Chapter 6 discusses high-speed LAN technologies, including Fast Ethernet, Gigabit Ethernet, and Fibre Channel, addressing the evolution driven by increasing computing power and network requirements. It covers classical Ethernet's limitations, solutions like CSMA/CD protocol, and the advantages of layer 2 switches over hubs. The chapter also outlines the specifications and requirements for Fibre Channel and wireless LANs, highlighting the essential features needed for high-speed connectivity and performance.

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Chapter 6
High-Speed LANs

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Introduction
 Fast Ethernet and Gigabit Ethernet
 Fibre Channel
 High-speed Wireless LANs

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Table 6.1

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Emergence of High-Speed LANs
 2 Significant trends
– Computing power of PCs continues to grow
rapidly
– Network computing
 Examples of requirements
– Centralized server farms
– Power workgroups
– High-speed local backbone

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Classical Ethernet
 Bus topology LAN
 10 Mbps
 CSMA/CD medium access control
protocol
 2 problems:
– A transmission from any station can be
received by all stations
– How to regulate transmission

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Solution to First Problem
 Data transmitted in blocks called frames:
– User data
– Frame header containing unique address of
destination station

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Figure 6.1

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CSMA/CD
Carrier Sense Multiple Access/ Carrier Detection
1. If the medium is idle, transmit.
2. If the medium is busy, continue to listen until
the channel is idle, then transmit immediately.
3. If a collision is detected during transmission,
immediately cease transmitting.
4. After a collision, wait a random amount of
time, then attempt to transmit again (repeat
from step 1).

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Figure 6.2

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Figure 6.3

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Medium Options at 10Mbps
 <data rate> <signaling method> <max length>
 10Base5
– 10 Mbps
– 50-ohm coaxial cable bus
– Maximum segment length 500 meters
 10Base-T
– Twisted pair, maximum length 100 meters
– Star topology (hub or multipoint repeater at central point)

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Figure 6.4

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Hubs and Switches
Hub
 Transmission from a station received by central
hub and retransmitted on all outgoing lines
 Only one transmission at a time
Layer 2 Switch
 Incoming frame switched to one outgoing line
 Many transmissions at same time

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Figure 6.5

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Bridge
 Frame handling done
in software
 Analyze and forward
one frame at a time
 Store-and-forward
Layer 2 Switch
 Frame handling done
in hardware
 Multiple data paths
and can handle
multiple frames at a
time
 Can do cut-through

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Layer 2 Switches
 Flat address space
 Broadcast storm
 Only one path between any 2 devices
 Solution 1: subnetworks connected by
routers
 Solution 2: layer 3 switching, packet-
forwarding logic in hardware

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Figure 6.6

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Figure 6.7

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Figure 6.8

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Figure 6.9

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Figure 6.10

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Figure 6.11

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Benefits of 10 Gbps Ethernet over
ATM
 No expensive, bandwidth consuming
conversion between Ethernet packets and
ATM cells
 Network is Ethernet, end to end
 IP plus Ethernet offers QoS and traffic
policing capabilities approach that of ATM
 Wide variety of standard optical interfaces
for 10 Gbps Ethernet

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Fibre Channel
 2 methods of communication with
processor:
– I/O channel
– Network communications
 Fibre channel combines both
– Simplicity and speed of channel
communications
– Flexibility and interconnectivity of network
communications

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Figure 6.12

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I/O channel
 Hardware based, high-speed, short
distance
 Direct point-to-point or multipoint
communications link
 Data type qualifiers for routing payload
 Link-level constructs for individual I/O
operations
 Protocol specific specifications to support
e.g. SCSI

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Fibre Channel Network-Oriented
Facilities
 Full multiplexing between multiple
destinations
 Peer-to-peer connectivity between any pair
of ports
 Internetworking with other connection
technologies

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Fibre Channel Requirements
 Full duplex links with 2 fibres/link
 100 Mbps – 800 Mbps
 Distances up to 10 km
 Small connectors
 high-capacity
 Greater connectivity than existing multidrop
channels
 Broad availability
 Support for multiple cost/performance levels
 Support for multiple existing interface command
sets

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Figure 6.13

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Fibre Channel Protocol
Architecture
 FC-0 Physical Media
 FC-1 Transmission Protocol
 FC-2 Framing Protocol
 FC-3 Common Services
 FC-4 Mapping

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Wireless LAN Requirements
 Throughput
 Number of nodes
 Connection to backbone
 Service area
 Battery power consumption
 Transmission robustness and security
 Collocated network operation
 License-free operation
 Handoff/roaming
 Dynamic configuration

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Figure 6.14

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IEEE 802.11 Services
 Association
 Reassociation
 Disassociation
 Authentication
 Privacy

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Figure 6.15

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Figure 6.16