process to another process on another computer. Important communication protocols to access the Internet Objective #2 Fundamentals of network security Objective #3 Advance topics in computer networks 3

4 Objective #1 Course Outline To transport messages from a process on one machine to another process on another machine IP TCP Server Process Client Process DLC IP IP PHY/MAC DNS DNS 4

5 Course Outline: Realize Objective #1 Physical +Medium Access Control (MAC) layers Data Link Control (DLC) layer Internet Protocol (IP) layer Transmission Control Protocol (TCP) layer Application Layer Protocols 5

6 Course Outline Objective #2: Achieve secure communication Security User Authentication Privacy (Confidentiality) Data Authentication (Data Integrity) Techniques DES, Public-key cryptography, key generation, security protocols 6

7 Objective #3 Course Outline Advance topics in communication networks Cellular communication network GSM/ GPRS Wireless backbone networks WiMAX Vehicular networks 7

8 Evaluation Two assignments 15% Mid-term exam 25% Final 60% 8

9 Reading Resources Text Computer Networks, A. S. Tanenbaum, Prentice Hall Computer Networking, Kurose and Ross, Addison Wesley TCP/IP Protocol Suite, B. A. Forouzan, McGraw Hill, 3 rd ed. Online notes to be posted Course URL 9

10 Teaching Assistants Towhidul Islam Rajesh Palit 10

11 Teaching Style Balanced coverage of functional, non-functional and design aspects of network protocols Functional aspect: what the protocols do Non-functional aspect: Quality of Service (QoS) Design aspects: choices and parameters View this course as a window to the larger world of computer networks. Stay close to real protocols with a combination of abstraction and details. 11

12 Near exam times Tutorial Style Exam related questions and answers Otherwise Protocols and their details related to in-class materials 12

13 My assumption about class level Beginner Moderate Topically high 13

14 Physical + MAC layers C C C Wired media C C C Wireless medium Ethernet cable C C C Hub Wireless Access Point 14

15 Physical layer Physical + MAC layers Actual movement of bits over comm. medium Different communication media Wire (fiber optics, coaxial cable, telephone line) Free space wireless communication Main function Bit stream electrical signal/ electromagnetic waves Strive for media efficiency Concepts: Frequency, Time, and Code division multiplexing 15

16 Media Physical + MAC layers Shared: Ethernet, free space Dedicated: a dial-up link MAC layer Uses the services of the underlying PHY layer. Tells the PHY layer WHEN to transmit. Transmission may not be successful: packet loss. Mechanisms for reducing packet loss 16

17 DLC layer Data Link Control layer Runs on top of a MAC layer (unreliable) Provides a sense of reliability: ACK mechanism Synchronize source transmission rate with the sink s acceptance rate. Flow control Data multiplexing/ demultiplexing Data is broken up into frames 17

18 IP (Network) layer IP layer Runs on top of a DLC layer. Route packets from one computer to another. Builds routing tables for hop-by-hop routing. 18

19 TCP layer Transport layer Runs on top of IP layer. Provides end-to-end communication symantic. Packet delivery Lossless In-order Single copy (No duplicate) Confirmation Two control mechanisms: flow and congestion 19

20 Applications Internet Directory Service DNS Web Access HTTP protocol Session Initiated Protocol (SIP) 20

21 Communication Protocols Medium Access Control (MAC) Lets two nodes communicate directly. Node: a computer or a router Data (Logical) Link Control (DLC/LLC) Lets us have a reliable link between two adjacent nodes. Internet Protocol (IP) Routes packets from one computer to another. Uses the services of BGP, OSPF, and RIP Transmission Control Protocol (TCP) Lets us have end-to-end semantics between applications. 21

22 Media/Physical Layer Computers are physically connected by a medium Wired medium (Ex.: Ethernet Local Area Network) Wireless medium (Ex.: Free space WLAN, Cellular network) Physical layer A layer of protocol controlling the hardware system that actually moves bits from one computer to another Abstraction: Transmitter and Receiver Tx Rx Node Node 2 Rx Medium Tx 22

23 Medium Access Control (MAC) Protocols for LAN and WLAN 23

24 Some Basic Ideas Concept of layering Segment/ Packet/ Frame Packet Header Five Basic Assumptions Aloha Protocols Throughput 24

25 Concept of Layering App. TCP IP DLC1 MAC1 DLC1 MAC1 IP DLC2 MAC2 App. TCP IP DLC2 MAC2 PHY PHY PHY PHY LAN1 Note: Protocols are executed in - hardware, kernel space, and user space LAN2 25

26 Concepts of segment/packet/frame, and header Packet: A formatted stream of bits with the following info. H - Type: The receiver knows what to do with this. E A - Addresses: Destination and source D E R - Control information: Layer related - Data: optional App. TCP IP DLC1 MAC1 PHY User Data User Data User Data User Data User Data User Data User Data User Data User Data User Data User Data User Data App. TCP IP DLC1 MAC1 PHY 26

27 MAC Protocols Function: Send packets from one node to another sharing the same medium Sharing => Nodes compete for transmission Key problem to resolve Each node finds a good time for transmission with the hope that it will not collide with another. The decision must be made largely independently Ignore what others are doing Look for possible Tx from others (sense carrier) Take permission from the receiver 27

28 MAC Protocols (5 key assumptions) Station Model Nodes are independent. When a node generates a packet for Tx, subsequent packets are queued up for Tx. Single channel model only one can Tx at a time Collision assumption Two packets are transmitted at the same time => signal is potentially garbled (collision occurs) at the receiver. Collision occurs at receivers. NOTE Transmitter needs to know the occurrence of collision A Tx can t actually detect a collision A Tx can sometimes infer a collision Collision detection is not possible in WLAN 28

29 MAC Protocols (5 key assumptions) Time model Continuous: A packet Tx can begin at any instant Slotted: Packets are transmitted at well-known instants defined by slots. Carrier sense No carrier sense: Don t try to detect an on-going Tx Carrier sense Mechanism to sense carrier Utilize its absence 29

30 We will study Aloha protocols MAC Protocols CSMA/CD (Carrier Sense Multiple Access/ Collision Detection) CSMA/CA (CSMA/ Collision Avoidance) 30

31 Aloha Protocol Developed in the 1970s at U of Hawaii To interconnect terminals with mainframes LAN/ WLAN: Possible, but not used GSM: Phones use this protocol to request a channel from the base stations Two types Pure Aloha (Continuous time) Slotted Aloha 31

32 Pure Aloha Exponential backoff Wait T B = R*Tp R = Random(0,2 i -1) No Start: i = 0 Transmit Frame Start a timer T = 2*Tp + Δ i > Kmax i++ Timeout ACK received Cancel timer Error Yes Success 32

33 (Pure Aloha: Performance Measure) Throughput: A commonly used performance metric. Input/ Output System Input I/O System Output Throughput: The output rate. Output rate Input rate 33

34 Pure Aloha: Performance Measure Throughput Throughput = Total input rate (G) * Prob. of successful packet transmission G*e -2G Throughput peaks at G = 0.5 units of packet/x sec, where X is the packet transmission time. Max throughput = packets/x sec. Oblivious to collision while transmitting => Loss of available bandwidth 34

