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PC Peripherals for
Technicians
Chapter 5
LAN Overview
Systems Manufacturing Training
and Employee Development
Copyright © 1998 Intel Corp.
1
Local Area Network
Overview
OBJECTIVES: At the end of this section, the
student will be able to do the following:

Discuss the architecture of Local Area Networks

Describe Ethernet Standards and Topologies.

Discuss Ethernet operation and Ethernet LAN Media.

Describe 100 Mbps Fast Ethernet.

Explain the functions of a Network Interface Card.

List common devices used for extending LANs.
2
Introduction to Local Area Networks
A Network is a collection of independent computers that
communicate with one another over a shared network medium
My PC
EMail
EMail
Your PC
Network
OS
Network
OS
Adapter
Drivers
Adapter
Drivers
Network
Interface
Card
The
Network
Network
Interface
Card
3
Introduction to Local Area Networks

A Network is a way of connecting a bunch of
computers (nodes, clients, workstations, or servers)
and peripherals together.
Allows
»
sharing of Peripherals, Applications, and Data.
E-mail, Web browsing, and sharing a printer or disk drive.
Ethernet
is the most widely used network protocol
and is the focus of this chapter.

Stations are generally connected to the Network
through an intelligent interface known as a Network
Interface Card (NIC), Network Adapter Card, LAN
Adapter, or Ethernet Card.
The
NIC provides a physical connection between the
network cable and the computer’s internal bus.
4
Introduction to Local Area Networks


Local Area Networks (LANs) encompass Computers,
Workstations, Peripherals, Cabling and Software.
»
LANs are networks confined to a moderate sized
geographic area (typically 0.1 to 1 km) such as a campus,
building, floor, or a room.
»
LANs may link hundreds of computers used by thousands
of users.
LANs can be interconnected to form larger networks
called Wide Area Networks (WANs).
A
Wide Area Network is the connecting of multiple LANs
that are geographically separated (100 km to 10,000
km).
A
WAN connects the different LANs using
telecommunications services including phone lines and5
satellite links.
Introduction to Local Area Networks

A SERVER is a device on a network that manages
network resources.
Servers
are often dedicated--they perform no other tasks
besides their server tasks.
»
Computers connected to the server are called “clients”.
The
most common types of servers are file servers, print
servers, mail servers, database servers, and
communication gateway servers.
»
A file server is a computer dedicated to network accessible
file storage.
>
>
»
Any user on the network can access files on the server.
Can be thought of as a remote hard disk
A print server is a computer that manages one or more
printers.
6
Introduction to Local Area Networks
7 Layered Model of Computer Networks
PC #1
PC #2
Network Interface Cards
are part of Layers 1 & 2
The rest is software!
7
Application
Application
6
Presentation
5
Session
Session
4
Transport
Transport
3
Network
Network
2
Data Link
(MAC)
Data Link
(MAC)
1
Physical
Presentation
SOFTWARE
HARDWARE
Routing
Physical
7
Introduction to Local Area Networks

7 Layered Model of Computer Networks (Cont.)
Upper
»
Provide user oriented services (email, file transfer, etc.),
maintains & terminates connections, and provides address
translation, text compression & encryption when necessary.
Data
»
Layers (3-7): Software
Link - Layer 2: Hardware
Applies protocol which makes layer 1 appear as error free
point to point link to layer 3 (e.g ENET, Token Ring).
>
MAC (Medial Access Control) & LLC (Logical Link Control)
Physical
-Layer 1: Hardware
»
Deals with transmission of raw bits - converts digital signals
to electrical signals the network can understand.
»
Specifies hardware, cable, connectors, signaling speed.
8
Introduction to Local Area Networks

Network Interface Cards (NICs) provide the physical
connection between the network cable and the computer's
internal bus (More NIC details later in chapter).
A
software Device Driver enables the NIC in a computer to:
»
Encode data from the operating system for transmission by
the Ethernet card through the network.
»
Decode received packets and send them to the O/S.
Network
Cable
PC
Packet
Formation
PC/NIC
Interface
Buffer
(FIFO)
Data Packets
(Serial)
Encode/
Decode
Parallel
Data`
Transceiver
Data Bits
(1’s/0’s
NIC/Cable
Interface
Network Interface Card (NIC)
9
Introduction to Local Area Networks
Baseband vs. Broadband Signaling
Baseband
HOST PC
1
1
0
NETWORK
MEDIA
NETWORK
INTERFACE CARD
1
1
1
0
0 0
1
0
1
1
0
0 0
FULL CAPACITY OF
NETWORK MEDIA

