CSCI-235CSCI-235Micro-Computer in ScienceMicro-Computer in Science

The NetworkThe Network

© Prentice-Hall, Inc

CommunicationsCommunications CommunicationCommunication is the process is the process

of sending and receiving of sending and receiving messagesmessages

Communication channelsCommunication channels are are the paths through which the paths through which messages are passedmessages are passed

Communication devicesCommunication devices transform electronic signals transform electronic signals

1.3

Five components of data communication

1.4

Data flow (simplex, half-duplex, and full-duplex)

NetworksNetworks

A A networknetwork is a set of devices (often referred to is a set of devices (often referred to as as nodesnodes) connected by communication ) connected by communication linkslinks. .

A node can be a computer, printer, or any A node can be a computer, printer, or any other device capable of sending and/or other device capable of sending and/or receiving data generated by other nodes on the receiving data generated by other nodes on the network.network.

1.6

Types of connections: point-to-point and multipoint

1.7

Categories of topology

1.8

A fully connected mesh topology (five devices)

1.9

Figure 1.6 A star topology connecting four stations

1.10

A bus topology connecting three stations

1.11

A ring topology connecting six stations

1.12

A hybrid topology: a star backbone with three bus networks

1.13

An isolated LAN connecting 12 computers to a hub in a closet

1.14

A heterogeneous network made of four WANs and two LANs

© Prentice-Hall, Inc

Data Rate and BandwidthData Rate and Bandwidth

Any transmission system has a limited Any transmission system has a limited band of frequenciesband of frequencies

This limits the This limits the data ratedata rate that can be carried that can be carried

BandwidthBandwidth BandwidthBandwidth is usually used to refer to the data is usually used to refer to the data

rate (i.e., the amount of data that can be rate (i.e., the amount of data that can be transmitted through a communications transmitted through a communications channel)channel)

Digital bandwidth is measured in bits per Digital bandwidth is measured in bits per second (bps), kilobits per second (Kbps), second (bps), kilobits per second (Kbps), megabits per second (Mbps), or gigabits per megabits per second (Mbps), or gigabits per second (Gbps)second (Gbps)

Low bandwidth is 56 Kbps and high bandwidth Low bandwidth is 56 Kbps and high bandwidth is 622 Mbpsis 622 Mbps

ProtocolProtocol ProtocolsProtocols are fixed, formalized standards that are fixed, formalized standards that

specify how computers can communicate over a specify how computers can communicate over a networknetwork

Set of conventions between two entities involved in Set of conventions between two entities involved in a communicationa communication

ElementsElements syntax : data format and signal levelssyntax : data format and signal levels

concerns the format of the data blocksconcerns the format of the data blocks semantics : include control information for semantics : include control information for

coordination and error handling coordination and error handling timing : speed matching and sequencingtiming : speed matching and sequencing

Protocol ArchitectureProtocol Architecture

Software structure that implements the Software structure that implements the communication functioncommunication function

Consists of a layered set of protocolsConsists of a layered set of protocols Separate layers or protocols implemented Separate layers or protocols implemented

in separate modulesin separate modules Different applications have different Different applications have different

requirements at each layerrequirements at each layer

2.19

Tasks involved in sending a letter

2.20

Seven layers of the OSI model

2.21

The interaction between layers in the OSI model

2.22

An exchange using the OSI model

2.23

Physical layer

© Prentice-Hall, Inc

Modulation

DigitalAnalog

Analog Digital

Demodulation

Modems: From Digital to Analog Modems: From Digital to Analog and Backand Back

ModemsModems are devices that transform signals when are devices that transform signals when sending and receiving transmissionssending and receiving transmissions ModulationModulation – Transforming digital signals to analog – Transforming digital signals to analog DemodulationDemodulation – Transforming analog signals to digital – Transforming analog signals to digital

© Prentice-Hall, Inc

Circuit switchingCircuit switching Networks create an end-Networks create an end-

to-end circuit between the to-end circuit between the sending and receiving sending and receiving computerscomputers

Electronic switches Electronic switches establish and maintain establish and maintain the connectionthe connection

Switching and Routing TechniquesSwitching and Routing TechniquesPacket switchingPacket switching

