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AgendaAgendaOverview

What is a Network?

Establishing Network Connectivity

OSI Model

Physical Components

DataLink Protocols

Network Protocols

Other Terms and Definitions

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ObjectivesObjectivesUpon completion of this course, the participant will

be able to:

Explain the network concept

Explain how to connect to a network

Describe the OSI Model layers

Differentiate between Physical layer components

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Objectives (continued)Objectives (continued)

Identify characteristics of Ethernet and TokenRing Protocols

Explain Network Protocols

Define DNS, DHCP, WINS, Domain

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OverviewOverview

This course provides an agent with a fundamentalknowledge of basic networking

The foundation this class provides is built upon

in troubleshooting TCP/IP and Wireless

Networking

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What is a Network?What is a Network?A network exists when information and resources

can be shared

A network provides a mechanism for makingbetter use of our resources

When computers are linked to share resources anetwork exists

Two computers connected by a crossover cablecrossover cable comprise the smallest computer network

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What is a Network?What is a Network?One way to describe a network is by the area it spans

LAN – Local Area NetworkLAN – Local Area Network 

• Computer network that spans a relatively small area

• Most are confined to a single building or group of buildings

• All the computers use the same datalink protocol

WAN – Wide Area NetworkWAN – Wide Area Network

• Group of connected LANs

• One LAN can be connected to other LANs over any distance via telephone

lines, leased lines, fiber runs, or radio waves

• The Internet is the largest

MAN – Municipal Area NetworkMAN – Municipal Area Network

• A network within a city or town

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What is a Network?What is a Network?

A network can also be described by the architecture

the computers use to communicate with one another 

Peer-to-Peer Model

• Each computer can share resources and get resources from

another computer in the network• Access is determined by user’s security permissions on each

machine

Client and Server Client and Server  

Can I use the Printer?

Can I use the customer file?

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What is a Network?What is a Network?

Client/Server 

• All computers get resources from the server 

• Access is determined by the user’s security permissions on the

network

Server 

Client

Client

Can I use your printer?

Can I get the customer 

file?

Client

Can I add to the

database?

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What is a Network?What is a Network?

When using Client/Server model, the server operating

system is a Network Operating System (NOS)Network Operating System (NOS)

• Windows 2000/XPWindows 2000/XP and Novell NetwareNovell Netware are the most common

• NOS contains a database of user accounts

• Every user must logon and receive network credentials to access

network resources

• Security permissions are attached to resources

• A specific user may have no access, read only access, or fullno access, read only access, or full

controlcontrol of the resource

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What is a Network?What is a Network?

• In a NOS, users can be combined in groups

• The groups can then be given access to a specific resource

• This reduces administration of security permissions

• In Windows, the server that verifies a user’s right to logon

the network is called a domain controller domain controller 

• The domain controller domain controller contains the Security AccountSecurity Account

Manager (SAM)Manager (SAM)

• This is the database of users

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Establishing Network ConnectivityEstablishing Network Connectivity

Requires four stepsfour steps:

 

• Install the network interface card (NIC)

• Install the NIC driver 

• Install the client software

• Install and configure the network communications protocol

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Establishing Network ConnectivityEstablishing Network Connectivity

Install the NIC

• The NIC is an Input/Output (I/O) cardInput/Output (I/O) card plugged into a slot on themotherboard

Install and Configure the NIC Driver 

• I/O driver is the translator between the device and the operatingsystem

• Think of the operating system as speaking French and the networkas speaking Mandarin

• Driver must speak both languages to allow them to communicateeffectively

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Establishing Network ConnectivityEstablishing Network Connectivity• Most NIC’s are PnP compatiblePnP compatible

• Resources are automatically assigned to the driver while the systemis booting

• These include Interrupt Request (IRQ), I/O Memory, Memory, andInterrupt Request (IRQ), I/O Memory, Memory, andDMADMA

Install the Client Software

• Client software is specific to the NOS

• If server is running Novell Netware, the Netware client must be

installed on the client computer 

• Many Microsoft operating systems install the Microsoft client bydefault

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Establishing Network ConnectivityEstablishing Network Connectivity

Install and Configure the Network Communications

Protocol

• Package and address the network packets ensuring that they are

delivered within the LAN

• Protocol is determined by the NOS

• Windows and the Internet communicate using the TCP/IP protocolTCP/IP protocol

• Novell Netware uses IPX/SPXIPX/SPX and/or TCP/IPTCP/IP

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Establishing Network ConnectivityEstablishing Network Connectivity• The properties for the protocol must be configured in the properties

for the protocol

• With TCP/IP -- an IP address, subnet mask, and default gateway arerequired

• Can be automatically acquired with access to a Dynamic HostDynamic HostConfiguration Protocol (DHCP)Configuration Protocol (DHCP)

