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What happens when you summon a page
Next time you have to wait for a page....
- You, the client, first make a request of a web server, your Internet
Service Provider or ISP.
- The request contains the return address of the calling computer. This is known as the
IP address which is a set of numbers that allows the Internet to send the page
back to you.
- The server meanwhile checks the request to see if the page exists. It does this by asking the Domain Name
Server (DNS) where the domains are registered. The domain is the first part
of the name. Our domain is writersservices.com. (But WritersServices.com is
also 195.40.15.102)
- The server then requests the particular page in the web from the computer
hosting the web domain you want to see.
- If the page does not exist, an
error message is returned.
- If the page exists, the web server checks if any special processing is
required, such as Java or ASP.
 | This processing is normally done by a third
party application, perhaps on yet another server, before returning it to your web server. |
| The server adds any default or custom header information to
the page. |
| The page itself might incorporate graphics or applications which
themselves have to be called in exactly the same way as you request a
page. |
The page is sent back to you, the
client.
In fact it is even more complex, as there can be mirror sites and caches of
frequently called pages. The Internet is a robust, flexible and sophisticated
communications system!
If you want to explore the organisation that makes it all work, go to w3.org |
What are
domain names?
Every connection to the
Internet has a 32 bit Internet Protocol (IP) address. This translates into a
digital number which is normally expressed as four blocks of 3 numbers,
separated by full stops. When you log on, your provider will dynamically issue
you a number for that session. That is a Point to Point protocol (PPP) but the
providers will have a Serial Line IP (SLIP) that is fixed.
But remembering numbers is
tough and typing them in is error prone. So the Domain Name System (DNS) was
developed. Many countries have a suffix while organisations can have a generic
suffix such as .com. Special servers keep track of the names and convert them
into addresses. If you watch the little box at the bottom of the screen next
time you are on the net, you will see this happening and the name being
converted into numbers.
What is a page header? |
Internet Protocol version 6 (IPv6) is a network layer IP standard used by
electronic devices to exchange data across a packet-switched internetwork. It
follows IPv4 as the second version of the Internet Protocol to be formally
adopted for general use.
The main improvement brought by IPv6 is the increase in the number of addresses
available for networked devices, allowing, for example, each cell phone and
mobile electronic device to have its own address. IPv4 supports 4.3×109 (4.3
billion) addresses, which is inadequate for giving even one address to every
living person, much less support the burgeoning emerging market for connective
devices. IPv6 supports 3.4×1038 addresses, or 5×1028(50 octillion) for each of
the roughly 6.5 billion people alive today, or 56.9 billion addresses for each
gram of matter on Earth.
A technical reason for selecting 128-bit for the address length is that since
most future network products will be based on 64 bit processors, it is more
efficient to manipulate 128-bit addresses. The drawback of the large address
size is that IPv6 is less efficient in bandwidth usage, and this may hurt
regions where bandwidth is limited.
composed of two logical parts: a 64-bit (sub-)network prefix, and a 64-bit
host part
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