Devices on a baseband network, such as Ethernet, use the
entire frequency spectrum, so that only one transmission can
take place at a time.
 An
analogy is a single phone line: Only one person can talk at a
time--if more than one person wants to talk everyone has to take
turns.
10
Introduction to Local Area Networks
Baseband vs. Broadband Signaling
Broadband
NETWORK
INTERFACE
CARD
HOST PC
1
1
0

NETWORK
MEDIA
Modulator/
Demodulator
1
1
0
0 0
1 0 11 0
1 00
Broadband uses only a portion of the spectrum for each
transmission, so that multiple channels can share the same
medium using frequency division multiplexing.
 One
of several “Channels” on Network Media.
»
The signals need to be multiplexed onto a carrier frequency.
A
broadband example is a television signal over the cable line.
11
Ethernet Standards & Topologies
Ethernet is the most widely used LAN technology
»
Ethernet is a type of network cabling and signaling
specifications (OSI Model layers 1 [physical] & 2 [data link])
802.3 - “Ethernet”: All Ethernet equipment since
1985 is built according to this standard.
IEEE
»
10BASE-5
Thick coax
»
10BASE-2
Thin coax - “Cheapernet”
»
10BASE-T
Twisted Pair Ethernet - “TPE”
»
10BASE-FL Fiber Optic Link
»
Note: IEEE 802.3u known as 100BASE-xx presented later.
IEEE
»
802.5--Token Ring is an alternative LAN standard .
A special bit pattern, called a token, passes around -- if a
station wants to transmit, it has to wait until it gets the token.
12
Ethernet Standards & Topologies
802.3 Naming Conventions: Example: 10BASE-5

IEEE identifiers include three pieces of information.
First
»
item, "10", stands for the media speed of 10-Mbps.
Data Rate: 1, 10, or 100 Megabits per second
BASE/BROAD:
3rd
Baseband vs. Broadband signaling.
part is a rough indication of segment type or length.
»
For thick coax the "5" indicates the 500 meter maximum
length allowed for individual segments of thick coaxial
cable.
»
For thin coax the "2" is rounded up from the 185 meter
maximum length for individual thin coaxial segments.
»
The "T' and "F" stand for "twisted-pair" and "fiber optic," and
indicate the cable type--they do not imply a specific length.
13
Ethernet Standards & Topologies
BUS TOPOLOGY
Thin Ethernet
Thick
Ethernet
A
bus topology consists of nodes linked together in
series with each node connected to a long cable or bus.
»
All stations connect in a single row to the same segment.
The
BUS is the simplest (and the traditional) topology.
»
Standard Ethernet (10BASE5) & Thin Ethernet (10BASE2),
both based on coaxial cable systems, use the bus.
»
A cable break will cause the segment to be inoperable.
Both
ends of a segment should be terminated .
14
Ethernet Standards & Topologies
Twisted Pair Ethernet (TPE)
STAR TOPOLOGY
In a star topology, all attached nodes
(workstations) are wired directly to a
central hub, which establishes and
maintains connections between them.

hub
The Star topology is used for twisted-pair cabling
(10BASE-T Ethernet), fiberoptic links, & Fast Ethernet.
The
advantage of a star topology is that it is easy to
isolate a problem node.
»
Point to Point--dedicated line between two endpoints.
The
disadvantage is that if the hub fails, the entire
system is compromised.
15
Basic Operation of an Ethernet LAN

Individual computers are generally connected to the
LAN through an intelligent interface unit, the NIC.
»
The NIC implements CSMA/CD in Layer 2 (MAC).
Carrier
Sense Multiple Access with Collision Detection
(CSMA/CD) allows many stations to share a single
common media and resolve contention (collisions).
»
Multiple stations access a medium (Multiple Access) by
listening until no signals are detected (Carrier Sense).
»
Then they transmit and check to see if more than one signal
is present (Collision Detection).
»
If the sending station detects the collision, it sends a jam
signal to insure that all nodes are aware of the collision.
»
If there is a collision, each station attempts to retransmit
after a preset delay, which varies for each station.
16
Basic Operation of an Ethernet LAN

