Transcript A Guide to Designing and Implementing Local and Wide Area

Network Transmission
Equipment
Chapter 4
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Learning Objectives
Describe the purpose of LAN network
transmission equipment:
NICs, repeaters, MAUs, hubs, bridges, routers,
brouters, switches, and gateways
Explain how LAN network equipment
works
continued…
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Learning Objectives
Describe the purpose of WAN network
equipment:
Multiplexers, channel banks, private telephone
networks, types of modems, ISDN adapters,
access servers, and routers
Explain how WAN network equipment
works
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LAN Transmission Equipment
NICs
Repeaters
MAUs
Hubs
Bridges
Routers
Brouters
Switches
Gateways
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NIC
Enables network device to connect to
network
Network connection requirements
Appropriate connector for network medium
Transceiver
Controller to support MAC sublayer of Data
Link layer
Protocol control firmware
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A Combination NIC
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Role of MAC Controller Unit
Works with firmware to correctly
encapsulate:
Source and destination address information
Data to be transported
CRC error control information
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Transport and
Transmission Options
Transport options
Combined transport options make it easy to
upgrade a network for high-speed
communication
Transmissions options
Half-duplex transmissions
Full-duplex transmissions
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FDDI NICs
Connect host systems/file servers to FDDI
network equipment using single attachment
Attach network equipment to FDDI cabling
via dual attachment
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ATM NICs
Connect ATM switches or servers to an
ATM network
Available to desktop
Relatively expensive
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Wireless NIC
Modes
Ad hoc peer-to-peer communication with
another wireless NIC
Communication with an access point
Provide flexibility and convenience
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Buses and NICs
Industry Standard Architecture (ISA)
Extended Industry Standard Architecture (EISA)
Microchannel Architecture (MCA)
Peripheral Computer Interface (PCI)
SPARC Bus (SBUS)
NuBus
Universal Serial Bus (USB)
VESA local bus (VL-bus)
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Choosing a NIC
For host computer, server, or workstation?
Network media and network transport methods in
use?
Manufacturer?
Computer or network equipment bus type?
Operating system used by the computer?
Use of half- or full-duplex communications?
How does it attach to network (for special
application)?
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Repeater
Amplifies and retimes a packet or cellcarrying signal so that it can be sent along
all outgoing cable segments attached to that
repeater
Filters out signal disturbance or noise
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Repeaters Are Used to…
Extend cable segment
Increase number of nodes beyond limit of
one segment
Sense network problem and shut down
cable segment (partitioning)
Connect to components in other network
devices
continued…
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Repeaters Are Used to…
Connect segments that use different media
Extend backbone cable segments in LANs
and WANs
Extend long, fiber-optic cable segments
Increase communications distance of
T-carrier lines
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A Multiport Repeater
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Repeaters
Advantage
Inexpensive way to extend a network
Disadvantage
Can create excessive amount of network traffic
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Multistation Access Unit
(MAU)
Central hub that links token ring nodes into
a topology that physically resembles a star
but in which data signals are transferred in a
logical ring pattern
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MAUs Are Used to…
Connect workstations into a logical ring
through physical star topology
Move token and frames around the ring
Amplify data signals
Connect in a daisy-chained manner to
expand token ring network
Provide for orderly movement of data
Shut down ports to malfunctioning nodes
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MAUs
Passive hub
Active hub
Patch cables and lobe cables
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Ring In and Ring Out Ports
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Token Ring MAU
Specifications
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Hub
Central network device used in star
topology to join networks
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Hubs Are Used to…
Provide a central unit from which to connect
multiple nodes into one network
Permit many computers to be connected on single
or multiple LANs
Provide multiprotocol services
Consolidate network backbone
Provide connections for different media types
Enable centralized network management and
design
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Types of Network Hubs
Unmanaged hubs
Dual-speed hubs
Workgroup hubs
Stackable hubs
Chassis hubs
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Bridge
Connects different LANs or LAN segments
using the same access method
Operates in promiscuous mode; can look at
frame addresses (unlike repeaters)
Operates at MAC sublayer of OSI Data
Link layer
Protocol independent; only look at MAC
address
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Bridges Are Used to…
Extend a LAN when maximum connection
limit has been reached
Extend a LAN beyond the length limit
Segment LANs to reduce data traffic
bottlenecks
Prevent unauthorized access to a LAN
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Bridged Network
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Bridge Functions
Learning
Filtering
Forwarding
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Cascade Bridging
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Advantages of Bridges
Limit traffic to certain network segments;
enhance performance
Can use as a firewall to keep intruders out
of a network
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Types of Bridges
Local bridge
Connects networks in close proximity
Can be used to segment a portion of a network
to reduce heavy traffic problems
Remote bridge
Joins networks across the same city, between
cities, and between states to create one network
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Bridge
Token ring source-route bridge
Incorporated into 802.5 token ring LAN
specification
Performs routing at OSI Network layer
Spanning tree algorithm
Ensures that frames are not transmitted in an
