Multistation Access Units
(MAUs)
Chapter 6





Connect workstations in a logical ring
through a physical star topology
Move the token and packets around the
ring
Amplify data signals
Connect in a daisy-chained manner to
expand a token ring network
Provide orderly movement of data
Multistation Access Units
(MAUs)
Chapter 6


A passive hub connects nodes in a star
topology, performing no signal enhancement as the packet moves from one
node to the next through the hub.
An active hub connects nodes in a star
topology, regenerating, retiming, and
amplifying the data signal each time it
passes through the hub.
MAU with Eight Connections
Chapter 6
Ring-in (RI)
connection
Ring-out (RO)
connection
MAU
MAUs Connected
Using the RI and RO Ports
Chapter 6
Type 6 patch cable
RI
RO
RI
RO
Type 6
patch cable
RI
RO
To Draw the Network Diagram
Chapter 6

Drawing the token
ring network in
Microsoft Paint
Multiplexers
Chapter 6


A multiplexer is a switch that divides a
communication medium into multiple
channels so several nodes can
communicate at the same time.
A signal that is multiplexed must be
demultiplexed at the other end.
Multiplexers
Chapter 6
Multiplexers
Chapter 6

Work at the OSI physical level,
switching from channel to channel using
one of three physical methods:
 Time
division multiple access (TDMA)
 Frequency division multiple access (FDMA)
 Statistical multiple access
Multiplexers
Chapter 6



TDMA enables multiple devices to communicate over the same communications medium
by creating time slots in which each device
transmits.
FDMA creates separate channels on one
communication medium by establishing
different frequencies for each channel.
Statistical multiple access multiplexing
allocates the communication resources
according to what is needed for the task.
Repeaters
Chapter 6


A repeater amplifies and retimes a
packet-carrying signal so it can be sent
along all cable segments.
As used in this context, a segment of
cable is one cable run within the IEEE
specifications.
How Repeaters Are Used
Chapter 6




To extend a cable segment
To increase the number of nodes
beyond the limit of one segment
To sense a problem and shut down a
cable segment
To amplify and retime a signal (as a
component in other network devices)
Using a Repeater
to Extend a Network
Chapter 6
Research lab
Research lab
Repeater
Business office
President’s office
Repeaters
Chapter 6


An attached unit interface (AUI)
connects coax or fiber-optic backbone
cable to a network node, such as a
repeater.
A partitioned segment is one that has
been shut down because a portion of
the segment is malfunctioning.
To Diagram the Interoffice
Network
Chapter 6

Microsoft Paint
diagram of two
rooms connected
by a repeater
Bridges
Chapter 6

A bridge is a network device that
connects different LAN segments using
the same access method.
How Bridges Are Used
Chapter 6




To extend a LAN when the maximum
connection limit has been reached
To extend a LAN beyond the length limit
To segment LANs to reduce data traffic
bottlenecks
To prevent unauthorized access to LAN
(for security)
Bridged Network
Chapter 6
Bridge
Bridges
Chapter 6

A network device that operates in
promiscuous mode reads frame
destination address information before
sending a packet onto other connected
segments of the network.
Types of Bridges
Chapter 6


A local bridge connects networks in
close proximity and is used to segment
a portion of a network to reduce
problems caused by heavy traffic.
A remote bridge joins networks across
the same city, between cities, and
between states to create one network.
Important Functions of a Bridge
Chapter 6



Learning
Filtering
Forwarding
Cascaded Network Segments
Chapter 6
LAN 1
Bridge A
LAN 2
Bridge B
LAN 3
Token Ring Bridging
Chapter 6


Token ring bridges
use source routing
to forward packets
on the network.
Hops are the
number of times a
packet travels pointto-point from one
network to the next.
Source route bridging
Routers
Chapter 6


A router connects networks having the
same or different access methods.
It forwards packets to networks by using
a decision-making process based on:
 Routing
table data
 Discovery of the most efficient routes
 Preprogrammed information from the
network administrator
How Routers Are Used
Chapter 6





To efficiently direct packets from one network
to another, reducing excessive traffic
To join neighboring or distant networks
To connect dissimilar networks
To prevent network bottlenecks by isolating
portions of a network
To secure portions of a network from intruders
A Router Forwarding a Frame to
the Right Network
Chapter 6
Static and Dynamic Routing
Chapter 6


Static routing involves control of routing
decisions by the network administrator
through preset routing instructions.
In dynamic routing, the router constantly:
 Checks
the network configuration
 Automatically updates routing tables
 Makes its own decisions about how to route
frames
Routing Tables and Protocols
Chapter 6

Routers maintain information about node
addresses and network status in databases.
 The
routing table database contains the addresses
of other routers and each end node.