35 Slotted Aloha Protocol Similar to pure Aloha Difference Time is slotted A terminal transmits a packet at the beginning of a slot. Throughput G*e -G Peaks at G = 1, and throughput = packets/x sec 35

36 Carrier Sense Multiple Access with Collision Detection (CSMA/CD) 36

37 CSMA/CD Concepts of Carrier Sense and Collision Detection Collision? MAC/ PHY Data Compare Carrier? Tx Rx Medium 37

38 10Base5 IEEE 802.3: PHY Thick co-ax (10 mm diameter) 500 m segment Bus 10BaseT Twisted pair 100 m Star 38

39 CSMA/CD Assumption A Tx from one node can reach all on the LAN. 39

40 CSMA/CD Start: i = 0 Wait T B = R*Tp Sense medium Y Busy N Wait R = Random(0,2 i -1) No i > Kmax Yes Error i++ Collision Send jamming Signal + Abort Transmit frame WHILE detecting collsion No collision Success 40

41 CSMA/CD Time for collision detection 2 * T p (where T p is max propagation time between two nodes) Propagation time Includes transceiver delay + physical propagation time Of the order of 25 microseconds Minimum packet length Frame transmission time is T f T f = 2* T p Whatever can be transmitted in T f 41

42 Aloha vs. CSMA/CD No carrier sense ACK Oblivious to collision No jamming signal Low throughput Carrier sense No ACK Collision => Abort Jamming signal Let all hear the collision Higher throughput 42

43 Wireless LAN IEEE /a/b/g 43

44 Reminder Note CSMA/CD Assumption Signal from one node can reach all nodes. The assumption may not hold in WLAN Collision detection is out of question (Use CA) Two nodes may not be able to comm. directly Use an intermediate node <= AP (Access Point) 44

45 WLAN View C: Computer, AP: Access Point C Radio range of the AP Access Point IEEE protocol C Router To the rest of the network Other AP Basic Service Set (BSS): BSSID = MAC address of AP Independent BSS (IBSS)= BSS - AP Extended Service Set (ESS): A collection of BSS connected by a Distribution System 45

46 IEEE /a/b/g Family IEEE Technique Band Rate Mbps DSSS FHSS 2.4 GHz 2.4 GHz 1 and 2 1 and a OFDM GHz b DSSS 2.4 GHz 5.5 and g OFDM 2.4 GHz 22 and 54 46

47 Different Modes of Operation of MAC in IEEE Modes of IEEE MAC Distributed Coordination Function (DCF) mode Point Coordination Function (PCF) mode With Hand-shake Without Hand-shake 47

48 The AP PCF Mode: Optional Acts as the central controller for all nodes within its range. Decides who transmits and when. Can follow a round-robin policy to allocate slots. Note: There is no contention for medium access. This mode Can support real-time traffic due to periodic scheduling. Leads to waste of bandwidth if a scheduled node has no traffic. Is optional <= Spec. 48

49 An AP DCF Mode: Mandatory Not necessarily to be used. Computers can communicate among themselves <= Ad hoc. Is used to provide connectivity to the Internet. In DCF All nodes, including the AP, compete for medium access. The AP does not act as a central controller. Contention => No guarantee of bandwidth» Delivery is best effort 49

50 Alternative use of PCF and DCF The WLAN operates In the PCF mode for T1 seconds Bandwidth guarantee for some nodes In the DCF mode for T2 seconds Nodes with additional traffic can contend for a share of the bandwidth PCF DCF PCF DCF PCF DCF T1 T2 T3 T4 Time 50

51 DCF with hand-shake A sender obtains permission from the receiver before transmitting a data frame. Hand-shake mechanism Sender transmits a Request To Send (RTS) frame Receiver gives permission by sending back a Clear To Send (CTS) frame Used to increase the probability of successful Tx when Traffic is high Packet length is long. ( dotrtsthreshold holds the value.) Incurs additional cost loss of some bandwidth 51

52 DCF with and without hand-shake The two modes are not mutually exclusive. A node decides what mode to use on a frame/frame basis. The MAC management database contains a variable dotrtsthreshold: integer in bytes Length of a data frame >= dotrtsthreshold» Use hand-shake Length of a data frame < dotrtsthreshold» Do not use hand-shake PCF DCF PCF DCF PCF No hand-shake Hand-shake } Mode of operation of the same node 52

53 DCF without hand-shake A sender does not obtain permission from the receiver before transmitting a data frame. RTS/CTS mechanism is NOT used. There is no prior coordination between sender and receiver A sender transmits a frame when some medium sensing conditions are satisfied. To follow When traffic is low OR data frames are short Use this to save bandwidth 53

54 Problems in WLAN Hidden Terminal Problem Exposed Terminal Problem Inability to detect collision (at the receiver) Assumption All nodes have identical radio range Note how far away their signal can be received The assumption does not cause the problems to surface. Without this assumption, the problems become worse. 54

55 Hidden Terminal Problem D A B C Tx Problem - C is transmitting a frame to B. - A is unaware of C s Tx. - Now, if A transmits, A s Tx will collide with C s at B The above problem is due to C being hidden from A. 55

56 Exposed Terminal Problem A B C D Tx Problem - A is transmitting a frame to D. - B is aware of the ongoing Tx. - If B transmits a frame to C, no harm is caused. - However, B does not transmit because it is unaware of D s location. The above problem is due to B being exposed to A s Tx. 56

57 No collision detection Fact: Collision occurs at receivers. In a wired LAN Collision is indirectly detected by the sender by enforcing the following assumption: Signal from one node can reach all nodes. In a WLAN The assumption does not hold. Evidence: The hidden terminal problem Collision is avoided (CA), rather than detected 57

58 WLAN MAC: CSMA/CA In CSMA/CA, collision is avoided using PHY-level carrier sensing: Done by receiver hardware Virtual carrier sensing: Done by Processing all frame headers (RTS, CTS, DATA) A duration field in frame headers indicates for how long the sender of the frame may use the medium. A Network Allocation Vector is managed using duration fields Each node has a NAV essentially an integer NAV > 0: A node had announced its intention to use the medium now. NAV = 0: Nobody had announced its intention to use the medium now. Transmit condition: When medium is idle (Absence of carrier) AND (NAV = 0) 58

59 NAV Update Mechanism Each node has its own NAV. NAV represents the length of time for which the medium is likely to remain busy Initially: NAV = 0. With each passing μs NAV = NAV 1 Decrementing stops if NAV = 0. NAV is updated using the duration field in a received frame NAV = Max(NAV, duration) 59

60 Frame format RTS and CTS Frames RTS Frame Control Duration RA TA FCS bytes CTS/ ACK Frame Control Duration RA FCS bytes FCS: Frame Check Sequence 60

61 DATA Frame Frame format Frame Control Duration/ ID Seq. A1 A2 A3 A4 Control Frame Body FCS RA TA 61

62 Timing Intervals The IEEE MAC defines 4 timing intervals 2 at the PHY level SIFS: Short InterFrame Space aslot 2 at the MAC level PIFS: Priority (in PCF) IFS DIFS: Distributed IFS 62

