ips ecommerce lecture2 notes

8/3/2019 IPS Ecommerce Lecture2 Notes

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A set of interconnectedresources

Hosts that run networkapplications software

Clients and servers

Set of peers The network infrastructure that

interconnects the hosts

The networking hardwareand software

Network node devicessuch as routers andswitches

Links: cables,connectors, networkinterfaces

Anatomy of a network


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Transmission links

Convey bits, bytes, packets Physical medium

Copper (or aluminium)

Optical fibre

Glass, plastic

Free-space optical

Laser

Radio

Satellite, microwave link, mobile, wireless LAN,Bluetooth

Mode

Point-to-point

Shared medium (multicast)

Broadcast


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Representing data: bits and bytes

Bits

Different codes used in different interface standards

Images, multi-media

Require special bit pattern as delimiter

Bytes

Text is usually ASCII or Unicode characters

Text files, documents

Character set includes special control characters

01100001011000111 01110101

Bits Bytes

00000010 10000000 10100001


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Computer network

An interconnectedcollection of computers

ComputerNetwork Workstations(Local Processing)

FileServers

ApplicationServers

Client-Server Model


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Classifications of Networks

Based on size:System/Storage area networks (SAN)

within the same room

Local area networks (LAN)

in a close proximity

Metropolitan area networks (MAN)

span a city

Wide area networks (WAN) connecting computers situated anywhere

Connects many networks together


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Interconnecting LANs and WANs

To offsite

LANs

To the

Internet

Host systems usually connect into aLAN switch

Number of hosts limited by thenumber of ports on the switch

Routers have two main uses

Interconnecting LANs

Connecting to a WAN or to the

Internet

Routers interconnect LANs

To separate the users

To separate the traffic

switch

router


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Basic terminologies

Web Server

Machine that initiates internet request

Web Server

Machine that services internet request

Browser

Software at the client side to interact with data


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Basic terminologies

IntranetAn internal network of computer confined to a

simple place.ExtranetWhen two or more intranets are connected with

each other, they form an Extranet eg. VirtualPrivate Network (VPN)

InternetGlobal network of networks


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Basic terminologies

World Wide Web (WWW)It is a protocol that uses the internet as the

communication structure.Protocol

Hypertext Transfer Protocol (HTTP)Native protocol of WWW designed for making

web page requests


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Whats the Internet

The Internet is a collection ofnetworksconnected by interconnectingdevices.

The connecting devices

are specialized computing devices, e.g. routers

forward data from one network to another.


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Network Protocol

a human protocol and a computer network protocol:

Hi

Hi

Got thetime?

2:00

TCP connection

req.TCP connectionreply.

Get http

time


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Internetwork A collection of networks


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The Internet Topology

See http://www.cybergeography.org/atlas/topology.html for more Internet topologies.


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Communicating over the Internet

To communicate over the Internet, the computersmust:

use a common language or a protocol to govern theexchange of messages.

have a way to address one another.

Protocol:

specifies exact format, order of messages sent andreceived among network entities, and actions taken onmessage transmission and receipt.

Addressing:

defines where to deliver the messages.


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Protocol Layering Internet has a large collections of protocols

organized in a layering model. Application: enables the user, whether human or

software, to access the network.

Transport: responsible for reliable source-to-destination

(end-to-end) delivery of the entire message. Network: responsible for routing a packet (also called

datagram) from source-to-dest (possibly) acrossmultiple (different) networks.

Data link (also called network interface): specify howto organize data into frames and how to deliver a frameover a network.

Physical: coordinates the functions required to transmit

a bit stream over a physical medium.


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Protocol Layering

Two key protocols are:

IP (Internet Protocol)

Oversee end-to-end delivery of individual packets

Does not recognize relationships among packets

Treats each packet independently, as if they belong to

different message

TCP (Transport Control Protocol)

Ensure whole message arrive intact and in order

(eg, check if packets are missing or arrive out of order)


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Internet Addresses

Every Computer Is Assigned A Unique

Address

Each computer attached to the Internet must beassigned a unique address.

IP Addresses Are Not Random

Computers on the same network have the sameprefix (Netid).


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Internet Addressing

IP or Internet address is a 32-bit (4 byte)

address that uniquely defines every

computing devices on the Internet.

Decimal notation to make it easier to read.


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3.2 Classes of IP addresses Designers chose a compromise - multiple address formats that allow

both large and small prefixes Each format is called an address class

Class of an address is identified by first four bits

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