Routers regularly exchange information about
network traffic, the network topology, and the
status of network lines.
Routers exchange information by using one
or more routing protocols.
Local and Remote Routers
Chapter 6



A local router joins networks in the same
building or between buildings in close
proximity.
A firewall is software and/or hardware
employed to restrict who has access to a
network, to specific network segments, or to
certain network resources (such as servers).
A remote router joins networks across large
geographical areas, such as between cities,
states, and countries.
A Local Router Connecting
Networks in Adjacent Buildings
Chapter 6
Business building
Router
Manufacturing building
Brouters
Chapter 6


A brouter, also called a multiprotocol
router, is a network device that acts like
a bridge or a router, depending on how
it is set up to forward a given protocol.
It is used on networks that operate with
several different protocols.
How Brouters Are Used
Chapter 6




For efficient packet handling on a
multiprotocol network with some protocols
that can be routed and some that cannot
To isolate and direct network traffic to
reduce congestion
To join networks
To secure a certain portion of a network
by controlling who can access it
Hubs
Chapter 6


A hub is a central network device that
connects network devices in a star
topology.
It is also referred to as a concentrator
(or switch), which is a device that can
have multiple inputs and outputs all
active at one time.
Services Offered by Hubs
Chapter 6




Provide a central unit from which to
connect multiple nodes into one network
Permit large numbers of computers to be
connected on single or multiple LANs
Reduce network congestion through
centralizing network design
Provide multiprotocol services
Types of Hubs
Chapter 6




MAUs
10BASE-T hubs
100BASE-X hubs
Intelligent and modular hubs
10BASE-T Hubs
Chapter 6




One of the simplest hubs
Popular way to connect workgroups on
small and large LANs
Uses physical star topology to connect
PCs to the central hub
Additional hubs are added by
connecting one hub to the next.
Switching Hubs
Chapter 6



Permit significant increase in the throughput
capability of an existing 4 Mbps, 10 Mbps, or
16 Mbps network by taking full advantage of
exiting bandwidth capabilities
Allow an existing network to be separated into
multiple smaller segments, each independent
of the others
Can be installed on LANs in a WAN where
specific LANs are experiencing increased
network traffic
100BASE-X Hubs
Chapter 6

Multimedia, video, and GUI client/server
applications have fostered the need for
high-bandwidth, high-speed
technologies.
Intelligent and Modular Hubs
Chapter 6



An intelligent hub has network management
and performance monitoring capabilities.
A modular hub, also called a chassis hub,
contains a backplane into which different
modules can be inserted.
A backplane is the main circuit board in
modular equipment, containing slots as plugins for modular cards. It provides connections
between the modular boards, a power source,
and grounding.
To Diagram 10BASE-T Star
Topology on Two Floors
Chapter 6

Network diagram of
10BASE-T network
segments connected
to an intelligent hub
Gateways
Chapter 6

A gateway enables communications
between two different types of
networked systems, such as between
complex protocols or between different
e-mail systems.
How Gateways Are Used
Chapter 6




To convert commonly used protocols to
a specialized protocol
To convert message formats from one
format to another
To translate different addressing
schemes
To link a host computer to a LAN
continued
How Gateways Are Used
Chapter 6



To provide terminal emulation for
connections to a host computer
To direct e-mail to the right network
destination
To connect networks with different
architectures
Systems Network Architecture
(SNA)
Chapter 6


SNA is a layered communications protocol
used by IBM for communications between
IBM mainframe computers and terminals.
It employs seven-layered communications
that are similar to the OSI model, but
there are differences in the way the
services are grouped within the layers.
IBM/Mainframe Connected
through an SNA Gateway
Chapter 6
SNA gateway
ATM Switches
Chapter 6

An ATM switch determines the network
channel used to transmit an ATM cell
received from a node, taking into
account the type of information in the
cell (voice, video, data) and the
transmission speed needed.
Capabilities of ATM Switches
Chapter 6




Provide high-speed communications on
a network backbone
Provide cell transmissions directly to the
desktop
Enable high-speed communication
between network hubs
Centralize network design for better
management
continued
Capabilities of ATM Switches
Chapter 6



Connect to very high speed networks,
such as SONET
Enable network design around
workgroup members at dissimilar
locations (virtual LANs)
Reduce network bottlenecks through
high-speed communications and
efficient traffic management through
workgroups
ATM Switch
Chapter 6
ATM
switch
Virtual LANs (VLANs)
Chapter 6

A virtual LAN (VLAN) uses switches,
routers, and internetworking software to
configure a network into subnetworks of
logical workgroups, independent of the
physical network topology.
Advantages of VLANs
Chapter 6



VLANs enable a network to operate at
the most efficient level; it is not limited
by physical topology.
Network resources can be managed
based on the actual work groupings of
users.
VLANs can be reconfigured to move a
user from an old workgroup to new one.
VLAN Workgroups through ATM
Switching
Chapter 6
ATM
switch
ATM
switch
Central ATM
switch
Networking Devices
and the OSI Model
Chapter 6
OSI Layer
Network Device
Application
Gateways
Presentation
Gateways
Session
Gateways
Transport
Gateways
Network
Gateways, routers, source-route bridges, brouters,
ATM switches
Data link
MAUs, intelligent hubs, bridges, gateways,
brouters, ATM switches
Physical
MAUs, multiplexers, passive and active hubs,
repeaters, gateways