Other LAN Technologies Chapter 5 Copyright 2003 Prentice-Hall Panko’s Business Data Networks and Telecommunications, 4 th edition

2 Other LAN Technologies Large Ethernet networks Wireless LANs ATM LANS and QoS Legacy LANs Token-Ring Networks 10 Mbps Ethernet co-axial cable LANs

3 Figure 5.1: Multi-Switch Ethernet LAN Switch 2 Switch 1 Switch 3 Port 5 on Switch 1 to Port 3 on Switch 2 Port 7 on Switch 2 to Port 4 on Switch 3 C3-2D-55-3B-A9-4F Switch 2, Port 5 A1-44-D5-1F-AA-4C Switch 1, Port 2 E5-BB D3-56 Switch 3, Port 6 D4-55-C4-B6-9F Switch 3, Port 2 B2-CD-13-5B-E4-65 Switch 1, Port 7

4 Switching Table Switch 1 PortStation 2A1-44-D5-1F-AA-4C 7B2-CD-13-5B-E4-65 5C3-2D-55-3B-A9-4F 5D C4-B6-9F 5E5-BB D3-56 Figure 5.1: Multi-Switch Ethernet LAN Switch 2 Switch 1 Port 5 on Switch 1 to Port 3 on Switch 2 A1-44-D5-1F-AA-4C Switch 1, Port 2 B2-CD-13-5B-E4-65 Switch 1, Port 7 E5-BB D3-56 Switch 3, Port 6

5 Figure 5.1: Multi-Switch Ethernet LAN Switch 2 Switch 1 Switch 3 Port 5 on Switch 1 to Port 3 on Switch 2 Port 7 on Switch 2 to Port 4 on Switch 3 C3-2D-55-3B-A9-4F Switch 2, Port 5 Switching Table Switch 2 PortStation 3A1-44-D5-1F-AA-4C 3B2-CD-13-5B-E4-65 5C3-2D-55-3B-A9-4F 7D C4-B6-9F 7E5-BB D3-56 E5-BB D3-56 Switch 3, Port 6

6 Figure 5.1: Multi-Switch Ethernet LAN Switch 2 Switch 3 Port 7 on Switch 2 to Port 4 on Switch 3 A1-44-D5-1F-AA-4C Switch 1, Port 2 D4-55-C4-B6-9F Switch 3, Port 2 Switching Table Switch 3 PortStation 4A1-44-D5-1F-AA-4C 4B2-CD-13-5B-E4-65 4C3-2D-55-3B-A9-4F 2D C4-B6-9F 6E5-BB D3-56 E5-BB D3-56 Switch 3, Port 6

7 Figure 5.2: Hierarchical Ethernet LAN Ethernet Switch F Server Y Server X Client PC1 Only One Possible Path Between Any Two Stations PC Client 2 Ethernet Switch E Ethernet Switch D Ethernet Switch B Ethernet Switch A Ethernet Switch C

8 Figure 5.3: Single Point of Failure in a Switch Hierarchy No Communication Switch 1 Switch 2 Switch 3 Switch Fails A1-44-D5-1F-AA-4C B2-CD-13-5B-E4-65 C3-2D-55-3B-A9-4F D C4-B6-9F E5-BB D3-56

9 Figure C.10: 802.1D Spanning Tree Protocol Switch 1 Switch 2 Switch 3 A1-44-D5-1F-AA-4C B2-CD-13-5B-E4-65 C3-2D-55-3B-A9-4F D C4-B6-9F E5-BB D3-56 Activated Deactivated Normal Operation Loop, but Spanning Tree Protocol Deactivates One Link Module C

10 Figure C.10: 802.1D Spanning Tree Protocol Switch 1 Switch 2 Switch 3 A1-44-D5-1F-AA-4C B2-CD-13-5B-E4-65 C3-2D-55-3B-A9-4F D C4-B6-9F E5-BB D3-56 Deactivated Activated Switch 2 Fails Module C

11 Figure 5.2: Hierarchical Ethernet LAN Core Workgroup Ethernet Switch F Server Y Server X Client PC1 PC Client 2 Workgroup Ethernet Switch E Workgroup Ethernet Switch D Core Ethernet Switch B Core Ethernet Switch A Core Ethernet Switch C

