jeffershaw...
Data sent across the internet is broken up into chunks
called 'packets':
From Mark Hazen's site on 'How the Net Works' on the
College of Family and Consumer Sciences website:
http://www.fcs.uga.edu/~mhazen/projects/smtp/glossary.html
"Packet:
A manageable chunk of data, broken off of a large data
transmission, to allow easier transmission and error
checking of data."
A more in-depth explanation from another of Mark's pages:
http://www.fcs.uga.edu/~mhazen/projects/smtp/compare.html
"The Internet Protocol uses its scheme of IP addresses, as
described earlier, to send information, broken down into
manageable chunks called packets, across the Internet.
Sometimes the packets being transmitted across the Internet
run into dead-ends, cannot find a path to get to the machine
for which they were addressed, or get stuck in a circle,
being bounced among several machines. A number stored in
the first part of an IP packet (the first part of an IP
packet is known as the "IP Header") called the "Time To
Live" value (TTL) gets decremented each time a packet gets
sent from machine to machine, trying to find a path to its
desired destination machine. When the TTL value hits zero,
the packet is discarded, and is considered to be "lost".
As each packet is transmitted individually, there is also
no guarantee that two consecutive packets will take the
same physical route through the Internet to reach their
destination, or that these packets, upon arriving, will
be in the same order they were transmitted in. This is
the main failing of the IP protocol; there is no numbering
of the data being sent to ensure that it can be reassembled
easily. Once a piece of information leaves the transmitting
computer, the sending machine washes its hands of the
transmitted information. There is a benefit to this,
however; as IP packets don't have to be concerned with
the order of the data sent, or whether the data gets there
or not, the speed of the IP protocol for transmitting data
across the Internet is, all in all, fairly unfettered. In
a perfect world, all data would be transmitted via the IP
protocol. In this imperfect reality, however, more reliable
transfers are necessary."
"The need for data accountability and information ordering
is where the Transmission Control Protocol (TCP) comes in.
TCP uses ordering numbers to indicate which part of a
particular transmission is contained within the current
packet, and what order the packets should be assembled in.
If a particular transmission, using TCP, arrives at the
destination machine with four out of six packets, and in
the order 1, 3, 5, 2, the destination machine properly
arranges, and then holds onto these packets, while sending
a message back to the origin of the transmission that
packets four and six need to be resent. When all of the
parts of a transmission are properly received by the
destination machine, the parts are assembled, and the
communication of that particular transmission is complete.
By using the TCP protocol, computers can simulate, over an
indirect and non-contiguous connection, a direct
machine-to-machine connection."
While it seldom occurs that this clever process fails,
in the event that it does, your computer will detect
that the file is corrupt when you try to activate, or
open, it. This is explained on the following page:
From Lalim Software's Frequently Asked Questions page:
http://www.angelfire.com/mb/lalim/faq.htm
Question 6:
"I recently tried to install a downloaded program and got
a 'not a valid Win32 application' error message. What does
this mean?"
Answer:
"It indicates either that the file you downloaded may be
corrupt or due to your firewall problem. In the case
of a corrupt file, Windows can read part of the file as
a valid executable program, then finds a damaged spot
and throws up an error. You'll have to download the file
again, preferably from a different site. After you've
saved the file, check its exact size (by right-clicking
the file in Windows Explorer and choosing Properties)
and compare it with the size listed on the download site.
An exact match, down to the last byte, should mean that
the file is good. If the saved file is off, even by a
byte, you may encounter errors."
Please do not rate this answer until you are satisfied that
the answer cannot be improved upon by means of a dialog
established through the "Request for Clarification" process.
sublime1-ga
Searches done, via Google:
how data is sent across the internet
://www.google.com/search?q=how+data+is+sent+across+the+internet
"corrupt file" "after download"
://www.google.com/search?q=%22corrupt+file%22+%22after+download%22 |
