1 the internet and networked multimedia. 2 the internet an interconnected set of networks a...

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The Internet and Networked Multimedia

The Internet and Networked Multimedia

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The InternetThe Internet

An interconnected set of networks A gigantic collection of millions of

computers, all linked together on a computer network

A home computer is usually linked to the Internet using a normal phone line and a modem that talks to an Internet Service Provider (ISP)freeservemsnfreeweb

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A computer in a business or university has a Network Interface Card (NIC) that directly connects it to a Local Area Network (LAN) inside the business

The business then connects its LAN to an ISP using a high speed phone line or optical cable

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JANETJANET

The University is connected to the Joint Academic Network (JANET) via the LEarning Network South East (LENSE)

LENSE is a 622Mbit network connecting higher education sites in the south east

Sussex’s connection to LENSE is 155Mbit

JANET (superJANET 4) is a 2.4 – 20Gbit network backbone connecting academic LANs

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LENSELENSE

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JANETJANET

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Development of the Internet

Originally developed by the U.S. Department of Defence

Development started in 1969 with the Advanced Research Projects Agency ARPAnet

Enabled communication between geographically dispersed research centres funded by ARPA

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Development of the InternetDevelopment of the Internet

ARPAnet was the first Wide Area Network (WAN)

Electronic mail was soon introduced using the Simple Mail Transfer Protocol (SMTP)

With the developments of other networks such as MILNET a protocol was required to enable these networks to be linked

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Development of the InternetDevelopment of the Internet

In the early 1980’s the current versions of the core Internet protocols TCP and IP were introduced

In the late 1980’s the Domain Name System (DNS) was introduced

In 1992 The Centre for European Nuclear Research (CERN) released the first version of the World Wide Web software

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Growth of the InternetGrowth of the Internet

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Key Properties of the Internet


Interoperable - any computer connected to the internet can communicate with any other computer connected to the internet - due to standardised protocols

Global - based on standardised and universal connectivity, using software that can be distributed throughout the Internet

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Easy to use - World Wide Web has made highly functional multimedia content easily available to users worldwide

Low cost - the cost of the network is shared across all users. A provider of information does not need to pay for the distribution system other than its own connection to the network

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Design Principles of the Internet


The main problem for the internet is how to build a system that can handle communication between two computers which may:have any type of operating systembe connected using any type of physical

medium

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To complicate matters:no connected system has any knowledge

about the other systemsand there is no way of knowing

• the location of that system

• what kind of software it uses

• what kind of hardware platform it runs on

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The main principles can be split into 5 concepts :Interoperability Uniform naming and addressing Layering SimplicityEnd-to-end protocols

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InteroperabilityInteroperability

Independent implementations of internet protocols work together

Systems can be assembled using client and server computers and software from different vendors

Buyers and sellers are not required to update simultaneously and from the same vendor to conduct commerce

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Uniform Naming and Addressing


The IP layer offers a uniform 32 bit addressing structure to each computer connected to the network

139.184.14.13Every device connected to the Internet

MUST have an IP address, whether it be a host, web server, name server or fridge

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The Domain Name Servers (DNS) offer a uniform way of translating IP addresses to human-readable names

139.184.14.13

www.sussex.ac.ukThe DNS system is a database – the

biggest distributed database on the planet and no other database on the planet gets this many requests

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Domain Name Servers (DNS)Domain Name Servers (DNS)

DNS has to cope with 5 major problems: There are billions of IP addresses currently in

use There are many billions of requests made to

domain name servers every dayDomain names and IP addresses change dailyNew domain names get created dailyMillions of people do the work to change and

add domain names and IP addresses every day

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Domain NamesDomain Names

The .COM, .UK and .NET portions of domain names are called the top-level domain or first-level domainThere are several hundred top-level domain names

Within every top-level domain there is a huge list of second-level domains. For example, in the COM first-level domain there are: microsoft fordplus millions of others...

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The left-most word, like www, encarta or cyril, is the host name

ames.central.sussex.ac.uk It specifies the name of a specific

machine or several machines which deal with requests to that host name

A given domain can, potentially, contain millions of host names as long as they are all unique within that domain

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All of the names in a given domain need to be uniqueNominet is the central authority that keeps

track of .UK top-level domainsNetwork Solutions is the domain registering

authority for .COMSussex Uni and EIT have several of their

own domain name servers and maintain the machines that implement their part of the DNS system

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Domain Name Servers (DNS)Domain Name Servers (DNS)

Every domain has a domain name server somewhere that handles its requests, and there is a person maintaining the records in that DNS

The DNS system is completely distributed throughout the world on millions of machines administered by millions of people, yet it behaves like a single, integrated database!