63 Hand-shake using RTS/CTS Value of duration in RTS A DIFS RTS SIFS DATA Value of duration in CTS B SIFS CTS SIFS ACK C Value of NAV of C D Value of NAV of D Time 63

64 DCF with Hand-shake: Tx F: a new data frame to be transmitted i = 0, CW = CW min NAV =0? End of backoff Idle medium for DIFS interval? Yes Send an RTS Start a timer No Random Backoff CTS is received ACK is received Cancel timer Send DATA (F) Start a timer Timeout Timeout i: Retry count, CW: Contention Window CWmin: Minimum value of CW (typical value is 32) CWmax: Maximum value of CW (typical value is 256) DIFS: Distributed Interframe Space SIFS < DIFS Important note Wait for fairness to others Cancel timer Wait for a random interval i = i+1 CW = CW min *2 i (At some point, CW saturates at CW max.) 64

65 Backoff Mechanism Backoff Time Counter (BTC) = Random(0,CW) The time unit of BTC is aslottime aslottime: propagation + transceiver switching time BTC is decremented as follows: Medium is idle for aslottime: BTC = BTC 1 Medium is busy: Stop decrementing Resume decrementing BTC after finding the medium to be idle for DIFS interval. Subsequent decrementing is done for every aslottime of idleness of the medium. 65

66 Backoff Mechanism Ch. Busy (A) Ch. Busy (C) Time B DIFS DIFS X X X X BTC = If the channel is busy, it has to remain idle for DIFS interval for BTC to be decremented by 1. X = aslottime If the channel is idle for at least DIFS interval, it has to remain idle for aslottime interval for BTC to be decremented by 1. 66

67 DCF with Hand-shake: Rx Receive an RTS Remain silent. NAV = 0? No Receive a DATA frame Yes Channel is idle for SIFS and the computer is ready to receive? No Ch. idle for SIFS? Yes No Yes Send an ACK Send a CTS Note: The above two fragments of flow-charts can be easily merged. 67

68 DCF Mode without Hand-shake A special case of DCF with hand-shake RTS/CTS frames are not exchanged The idea of NAV is still used in this mode All stations process the received RTS/CTS of others NOTE: A node may broadcast a DATA frame to all Done in DCF without hand-shake Receivers do not send back an ACK. 68

69 PCF Mode of Operation An AP acts as the controller of a BSS as follows AP alternates between PCF and DCF modes AP assumes the role of a controller as follows AP senses the medium at the start of a CF (Contention-Free) period for a PIFS (Priority IFS) interval. SIFS < PIFS < DIFS PIFS = SIFS + aslottime DIFS = SIFS + 2*aSlotTime If the medium is idle for PIFS, transmit a beacon frame Beacon contains a CFPMaxDuration field (Nodes receiving a beacon update their NAV to CFPMaxDuration)» These nodes perceive the medium to be busy for CFPMaxDuration 69

70 PCF Mode of Operation (Contd.) After transmitting a beacon, AP waits for SIFS before transmitting one of the following DATA frame CF Poll frame DATA+CF Poll frame ACK frame CF End frame 70

71 PCF Mode of Operation (Contd.) CF Poll frame AP User 1 User 2 AP User 1 CF Poll CF Poll SIFS DATA DATA SIFS ACK SIFS SIFS ACK The polled user sends data to another user. The polled user sends data to the AP. 71

72 PCF Mode of Operation (Contd.) DATA + CF Poll frame AP User 1 User 2 DATA+ CF Poll ACK SIFS DATA ACK SIFS The polled user receives data from the AP and sends data to another user. 72

73 PCF Mode of Operation (Contd.) DATA frame Contains user data from AP to a specific station. The receiver sends back an ACK after SIFS interval. AP does not receive an ACK Retransmit the DATA after a PIFS interval AP can broadcast a DATA frame These are not ACKed. 73

74 PCF Mode of Operation (Contd.) CF Poll frame AP grants permission to another node to transmit DATA to the AP or to a third node. Receiver of DATA frame sends an ACK to the sender. If the polled node has no data to send, it sends a null DATA frame. If the polled station does not receive an ACK, it can not retransmit its data frame until it is polled again. 74

75 PCF Mode of Operation (Contd.) CF End frame Identifies the end of CF period Sent by an AP under two conditions An AP has no data to send and no node to poll Can happen before the pre-announced CFPMaxDuration Receivers of CF End reset their NAV to 0. Normal end of CF period (Initially: CFPDurRemaining = CFPMaxDuration) CFPDurRemaining time expires 75

76 A node joining a WLAN with an AP (No need for such a procedure in a wired LAN) Two ways for a node to join a WLAN Passive scanning Scan a channel for a Beacon frame If a Beacon frame is received Negotiate Authentication and Association processes Active Scanning Transmit a Probe frame If a Probe Response is received Negotiate Authentication and Authorization processes 76

CSMA/CA. Information Networks p. 1

CSMA/CA. Information Networks p. 1 Information Networks p. 1 CSMA/CA IEEE 802.11 standard for WLAN defines a distributed coordination function (DCF) for sharing access to the medium based on the CSMA/CA protocol Collision detection is not

More information

802.11. Markku Renfors. Partly based on student presentation by: Lukasz Kondrad Tomasz Augustynowicz Jaroslaw Lacki Jakub Jakubiak

802.11. Markku Renfors. Partly based on student presentation by: Lukasz Kondrad Tomasz Augustynowicz Jaroslaw Lacki Jakub Jakubiak 802.11 Markku Renfors Partly based on student presentation by: Lukasz Kondrad Tomasz Augustynowicz Jaroslaw Lacki Jakub Jakubiak Contents 802.11 Overview & Architecture 802.11 MAC 802.11 Overview and Architecture

More information

CSE331: Introduction to Networks and Security. Lecture 6 Fall 2006

CSE331: Introduction to Networks and Security. Lecture 6 Fall 2006 CSE331: Introduction to Networks and Security Lecture 6 Fall 2006 Open Systems Interconnection (OSI) End Host Application Reference model not actual implementation. Transmits messages (e.g. FTP or HTTP)

More information

CS6956: Wireless and Mobile Networks Lecture Notes: 2/11/2015. IEEE 802.11 Wireless Local Area Networks (WLANs)

CS6956: Wireless and Mobile Networks Lecture Notes: 2/11/2015. IEEE 802.11 Wireless Local Area Networks (WLANs) CS6956: Wireless and Mobile Networks Lecture Notes: //05 IEEE 80. Wireless Local Area Networks (WLANs) CSMA/CD Carrier Sense Multi Access/Collision Detection detects collision and retransmits, no acknowledgement,

More information

ECE 358: Computer Networks. Homework #3. Chapter 5 and 6 Review Questions 1

ECE 358: Computer Networks. Homework #3. Chapter 5 and 6 Review Questions 1 ECE 358: Computer Networks Homework #3 Chapter 5 and 6 Review Questions 1 Chapter 5: The Link Layer P26. Let's consider the operation of a learning switch in the context of a network in which 6 nodes labeled

More information

... neither PCF nor CA used in practice

... neither PCF nor CA used in practice IEEE 802.11 MAC CSMA/CA with exponential backoff almost like CSMA/CD drop CD CSMA with explicit ACK frame added optional feature: CA (collision avoidance) Two modes for MAC operation: Distributed coordination

