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3.1.8

Explain why the speed of data transmission across a network can vary.

 

Teaching Note:

 

Sample Question:

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JSR Notes:

The following things can influence the speed of transmission across a network:

 

More purely varying factors from day to day, even minute to minute

- Number of people using the network

- All connecting from the same place

- Many people on the network downloading big files/watching videos at the same time. i.e. Netflix!!

- The size of the payloads being transferred at the same time can affect speed of data transmission, by leading to congestion

 

Other factors which won't change day-to-day, hour to hour, but which do affect network speed sdfasdfasdasdfasdfads

- BOTH the receiving hardware and the transmitting hardware (servers, routers, modems)

- The transmission media (kind of material the wires are made of) (i.e. Ethernet cable, fiber optic cable, ISDN/cable, microwaves etc.)

- Whether or not the data being sent is compressed

- Different protocols allow different levels of speed, and provide various means of managing control and preventing congestion. For example the UDP protocol is used by gamers because even though it's not too secure, it is fast. Whereas TCP/IP is used by most people on the Internet and is much more secure, has good error checking, but is therefore slow. The good analogy is having a package delivered in a big congested city by one of those "Messenger" guys on a motor bike, versus the local postal service.

- Distance from the ISP (Internet Service Provider)

- The more requests a computer requires from a network, the more priority it gets from the network, so if one computer is hogging the network that can slow down others' access speed.

- The use of IPV6 can speed up overall network activity, because more devices can have dedicated IP addresses (the number of possible IP addresses is almost infinitely more than the 4 billion of IPV4 - 128 bits per IP address versus 32) ?????

- (Note that encryption really should not be included in things that slow down a network, for even though there is processing time scrambling and un-scrambling information with sophisticated algorithms, such as sha1 and sha128, in the encryption process, this is done at the client and server computers, but not along the network path.)

 

And getting specific, as the St. Julian's site does, this is directly from Wikipedia, and an article called Packet Transfer Delay

Plus, there are four sources of packet transfer delay: (This is in addition to all of the factors listed above.)

 

In terms of how to answer a question about this assessment statement on an exam, you would do well to list three or four reasons from the general list above (at the top half of the page), making sure you include any explanation of why they slow things down, along with mentioning how even down to the packet level are things which delay transfer time, such as.... and then picking one above only you fully understand. Frankly, I think nodal processing is the best, since queuing overlaps with other general business of networks, and transmission delay and propagation delay are a bit trickier to explain.