• The IPX/SPX protocolIPX/SPX protocol uses an address based on the MediaMedia

Access Control (MAC)Access Control (MAC) address on the NIC

• All clients must use the same frame type

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OSI ModelOSI ModelOSI (Open Systems Interconnect) model was created by the ISO

(International Standards Organization)

• Sets the accepted procedures that govern the development of network

components

• Procedures provide standard interfaces that allow diverse programs and

hardware to interconnect

• Model addresses seven layers of network connectivity but a specific

component may only address one or two of the layers

• A network interface card (NIC), for example, only works at the Physical and

Data Link Layers

• The OSI model defines a consistent communication platform for 

manufacturers and developers of network components

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OSI ModelOSI Model

Application 7

Presentation 6

Session 5

Transport 4

DataLink 2

Network 3

Physical 1 Physical 1

DataLink 2

Network 3

Transport 4

Session 5

Presentation 6

Application 7

Computer A Computer B

bits

Data

Data

Data

Chunked Data

Packet

Frame

Bits

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OSI ModelOSI ModelApplication Layer 

Includes all the network applications a user interacts withincluding:

- HTTP – Hyper Text Transfer Protocol (www) is the protocol used on the world

wide web and determines what types of information can be transferred.

- FTP – File Transfer Protocol is the protocol used to transfer files between

computers

- SMTP – Simple Mail Transfer Protocol is used to send email.

- POP3 – Post Office Protocol 3 is used to receive mail.

- NNTP – Network News Transfer Protocol provides distribution, inquiry, retrieval

and posting of news articles, bulleting boards and chats.

- Gopher  – Gopher is a search engine.

- Telnet – Telnet allows a user to logon and control a remote computer.

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OSI ModelOSI Model

Presentation Layer 

Converts application layer information into a commonformat on the sending computer 

Converts the common format to the application format

at the receiving computer, formats include:

- ASCII – text files

- JPG, BMP, GIF – pictures

- MPG, AVI, MOV – videos

- MP3, WAV – music

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OSI ModelOSI Model

Session Layer 

Responsible for establishing a connection, maintainingthe connection and ending the connection

The decision to transmit data using half duplex or full

duplex is made at this layer 

- Half Duplex – This transmission type is similar to a one lane bridge.Cars can travel in both directions but not at the same time. With half duplex one computer send a message then waits for the other computer to respond.

- Full Duplex – This transmission type allows both computers to transmitand receive at the same time.

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OSI ModelOSI Model

Tools that facilitate this process are Remote ProcedureRemote Procedure

Calls (RPC)Calls (RPC) and named pipe

• RPCs are issued whenever a network resource is contacted

• An RPC server is the server providing the specific resource

• This could be a print server, a DHCP server, a domain controller or 

a file server 

• Named pipes are created to allow private communications to occur 

over a public network

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OSI ModelOSI ModelTransport Layer 

Responsible for breaking information into chunks and assigningaddresses to the different processes

• The process addresses are called ports

• These should not be confused with external ports

• These are virtual ports used to keep network applications separated in theoperating system

• Ports numbers are assigned based on the following:

- Well Known Ports 0-1023

- Registered Ports 1024 – 49,151

- Private Ports 49,151 – 65535

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OSI ModelOSI Model

Package being sent:

Package received:

Data from HTTP web page

Destination

80

DataSource

52,999

Destination

80

DataSource

52,999

Destination

80

DataSource

52,999

Data to HTTP web page

Destination

52,999

DataSource

80

Destination

52,999

DataSource

80

Destination

52,999

DataSource

80

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OSI ModelOSI ModelA private port address isassigned to the source port of the packet

A well-known port or a registeredport is assigned to thedestination port

This port is specific to theapplication that the packet wascreated for 

The following table lists somewell-known ports: Snmp3161 /tcp

Pop110/tcp

www http80/tcp

Gopher 70/tcp

Tftp69/udpDns53/tcp,udp

Smtp25/tcp, udp

Telnet23/tcp

Ftp20,21/tcp

ApplicationPort / Protocol

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OSI ModelOSI Model

Two types of commonly used transport protocols that

are part of the TCP/IP Protocol suite

- Transport Control Protocol (TCP) - At this layer the connection

oriented protocol, TCP, establishes flow control by agreeing on the

amount of data in each packet to be transferred (3 way handshake)and monitoring the packets that are received to ensure that lost

packets are resent.