The data is sent in packets (each station listens to all
the transmissions, picking up those addressed to it).
Preamble DA
SA
Type/Length
Data
CRC
A
block of data is called a "frame" which includes
address fields, a variable size data field, and an error
checking field (64-1518 bytes total).
»
»
The preamble is a string of alternating 1’s and 0’s used to
"lock on" to the sending station's encoded clock signal.
A frame contains a Destination Address & Source Address.
>
A unique 6-byte ENET address is pre-assigned to each
Ethernet card when it is manufactured (AKA: Ethernet address,
physical address, hardware address, or MAC address).
17
Basic Operation of an Ethernet LAN

The physical layer hardware monitors (receives) every
frame transmitted across the media (cable), picking up
those packets addressed to it.
Devices
look for their own MAC address in each packet
to determine whether they should capture it or not.
If
the Destination Address (first 6 bytes of frame)
matches the address of this station, the frame is stored
and passed up to the higher layers of protocol .
»
If the address does not match, the frame is ignored.
The
NIC asserts an interrupt to instruct the processor to
read the data.
18
ETHERNET LAN MEDIA


The Communication Channel, Transmission Medium,
or the LAN Medium defines the nature of the physical
path along which the data must travel.
There are three major types of media in use today:
Coaxial
cable
»
Thickwire for 10BASE5 networks.
»
Thin coax for 10BASE2 networks.
Twisted
pair cable (the most popular Ethernet cabling)
»
Unshielded twisted pair (UTP) for 10BASE-T networks.
»
Many newer buildings are already wired with 10BASE-T.
Fiber
»
optic cable.
10BASE-FL or Fiber-Optic Inter-repeater Link (FOIRL)
networks.
19
ETHERNET LAN MEDIA
Standard Ethernet (Coax) 10BASE5--Thickwire
MAU--100 max
per segment
AUI cable-- 50m max
Coax cable
500m max.
PC
PC
PC with adapter (NIC)

Thick Ethernet (10 Base-5) is the oldest form of Ethernet
and is laid out in a bus topology.
 The
most common coax cables used are RG-8 and RG-11 (50 ohm)
 Devices
attach to the backbone via a Medium Attachment Unit
(MAU), also known as the transceiver.
 Both
ends of segment should be terminated with a 50-ohm resistor.
 Today,
the most common use for 10 Base-5 is as a "backbone" used
to connect together multiple 10 Base-T Hubs.
20
ETHERNET LAN MEDIA
Thin Ethernet (Coax) 10BASE2--Cheapernet
coax cable
185m max
PC
MAU--(PC with Adapter)
30 max per segment

PC
PC
BNC T-Connector
10 Base-2, Thin Ethernet, or "Cheapernet" uses an RG58A/U (50 ohm) coaxial cable & is wired in a bus topology.
 Each
device is connected to the bus through a BNC "T" adapter, and
each end of the bus must have a 50 Ohm terminator attached.
»
Any unused connection must have a 50 ohm terminator.
 Typically
devices use Ethernet NICs with built-in BNC transceivers.
21
ETHERNET LAN MEDIA
Twisted Pair Ethernet (10BASE-T)
Standard Ethernet (Coax)
10BASE T Hub
100m Max
RJ-45
MAU - PC
Adapter

Workstations are connected to a central concentrator
("hub") in a STAR configuration.

10Base-T uses 2 pairs of Twisted wires in a star topology
which are terminated in an 8-pin RJ-45 connector
 An
RJ-45 connector looks like a large telephone-style connector.
Continued on next page
22
ETHERNET LAN MEDIA
Twisted Pair Ethernet (10BASE-T) Cont.

Cable is Unshielded Twisted Pair (UTP) ~standard
telephone wire (many buildings already wired with UTP).
 Uses
»
2 pairs of wires: One for transmit data, other for receive data.
Note: A small transformer couples the data from the network to
the LAN section and prevents damages caused by improper
power wiring, lightning strikes, power surges, etc.
Magnetics
(Transformer)
RJ45
Connector
TX+
1
Transmit
data
TX-
2
RX+
3
RX-
6
Recieve
data
Continued on next page
23
ETHERNET LAN MEDIA
Twisted Pair Ethernet (10BASE-T) Cont.
10
Base-T utilizes CAT 3 (or higher) 100 ohm UTP cable.
One
difference between the categories of UTP is the
tightness of the twisting of the copper pairs.
»
Category 1 Voice Only
(Telephone Wire)
»
Category 2 Data to 4 Mbps
(LocalTalk)
»
Category 3 Data to 10 Mbps (Ethernet)
»
Category 4 Data to 20 Mbps
»
Category 5 Data to 100 Mbps (Fast Ethernet)
(Token Ring)
The
two wires in each pair must be twisted together for
the entire length of the segment to reduce susceptibility
to interference from adjacent pairs & the environment.
»
Shielded twisted pair (STP) is suitable for environments with
electrical interference (e.g. factory floor)
24
ETHERNET LAN MEDIA
PVC Jacket
Fiberoptic Ethernet (FOIRL, 10BASE-FL)
Sleeve
Light
Source
10 Base-FL is wired in a star topology,
is half-duplex, & supports transmission
speeds from 200-1000 Mbits/sec.

