Internet Engineering Connecting to The Internet Ali Kamandi Fall - - PowerPoint PPT Presentation

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Ali Kamandi Fall 2007 kamandi@sharif.edu Sharif University of Technology

Internet Engineering Connecting to The Internet

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How Networks Link to the Internet

LAN Dial-up (Online

Service or ISP)

Cable Modem Digital Subscriber

Line (DSL) modem

Satellite

connection

…

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Connecting to the Internet

Direct connection: LANs or large computers such as mainframes Cable Modem: the Internet can be accessed over some cable TV

systems using the coaxial cable that carries television signals.

Cable modems might be capable of sending and receiving data at speeds 20-100 times as fast as conventional modems.

WebTV: You also can access the Internet directly on your TV set

by using a set-top box that dial in to the Internet and then displays web pages on your television set.

You also can use satellite dishes to access the Internet.

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Connecting to the Internet

Cellular access: Cellular telephones can send and

receive email and browse the Web.

Lower speed than regular dial-up modems The connections are available all the time

Wireless access: Laptops equipped with wireless

network cards that adhere to the WiFi (802.11) standard can get high-speed access (at airports, hotels,…)

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Online Services

Online services such as America Online provide a very

convenient way to use Internet resources.

These services have their own software that makes accessing

Internet resources such as Telnet and FTP easy.

They also allow you to use your own software or other

software instead of theirs.

Some services let you use special software such as Internet

Relay Chat (IRC)

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How DSL makes Its High-Speed Connection

One of the major benefits of DSL is that it doesn’t need

any special wires.

DSL, in fact refers to the modems being used, not to the

lines themselves.

DSL service requires that DSL modems be on each end

• f the connection

They don’t dial your telephone They provide an always-on connection to the Internet

when they are turned on.

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How DSL makes Its High-Speed Connection

Traditional analog transmissions and voice calls use

• nly a small portion of the potential bandwidth.

DSL enables people to talk on the telephone and use

the Internet at high speeds simultaneously

DSL modem must be located within a certain distance

from the phone company’s DSL modem.

For an 8.448 Mbps service, 9,000 feet At 2.048 Mbps: 16,000 feet.

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How DSL makes Its High-Speed Connection

DSL divides the phone line into three

channels: one for receiving data, one for sending data, and one for talking

• ver the telephone.

The phone line is not always physically

separated into these channels.

One form of ADSL might be able to

receive data at 1.5 Mbps, and send it at 640Kbps.

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How Internet/Television Connections Work

Every day, TV and the Internet are drawing closer to

each other.

The Internet is gaining more TV-like qualities, such as playing videos and music, to broadcasting live video feeds. Television technology is starting to use the Internet to add interactivity to the television experience.

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How Cable Modems Work

Cable modems offer extremely high-speed access to the

Internet.

They enable you to access the Net using the existing

coaxial TV cable that comes into your house.

Cable modems offer T1-like and faster speeds, but at a

fraction of the cost of T1 lines.

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How Cable Modems Work

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How Cable Modems Work

The cable company divides each town or city into

neighborhoods of about 500 homes, all of which are located on a single LAN or node.

All these 500 homes share the node. Both television and Internet data travel to and from

those 500 homes to the node over coaxial cables.

More simultaneous access: slower access

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How Cable Modems Work

The nodes are connected via high-speed fiber optic

lines to a head end cable facility.

A single head end typically handles all the nodes for 4-

10 towns.

The head end receives television transmissions from

satellites and has Internet access via high-speed links to the Internet.

Proxy Server

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Internet Enhanced TV

A different technology enables you to

browse the Web using your television set.

A set-top box connects your TV to the Net

via a modem, takes the signal from the modem, and sends it to the TV.

The enhanced signal can contain a variety

• f extra information (HTML)

A remote control-like device enables you to

browse the Web while watching TV at the same time.

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IPTV

Telephone companies are getting into the business of

delivering TV signals into people's homes over fiber-

• ptic lines. They do this using IPTV, which uses the

Internet's underlying protocols to deliver TV.

MPEG-2 The video streams are broken into IP packets. Quality of Service

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IPTV

Unlike with cable TV, not all channels are

simultaneously sent from local offices to individual houses

Multicast group

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Satellite Connection

You need a satellite dish on your home The request is sent via a normal modem to an ISP

(normal telephone line)

If provider is capable of using the satellite for both

upload and download, you don’t need a separate phone line.

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Satellite Connection

The web server sends the information to the satellite

company’s network operations center (NOC) (satellite ground station) via special high-speed links.

The NOC sends the information to a satellite above the

earth at 400kbps

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How Cell Phones Access the Internet

Wireless Access Protocol (WAP) and Wireless Markup

Language (WML)

The phone asks for authorization The base station looks at the telephone’s mechanical

serial number (MSN) and electronic serial number (ESN) to ensure that the phone is allowed to use the cellular network

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How Cell Phones Access the Internet

The base station sends the call to a telephone-wire-based

network (landline) and then to a network server and WAP gateway.

WAP gateway sends request to web server If the page is in normal HTML format, the gateway reformats

the page in WML

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How Wireless (WiFi) Networks Work

A key component of an 802.11 (WiFi network) is an

access point or router or AP.

AP consists of a radio transmitter and receiver as well

as an interface to a wired network …

AP serves as a base station and a bridge between the

wireless network and a larger network or the Internet

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How Wireless (WiFi) Networks Work

For a computer to become part of the network, it must be

equipped with an 802.11-compatible wireless network card

BSS (Basic Service Set): an AP and all its stations Stations communicate with AP using a method called

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

802.11 standard also allows stations to communicate

directly with one another

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How WiMax Works?

WiMax (Worldwide Interoperability for Microwave

Access) is similar to WiFi, but broadcast over an entire metropolitan area, using 802.16 standard.

Wireless ISP (WISP) provides WiMax Internet Service. WISP needs to connect to the Internet via a high-speed

backbone

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How WiMax Works?

Access Types:

Line-of-sight access: 70 Mbps Non-line-of-sight: less stable, lower speed

A single tower can broadcast up to 30 miles (100 feet

for WiFi)

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Questions?

Internet Engineering-Sharif University of Technology