More information

802.11 standard. Acknowledgement: Slides borrowed from Richard Y. Yang @ Yale

802.11 standard. Acknowledgement: Slides borrowed from Richard Y. Yang @ Yale 802.11 standard Acknowledgement: Slides borrowed from Richard Y. Yang @ Yale IEEE 802.11 Requirements Design for small coverage (e.g. office, home) Low/no mobility High data-rate applications Ability to

More information

TCP in Wireless Networks

TCP in Wireless Networks Outline Lecture 10 TCP Performance and QoS in Wireless s TCP Performance in wireless networks TCP performance in asymmetric networks WAP Kurose-Ross: Chapter 3, 6.8 On-line: TCP over Wireless Systems Problems

More information

802.11 Wireless LAN Protocol CS 571 Fall 2006. 2006 Kenneth L. Calvert All rights reserved

802.11 Wireless LAN Protocol CS 571 Fall 2006. 2006 Kenneth L. Calvert All rights reserved 802.11 Wireless LAN Protocol CS 571 Fall 2006 2006 Kenneth L. Calvert All rights reserved Wireless Channel Considerations Stations may move Changing propagation delays, signal strengths, etc. "Non-transitive"

More information

Lecture 17: 802.11 Wireless Networking"

Lecture 17: 802.11 Wireless Networking Lecture 17: 802.11 Wireless Networking" CSE 222A: Computer Communication Networks Alex C. Snoeren Thanks: Lili Qiu, Nitin Vaidya Lecture 17 Overview" Project discussion Intro to 802.11 WiFi Jigsaw discussion

More information

Wiereless LAN 802.11

Wiereless LAN 802.11 Tomasz Kurzawa Wiereless LAN 802.11 Introduction The 802.11 Architecture Channels and Associations The 802.11 MAC Protocol The 802.11 Frame Introduction Wireless LANs are most important access networks

More information

EECS 122: Introduction to Computer Networks Multiaccess Protocols. ISO OSI Reference Model for Layers

EECS 122: Introduction to Computer Networks Multiaccess Protocols. ISO OSI Reference Model for Layers EECS 122: Introduction to Computer Networks Multiaccess Protocols Computer Science Division Department of Electrical Engineering and Computer Sciences University of California, Berkeley Berkeley, CA 94720-1776

More information

Medium Access Control (MAC) Protocols for Ad hoc Wireless Networks - III

Medium Access Control (MAC) Protocols for Ad hoc Wireless Networks - III Medium Access Control (MAC) Protocols for Ad hoc Wireless Networks - III CS: 647 Advanced Topics in Wireless Networks Drs. Baruch Awerbuch & Amitabh Mishra Department of Computer Science Johns Hopkins

More information

Announcements : Wireless Networks Lecture 9: MAC. Outline. History. Page 1

Announcements : Wireless Networks Lecture 9: MAC. Outline. History. Page 1 Announcements 18-759: Wireless Networks Lecture 9: 80.11 Peter Steenkiste Departments of Computer Science and Electrical and Computer Engineering Spring Semester 016 http://www.cs.cmu.edu/~prs/wirelesss16/

More information

Attenuation (amplitude of the wave loses strength thereby the signal power) Refraction Reflection Shadowing Scattering Diffraction

Attenuation (amplitude of the wave loses strength thereby the signal power) Refraction Reflection Shadowing Scattering Diffraction Wireless Physical Layer Q1. Is it possible to transmit a digital signal, e.g., coded as square wave as used inside a computer, using radio transmission without any loss? Why? It is not possible to transmit

More information

IEEE 802.11 WLAN (802.11) ...Copyright. Renato Lo Cigno www.disi.unitn.it/locigno/didattica/nc/

IEEE 802.11 WLAN (802.11) ...Copyright. Renato Lo Cigno www.disi.unitn.it/locigno/didattica/nc/ WLAN (802.11) Renato Lo Cigno www.disi.unitn.it/locigno/didattica/nc/...copyright Quest opera è protetta dalla licenza Creative Commons NoDerivs-NonCommercial. Per vedere una copia di questa licenza, consultare:

More information

IEEE 802.11e WLANs / WMM. S.Rajesh (rajeshsweb@gmail.com) AU-KBC Research Centre, BroVis Wireless Networks, smartbridges Pte Ltd.

IEEE 802.11e WLANs / WMM. S.Rajesh (rajeshsweb@gmail.com) AU-KBC Research Centre, BroVis Wireless Networks, smartbridges Pte Ltd. IEEE 802.11e WLANs / WMM S.Rajesh (rajeshsweb@gmail.com) AU-KBC Research Centre, BroVis Wireless Networks, smartbridges Pte Ltd. Outline A short review of 802.11 MAC Drawbacks of 802.11 MAC Application

More information

Local & Metropolitan Area Networks

Local & Metropolitan Area Networks Local & Metropolitan Area Networks CS455 Yonshik Choi, Ph.D. Department of Computer Science Illinois Institute of Technology Rice Campus Local Area Networks Characteristic Smaller geographical area a

More information

Local Area Networks transmission system private speedy and secure kilometres shared transmission medium hardware & software

Local Area Networks transmission system private speedy and secure kilometres shared transmission medium hardware & software Local Area What s a LAN? A transmission system, usually private owned, very speedy and secure, covering a geographical area in the range of kilometres, comprising a shared transmission medium and a set

More information

Lecture 7 Multiple Access Protocols and Wireless

Lecture 7 Multiple Access Protocols and Wireless Lecture 7 Multiple Access Protocols and Wireless Networks and Security Jacob Aae Mikkelsen IMADA November 11, 2013 November 11, 2013 1 / 57 Lecture 6 Review What is the responsibility of the link layer?

More information

Based on Computer Networking, 4 th Edition by Kurose and Ross

Based on Computer Networking, 4 th Edition by Kurose and Ross Computer Networks Ethernet Hubs and Switches Based on Computer Networking, 4 th Edition by Kurose and Ross Ethernet dominant wired LAN technology: cheap $20 for NIC first widely used LAN technology Simpler,

More information

LAN Switching. 15-441 Computer Networking. Switched Network Advantages. Hubs (more) Hubs. Bridges/Switches, 802.11, PPP. Interconnecting LANs

LAN Switching. 15-441 Computer Networking. Switched Network Advantages. Hubs (more) Hubs. Bridges/Switches, 802.11, PPP. Interconnecting LANs LAN Switching 15-441 Computer Networking Bridges/Switches, 802.11, PPP Extend reach of a single shared medium Connect two or more segments by copying data frames between them Switches only copy data when

More information

Collision of wireless signals. The MAC layer in wireless networks. Wireless MAC protocols classification. Evolutionary perspective of distributed MAC

Collision of wireless signals. The MAC layer in wireless networks. Wireless MAC protocols classification. Evolutionary perspective of distributed MAC The MAC layer in wireless networks The wireless MAC layer roles Access control to shared channel(s) Natural broadcast of wireless transmission Collision of signal: a /space problem Who transmits when?