Sleeve
PVC Jacket
FOIRL (Fiber Optic InterRepeater Link) and the more
recent 10BASE-FL differ only in how far each will transmit
 FOIRL
is 1 km (0.6 miles); for 10BASE-FL it is 2 km (1.2 miles).

Fiber optic transmission requires conversion of the
electrical signals to light by a light source (e.g. LED/Laser)
incorporated in an external Fiber Optic MAU.

Fiber-optic cable is more expensive, but it is often used for
situations where electronic emissions (EMI), security, and
environmental hazards (e.g. lightning) are a concern. 25
ETHERNET LAN MEDIA

Wireless LANs typically use high frequency radio
signals or infrared light beams to communicate.
Each
workstation and file server has some sort of
transceiver/antenna to send and receive data as if they
were physically connected.
»

Longer distance communications can also take place
through cellular telephone technology or by satellite.
Wireless networks allows laptops & remote computers
to connect to the LAN and are also used in older
buildings where it may be difficult to install cables.
Wireless
LANs currently are expensive, susceptible to
errors from electrical interference, and provide poor
security unless encrypted.
26
100 Mbits/sec "Fast Ethernet"

Fast Ethernet (IEEE 802.3u - June 1995) transports
data at 100 Mbps over either UTP or fiber-optic cable.
Fast
Ethernet is an extension of 10BASE-T Ethernet &
retains the CSMA/CD protocol of 10 Mbps Ethernet.
»
Uses star topology and doesn't support coaxial cabling.
There
»
are three types of Fast Ethernet:
100BASE-TX--a two-pair system for data grade Cat 5 UTP.
>
Uses one pair of high quality wires for transmission and the
other pair for collision detection and receive.
»
100BASE-FX for use with multimode fiber-optic cable.
»
100BASE-T4 utilizes 4 pairs of wires with the relatively slow
Category 3 UTP cable.
>
"Demultiplexing" slows down each byte enough that the signal
won't overrun the slower Category 3 UTP cable.
27
Fast Ethernet Optional Features
Full
Duplex provides bi-directional communication and
delivers up to 100 Mbps in each direction (200 Mbps).
»
The full duplex mode of operation requires that each end of
the link only connects to a single device.
>
»
Can be used in a server connection, where the wiring is
dedicated and bi-directional operation is useful.
Full-duplex communication is implemented by disabling the
collision detection function.
Auto-Negotiation
allows devices to exchange information
about their abilities & to perform automatic configuration
to achieve the best possible mode of operation.
»
Auto-Negotiation detects the various modes that exist in the
device on the other end of the wire and automatically
switches to the correct technology--10Base-T, 100Base-TX,
100Base-T4, or Half/Full Duplex mode.
28
Network Interface Card Functions

The Network Interface Card (NIC) provides the physical
connection between the network and the PC.
 The
NIC takes the transmit data from the PC, puts it into the
appropriate format, and sends the serialized transmit data over
the media to another LAN interface card.
 The
NIC also receives the data, puts it into a form the PC
understands, and places data & status in shared memory for
the CPU to read.
Network
Cable
PC
Packet
Formation
PC/NIC
Interface
Buffer
(FIFO)
Data Packets
(Serial)
Encode/
Decode
Parallel
Data`
Transceiver
Data Bits
(1’s/0’s
NIC/Cable
Interface
Network Interface Card (NIC)
29
Network Interface Card Functions
Network
Cable
PC
Packet
Formation
Parallel
Data`
Buffer
(FIFO)
Data Packets
(Serial)
Encode/
Decode
Transceiver
Data Bits
(1’s/0’s
The NIC functions to get data from the memory of one PC
to the memory of another PC can be broken into tasks:
»
1 - PC/NIC communications
>
»
2 - Packet formation (Transmit sequence example)
>
»
Data is formatted into packets & converted from parallel-serial.
3 - Encoding/decoding
>
»
The CPU & NIC communicate via shared host PC memory to
move data between the Host PC & the LAN Coprocessor.
Manchester encoding is used to combine the clock and data.
4 - Transmission/reception
>
NIC accesses the cable using the CSMA/CD protocol.
30
Network Interface Card Functions