12 Figure C.8: Switching Matrix with Queue Switch Matrix Input Queue Incoming Signal Outgoing Signal Port 1 Port 2 Port 3 Port 4 Port 5 Port 6 Port 7 Port 8 Module C

13 Figure 5.4: Workgroup Switches versus Core Switches Ports = 4 Speed = 1 Gbps Maximum input = 4 Gbps Nonblocking switch matrix capacity = 4 Gbps 1 Gbps Switching Matrix 4Gbps Nonblocking

14 Figure 5.4: Workgroup Switches versus Core Switches Connects Typical Port Speeds Switching Matrix Workgroup Switches Client or Server to the Ethernet Network via An access line 10/100 Mbps Lower Percentage of Nonblocking Capacity But not less than 25% Core Switches Ethernet Switches to One Another via A trunk line 100 Mbps, Gigabit Ethernet, 10 Gbps Ethernet 80% or More of Nonblocking Capacity

15 Client A Client B Client C Server DServer E Server Broadcast Figure 5.5: Virtual LAN with Ethernet Switches Server Broadcasting without VLANS Frame is Broadcast Goes to all stations Creates congestion

16 Figure 5.5: Virtual LAN with Ethernet Switches Server Multicasting with VLANS Client A on VLAN1 Client B on VLAN2 Client C on VLAN1 Server D on VLAN2 Server E on VLAN1 Server Broadcast VLANs are collections of servers and their clients Multicasting (some), not Broadcasting (all)

17 Figure 5.6: Tagged Ethernet Frame Source Address (6 Octets) Length (2 Octets) Length of Data Field in Octets 1,500 (Decimal) Maximum Tag Protocol ID (2 Octets) hex; 33,024 decimal Larger than 1,500, So not A Length By looking at the value in the 2 octets after the addresses, the switch can tell if this frame is basic (value < 1,500) or tagged (value = 33,024) Basic MAC FrameTagged MAC Frame Source Address (6 Octets) Tag Control Information (2 Octets) Priority Level (0-7) (3 bits); VLAN ID (12 bits) (1 other bit) Length (2 Octets) Data Field (variable)

18 Figure 5.7: Ethernet Physical Layer Standards Physical Layer Standard Speed Maximum Run Length UTP 10Base-T 100Base-TX 10 Mbps 100 Mbps 100 meters Medium 4-pair Category 3, 4, or 5 4-pair Category Base-T1,000 Mbps100 meters 4-pair Category 5, 4-pair Enhanced Category 5 is preferred

19 Figure 5.7: Ethernet Physical Layer Standards Physical Layer Standard Speed Maximum Run Length Optical Fiber Medium 10Base-F*10 MbpsUP to 2 km* 62.5/125 micron multimode, 850 nm. 100Base-FX100 Mbps412 m 62.5/125 multimode, 1,300 nm, hub 100 Base-FX100 Mbps2 km 62.5/125 multimode, 1,300 nm, switch * Several 10 Mbps fiber standards were defined in 10Base-F.

Wireless LANs

21 Figure 5.8: Typical Wireless LAN Operation with Access Points Switch Client PC Server Large Wired LAN Access Point A Access Point B UTPRadio Link Handoff If mobile computer moves to another access point, it switches service to that access point Notebook CSMA/CA+ACK UTP

22 Figure 5.8: Typical Wireless LAN Operation with Access Points Wireless Notebook NIC Access Point Industry Standard Coffee Cup To Ethernet Switch Antenna (Fan) PC Card Connector

23 Figure 5.8: Typical Wireless LAN Operation with Access Points D-Link Wireless Access Point Using Two Antennas Reduces Multipath Interference (See Ch. 3)

24 Linksys Switch With Built-In Wireless Access Point Using Two Antennas Reduces Multipath Interference (See Ch. 3) Figure 5.8: Typical Wireless LAN Operation with Access Points

25 Figure 5.8: Typical Wireless LAN Operation with Access Points The Wireless Station sends an frame to a server via the access point The access point is a bridge that converts the frame into an Ethernet frame and sends the frame to the server Mobile Station Access Point Ethernet Switch Server Frame Frame