More information

Basic processes in IEEE802.11 networks

Basic processes in IEEE802.11 networks Module contents IEEE 802.11 Terminology IEEE 802.11 MAC Frames Basic processes in IEEE802.11 networks Configuration parameters.11 Architect. 1 IEEE 802.11 Terminology Station (STA) Architecture: Device

More information

Wireless Networks. Reading: Sec5on 2.8. COS 461: Computer Networks Spring 2011. Mike Freedman

Wireless Networks. Reading: Sec5on 2.8. COS 461: Computer Networks Spring 2011. Mike Freedman 1 Wireless Networks Reading: Sec5on 2.8 COS 461: Computer Networks Spring 2011 Mike Freedman hep://www.cs.princeton.edu/courses/archive/spring11/cos461/ 2 Widespread Deployment Worldwide cellular subscribers

More information

WLAN (802.11) Nomadic Communications. Renato Lo Cigno - Tel: 2026. Dipartimento di Ingegneria e Scienza dell Informazione

WLAN (802.11) Nomadic Communications. Renato Lo Cigno - Tel: 2026. Dipartimento di Ingegneria e Scienza dell Informazione Nomadic Communications WLAN (802.11) Renato Lo Cigno LoCigno@disi.unitn.it - Tel: 2026 Dipartimento di Ingegneria e Scienza dell Informazione Home Page: http://isi.unitn.it/locigno/index.php/teaching-duties/nomadic-communications

More information

Random Access Protocols

Random Access Protocols Lecture Today slotted vs unslotted ALOHA Carrier sensing multiple access Ethernet DataLink Layer 1 Random Access Protocols When node has packet to send transmit at full channel data rate R. no a priori

More information

MAC Algorithms in Wireless Networks

MAC Algorithms in Wireless Networks Department of Computing Science Master Thesis MAC Algorithms in Wireless Networks Applications, Issues and Comparisons Shoaib Tariq Supervisor: Dr. Jerry Eriksson Examiner: Dr. Per Lindström Dedicated

More information

Chapter 7 Low-Speed Wireless Local Area Networks

Chapter 7 Low-Speed Wireless Local Area Networks Wireless# Guide to Wireless Communications 7-1 Chapter 7 Low-Speed Wireless Local Area Networks At a Glance Instructor s Manual Table of Contents Overview Objectives s Quick Quizzes Class Discussion Topics

More information

10. Wireless Networks

10. Wireless Networks Computernetzwerke und Sicherheit (CS221) 10. Wireless Networks 1. April 2011 omas Meyer Departement Mathematik und Informatik, Universität Basel Chapter 6 Wireless and Mobile Networks (with changes CS221

More information

Mustafa Ergen June 2002 ergen@eecs.berkeley.edu. Department of Electrical Engineering and Computer Science University of California Berkeley

Mustafa Ergen June 2002 ergen@eecs.berkeley.edu. Department of Electrical Engineering and Computer Science University of California Berkeley Mustafa Ergen June 2002 ergen@eecs.berkeley.edu Department of Electrical Engineering and Computer Science University of California Berkeley 2 Abstract This document describes IEEE 802.11 Wireless Local

More information

An Overview of Wireless LAN Standards IEEE 802.11 and IEEE 802.11e

An Overview of Wireless LAN Standards IEEE 802.11 and IEEE 802.11e An Overview of Wireless LAN Standards IEEE 802.11 and IEEE 802.11e Jahanzeb Farooq, Bilal Rauf Department of Computing Science Umeå University Sweden Jahanzeb Farooq, 2006 (tipputhegreat@hotmail.com) Chapter

More information

Adaptive DCF of MAC for VoIP services using IEEE 802.11 networks

Adaptive DCF of MAC for VoIP services using IEEE 802.11 networks Adaptive DCF of MAC for VoIP services using IEEE 802.11 networks 1 Mr. Praveen S Patil, 2 Mr. Rabinarayan Panda, 3 Mr. Sunil Kumar R D 1,2,3 Asst. Professor, Department of MCA, The Oxford College of Engineering,

More information

Video Transmission over Wireless LAN. Hang Liu Hang.liu@thomson.net

Video Transmission over Wireless LAN. Hang Liu Hang.liu@thomson.net Video Transmission over Wireless LAN Hang Liu Hang.liu@thomson.net Page 1 Introduction! Introduction! Wi-Fi Multimedia and IEEE 802.11e for QoS Enhancement! Error Control Techniques Page 2 Introduction!

More information

CS263: Wireless Communications and Sensor Networks

CS263: Wireless Communications and Sensor Networks CS263: Wireless Communications and Sensor Networks Matt Welsh Lecture 4: Medium Access Control October 5, 2004 2004 Matt Welsh Harvard University 1 Today's Lecture Medium Access Control Schemes: FDMA TDMA

More information

CSE 123A Computer Networks

CSE 123A Computer Networks CSE 123A Computer Networks Winter 2005 Lecture 5: Data-Link II: Media Access Some portions courtesy Srini Seshan or David Wetherall Last Time Framing: How to translate a bitstream into separate packets

More information

Ethernet. Ethernet Frame Structure. Ethernet Frame Structure (more) Ethernet: uses CSMA/CD

Ethernet. Ethernet Frame Structure. Ethernet Frame Structure (more) Ethernet: uses CSMA/CD Ethernet dominant LAN technology: cheap -- $20 for 100Mbs! first widely used LAN technology Simpler, cheaper than token rings and ATM Kept up with speed race: 10, 100, 1000 Mbps Metcalfe s Etheret sketch

More information

Link Layer Standards and Protocols

Link Layer Standards and Protocols Link Layer Standards and Protocols Link Layer Standards IP Layer (Network Layer) LLC IEEE 802.2 MAC IEEE 802.X Physical Layer Medium Access Control Layer Services Concerned with the following Channel allocation

More information

Unit of Learning # 2 The Physical Layer. Sergio Guíñez Molinos sguinez@utalca.cl 2-2009

Unit of Learning # 2 The Physical Layer. Sergio Guíñez Molinos sguinez@utalca.cl 2-2009 Unit of Learning # 2 The Physical Layer Sergio Guíñez Molinos sguinez@utalca.cl 2-2009 Local Area Network (LAN) Redes de Computadores 2 Historic topologies more used in LAN Ethernet Logical Bus and Physical

More information

Multiple Access Techniques PROF. MICHAEL TSAI 2011/12/8

Multiple Access Techniques PROF. MICHAEL TSAI 2011/12/8 Multiple Access Techniques PROF. MICHAEL TSAI 2011/12/8 Multiple Access Scheme Allow many users to share simultaneously a finite amount of radio spectrum Need to be done without severe degradation of the

More information

TCOM 370 NOTES 99-12 LOCAL AREA NETWORKS AND THE ALOHA PROTOCOL

TCOM 370 NOTES 99-12 LOCAL AREA NETWORKS AND THE ALOHA PROTOCOL 1. Local Area Networks TCOM 370 NOTES 99-12 LOCAL AREA NETWORKS AND THE ALOHA PROTOCOL These are networks spanning relatively short distances (e.g. within one building) for local point-to-point and point-to-multipoint

More information

Communication Networks. MAP-TELE 2011/12 José Ruela

Communication Networks. MAP-TELE 2011/12 José Ruela Communication Networks MAP-TELE 2011/12 José Ruela Network basic mechanisms Multiple Access Multiple Access In early data communication systems, one solution to provide access of remote terminals to a

