CIS 267 LAN Systems Lecture Chapter 15

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CIS 267 LAN SystemsLecture Chapter 15

• Vaughn L. Lucas

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High-Speed LANs

• Why?
• Extraordinary growth in speed, power, and storage
  capacity of PCs
• Increasing use of LANs as computing platforms
• Examples
• Server farms
• Workgroups with power requirements
• High-speed backbones

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Traditional Ethernet

• Ethernet and CSMA/CD (IEEE 802.3)
• Carrier sense multiple access with collision
  detection
• Four step procedure
• If medium is idle, transmit
• If medium is busy, listen until idle and then
  transmit
• If collision is detected, cease transmitting
• After a collision, wait a random amount of time
  before retransmitting

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802.3 Medium Notation

• Notation formatltdata rate in Mbpsgtltsignaling
  methodgtltmaximum segment length in hundreds of
  metersgt
• e.g 10Base5 provides 10Mbps baseband, up to 500
  meters
• T and F are used in place of segment length for
  twisted pair and fiber

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802.3 10BaseX Media Options
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Fast Ethernet (100Mbps)

• Easy to integrate with existing systems
• Can use UTP (-TX) or fiber (-FX)
• Uses star-wired topology, using a central
  multiport repeater (broadcast method)
• If NICs support full-duplex mode, switched hub
  must be used

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802.3 100Base-T Options
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802.3 100BaseX Media Options
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Example 100-Mbps Ethernet Backbone Strategy
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Gigabit Ethernet

• Still under development
• Retains CSMA/CD protocol and Ethernet format,
  ensuring smooth upgrade path
• Uses optical fiber over short distances
• 1-gbps switching hub provides backbone
  connectivity

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Gigabit Ethernet Configuration
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Gigabit Ethernet Media Options
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Token Ring LANs (802.5)Medium Access Control

• Token seized by changing a bit on the
  circulating frame to indicate start of frame
  rather than token
• Default configuration requires sender to complete
  transmission and begin receiving transmitted
  frame before releasing the token
• Early token release allows release of token
  after transmission but before receipt of frame

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802.5 Transmission Media

• Original specified shielded twisted pair with
  data rates of 4 and 16mbps
• New addition to standard allows use of UTP for
  4mbps
• Utilizes differential Manchester encoding
• 1997 update to IEEE 802.5 introduced dedicated
  token ring (DTR).

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Token Ring Operation
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Fibre Channel

• combine the best features of channel and
  protocol-based technologies
• the simplicity and speed of channel
  communications
• the flexibility and inter-connectivity that
  characterize protocol-based network
  communications.
• more like a traditional circuit-switched or
  packet-switched network, in contrast to the
  typical shared-medium LAN

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Fibre Channel Goals

• Full-duplex links with two fibers per link
• Performance from 100 Mbps to 800 Mbps on a single
  link (200 Mbps to1600 Mbps per link)
• Support for distances up to 10 km
• Small connectors
• High-capacity utilization with distance
  insensitivity

• Greater connectivity than existing multidrop
  channels
• Broad availability (i.e., standard components)
• Support for multiple cost/performance levels,
  from small systems to supercomputers
• Ability to carry multiple existing interface
  command sets for existing channel and network
  protocols

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Five Applications of Fibre Channel

• See Figure 15.9 on page 420 of text

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Fibre Channel Elements

• Nodes
• The end systems
• Includes one or more N_ ports for interconnection
• Fabric
• Collection of switching elements s between
  systems
• Each element includes multiple F_ ports
• Responsible for buffering and for routing frames
  between source and destination nodes

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Fibre ChannelProtocol Architecture

• FC-0 Physical Media Includes optical fiber,
  coaxial cable, and shielded twisted pair, based
  on distance requirements
• FC-1 Transmission Protocol Defines the signal
  encoding scheme
• FC-2 Framing Protocol Defines topologies, frame
  format, flow/error control, and grouping of
  frames
• FC-3 Common Services Includes multicasting
• FC-4 Mapping Defines the mapping of various
  channel and network protocols to Fibre Channel

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Wireless LANS

• LAN extension
• Wireless network connected to a main wire-based
  network
• Cross-building interconnect
• Point-to-point link between networks in separate
  buildings
• Nomadic access
• Wireless link between a LAN hub and a mobile data
  terminal
• Ad hoc networks
• a peer-to-peer network (no centralized server)
  set up temporarily to meet some immediate need.

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Wireless LAN Requirements

• Throughput
• Number of nodes
• Connection to backbone LAN
• Service area
• Battery power consumption

• Transmission robustness and security
• Co-located network operation
• License-free operation
• Handoff/roaming
• Dynamic configuration

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Multiple-Cell Wireless LAN
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IEEE 802.11 Standards

• Association/Re-Association/Disassociation
• Authentication
• Privacy
• Physical Media
• Infrared at 1 or 2 Mbps at a wavelength of
  850-950 nm
• Direct-sequence spread spectrum in the 2.4-GHz
  ISM band
• Frequency-hopping spread spectrum in the 2.4-GHz
  ISM band, at data rates of 1 and 2 Mbps.