- User Datagram Protocol (UDP) – At this layer the connectionless

protocol, UDP, sends a packet and assumes the destination computer receives it. There is no check performed to ensure the packet arrived

intact.

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OSI ModelOSI Model

Network Layer 

• At this layer a packet is created

• Packet includes information from the upper layers and the network

address for the source and destination computer 

• The IP address is the network address assigned to a TCP/IPpacket

• The IPX address is the network address assigned to the IPX/SPX

packet

• The information in the packet is ordered based on the network

protocol

• A receiving computer will look for information in a specific place in

the packet based on the protocol

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OSI ModelOSI Model

Version IHL Type of Service Total Length ID Flags Fragment Offset TTL

Protocol Checksum Source Address Destination Address Data

IP Packet

Checksum Packet Length Transport Control Packet Type Destination Network

Dest. Node Dest. Socket Source Network Source Node Data

IPX Packet

Source Socket

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OSI ModelOSI Model

Data-Link Layer 

• Controls the movement of data on the network

• The packet from the network layer is modified to include the frame

source and destination address

• This address is the media access control (MAC) address on the NIC

• Once these addresses are added the packet is called a frame

• Data-link protocols differ in the way frame is sent on the network

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OSI ModelOSI Model

Ethernet Protocol (IEEE 802.3)

• Based on the bus physical topology and uses Carrier Sense,Carrier Sense,

Multiple Access with Collision Detection (CSMA/CD)Multiple Access with Collision Detection (CSMA/CD)

• Means the computer that wants to send a message listens on themedia, sends the message if it hears nothing

• If two computers send a message at the same time, a collision occurs

• When a collision occurs the sending computers wait a random

amount of time, listen, and resend the message

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OSI ModelOSI Model

Token Ring Protocol (IEEE 802.5)

• Based on the ring physical topology and puts a token message on

the ring

• The computer that wants to send a message must first control thetoken

• The message is sent, then the token is re-released

• This ensures that only one message is on the ring at a time

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OSI ModelOSI ModelWireless Protocol (IEEE 802.11x) (Similar to Ethernet)

• The computer listens for traffic on the radio waves, if there is nonethe package is transmitted

• If a collision occurs the package is retransmitted

• This protocol is affected by anything else transmitting in the sameradio wave space

• Examples include cell phones and microwaves, common examples

are 802.11b, 802.11g. and 802.11f 

• They vary in transmission speed and frequency

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OSI ModelOSI Model

Physical Layer 

A frame is conveyed as bits onto the media

The physical topology and the components are theissues at this layer 

Physical components include the media (cabling, radiowaves, etc), the connectors, the NIC and the signal

repeating devices like the hub and repeater 

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Physical Components (Layer 1)Physical Components (Layer 1)

Network Topologies

Bus

• A bus topology is a single cable that connects all computers in a line

• Each end must be terminated, one must be grounded

Computer A Computer B Computer C Computer D Computer E

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Physical Components (Layer 1)Physical Components (Layer 1)

Ring

• A ring topologyring topology 

connects all

computers on a single

cable

• Ends are not

terminated, a loop is

formed that connects

the last computer to

the first computer 

Computer F

Computer BComputer A

Computer C

Computer D

Computer E

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Physical Components (Layer 1)Physical Components (Layer 1)

Star 

• In a star topologystar topology the computers are connected to a central HUB

via cable segments

HUB

Computer A

Computer B

Computer C

Computer D

Computer E

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Physical Components (Layer 1)Physical Components (Layer 1)Mesh

• Commonly used inWAN configurations

• Routers areconnected to multiple

links for redundancy

• Provides the ability todetermine thequickest route to a

destination and tochange routes whena connection isbroken

Router A

Router B

Router C

Router D

Router E

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Physical Components (Layer 1)Physical Components (Layer 1)Network Media

• Transmission of a signal from one computer to another occurs on the media

• Can be a physical cable or the atmosphere

• In data networks, two types of signal can be sent

• Both are generated by electrical current and are measured in voltage

Analog Signal

• With analog signals, the voltage varies continuously, resemble waves

• Strength of an analog signal is measured in amplitude

• Phones transmit analog signals

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Physical Components (Layer 1)Physical Components (Layer 1)Digital Signal

• Turn on and off continuously• Voltage varies from 0 to a specific positive voltage