More information

COMP 3331/9331: Computer Networks and Applications

COMP 3331/9331: Computer Networks and Applications COMP 3331/9331: Computer Networks and Applications Week 10 Wireless Networks Reading Guide: Chapter 6: 6.1 6.3 Wireless Networks + Security 1 Wireless and Mobile Networks Background: # wireless (mobile)

More information

Efficient MAC Protocol for Heterogeneous Cellular Networks (HC-MAC)

Efficient MAC Protocol for Heterogeneous Cellular Networks (HC-MAC) Vol.2, Issue.2, Mar-Apr 2012 pp-078-083 ISSN: 2249-6645 Efficient MAC Protocol for Heterogeneous Cellular Networks (HC-MAC) 1 Y V Adi Satyanarayana, 2 Dr. K Padma Raju 1 Y V Adi Satyanarayana, Assoc. Professor,

More information

Data Center Networks, Link Layer Wireless (802.11)

Data Center Networks, Link Layer Wireless (802.11) Internet-Technologien (CS262) Data Center Networks, Link Layer Wireless (802.11) 1.4.2015 Christian Tschudin Departement Mathematik und Informatik, Universität Basel 6 Wiederholung Warum «multiple access»?

More information

LANs. 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. 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 information

ECE/CS 372 introduction to computer networks. Lecture 13

ECE/CS 372 introduction to computer networks. Lecture 13 ECE/CS 372 introduction to computer networks Lecture 13 Announcements: HW #4 hard copy due today Lab #5 posted is due Tuesday June 4 th HW #5 posted is due Thursday June 6 th Pickup midterms Acknowledgement:

More information

CSCI 362 Computer and Network Security

CSCI 362 Computer and Network Security The Purpose of ing CSCI 362 Computer and Security Introduction to ing Goals: Remote exchange and remote process control. A few desirable properties: Interoperability, Flexibility, Geographical range, Scalability,

More information

Mobile Communications Exercise: Satellite Systems and Wireless LANs. Georg von Zengen, IBR, TU Braunschweig, www.ibr.cs.tu-bs.de

Mobile Communications Exercise: Satellite Systems and Wireless LANs. Georg von Zengen, IBR, TU Braunschweig, www.ibr.cs.tu-bs.de Mobile Communications Exercise: Satellite Systems and Wireless LANs N 1 Please define the terms inclination and elevation using the following two figures. How do these parameters influence the usefulness

More information

RTT 60.5 msec receiver window size: 32 KB

RTT 60.5 msec receiver window size: 32 KB Real-World ARQ Performance: TCP Ex.: Purdue UCSD Purdue (NSL): web server UCSD: web client traceroute to planetlab3.ucsd.edu (132.239.17.226), 30 hops max, 40 byte packets 1 switch-lwsn2133-z1r11 (128.10.27.250)

More information

IEEE 802.11 Technical Tutorial. Introduction. IEEE 802.11 Architecture

IEEE 802.11 Technical Tutorial. Introduction. IEEE 802.11 Architecture IEEE 802.11 Technical Tutorial Introduction The purpose of this document is to give technical readers a basic overview of the new 802.11 Standard, enabling them to understand the basic concepts, principle

More information

Express Forwarding : A Distributed QoS MAC Protocol for Wireless Mesh

Express Forwarding : A Distributed QoS MAC Protocol for Wireless Mesh Express Forwarding : A Distributed QoS MAC Protocol for Wireless Mesh, Ph.D. benveniste@ieee.org Mesh 2008, Cap Esterel, France 1 Abstract Abundant hidden node collisions and correlated channel access

More information

Wireless LAN Services for Hot-Spot

Wireless LAN Services for Hot-Spot Wireless LAN Services for Hot-Spot Woo-Yong Choi Electronics and Telecommunications Research Institute wychoi53@etri.re.kr ETRI Contents Overview Wireless LAN Services Current IEEE 802.11 MAC Protocol

More information

A TCP-like Adaptive Contention Window Scheme for WLAN

A TCP-like Adaptive Contention Window Scheme for WLAN A TCP-like Adaptive Contention Window Scheme for WLAN Qixiang Pang, Soung Chang Liew, Jack Y. B. Lee, Department of Information Engineering The Chinese University of Hong Kong Hong Kong S.-H. Gary Chan

More information

06/02/ Local & Metropolitan Area Networks. Overview. Medium Access Sublayer (1) ACOE322

06/02/ Local & Metropolitan Area Networks. Overview. Medium Access Sublayer (1) ACOE322 1 Local & Metropolitan Area Networks ACOE322 Lecture 2 Medium Access Control and Logical Link Control 1 Overview The architecture of a LAN is best described in terms of a layering of protocols that organize

More information

IEEE 802 Protocol Layers. IEEE 802.11 Wireless LAN Standard. Protocol Architecture. Protocol Architecture. Separation of LLC and MAC.

IEEE 802 Protocol Layers. IEEE 802.11 Wireless LAN Standard. Protocol Architecture. Protocol Architecture. Separation of LLC and MAC. IEEE 802.11 Wireless LAN Standard IEEE 802 Protocol Layers Chapter 14 Protocol Architecture Functions of physical layer: Encoding/decoding of signals Preamble generation/removal (for synchronization) Bit

More information

Philippe Klein. avb-phkl-802-11-qos-overview-0811-1

Philippe Klein. avb-phkl-802-11-qos-overview-0811-1 802.11 QoS Overview Philippe Klein IEEE Plenary Meeting Nov 08 Dallas, TX avb-phkl-802-11-qos-overview-0811-1 Disclaimer This presentation is not a highly detailed technical presentation but a crash course

More information

IEEE802.11 Wireless LAN

IEEE802.11 Wireless LAN IEEE802.11 The broadband wireless Internet Maximilian Riegel wlan-tutorial.ppt-1 (28.11.2000) WLAN Dream Finally Seems to Happen... Recently lots of serious WLAN activities have been announced Big players

More information

Controlled Random Access Methods

Controlled Random Access Methods Helsinki University of Technology S-72.333 Postgraduate Seminar on Radio Communications Controlled Random Access Methods Er Liu liuer@cc.hut.fi Communications Laboratory 09.03.2004 Content of Presentation

More information

The Wireless Network Road Trip

The Wireless Network Road Trip The Wireless Network Road Trip The Association Process To begin, you need a network. This lecture uses the common logical topology seen in Figure 9-1. As you can see, multiple wireless clients are in

More information

Lecture 6.1 Introduction. Giuseppe Bianchi, Ilenia Tinnirello

Lecture 6.1 Introduction. Giuseppe Bianchi, Ilenia Tinnirello PART 6 IEEE 802.11 Wireless LANs Lecture 6.1 Introduction WLAN History Ł Original goal: Deploy wireless Ethernet First generation proprietary solutions (end 80, begin 90) WaveLAN (AT&T)) HomeRF (Proxim)

