Networking and the Internet
Derek Bridge
Department of Computer Science,
University College Cork
Networking and the Internet
Aims:
- to know the main components in a LAN
- to know the main components in a WAN
- to know the main components in an internet
- to know who owns, runs and pays for the Internet
Internets and the Internet
- A network of networks is an internet
- The best-known internet is the Internet
- The Internet is not the World Wide Web
- The World Wide Web is an application of the Internet
- Email is another application of the Internet
Types of Computer Network
We can classify by distances between devices:
- Local Area Networks (LANs)
-
LANs connect together computers that are relatively close to each other,
typically within the same room or building
- Wide Area Networks (WANs)
-
WANs connect together devices or other networks over a greater distance
than is practical for local area networking
LANs: Ethernet
- Ethernet was developed in Xerox in the early 1970s
- Digital, Intel and Xerox standardised it in 1980
- Competitors included ARCNET; token ring; and token bus
- Ethernet triumphed after adopting ARCNET's
star
topology using switches & twisted pair cabling
- Now, twisted pair and/or fibre optic Ethernet are the most
common LAN technologies
- Wi-Fi is used in homes or in addition to Ethernet
- The fastest Ethernet technologies are now also being used in WANs
Wide Area Networks (WANs)
Before the (public) Internet, an organisation wanting to connect
distant computers or LANs had three main options:
- Lay a cable (unlikely!)
- lease a line from a common carrier, or
- dial-up
Networks of networks: internets
An internet is a network of networks, formed by connecting two
or more distinct computer networks together
-
Devices called routers are used to connect the networks together
- If different networks are to inter-operate, we need protocols,
i.e. agreements that specify how two computers will exchange
messages
Image of the Fujitsu GeoStream R980 router from HowStuffWorks
The Internet
- The Internet is a global internet that operates according to a
set of protocols known as the TCP/IP Protocol Suite
- The Internet backbone was the central network to which other
networks connected (e.g. ARPAnet and NSFnet)
- Now, there are multiple interconnected high-speed backbones
- A midlevel network (either a regional network or a
company WAN) will connect to one of the backbone networks
- Backbone networks are connected to each other and to midlevel networks
at routers called Internet exchange points (also called
'peering points' and previously called 'network access points')
- A company or university LAN will connect to a midlevel network
More Internet terminology
- A Point of Presence (POP) is a computer that is connected to
the Internet (to a midlevel or backbone network)
- An Internet Service Provider (ISP) is a company whose network
allows end-users (e.g. home users) to connect to a POP
The Internet
Who owns the Internet?
- Physical infrastructure:
- Hosts, routers and other devices are owned by various individuals and organisations
- Links are owned by telecommunications companies
- Links may be leased by other organisations
- Intangibles (protocols, standards, numbering & naming schemes, etc.)
- No-one owns these/we all own these
- Why care?
Who runs the Internet?
No one runs the Internet! But various organisations are involved in defining standards
Organisational chart from The TCP/IP Guide
Who pays for the Internet?
- Home users pay their ISPs who in turn pay their network service providers
- Orgnisations may pay rent to telecoms companies for lines that they lease
- Organisations may pay fees to the various co-ordinating bodies to which they belong
- Governments may subsidise some of these activities