• Computers use a series of 1s and 0s to create the digital pattern

• Digital signaling is more efficient than analog signaling because fewer errors

occur so there is less need to resend the message

Data Modulation

• Data must be modulated when it is sent from a digital medium to an analog

medium

• A modem is a modulator/demodulator 

• A modem takes a digital signal and converts it to analog to transmit it toanother computer through a phone line

• At the other end the analog signal is converted back to a digital signal or 

demodulated

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Physical Components (Layer 1)Physical Components (Layer 1)

Baseband and Broadband

• BasebandBaseband transmits one digital signal at a time on the media

• The digital signal has exclusive use of the wire until the transmission

is complete

• BroadbandBroadband modulates signals into radiofrequency (RF) analog

signals using different frequencies

• Because different frequencies are being used, signals can travel on

multiple channels at the same time

• Because a signal on a wire can only travel in one direction, two wires

are required to send and receive

• Cable TV is an example of a broadband transmission

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Physical Components (Layer 1)Physical Components (Layer 1)Types of Cable

• Three types of cable used today• Two of the types, coaxial and twisted pair, use copper as the transmission

media for an electrical signal

• The third type, fiber optic, uses glass as the transmission media, the signal is

light

Coaxial Cable

• Coaxial cable was used for many years with Ethernet bus networks

• In most networks today, twisted pair in a star configuration has replaced

coaxial

• There are two types of coaxial cable, Thicknet (RG-58) and Thinnet(RG-8)• Thicknet has less bend radius than Thinnet but a signal can travel further 

without disruption

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Physical Components (Layer 1)Physical Components (Layer 1)

 

BNC barrel

connector to the

computer and BNC

T connector to

network

185 meters with no

more than 30

nodes per segment

no closer than 2.5

meters

10Mbps10BaseThinnet

AUI connector (also called DIX or 

DB15) to

transceiver and

computer and

vampire tap to

network

500 meters with nomore than 100

connections per 

segment no closer 

than 2.5 meters

10Mbps10Base5Thicknet

Connector Cable LengthThroughputEthernet

Designation

Cable type

 BNC Connector 

Coaxial Cable

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Physical Components (Layer 1)Physical Components (Layer 1)

Twisted Pair CableTwisted Pair Cable

• Consists of 4 to 8 color-coded wires

• Each pair is twisted to reduce the effects of crosstalk on the wire

• Crosstalk occurs when signals on nearby wires cross over andinterfere with the signal traveling on each wire

• Two types of twisted pair wire, shieldedshielded and unshieldedunshielded

- Shielded twisted pair (STP)Shielded twisted pair (STP) is insulated to reduce noise on the wire

- Unshielded twisted pair (UTP)Unshielded twisted pair (UTP) is more common and less expensive

than STP

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Physical Components (Layer 1)Physical Components (Layer 1)

Twisted Pair Cable (Continued)Twisted Pair Cable (Continued)

• TIA/EIA developed the standards for twisted pair 

• Standards describe categories of the cable

• Cat5E is current minimum standard for new Ethernet networks

• Cat 5 is the most common in existing networks

• Cat 5 or 5E uses 2 or 4 pairs of wires, both support throughput of 100Mbps at a 100MHz signal rate

• Cat 3 uses 2 pairs of wires but only supports data rates of 10Mbps at20MHz

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Physical Components (Layer 1)Physical Components (Layer 1)

Uses NICs and

connectors specific to

100BaseVG

100 meters with one

node

100Mbps100BaseVGvoice

gradedoes not

support full duplex

transmissions on

Ethernet or Token

Ring

UTP Cat3 or 

higherUses 4 pair 

RJ45100 meters with one

node per segment

100Mbps100BaseT4does not

support full duplextransmissions

UTP Cat3 or higher 

Uses 4 pair 

RJ45100 meters with one

node per segment

100Mbps100BaseTXUTP Cat5 or 

higherUses 2 pair 

RJ45100 meters with onenode per segment

10Mbps10BaseTUTP Cat3 or higherUses 2 pair 

Connector Cable LengthThroughputEthernet

Designation

Cable type

Twisted Pair RJ45 Connector  

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Physical Components (Layer 1)Physical Components (Layer 1)

Fiber Optic CableFiber Optic Cable

• Fiber optic cable contains one or several pure glass tubes

• Light is sent through the glass using a light-emitting diode (LED)

