Internetworking-basics

Internetworking Basics

Agenda

Networking History

How a LAN Is Built

LAN Topologies

LAN/WAN Devices

NETWORKING HISTORY

Early Networks

Samuel MorseSamuel Morse

Alexander Graham BellAlexander Graham Bell

Emile BaudotEmile Baudot

Telephone Network

Analog Network

Bell TelephoneBell Telephone

Important Developments

1966—1966—Carterphone attached to phone lines to transmit radio calls to

construction workers

1975—1975—FCC ruled that equipment can attach

to phone lines if it meets specifications

1977—1977—FCC Part 68 enacted to define

technical specifications

1984—1984—Court ordered Bell System/AT&T

breakup

Telephone Network

Bell Bell AtlanticAtlanticMCIMCI

AT&TAT&T

Pacific BellPacific Bell

1960s–1970s Communications

IBM Host Computer Systems Network Architecture (SNA)• Application Programs• Database• Printing

Low-Speed Access Lines

Digital NetworkDigital Network

Problem…

Analog

Analog

Digita

l

Digita

l

Analog and Digital Signals

Digital Transmission—Digital Transmission— 1’s and 0’sOn or Off

Computer-speak

1 0 1 0 0 1 1 0 1“1” bit

“0” bit

StartBit

StopBit

Analog Transmission—Analog Transmission— Wires or wireless,

Audio tonesInfo conveyed through

signal amplitude, frequency, and phase

Solution—Modems

Modem—Modem—Modulator/Demodulator

Translates digital computer signals to analog signals which the telephone

world can understand and vice versa

Solution—Modems

Modem—Modem—Modulator/DemodulatorTranslates digital computer signals to analog signals which the telephone world can understand and vice versa

Modem Modem

POTS (Plain Old Telephone Service)

MainframeHost

POTS

Another Solution—Multiplexing

BasebandBaseband—Carries only one signal at a time

BroadbandBroadband—Able to carry multiple signals simultaneously

Multiplexer—Multiplexer—Allows multiple signals to be carried across a single physical medium

MainframeHost

Broadband— Wide-Area Network (WAN)

Baseband— Local-Area Network(LAN)

Baseband versus Broadband

1960s–1970s Communications

DigitalDigital

MainframeHost

Sunnyvale Branch

Headquarters,San Francisco

POTS

1960s–1970s Communications

Dialup ModemConnection

Morgan Hill Branch

Digital

MainframeHost

Headquarters,San Francisco

Digital Digital

Dedicated Leased Lines

Sunnyvale Branch

POTS

Birth of the Personal Computer

Applications

File storage

Processing power

Printing options

Smart terminals

The Internet—1970s and 1980s

ARPANET—Advanced Research Projects Agency Network, Dept. of Defense

Developed in mid 1960s

Funded research to universities and companies

First packet-switched network built by BBN—Dec 1969

Many LANs connected to the ARPANET with TCP/IP

Shut down in 1990 due to newer networks emerging

NSFNET—National Science Foundation, late 1970s High-speed successor to ARPANET

Six supercomputers: San Diego, Boulder, Champaign, Pittsburgh, Ithaca, and Princeton

Supercomputers given a microcomputer which spoke TCP/IP

Overloaded from the word “go”

The Internet

ANSNET (Advanced Networks and Services) Took over NFSNET in 1990 Formed by MCI, MERIT, and IBM for commercial uses Upgraded 1.5-Mbps links to 45 Mbps, sold to AOL in 1995

NFS awarded contracts to four NAPs Pacific Bell (San Francisco), Ameritech (Chicago), MFS (Washington, D.C.), Sprint (New York

City) Additional government backbones

Mid 1980s, collection of networks viewed as “The Internet”

TCP/IP is the glue that holds it together January 1992, “Internet Society” formed Primary applications

E-mail, news, remote login, file transfer, WWW

1990s—Global Internetworking

• 1992—1 major backbone, 3,000 networks, 200K computers

• 1995—Multiple backbones, hundreds of regional nets, tens of thousands of LAN’s, millions of hosts, tens of millions of users

Doubling every year!

HOW LAN IS BUILT

Local-Area Network—LAN

What is a LAN? A collection of computers, printers, modems, and other devices that can

communicate with each other in a small area (< ~ 3000 m or 1000 feet)

What are the components? Computers, operating system (OS),

network interface card (NIC), and hubs

How is a LAN controlled? Protocols—Formal descriptions of sets of rules and conventions that govern

how devices on a network exchange information Standards—Sets of rules or procedures that are either widely used or

officially specified

Local-Area Networks

• LANs are designed to:– Operate within a limited geographic area

– Allow multi-access to high-bandwidth media

– Control the network privately under local administration

– Provide full-time connectivity to local services

– Connect physically adjacent devices

Network Operating System (OS)

Software that allows communicating

and sharing of data and network

resources

Examples:

AppleTalk

NetWare

Banyan VINES

PC or WorkstationLoaded with NOS

Connector Port

PC or WorkstationLoaded with NOS

Network Interface Card (NIC)

Network Interface Card

Amplifies electronic signals

Packages data for transmission

Physically connects computer to transmission media (cable)

Printer(Also has a NIC)

PC or WorkstationLoaded with NOS

NIC

Wiring Hub

Serves as center of network

Contains multiple independent but connected modules where network equipment can be connected

WiringHub

Printer(Also has a NIC)

NIC

PC or WorkstationLoaded with NOS

Wiring Hub

Cables or Transmission Media

Physical environments through which transmission signals pass Twisted pair

Coaxial cable

Connectors (RJ-11, RJ-45, etc.)