More information

IEEE 802.11 Wireless LAN Standard. Updated: 5/10/2011

IEEE 802.11 Wireless LAN Standard. Updated: 5/10/2011 IEEE 802.11 Wireless LAN Standard Updated: 5/10/2011 IEEE 802.11 History and Enhancements o 802.11 is dedicated to WLAN o The group started in 1990 o First standard that received industry support was 802.11b

More information

IT4405 Computer Networks (Compulsory)

IT4405 Computer Networks (Compulsory) IT4405 Computer Networks (Compulsory) INTRODUCTION This course provides a comprehensive insight into the fundamental concepts in data communications, computer network systems and protocols both fixed and

More information

Medium Access Control (MAC) and Wireless LANs

Medium Access Control (MAC) and Wireless LANs Medium Access Control (MAC) and Wireless LANs Outline Wireless LAN Technology Medium Access Control for Wireless IEEE 802.11 Wireless LAN Applications LAN Extension Cross-building interconnect Nomadic

More information

Note! The problem set consists of two parts: Part I: The problem specifications pages Part II: The answer pages

Note! The problem set consists of two parts: Part I: The problem specifications pages Part II: The answer pages Part I: The problem specifications NTNU The Norwegian University of Science and Technology Department of Telematics Note! The problem set consists of two parts: Part I: The problem specifications pages

More information

J.GODWIN PONSAM & S.CHRISTOBEL DIANA ASST.PROFESSOR SRM University, Kattankulathur

J.GODWIN PONSAM & S.CHRISTOBEL DIANA ASST.PROFESSOR SRM University, Kattankulathur 8/22/2011 School of Computing, Department of IT IT 0305 COMPUTER NETWORKS FIFTH SEMESTER UNIT III J.GODWIN PONSAM & S.CHRISTOBEL DIANA ASST.PROFESSOR SRM University, Kattankulathur 1 Unit iii School of

More information

ISSN: 2319-5967 ISO 9001:2008 Certified International Journal of Engineering Science and Innovative Technology (IJESIT) Volume 2, Issue 5, September

ISSN: 2319-5967 ISO 9001:2008 Certified International Journal of Engineering Science and Innovative Technology (IJESIT) Volume 2, Issue 5, September Analysis and Implementation of IEEE 802.11 MAC Protocol for Wireless Sensor Networks Urmila A. Patil, Smita V. Modi, Suma B.J. Associate Professor, Student, Student Abstract: Energy Consumption in Wireless

More information

WiFi. Is for Wireless Fidelity Or IEEE 802.11 Standard By Greg Goldman. WiFi 1

WiFi. Is for Wireless Fidelity Or IEEE 802.11 Standard By Greg Goldman. WiFi 1 WiFi Is for Wireless Fidelity Or IEEE 802.11 Standard By Greg Goldman WiFi 1 What is the goal of 802.11 standard? To develop a Medium Access Control (MAC) and Physical Layer (PHY) specification for wireless

More information

A Technical Tutorial on the IEEE 802.11 Protocol

A Technical Tutorial on the IEEE 802.11 Protocol A Technical Tutorial on the IEEE 802.11 Protocol By Pablo Brenner Director of Engineering copyright BreezeCOM 1997 Introduction The purpose of this document is to give technical readers a basic overview

More information

11/22/2013 1. komwut@siit

11/22/2013 1. komwut@siit 11/22/2013 1 Week3-4 Point-to-Point, LAN, WAN Review 11/22/2013 2 What will you learn? Representatives for Point-to-Point Network LAN Wired Ethernet Wireless Ethernet WAN ATM (Asynchronous Transfer Mode)

More information

VoIP in 802.11. Mika Nupponen. S-72.333 Postgraduate Course in Radio Communications 06/04/2004 1

VoIP in 802.11. Mika Nupponen. S-72.333 Postgraduate Course in Radio Communications 06/04/2004 1 VoIP in 802.11 Mika Nupponen S-72.333 Postgraduate Course in Radio Communications 06/04/2004 1 Contents Introduction VoIP & WLAN Admission Control for VoIP Traffic in WLAN Voice services in IEEE 802.11

More information

What is it all about? Some simple solutions. Multiple Access. Contexts for the multiple access problem. Outline. Contexts

What is it all about? Some simple solutions. Multiple Access. Contexts for the multiple access problem. Outline. Contexts Multiple Access An Engineering Approach to Computer Networking What is it all about? ider an audioconference where if one person speaks, all can hear if more than one person speaks at the same time, both

More information

Department of Computer Science Columbia University

Department of Computer Science Columbia University Towards the Quality of Service for VoIP traffic in IEEE 82.11 Wireless Networks Sangho Shin Henning Schulzrinne Email: sangho, hgs@cs.columbia.edu Department of Computer Science Columbia University 28

More information

then, we require that, in order to support the offered load, (1)

then, we require that, in order to support the offered load, (1) Capacity of an IEEE 802.11b Wireless LAN supporting VoIP To appear in Proc. IEEE Int. Conference on Communications (ICC) 2004 David P. Hole and Fouad A. Tobagi Dept. of Electrical Engineering, Stanford

More information

Measuring the service level in the 2.4 GHz ISM band

Measuring the service level in the 2.4 GHz ISM band Measuring the service level in the 2.4 GHz ISM band Internal report Jan-Willem van Bloem and Roel Schiphorst University of Twente Department of Electrical Engineering, Mathematics & Computer Science (EEMCS)

More information

Enhanced Power Saving for IEEE 802.11 WLAN with Dynamic Slot Allocation

Enhanced Power Saving for IEEE 802.11 WLAN with Dynamic Slot Allocation Enhanced Power Saving for IEEE 802.11 WLAN with Dynamic Slot Allocation Changsu Suh, Young-Bae Ko, and Jai-Hoon Kim Graduate School of Information and Communication, Ajou University, Republic of Korea

More information

Ethernet, VLAN, Ethernet Carrier Grade

Ethernet, VLAN, Ethernet Carrier Grade Ethernet, VLAN, Ethernet Carrier Grade Dr. Rami Langar LIP6/PHARE UPMC - University of Paris 6 Rami.langar@lip6.fr www-phare.lip6.fr/~langar RTEL 1 Point-to-Point vs. Broadcast Media Point-to-point PPP

More information

Can I add a VoIP call?

Can I add a VoIP call? Can I add a VoIP call? Sachin Garg Avaya Labs Basking Ridge, NJ 07920 Email: sgarg@avaya.com Martin Kappes Avaya Labs Basking Ridge, NJ 07920 Email: mkappes@avaya.com Abstract In this paper, we study the

More information

ECE 333: Introduction to Communication Networks Fall 2001

ECE 333: Introduction to Communication Networks Fall 2001 ECE 333: Introduction to Communication Networks Fall 2001 Lecture 17: Medium Access Control V Perfectly scheduled approaches Token ring networks 1 We have categorized channel allocation techniques as either

More information

Wireless and Mobile Networks

Wireless and Mobile Networks Wireless and Mobile Networks Reading: Sec7ons 2.8 and 4.2.5 COS 461: Computer Networks Spring 2009 (MW 1:30 2:50 in COS 105) Mike Freedman Teaching Assistants: WyaO Lloyd and Jeff Terrace hop://www.cs.princeton.edu/courses/archive/spring09/cos461/

More information

Chapter 6: Medium Access Control Layer

Chapter 6: Medium Access Control Layer Chapter 6: Medium Access Control Layer Chapter 6: Roadmap Overview! Wireless MAC protocols! Carrier Sense Multiple Access! Multiple Access with Collision Avoidance (MACA) and MACAW! MACA By Invitation!

