A network is a connected (via some form of cables) system of
computer hardware. The Birkbeck College Department of Crystallography has a
local network which consists of all electronically connected computers within
the department. Such a network is called a Local Area Network (LAN).
Other LANs within the College might include those of the Chemistry, Biology,
Physics, English, German (and so on !) departments.
Some of Birkbecks computers are at a different location within the city ;
however, they are still connected to each other and hence also constitute a LAN.
When several such LANs are connected to each other (over wider distances) we
refer to the ensuing structure as a Wide Area Network (WAN) !
The Internet is the world-wide conglomerate of LANs and WANS, ethernet
links and dedicated phone lines, a network of networks. The Internet spans
political and geographical borders and through connectivity of all manner of
computers it provides information on a wealth of topics, from apple pie over atomic
decay to zeta particles !
The Crystallography department is itself connected to the Internet which is
how you can actually access our computers - and read this file !
Computers on the Internet can be accessed by specifiying their address.
This can be done in two ways:
- Using the Internet Protocol (IP) address. This consists of four
numbers separated by a full stops (the dotted quad), and is known
as the IP Number, for example 18.104.22.168
- Using the Domain Name System (DNS):. The DNS Address consists of letters
(sometimes containing a numerical digit or two) and there are not necessarily four
parts to the address as with the IP Number.
For example mv3b.cryst.bbk.ac.uk denotes the VAX computer called
mv3b in the crystallography department at
Birkbeck College in the Academic Community
in the United Kingdom !
You can probably see that the DNS address is more user-friendly than IP
numbers. DNS addresses are hierarchical and its often possible to guess
addresses based on abbreviations and country codes. For example:
- Educational establishments often contain or end in edu (short for
- Companies often have an address ending in com, Government sites may
end their address with gov and military sites terminate in mil !
- Especially in Europe, many site addresses have the international country code
as their last entry. Examples include at for Austria, ch for
Switzerland or au for Australia.
- World Wide Web address often start with the WWW qualifier while
ftp denotes a File Transport Protocol (FTP) server. This is not always
the case though !
- Company addresses are typically composed of a www followed by the
company name or abbreviation and ended with com. Known examples
include www.ibm.com, www.apple.com and so on.
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