Hardware Reference
In-Depth Information
Broadband Router
Nearly all of the various broadband Internet connection technologies can be shared
on a LAN by using a broadband router. A
broadband router
is basically a regular
consumer-level router, but it may come with software, instructions, or other extras that
make it especially easy for an average person to set up to share a broadband Internet
connection.
To share an Internet connection, connect an Ethernet cable from the Internet source (for
example, the cable modem to the Internet or uplink or input jack on the back of the router).
Then connect all the computers in your network to the router, either with Ethernet cables
or wirelessly (if it's a wireless router). The router handles the
network address translation
(NAT)
required for each of the computers to use that single Internet connection.
DNS Servers
Earlier in the chapter, you learned that IP addresses are 32-bit binary numbers expressed
as sets of four decimal numbers like this:
208.215.179.220
. All Internet servers must
have an IP address in order to be able to communicate. For our purposes, though, domain
names like
Microsoft.com
are used instead of the numbers, because they're easier to
remember.
Domain Name System (DNS)
servers translate between the numeric addresses and the
friendlier domain names. These servers store and provide access to translation tables based
on information they get from domain registrar companies.
There is a misconception that all web addresses must start with
www
. This
is only customary, not required. Large sites, such as Microsoft, divide the
websites into multiple servers, each one having a different prefix, like
support.microsoft.com
and
office.microsoft.com
.
DNS works from right to left, with each part of the address separated by periods. To
look up the IP address for a web address (a
uniform resource locator
, or
URL
) is known as
resolving
the address.
An organization called InterNIC controls the issuing of Internet addresses. It manages a
group of registrars, who in turn manage a range of domains and ensure that DNS lookup
information is available for them worldwide.
For example, to resolve
www.biguniversity.ac.uk
, the browser fi rst consults a top-level
DNS server, which contains only information about where other DNS servers are stored
for the various top-level codes. This fi rst DNS server, owned by InterNIC itself, directs
the request to a DNS server, managed by Nominet, which handles only domain names
that end in
.uk
. That server, in turn, sends the request to another DNS server, managed by
JANET (Joint Academic Network), which manages
.ac
and
.gov
addresses. Finally, the
request is sent to the university's own DNS server, which manages its own domain and any
subordinate domains.