26 Figure 5.8: Typical Wireless LAN Operation with Access Points The server responds, sending an frame to the access point The access point converts the frame into an frame and sends the frame to the mobile station. Mobile Station Access Point Ethernet Switch Server Frame Frame

Wireless LAN Speeds Mbps (rare) 2.4 GHz band (limited in bandwidth) b11 Mbps, 2.4 GHz 3 channels/access point a54 Mbps, 5 GHz (> bandwidth than 2.4 GHz) 11 channels/access point g54 Mbps, 2.4 GHz limited bandwidth

Broadcast Operation The Wireless Stations and Access Points Broadcast their Signals. Only one access point or wireless station may transmit at any moment or signals will become scrambled. Collision About to Occur Access Point Wireless Station Wireless Station

29 Figure 5.9: CSMA/CA + ACK in Wireless LANs CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) Station or access point sender listens for traffic If there is no traffic, can send if there has been no traffic for a specified amount of time If the specified amount of time has not been met, must wait for the specified amount of time. Can then send if the line is still clear Correction

30 Figure 5.9: CSMA/CA + ACK in Wireless LANs CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) Station or access point sender listens for traffic If there is traffic, the sender must wait until traffic stops The sender must then set a random timer and must wait while the timer is running If there is no traffic when the station or access point finishes the wait, it may send Correction

31 Figure 5.9: CSMA/CA + ACK in Wireless LANs ACK (Acknowledgement) Receiver immediately sends back an acknowledgement; no waiting because ACKs have highest priority If sender does not receive the acknowledgement, retransmits using CSMA/CA

32 Who Implements CSMA/CA+ACK? Stations (when they send) Access Points (when they send) Mobile Station Access Point Frame CSMA/CA+ACK

33 Request to Send (RTS) / Clear to Send (CTS) There is a widely used option we should cover. After a station may send, its first message may be a Request-to-Send (RTS) message instead of a data message Only if the other party sends a Clear-to-Send (CTS) message does the sender begin sending data Mobile Station Access Point RTS CTS New

34 Ad Hoc Networks Ad Hoc Mode There is no access point. Stations broadcast to one another directly Not scalable but can be useful for SOHO use NICs automatically come up in ad hoc mode Module C

35 Wired Core / Wireless to the Desktop Normal Networks: Core & Workgroup Switches Core Workgroup Ethernet Switch F Workgroup Ethernet Switch D Core Ethernet Switch B Core Ethernet Switch A Core Ethernet Switch C Workgroup Switches Attach to Stations By UTP Module C

36 Wired Core / Wireless to the Desktop With High-Speed Wireless LANs, Replace Workgroup Switches with Access Points Core Access Point 2 Access Point 1 Core Ethernet Switch B Core Ethernet Switch A Core Ethernet Switch C Access Points Serve Stations Module C

Security Attackers can lurk outside your premises In “war driving,” drive around sniffing out unprotected wireless LANs In “drive by hacking,” eavesdrop on conversations or mount active attacks. Site with WLAN Outside Attacker New

Security By default, security on WLAN NICs and access points is turned off, making external attacks trivial WLAN vendors offer Wired Equivalent Privacy (WEP), but this is weak and easily broken. The Working Group is working on a temporary replacement (TKIP) and longer-term security replacement, i Even if corporate access points can be secured, many departments create unauthorized rogue access points that are seldom secured. New

39 Personal Area Networks (PANs) Connect Devices On or Near a Single User’s Desk PC, Printer, PDA, Notebook Computer, Cellphone Connect Devices On or Near a Single User’s Body Notebook Computer, Printer, PDA, Cellphone The Goal is Cable Elimination

40 Personal Area Networks (PANs) There May be Multiple PANs in an Area May overlap Also called piconets

41 Figure 5.10: versus Bluetooth LANs Focus Speed Bluetooth Large WLANsPersonal Area Network 11 Mbps to 54 Mbps In both directions 722 kbps with back channel of 56 kbps. May increase. Distance 100 meters for b (but shorter in reality) Shorter of a Number of Devices Limited in practice only by bandwidth and traffic Only 10 piconets, each with 8 devices maximum 10 meters (may increase)