1 - The CPU & the NIC communicate via shared memory to
move Data between the Host PC & the LAN Coprocessor
 The
CPU places commands and transmit data in shared memory in
the host PC and notifies the NIC that data is available.
»
Either Programmed I/O, DMA, or Bus Master DMA is used to
transfer the data between the NIC & PC main memory, depending
on NIC architecture, bus type (ISA, PCI, etc), & the Network O/S.
 The
NIC also receives packets from the physical layer, places data &
status in shared memory, and notifies the CPU that data is available
using the IRQ line.
Shared Memory
CPU
config
status
commands
Rx Buffer
Tx Buffer
LAN
Coprocessor
LAN
Data
31
Network Interface Card Functions

2 - Packet formation: Data is sent as packets and
converted from parallel-serial.
»
A packet has three sections: header (synch information,
destination address, & source address), data, and trailer.
>
»
Each NIC is identified by a unique 12 digit (6-byte) hex address
which is usually stored in an EEPROM or FLASH on the NIC.
The trailer includes a CRC calculated by the sending NIC.
A
transmit and receive buffer (FIFO) hold data moving
into and out of the NIC (e.g. 3Kbytes; ~2 packets).
»
Data often moves into or out of the card faster than it can be
processed by the NIC.
The
»
NIC performs parallel-serial conversion & vice versa.
The packets must be converted to serial form to be sent
over the cable one bit at a time.
32
Network Interface Card Functions

3 - Encoding/decoding
Once
a packet is formed and changed from parallel to
serial, it is encoded using Manchester encoding to
combine the clock & data into one serial data stream.
With
Manchester encoding, the encoded data has a
transition at the center of each data bit.
»
A change from negative to positive represents a 1.
»
A change from positive to negative represents a 0.
BIT CELL
Actual
Data
“1”
“0”
“1”
“1”
“0”
“0”
“1”
“0”
“0”
“1”
“0”
“0”
Manchester
Encoded Data
33
Network Interface Card Functions

4 - Transmission/reception: Before data can be sent
the NIC accesses the cable using CSMA/CD protocol.
Ethernet
uses the CSMA/CD protocol as a means for
many stations to share a single common media and
resolve contention (collisions).
»
The entire protocol for the access method, all the circuitry
and firmware, resides on the Network Interface Card.
The
Medium Attachment Unit (MAU), also known as the
transceiver, performs the task of transmitting the frames
onto the cable and receiving them from it.
»
The transceiver can either be external or on-board the NIC.
>
Many NICs contain a built-in 10BASE-T or 10BASE2
transceiver, allowing them to be connected directly to Ethernet
without requiring an external transceiver.
Continued on next page
34
Network Interface Card Functions

4 - Transmission/reception (cont.):
At
the receiving end, a transceiver is waiting to accept
the signal and begin the whole process in reverse:

»
Decoding the signal, Serial-Parallel conversion, and
depacketizing to a PC-readable data format.
»
When the NIC receives the data it asserts an interrupt
request line, and an Interrupt Service Routine (ISR)
instructs processor to read the data.
Note: An optional “Boot Rom” may be used to connect
to a server to download the O/S at boot time.
A
Boot Rom enables diskless workstations to remote
boot an operating system at startup.
»
The Prom or Flash chip contains the instructions necessary
to access a disk image on the server.
35
Extending LANs

Bridges, Routers, and Gateways are Internetworking
devices that provide communications between local
area network (LAN) segments.
»
Internetworking refers to linking individual LANs together.
Geographically
distant company sites can be tied
together in the enterprise-wide internetwork.
Workgroup
LANs on different floors or in separate
buildings can be linked together so that all of the
computing systems at that site are interconnected.
»
Internetworking provides network connectivity for more
people, or extends coverage to a larger area.
»
Internetworking is also used to segment LANs to maintain
performance by reducing the number of users per segment.
36
Extending LANs - HUBS