More information

Protocolo IEEE 802.15.4. Sergio Scaglia SASE 2012 - Agosto 2012

Protocolo IEEE 802.15.4. Sergio Scaglia SASE 2012 - Agosto 2012 Protocolo IEEE 802.15.4 SASE 2012 - Agosto 2012 IEEE 802.15.4 standard Agenda Physical Layer for Wireless Overview MAC Layer for Wireless - Overview IEEE 802.15.4 Protocol Overview Hardware implementation

More information

Computer Networks. Chapter 5 Transport Protocols

Computer Networks. Chapter 5 Transport Protocols Computer Networks Chapter 5 Transport Protocols Transport Protocol Provides end-to-end transport Hides the network details Transport protocol or service (TS) offers: Different types of services QoS Data

More information

Local Area Networks. Ethernet 802.3 LAN - 7-1.

Local Area Networks. Ethernet 802.3 LAN - 7-1. Local Area Networks Ethernet 802.3 LAN - 7-1 Local Area Networks (Lokale Netze) Wide Area Network LAN - 7-2 Local Area Networks What is a LAN? Multiple systems attached to an often shared medium high total

More information

Lecture 6: Media Access Control. CSE 123: Computer Networks Stefan Savage

Lecture 6: Media Access Control. CSE 123: Computer Networks Stefan Savage Lecture 6: Media Access Control CSE 123: Computer Networks Stefan Savage Today: Media access How to share a channel among different hosts? Channel partitioning FDMA (frequency division multiple access)

More information

Medium Access Sublayer

Medium Access Sublayer Medium Access Sublayer Topology of the Network Bus, Ring, Tree Protocols IEEE 802.3 for bus topology IEEE 802.4 for token bus IEEE 802.5 for token ring FDDI for fibre ring IEEE 802.11 for wireless networks

More information

Computer Networks CS321

Computer Networks CS321 Computer Networks CS321 Dr. Ramana I.I.T Jodhpur Dr. Ramana ( I.I.T Jodhpur ) Computer Networks CS321 1 / 22 Outline of the Lectures 1 Introduction OSI Reference Model Internet Protocol Performance Metrics

More information

Transport and Network Layer

Transport and Network Layer Transport and Network Layer 1 Introduction Responsible for moving messages from end-to-end in a network Closely tied together TCP/IP: most commonly used protocol o Used in Internet o Compatible with a

More information

Performance Evaluation of Priority based Contention- MAC in Mobile Ad-Hoc Networks

Performance Evaluation of Priority based Contention- MAC in Mobile Ad-Hoc Networks International Journal of Computer Applications (975 7) Volume 5 No.1, June 11 Performance Evaluation of Priority based Contention- MAC in Mobile Ad-Hoc Networks Soni Sweta Arun Nahar Sanjeev Sharma ABSTRACT

More information

An Experimental Study of Throughput for UDP and VoIP Traffic in IEEE 802.11b Networks

An Experimental Study of Throughput for UDP and VoIP Traffic in IEEE 802.11b Networks An Experimental Study of Throughput for UDP and VoIP Traffic in IEEE 82.11b Networks Sachin Garg sgarg@avaya.com Avaya Labs Research Basking Ridge, NJ USA Martin Kappes mkappes@avaya.com Avaya Labs Research

More information

ALOHA Class of Multiple Access Protocols

ALOHA Class of Multiple Access Protocols ALOHA Class of Multiple Access Protocols ALOHA, also called pure ALOHA: Whenever a user has a frame to send, it simply transmits the frame. If collision occurs, it waits for a random period of time and

More information

Wireless Network Measurement: VoIP and 802.11e

Wireless Network Measurement: VoIP and 802.11e Wireless Network Measurement: VoIP and 82.11e by Ian Dangerfield, B.A Masters Thesis Hamilton Institute National University of Ireland Maynooth Maynooth Co. Kildare December 27 Research Supervisor: Dr.

More information

4. MAC protocols and LANs

4. MAC protocols and LANs 4. MAC protocols and LANs 1 Outline MAC protocols and sublayers, LANs: Ethernet, Token ring and Token bus Logic Link Control (LLC) sublayer protocol Bridges: transparent (spanning tree), source routing

More information

Performance Evaluation of Wired and Wireless Local Area Networks

Performance Evaluation of Wired and Wireless Local Area Networks International Journal of Engineering Research and Development ISSN: 2278-067X, Volume 1, Issue 11 (July 2012), PP.43-48 www.ijerd.com Performance Evaluation of Wired and Wireless Local Area Networks Prof.

More information

Comparison of IEEE & IEEE MAC Protocol

Comparison of IEEE & IEEE MAC Protocol ASSIGNMENT 1 EEET1149: LOCAL AND METROPOLITAN AREA NETWORKS 1 ASSIGNMENT 01 Comparison of IEEE 802.3 & IEEE802.11 MAC Protocol EEET1149 LOCAL AND METROPOLITAN AREA NETWORKS LECTURER: IAN PALMER SUBMITTED

More information

Throughput Analysis of WEP Security in Ad Hoc Sensor Networks

Throughput Analysis of WEP Security in Ad Hoc Sensor Networks Throughput Analysis of WEP Security in Ad Hoc Sensor Networks Mohammad Saleh and Iyad Al Khatib iitc Stockholm, Sweden {mohsaleh, iyad}@iitc.se ABSTRACT This paper presents a performance investigation

More information

A Comparative Study of MAC Layer Protocols for Mobile Ad-Hoc Networks

A Comparative Study of MAC Layer Protocols for Mobile Ad-Hoc Networks International Journal of Information and Computation Technology. ISSN 0974-2239 Volume 4, Number 4 (2014), pp. 351-362 International Research Publications House http://www. irphouse.com /ijict.htm A Comparative

More information

Ring Local Area Network. Ring LANs

Ring Local Area Network. Ring LANs Ring Local Area Network Ring interface (1-bit buffer) Ring interface To station From station Ring LANs The ring is a series of bit repeaters, each connected by a unidirectional transmission link All arriving

More information

802.11 Arbitration. White Paper. September 2009 Version 1.00. Author: Marcus Burton, CWNE #78 CWNP, Inc. marcus.burton@cwnp.com

802.11 Arbitration. White Paper. September 2009 Version 1.00. Author: Marcus Burton, CWNE #78 CWNP, Inc. marcus.burton@cwnp.com 802.11 Arbitration White Paper September 2009 Version 1.00 Author: Marcus Burton, CWNE #78 CWNP, Inc. marcus.burton@cwnp.com Technical Reviewer: GT Hill, CWNE #21 gt@gthill.com Copyright 2009 CWNP, Inc.

More information

Computer Network. Interconnected collection of autonomous computers that are able to exchange information

Computer Network. Interconnected collection of autonomous computers that are able to exchange information Introduction Computer Network. Interconnected collection of autonomous computers that are able to exchange information No master/slave relationship between the computers in the network Data Communications.

More information