Cable

– Fiber-optic cable– Atmosphere

Connectors

RJ-45Connector

Network Cabling

Media connecting network components

NIC cards take turns transmitting on the cable

LAN cables only carry one signal at a time

WAN cables can carry multiple signals simultaneously

Three primary types of cabling

Twisted-pair (or copper)

Coaxial cable

Fiber-optic cable

Twisted-Pair (UTP and STP)

Speed and throughput: 10/100 Mbps

Relative cost: Least costly

Media and connector size: Small

Maximum cable length: 100 m

RJ-45Connector

Color-CodedPlastic Insulation

Twisted-Pair

Outer Jacket

STP only: Shielded Insulation

to Reduce EMI

Coaxial Cable

Speed and throughput: 10/100 Mbps

Relative cost: More than UTP, but still low

Media and connector size: Medium

Maximum cable length: 200/500 m

OuterJacketBraided Copper Shielding

Plastic Insulation

Copper Conductor

BNC Connector

Fiber-Optic Cable

Outer JacketKevlar ReinforcingMaterial

PlasticShield Glass Fiber

and Cladding

Single mode: One stream of laser-generated light (100 km)

Multimode: Multiple streams of LED-generated light (2 km)

Speed and throughput: 100+ Mbps

Average cost per node: Most expensive

Media and connector size: Small

Maximum cable length: Up to 2 km

MultimodeConnector

Throughput Needs !!

2,457,000 bits/screen30 screens/second73,728,000 bps

100,000 bits

64,000 bps

841,000 bits202,000,000 bits

7,300,000 bits/screen30 pictures/second224,000,000 bps!!!

Throughput Rate and Bandwidth

Throughput rate

The rate of information arriving at, and possibly passing through, a

particular point in a network

Bandwidth

The total capacity of a given network medium or protocol

THROUGHPUT = BANDWIDTH - OVERHEAD

Throughput Rate

10,000 pages= 53 MB

(Megabytes)

NetworkingMade Easy

Speed Transmit Time

9,600 bps = 12.27 hrs

24,000 bps = 4.91 hrs

56 Kbps = 2.1 hrs

1 Mbps = 7.1 min

10 Mbps = 42.4 sec

100 Mbps = 4.24 sec

1 Gbps = 0.42 sec

1 Byte = 8 bits

LAN TOPOLOGIES

LAN Topologies

Define network device organization

Four common types Bus topology

Tree topology

Star topology

Ring topology

Topologies are logical architectures Actual devices need not be physically

organized in these configurations

Bus and Tree Topology

Tree topology“branch” withmultiple nodes

Star Topology (LAN)

Center: hub, repeater, or

concentrator

Typically used

in both Ethernet

and Token Ring

5 to 100+ devices

Ring Topology (LAN)

Redundant ring to avoid network failure

• Repeaters at each component

• Unidirectional transmission links

• Closed loop

• Typically used in FDDI networks

LAN/WAN DEVICES

• Hubs

• Bridges

• Switches

• Routers

LAN/WAN Devices

Hub

• Device that serves as the center of Device that serves as the center of a star topology network, a star topology network, sometimes referred to as a sometimes referred to as a multiport repeatermultiport repeater, or in Ethernet, a , or in Ethernet, a concentratorconcentrator; ; no forwarding no forwarding intelligenceintelligence

Hubs

123123

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Hub

DataDataDataData

Amplifies signals Propagates signals through the network Does not filter data packets based on destination No path determination or switching Used as network concentration point

Bridge

• Device that connects and passes Device that connects and passes packets between two network packets between two network segments.segments.

• More intelligent than hub—analyzes More intelligent than hub—analyzes incoming packets and forwards (or incoming packets and forwards (or filters) them based on addressing filters) them based on addressing information. information.

Bridge

Segment 1 Segment 2

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124124

125125

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128128

Corporate Intranet

Hub Hub

More intelligent than a hub—can analyze incoming packets and forward (or filter) them based on addressing information

Collects and passes packets between two network segments Maintains address tables Different types of bridges: transparent and source route (used primarily in Token Ring

LANs)

Bridge Example

Switches

Use Use bridging technologybridging technology to to forward traffic between ports. forward traffic between ports.

Provide full Provide full dedicateddedicated data transmission rate between data transmission rate between two stations that are directly connected to the switch two stations that are directly connected to the switch ports.ports.

Build and maintain Build and maintain address address tablestables called content-addressable memory (CAM).called content-addressable memory (CAM).

10-MbpsUTP Cable

“Dedicated”

Workstation

3131

Switch

Corporate Intranet

3232

333636

100 Mbps 100 Mbps

Uses bridging technology to forward traffic (i.e. maintains address tables, and can filter)

Provides full dedicated transmission rate between stations that are connected to switch ports

Used in both local-area and in wide-area networking All types available—Ethernet, Token Ring, ATM

Switching—“Dedicated” Media

3535

3434

Routers

Interconnect LANs and WANsInterconnect LANs and WANs

Provide path determination using metricsProvide path determination using metrics

Forward packets from one network to anotherForward packets from one network to another

Control broadcasts to the networkControl broadcasts to the network

Interconnect LANs and WANsInterconnect LANs and WANs

Provide path determination using metricsProvide path determination using metrics

Forward packets from one network to anotherForward packets from one network to another

Control broadcasts to the networkControl broadcasts to the network

Summary

LANs are designed to operate within

a limited geographic area

Key LAN components are computers, NOS, NICs, hubs, and cables

Common LAN topologies include

bus, tree, star, and ring

Common LAN/WAN devices are hubs, bridges, switches, and

routers