endless loop
Enables frames to be sent along most costeffective network path
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Bridge Protocol Data Units
(BPDUs) Frame Format
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Router
Connects networks having the same or different
access methods and media
Forwards packets to networks by using decisionmaking process based on:
Routing table data
Discovery of most efficient routes
Preprogrammed information from network
administrator
Connects LAN at Network layer of OSI model
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Routers Are Used to…
Efficiently direct packets from one network
to another, reducing excessive traffic
Join neighboring or distant networks
Connect dissimilar networks
Prevent network bottlenecks by isolating
portions of a network
Secure portions of a network from intruders
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Static and Dynamic Routing
Static routing
Controls routing decisions by network
administrator through preset routing
instructions
Dynamic routing
Constantly checks network configuration
Automatically updates routing tables
Makes decisions about how to route packets
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Routing Tables and Protocols
Routing tables
Contain addresses of other routers
Routing protocols
Routing Information Protocol (RIP)
Communicates entire contents of routing tables to
other routers
Open Shortest Path First (OSPF) protocol
Communicates information about immediate links to
other nodes
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Advantages of OSPF Protocol
Sends only the portion of routing table that
pertains to its most immediate router links
Packages routing information in more
compact format that RIP
Only updated routing table information is
shared among routers, rather than the entire
routing table
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Brouter
Acts as a bridge or a router, depending on
how it is set up to forward a given protocol
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Brouters Are Used to…
Handle packets efficiently on a multiprotocol
network that includes some protocols that can be
routed and some that cannot
Isolate and direct network traffic to reduce
congestion
Join networks
Secure a certain portion of a network by
controlling who can access it
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Switch
Links network segments
Forwards and filters frames between
segments
Provides bridging capacity and the ability to
increase bandwidth on existing networks
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Switching Techniques
Cut-through switching
Store-and-forward switching (buffered
switching)
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Gateway
Enables communications between two
different types of networked systems
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Gateways Are Used to…
Convert commonly used protocols to a specialized
protocol
Convert message formats
Translate different addressing schemes
Link a host computer to a LAN
Provide terminal emulation
Direct electronic mail to the right network
destination
Connect networks with different architectures
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Gateway
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WAN Transmission Equipment
Designed to work over POTS and leased
telephone lines (T-carrier and ISDN)
May be analog or digital
Either converts a signal for long-distance
communications or creates multiple
channels
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Examples of Basic WAN
Transmission Equipment
Multiplexers
Channel banks
Private telephone
networks
Telephone modems
ISDN adapters
Cable TV modems
DSL modems and
routers
Access servers
Routers
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Multiplexer (MUX)
Can receive multiple inputs and transmit them to a
shared network medium
Works at OSI Physical layer, switching from
channel to channel using:
A single method for optical transmissions (wavelength
division multiplexing or WDM), or
One of three electrical switching methods
Time division multiple access (TDMA)
Frequency division multiple access (FDMA)
Statistical multiple access
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Using Multiplexers
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Channel Bank
Large-scale multiplexer that combines
telecommunications channels in a
centralized location
First used in voice applications, now handle
voice, data, and video
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Private Telephone Networks
Private branch exchanges (PBXs)
Private automatic exchanges (PAXs)
Private automatic branch exchanges
(PABXs)
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Telephone Modems
Convert computer’s outgoing digital signal
to analog signal that can be transmitted over
a telephone line
Also convert incoming analog signal to a
digital signal the computer can understand
Attached internally or externally
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Telephone Modems
Types of connectors (DB-25, DB-9, PS/2,
universal serial bus or USB)
Modem data transfer rate measured by baud
rate or bits per second (bps)
Synchronous or asynchronous
communication format
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ISDN Adapters
Connect a computer or fax to an ISDN line
Terminal adapter (TA) converts digital
signal to a protocol that can be sent over a
digital telephone line
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Cable TV Modems
Digital modem devices designed for use
with cable TV system, providing high-speed
data transfer
Share bandwidth with others, but
dynamically allocate unused cable
bandwidth
Either internal or external
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DSL Modems and Routers
Digital Subscriber Line (DSL)
Uses advanced modulation technologies on
existing telecommunications networks for highspeed networking between subscriber and telco
Communication speeds up to 60 Mbps
Dedicated to single user; employs full
bandwidth of the line
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Connecting to DSL
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Access Servers
Connect synchronous and asynchronous
devices to a network, providing routing for
both types of communications
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Using an Access Server
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Remote Routers
Join networks in WANs over long distances
Connect ATM, ISDN, frame relay, highspeed serial, and X.25 networks
Can support multiple protocols
Can be set up as firewalls
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Chapter Summary
Network transmission equipment used on
LANs, WANs, or both
Modems
Bridges
Gateways
Channel banks
Access servers
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