• A layer of impure glass surrounds the tubes

• This is called cladding

• The cladding reflects the light back into the tube allowing the signal

to travel for very long distances

• There are two types of fiber, single-modesingle-mode and multi-modemulti-mode 

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Physical Components (Layer 1)Physical Components (Layer 1)Single-mode 

• Cable using one narrow tube (10 microns in diameter)

• The light has very little room to reflect enabling it to travel longdistances without requiring attenuators

• Single mode is used to connect buildings

Multi-mode 

• Cable is 50 to 100 microns in diameter 

• Light reflects much more so the signal cannot travel as far and it may

carry more than one signal

• Multi-mode is much cheaper than signal mode

• Multi-mode is usually used to connect wiring closets within a building

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Physical Components (Layer 1)Physical Components (Layer 1)

ST2km10 Mbps to 1Gbps10BaseFFull

Duplex

Multi-mode2

strands

10 excepted

connectors but ST

or SC are the most

common

3km100 Mbps to

1Gbps

100BaseFXSingle Mode

Connector Cable LengthThroughputEthernet

Designation

Cable type

Fiber Optic Cable

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DataLink ProtocolsDataLink ProtocolsDataLink Protocols

• Most common Datalink protocols are Ethernet and Token Ring

• Also referred to as the logical topology or network transport system

• Datalink protocol determines how a message will transmit across the

media

• At this layer the frame packaging is determined

• Frame must include a source and destination MAC address

• The Media Access Control (MAC) address is hard-coded on thenetwork interface card

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DataLink ProtocolsDataLink ProtocolsEthernet (IEEE 802.3)

• Requires a bus topology and uses the Carrier Sense Multiple Accesswith Collision Detection (CSMA/CD) method for controlling hownetwork nodes will communicate

• Requires all nodes to listen on the media

• If no messages are being transmitted, the node may transmit

• If two nodes transmit at the same time a collision will occur 

• All nodes hear the collision

• The two nodes that had messages that collided will wait a randomamount of time within a short window then retransmit

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DataLink ProtocolsDataLink ProtocolsEthernet (IEEE 802.3) continued

• The other computers must wait longer to ensure the messages aretransmitted

• Every computer in an Ethernet network receives the message and mustassemble it in memory

• If the destination MAC address belongs to the receiving computer themessage is sent up the OSI model and read

• If the MAC address does not belong to the computer, it is dumped

• Switches reduce collisions by directing messages to specific nodes within an

Ethernet network but cannot stop broadcasts

• A broadcast will not stop until it reaches a router 

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DataLink ProtocolsDataLink Protocols

Token Ring (IEEE 802.5)

• A Token Ring uses a ring topology

• The ring can be located in the hub called a Multiple Access Unit

(MAU)

• A token is released on the ring

• A token is a 24 bit frame

Starting Deliminator 8bits

Access Control 8bits

Ending Deliminator 8bits

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DataLink ProtocolsDataLink ProtocolsToken Ring (IEEE 802.5) (continued)

• When a node wants to send a message it must grab the token

• The node can then send the message

• No other node can transmit without possession of the token

• When the message has come completely around the circle, the token isreleased and another node can pick it up

• No collisions occur on a Token Ring network

• Only one node transmits at a time

• Every node must read the message and discard it if the MAC address doesnot match the MAC address of the node

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Network ProtocolsNetwork ProtocolsA network protocol is an agreed-upon format for transmitting databetween two devices

The protocol determines the following:

• The type of error checking to be used for Data Compression method, if any

• How the sending device will indicate that it has finished sending a message

and how the receiving device will indicate that it has received a message• The order and contents of the package

There are a variety of standard protocols from which programmerscan choose

Each has particular advantages and disadvantages; for example,some are simpler than others, some are more reliable, and someare faster 

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Network ProtocolsNetwork Protocols

TCP/IP

• Transport Control Protocol/Internet Protocol is the protocol used onthe Internet and by Windows networked operating systems

• TCP/IP uses 32 bit IP addresses and subnet masks to identify thenetwork and node

IPX/SPX

• Novell Netware uses this protocol that is easier to configure butboth nodes must use the same frame type for communication to

work

• The IPX address is based on the node MAC address

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Network ProtocolsNetwork Protocols

NetBEUI (the enhanced version of NetBIOS protocol)

• This protocol uses the SMB (Simple Message Block) Broadcast

recognized within Windows operating systems

• It requires no configuration but is not a routable protocol

• Because of this, it is limited to use on small networks of 25 nodes or 

less

For more detailed information on protocols, go to:

• http://www.protocols.com/pbook/

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Other Terms and DefinitionsOther Terms and DefinitionsIP address

• The IP address is a 32 bit binary address unique to the specific

computer. The IP address identifies the network and the node.