Outgoing messages are Outgoing messages are divided into fixed-size divided into fixed-size data units called data units called packetspackets

Packets are numbered Packets are numbered and addressed to the and addressed to the receiving computerreceiving computer

Routers examine the Routers examine the packets and send them to packets and send them to

their destinationtheir destination

CIRCUIT SWITCHING

IN

OUT

IN

OUT

Telephone Node

Telephone Node

© Prentice-Hall, Inc

AdvantagesAdvantages DisadvantagesDisadvantages

CircuitCircuit switchingswitchingVoice and real-time Voice and real-time transmissiontransmission

No delivery delaysNo delivery delays

CostlyCostly

A direct electrical A direct electrical connection between connection between the computers is the computers is requiredrequired

Packet switchingPacket switching

Efficient, less Efficient, less expensive, and expensive, and reliablereliable

Will function if part Will function if part of the network is of the network is downdown

Delays in receiving Delays in receiving packetspackets

Not ideal for real-Not ideal for real-time voice time voice communicationcommunication

Advantages and Disadvantages Advantages and Disadvantages of Circuit and Packet Switchingof Circuit and Packet Switching

2.28

Data link layer

2.29

Hop-to-hop delivery

2.30

Network layer

2.31

Source-to-destination delivery

2.32

Transport layer

2.33

Reliable process-to-process delivery of a message

2.34

Session layer

2.35

Presentation layer

2.36

Application layer

2.37

Summary of layers

2.38

TCP/IP and OSI model

© Prentice-Hall, Inc

Local Area Network Local Area Network (LAN)(LAN)

Links computers within a Links computers within a building or group of building or group of buildingsbuildings

Uses direct cables, radio, Uses direct cables, radio, or infrared signalsor infrared signals

Types of Computer NetworksTypes of Computer Networks

Wide Area Network Wide Area Network (WAN)(WAN)

Links computers separated Links computers separated by a few miles or by a few miles or thousands of milesthousands of miles

Uses long-distance Uses long-distance transmission mediatransmission media

© Prentice-Hall, Inc

Local Area Networks (LANs)Local Area Networks (LANs) Network access is controlled by a network Network access is controlled by a network

administratoradministrator

Users can access software, data, and Users can access software, data, and peripheralsperipherals

LANs require special hardware and softwareLANs require special hardware and software

Computers connected to a LAN are called Computers connected to a LAN are called workstations workstations or or nodesnodes

© Prentice-Hall, Inc

LAN Hardware and SoftwareLAN Hardware and Software

Networking HardwareNetworking HardwareNetwork interface card Network interface card

(NIC)(NIC) – Provides the – Provides the connection between the connection between the computer and the networkcomputer and the network

Inserted into a computer’s Inserted into a computer’s expansion slotexpansion slot

Networking SoftwareNetworking SoftwareOperating system that Operating system that

supports networking supports networking (Unix, Linux, Windows, (Unix, Linux, Windows, Mac OS)Mac OS)

Additional system Additional system softwaresoftware

NIC

© Prentice-Hall, Inc

Client-Server NetworksClient-Server Networks

Typical corporate networks are Typical corporate networks are client-serverclient-server

Clients send requests to servers for programs Clients send requests to servers for programs and data, and to access peripheralsand data, and to access peripherals

© Prentice-Hall, Inc

Peer-to-Peer NetworksPeer-to-Peer Networks

All computers on the network are treated as equalAll computers on the network are treated as equalUsers decide which files and peripherals to shareUsers decide which files and peripherals to sharePeer-to peer is not suited for networks with many Peer-to peer is not suited for networks with many

computerscomputersPeer-to-peer is easy to set up. Example: home networksPeer-to-peer is easy to set up. Example: home networks

© Prentice-Hall, Inc

Wide Area Networks (WANs)Wide Area Networks (WANs)

WANsWANs are similar to long-distance are similar to long-distance telephone systemstelephone systems

© Prentice-Hall, Inc

WAN ApplicationsWAN Applications

LAN-to-LANLAN-to-LAN WANs are used to connect LANs at two or WANs are used to connect LANs at two or

more geographic locationsmore geographic locations

Companies use WANs to connect their Companies use WANs to connect their branches to one network systembranches to one network system

The largest WAN is the InternetThe largest WAN is the Internet