A HUB takes an ENET packet transmitted to it by one
station, & repeats it to all of the other ports of the hub.
Hubs
are generally associated with 10BASE-T Ethernet
networks and are necessary in star topologies.
»
If the hub is attached to a backbone, then all computers at
the end of the twisted pair segments can communicate with
all the hosts on the backbone.
Passive
hubs are simple splitters or combiners that
group workstations into a single segment.
»
Requires no power and does no processing of traffic.
Active
hubs contain circuitry, include a repeater function,
and are capable of supporting many more connections.
37
Extending LANs - Bridges

Bridges connect LANs & forward or filter data packets
based on the destination address--forward if not local.
Bridges
operate at the data link level (a layer 2 relay)
»
Bridges know the addresses of all computers on each side
of the network.
»
If a packet's destination is on the same segment (usually
referring to a physical length of wire), it is not forwarded.
»
If it is destined for a station on another LAN, it is connected
to a different bridge port and forwarded to that port.
Bridges
are transparent to client & server workstations.
Bridges
normally connect similar LANs that use the same
protocol but may have different types of cabling (e.g.
Ethernet Coax to Ethernet 10BaseT)
38
Extending LANs - Routers

A Router is an OSI layer 3 device.
Routers
are more complex and typically more expensive
than bridges, and are often PC based.
»
Bridging occurs at a lower level (more a hardware function)
whereas routing occurs at a higher level where the software
component can perform more complex path analysis.
Routers
communicate with each other and share
information that allows them to determine the best route.
»
A router maintains a list of all stations & determines the
optimal routing paths (which cable to send out information).
>
»
Routers know the addresses of computers, bridges, and other
routers on the network.
A router can convert from different access methods
(CSMA/CD, Token Ring, etc).
39
Extending LANs - Gateways

A Gateway is a protocol converter between dissimilar
networks.
Gateways
are complex and relatively slow and can
connect dissimilar networks that differ in all details.
»
Gateways can translate all protocol levels from the Physical
layer up through the Applications layer of the OSI model.
»
Can convert a TCP/IP packet to a Netware IPX packet.
Gateways
capabilities can include:
»
Terminal emulation - So a PC can act like an IBM 3270
mainframe terminal.
»
File transfer - A Novell user could download a file from a
Unix machine.
»
Mail - Exchanging messages between users on different email systems.
40
REVIEW & SUMMARY
WE HAVE DISCUSSED THE FOLLOWING:

The architecture of Local Area Networks.
A
Network is a collection of computers that communicate
with one another over a shared network medium.
NICs
provide the physical connection between the
network cable and the computer's internal bus.

Ethernet Standards and Topologies.
Ethernet
is the most widely used type of network cabling
and signaling specification.
The
BUS is the simplest (and the traditional) topology.
The
Star topology is used for twisted-pair cabling
(10BASE-T Ethernet), fiberoptic links, & Fast Ethernet.
41
REVIEW & SUMMARY

Ethernet operation and Ethernet LAN Media.
CSMA/CD
allows many stations to share a single
common media and resolve contention (collisions)
»
The data is sent in packets and each station listens to all
the transmissions, picking up those addressed to it.
»
If the Destination Address matches this station, the frame is
stored and passed up to the higher layers of protocol .
There
»

are three major types of media in use today:
Coax cable--Thickwire (10BASE5) & Thin coax (10BASE2);
Twisted pair cable (the most popular); and Fiber optic cable.
100 Mbps Fast Ethernet.
Fast
Ethernet is an extension of 10BASE-T Ethernet,
uses star topology and doesn't support coaxial cabling.
42
REVIEW & SUMMARY

The functions of a Network Interface Card.
NIC

functions can be broken into tasks:
»
1 - PC/NIC communications (via shared host PC memory)
»
2 - Packet formation and conversion from parallel-serial.
»
3 - Manchester encoding to combine the clock and data.
»
4 - Transmission/reception--access cable using CSMA/CD.
Common devices used for extending LANs.
»
HUB repeats packet to all of the other ports of the hub.
»
Bridges connect LANs and forward if not local.
»
Routers are more complex than bridges, are often PC
based, and determine the optimal routing paths.
»
A Gateway is a protocol converter between dissimilar
networks (more complex than a Bridge or Router).
End of Chapter 5-1
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