Subnet Mask

• The subnet mask is a 32 bit binary number that masks the network

portion of the address enabling a router to direct a message to its

proper destination.Default Gateway

• The default gateway is a combination of hardware and software that

links two different types of networks. Gateways between e-mail

systems, for example, allow users on different e-mail systems to

exchange messages. The normal default gateway address will bethe port on the router connected to the local area network (LAN).

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Other Terms and DefinitionsOther Terms and DefinitionsDHCP

• The Dynamic Host Configuration ProtocolDynamic Host Configuration Protocol is a server 

application. When a computer boots up on a network using DHCP,the computer will send a broadcast to all computers on the networklooking for IP address information. The DHCP server will respondby providing the information to the computer. The server leases theinformation to the computer. When half the leased time haspassed, the computer requests a new lease. Until a computer receives IP information, the computer cannot communicate on the

network.DNS

• Domain Name SystemDomain Name System (or (or ServiceService),), an Internet service thattranslates domain names into IP addresses. Because domainnames are alphabetic, they are easier to remember.

WINS

• Windows Internet Naming ServiceWindows Internet Naming Service, a system that determines theIP address associated with a particular network computer 

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Other Terms and DefinitionsOther Terms and DefinitionsFQDN

• A Fully Qualified Domain Name (FQDN)A Fully Qualified Domain Name (FQDN) is required for Windows 2000 and newer operating systems.

www.unisys.com is a FQDN for a web presence.

Tr1.astn.Unisys.com is a FQDN for a specific computer 

UNC

• The Universal Naming Convention (UNCThe Universal Naming Convention (UNC) structure is

\\server name\share name. The server name is normally the

NetBIOS name of the computer. The share name is

assigned when the folder or resource is shared.

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Other Terms and DefinitionsOther Terms and DefinitionsHub/Repeater 

• A hubhub is a device used to connect two or more computers.

• Uses a bus topology to connect computers. Because of this,

every computer receives every message.

• A hub can be passive which means it only acts as a

connection point, or it can be active, which means it can

regenerate the signal allowing it to travel further.

• Hubs work at Layer One of the OSI model. They are only

concerned with bits.

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Other Terms and DefinitionsOther Terms and DefinitionsBridge

• BridgesBridges are similar to repeaters. They are used to connectnetwork segments and can also connect dissimilar physicalmedia, like coaxial cable and twisted pair or fiber.

• A Bridge can also connect an Ethernet network with a Token

Ring network.

• Bridges can filter traffic between network segments bylooking at the MAC address. The frame is forwarded if it isnot on the same network as the source MAC address.

• A bridge operates at Layer 2 in the OSI model.

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Other Terms and DefinitionsOther Terms and DefinitionsSwitch

• A switchswitch is a high-speed multiport bridge that maintains abridging table with MAC addresses for the segments it

connects.

• A switch works at layer 2 of the OSI model.

• A switch can regenerate a signal but can also direct a

message to a specific node reducing collisions in an

Ethernet network.

• Switches are used more than hubs today.

O h T d D fi i i

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Other Terms and DefinitionsOther Terms and DefinitionsRouter 

• The router router is the device that forwards data packets from oneLocal Area Network (LAN) or Wide Area Network (WAN) to

another.

• Routers connect networks running at different speeds and

using different protocols. i.e. Ethernet and Token Ring.

• Based on routing tables and routing protocols, routers read

the network address in each transmitted frame and make a

decision on how to send it based on the most expedient

route (traffic load, line costs, speed, bad lines, etc.).

• Routers operate at Layer 3 of the OSI model.

• Because routers can route based on the network portion of 

the IP address, routers stop network broadcasts.

Oth T d D fi iti

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Other Terms and DefinitionsOther Terms and DefinitionsBrouter 

• A brouter brouter routes routable packets but acts as a bridge for non-routable protocols.

• Brouters operate at Layers 2 and 3 of the OSI model.

Gateway• A gatewaygateway is a networking device that translates information

between Internet protocols, like TCP/IP to IPX/SPX, or 

dissimilar LANs, like a TCP/IP network to an SNA mainframe

network.

• Gateways operate at Layers 1-7 of the OSI model.

Obj i R i i dObj ti R i it d

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Objectives RevisitedObjectives RevisitedExplain the network concept

Explain how to connect to a network

Describe the OSI Model layers

Differentiate between Physical layer components

R iR i

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