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The DNS ProcessThe DNS Process

When a request comes in, the name server can do one of four things with it: It can answer the request with an IP address because

it already knows the IP address for the domain It can contact another name server and try to find the

IP address for the name requested. It may have to do this multiple times

It can say, "I don't know the IP address for the domain you requested, but here's the IP address for a name server that knows more than I do"

It can return an error message because the requested domain name is invalid or does not exist

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The DNS ProcessThe DNS Process

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The DNS Look-up ProcessThe DNS Look-up Process

The name server would start its search for an IP address by contacting one of the root name servers

The root servers know the IP address for all of the name servers that handle the top-level domains and returns the appropriate IP address for that name serverE.g. the .UK name server if we are trying to find the IP

number for www.bandq.co.uk Your name server then sends a query to the

UK name server asking it if it knows the IP address for www.bandq.co.uk

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The DNS Look-up ProcessThe DNS Look-up Process

The name server for the UK domain returns the IP addresses for the name servers handling the banq.co.uk domain

Your name server then contacts the name server for banq.co.uk and asks if it knows the IP address for www.banq.co.uk

It actually does, so it returns the IP address to your name server, which returns it to the browser, which can then contact the server for www.banq.co.uk to get a web page

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IP AddressesIP Addresses The four numbers in an IP address are called

octets, because they are a byte long when viewed in binary form, giving a possible 256 values for each number

139.184.14.1310001011.10111000.00001110.00001101

The octets are used to create classes of IP addresses that can be assigned to a particular business, government or other entity based on size and need

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IP AddressesIP Addresses

The octets are split into two sections: Net - contains the first octet. It is used to identify the

network that a computer belongs toHost - identifies the actual computer on the network.

The Host section always contains the last octet

139.184.14.13

Net or host information depending on class

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IP AddressesIP Addresses

There are five IP classes plus certain special addresses: Class A – Class ENetwork IdentificationLoopbackBroadcast

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Class A IP AddressesClass A IP Addresses

This class is for very large networks, such as a major international company might have

IP addresses with a first octet from 1 to 126 are part of this class 18.181.0.31

The other three octets are used to identify each host. Thus, there are 126 Class A networks each with 16,777,214 possible hosts

Class A networks account for half of the total available IP addresses

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Class B IP AddressesClass B IP Addresses

Used for medium-sized networks such as sussex.ac.uk – 139.184.14.13

IP addresses with a first octet from 128 to 191 are part of this class. Class B addresses also include the second octet as part of the Net identifier

The other two octets are used to identify each host. This means that there are 16,384 (214) Class B networks each with 65,534 possible hosts

Class B networks make up a quarter of the total available IP addresses

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Class C IP AddressesClass C IP Addresses

Used for small to mid-size businesses IP addresses with a first octet from 192 to 223

are part of this class 194.83.112.43 Class C addresses also include the second

and third octets as part of the Net identifier. The last octet is used to identify each host. This means that there are 2,097,152 (221) Class C networks each with 254 hosts

Class C networks make up an eighth of the total available IP addresses

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Class D IP AddressesClass D IP Addresses

Used for multicastsClass D is slightly different from the

first three classes. Its first 3 bit values are 1, and fourth bit value of 0 (224 – 239)

1110xxxxThe other 28 bits are used to identify the

group of computers the multicast message is intended for

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Class E IP AddressesClass E IP Addresses

Used for experimental purposes onlySimilar to Class D, but with it’s first 4 bit

values set to 1 (240 -247)

1111xxxxThe other 28 bits are used to identify the

group of computers the message is intended for

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Special IP AddressesSpecial IP Addresses

There are several special IP addresses which are not assigned to specific hosts

An all zero host refers to the network itselfE.g. 129.152.0.0 refers to the network 129.152

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Special IP AddressesSpecial IP Addresses

The IP address 127.0.0.0 is used as the loopback addressThis means that it is used by the host

computer to send a message back to itself. It is commonly used for troubleshooting and network testing

Broadcast - Messages that are intended for all computers on a network are sent as broadcasts. These messages always use the IP address 255.255.255.255

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FinFin

Fin

1 the internet and networked multimedia. 2 the internet an interconnected set of networks a...

Documents

internet slide

network slide

internet arpanet

internet easy

internet interoperable

lense slide

janet slide

arpa slide