42 Figure 5.10: versus Bluetooth LANs Scalability Cost Battery Drain Bluetooth Good through having multiple access points Poor (but may get access points) Probably higherProbably Lower HigherLower DiscoveryNoYes Discovery allows devices to figure out how to work together automatically

43 Figure 5.11: Bluetooth Operation File Synchronization Client PC Slave Notebook Master Printer Slave Printing Cellphone Telephone Piconet 1

44 Figure 5.11: Bluetooth Operation Client PC Notebook Printer Slave Printing Call Through Company Phone System Cellphone Master Telephone Slave Piconet 2

45 Figure 5.11: Bluetooth Operation File Synchronization Client PC Slave Notebook Master Printer Slave Printing Call Through Company Phone System Cellphone Master Telephone Slave Piconet 1 Piconet 2

46 Figure 5.12: Normal Radio Transmission and Spread Spectrum Transmission Channel Bandwidth Required for a specific Signal speed Normal Radio: Use only the required Bandwidth to conserve The frequency spectrum Note: Height of Box Indicates Bandwidth of Channel Shannon’s Law: W = B log 2 (1/S/N) Defines minimum bandwidth needed for a signal of a specific speed.

47 Figure 5.12: Normal Radio Transmission and Spread Spectrum Transmission Channel Bandwidth Required for Signal Frequency Hopping Spread Spectrum (FHSS) Direct Sequence Spread Spectrum (DSSS) b Note: Height of Box Indicates Bandwidth of Channel Wideband but Low-Intensity Signal

48 Figure 5.13: Code Division Multiple Access (CDMA) Spread Spectrum Transmission Client PC 1 Client PC 2 Low-Density Orthogonal Signal 1 Low-Density Orthogonal Signal 2 Server A Server B Radio Spectrum Used in Some Cellular Telephone Systems

49 OFDM Orthogonal Frequency Division Multiplexing (OFDM) Divide a large channel into many subchannels Send part of the signal in each channel Stops using channels with impairment Used in a, g at 54 Mbps Module B Channel Subchannel Impaired Subchannel (Not Used)

50 Spread Spectrum Methods Spread Spectrum Techniques DSSSFHSS (Original ) b DSSS CDMA (Cellular Telephony) OFDM (802.11a, g)

51 Ultrawideband (UWB) EWB Uses Extremely Wide Channels EWB channels are enormously wide—often cutting across several entire service bands Extremely high speeds are possible Can travel through thick walls Because of concerns that EWB may it interfere with services in the service bands spanned, regulators require power to be kept extremely low New Not in Book

52 ATM (Asynchronous Transfer Mode) Ethernet competitor for switched LANs Quality of Service (QoS) for telephony and multimedia transmissions As scalable in speed as Ethernet Highly complex and expensive to buy and manage Not selling well for LANs Increasingly popular for WANs

53 Figure 5.15: Handling Brief Traffic Peaks Traffic Network Capacity Momentary Traffic Peak: Congestion and Latency Time Congestion and Latency

54 Figure 5.15: Handling Brief Traffic Peaks Traffic Network Capacity Traffic Peak Time Quality of Service (QoS) Guarantees in ATM Traffic with Reserved Capacity Always Goes (Voice) Other Traffic Must Wait (Data)

55 Figure 5.15: Handling Brief Traffic Peaks Traffic Overprovisioned Network Capacity Traffic Peak: No Congestion or Latency Time Overprovisioned Traffic Capacity in Ethernet

56 Figure 5.15: Handling Brief Traffic Peaks Traffic Network Capacity Peak Load Time Priority in Ethernet High-Priority Traffic First Low-Priority Waits

57 Figure 5.16: ATM Network with Virtual Circuits Server Client PC ATM Switch 1 ATM Switch 2 ATM Switch 3 ATM Switch 4 ATM Switch 5 ATM switches can be arranged in a mesh, so there are alternative paths. This makes switching slow and expensive.

58 Figure 5.16: ATM Network with Virtual Circuits Server Client PC ATM Switch 1 ATM Switch 2 ATM Switch 3 ATM Switch 4 ATM Switch 5 Virtual Circuit Virtual Circuit ATM selects a single path, called a Virtual circuit, before two stations Begin transmitting. This simplifies Switching and so lowers switching cost

59 Figure 5.16: ATM Network with Virtual Circuits Server Client PC ATM Switch 1 ATM Switch 2 ATM Switch 3 ATM Switch 4 ATM Switch 5 Virtual Circuit Virtual Circuit Virtual Circuit A... B... C... D... Port Switch 4 Switching Table ATM switching tables are as simple as Ethernet switching tables

60 ATM Reduces Switching Costs Virtual circuits simplify switching, reducing switching costs ATM (like Ethernet) is unreliable, also reducing switching costs by avoiding the expense of step-by-step error correction Switches are the most expensive element in most networks, so minimizing switching cost usually is a major goal in network standards

61 Figure 5.17: Virtual Circuit with VPI and VCI Virtual Path is a Path to a Site Virtual Channel is a Connection to a Particular Computer at the Site Switches in Backbone Only Have to Look at the Virtual Path Indicator (VPI) Virtual Channels Virtual Path Site 1 Site 2 ATM Backbone

62 Figure 5.17: ATM Cell Bit 1Bit 4Bit 3Bit 2Bit 8Bit 7Bit 6Bit 5 Virtual Channel Identifier Virtual Path IdentifierVirtual Channel Identifier Reserved Call Loss Priority Payload Type Header Error Check Payload (48 Octets) Virtual Path Identifier VPI: Specifies a VC to site VCI: Specifies a station at site Switches between sites only look at VPI 5 octets of header 48 octets of payload 53 octets total

63 ATM Cells ATM frames are short and fixed in length; called cells Only 53 octets long 5 octets of header 48 octets of data Short length reduces latency at switches Switch may have to wait until entire frame arrives before sending it back out—faster with short cells Fixed length gives predictability for faster processing

Token-Ring Networks Legacy LAN Technologies

65 Token-Ring Networks Ring Topology Inner Ring Outer Ring Frame Normal Operation Dual Ring; normally only one is used

66 Token-Ring Networks Ring is wrapped if there is a break The wrapped ring is still a full ring Break Wrapped Ring

67 Token-Ring Networks Special Frame Called Token Circulates when no station is transmitting For access control, station must have token to send Inner Ring Outer Ring Token

68 Ring Network Technologies Token-Ring Network FDDI (Fiber Distributed Data Interchange) SONET/SDH 16 Mbps100 Mbps: 200 km circumference 54 Mbps to several Gbps Small to Mid-size LANs LAN BackbonesTelephony Lost out to cheaper and eventually faster Ethernet Lost out to faster gigabit Ethernet Growing rapidly in the telephone network core

69 Figure 5.19: Token-Ring Network STP or UTP STP Or Fiber Wiring hubs are called multistation access units (MAUs). Prefers to use shielded twisted pair (STP) wire for runs to stations and to link MAUs but will use UTP for stations and fiber for trunks. STP has two twisted pairs. There is a metal mesh around each pair and around both pairs to reduce interference. STP is bulky and expensive. Multistation Access Unit (MAU)

70 Figure 5.18: Major Legacy Networks Early Ethernet Standards General Only 10 Mbps—shared by all stations Before switches and hubs Used coaxial cable (central wire surrounded by a conducting cylinder) You use this to connect your TV to your VCR Inner Wire Outer Conductor Wrapped in Jacket

71 Figure 5.18: Major Legacy Networks Early Ethernet Standards 10Base5 Multidrop topology Thick trunk cable uses coaxial cable technology; 500-meter limit Drop cable has 15 wires NIC has 15-hole Attachment Unit Interface (AUI) port Trunk Cable Drop Cable 15-Hole AUI Port

72 Figure 5.18: Major Legacy Networks Early Ethernet Standards 10Base2 Daisy chain topology Thin coaxial cable between stations Circular BNC connector BNC Connector

73 Figure 5.18: Major Legacy Networks Ethernet 10Base2 To Next Station T-Connector to Link NIC to next segments NIC

74 Figure 5.18: Major Legacy Networks RJ-45 UTP Connectors BNC Connector 10Base2 T-Connector UTP Thin Coax Ethernet 10Base2: UTP versus BNC Connectors

75 Figure 5.18: Major Legacy Networks Ethernet 10Base2 BNC Connector T-Connector To Next Station