CODEWITHSUNDEEP
network-programmingterminologycommunication
smwikipedia
smwikipedia

Reputation: 64333

Is it mis-use to use "bandwith" to describe the speed of a network?

I often heard people talking about a network's speed in terms of "bandwith", and I read from < Computer Networks: A Systems Approach > the following definiton:

The bandwidth of a network is given by the number of bits that can be transmitted over the network in a certain period of time.

AFAIK, the word "bandwith" is used to describe the the width of frequency that can be passed on some kind of medium. And the above definition describe something more like a throughput. So is it mis-use?

I have been thinking about this question for some time. I don't know where to post it. So forgive me if it is off topic.

Thanks.

Update - 1 - 9:56 AM 1/13/2011

I recall that, if a signal's cycle is smaller in time domain, its frequency belt will be wider in frequency domain, so IF the bit rate (digital bandwidth) is big, the signal's cycle should be quite small, and thus the analog bandwidth it required will be quite wide, but medium has its physical limit, the medium has the widest frequency it allows to pass, so it has the biggest bit rate it allows to transmit. From this point of view, I think the mis-use of bandwidth in digital world is acceptable.

Upvotes: 0

Views: 430

Answers (3)

ern0
ern0

Reputation: 3172

The term "bandwidth" is not a precise term, it may mean:

  • the clock frequency multiplied by the no-of-bits-transmitted-in-a-clock-tick - physical bandwidth,
  • minus bytes used for low-level error corrections, checksums (e.g. FEC in DVB),
  • minus bytes used by transmit protocol for addressing or other meta info (e.g. IP headers),
  • minus the time overhead of the handshake/transmit control (see TCP),
  • minus the time overhead of the administration of connection (e.g. DNS),
  • minus time spent on authentication (seeking user name on the host side),
  • minus time spent on receiving and handling the packet (e.g. an FTP server/client writes out the block of data received) - effective bandwidth, or throughput.

The best we can do is to always explain what kind of bandwidth we mean: with or without protocol overhead etc. Also, the users are often interested only in the last brutto value: how long does it take donwloading that stuff?

Upvotes: 1

user207421
user207421

Reputation: 310985

Bandwidth is only one aspect of network speed. Delay is also important.

Upvotes: 1

Mark Byers
Mark Byers

Reputation: 838686

The word bandwidth has more than one definition:

Bandwidth has several related meanings:

  • Bandwidth (computing) or digital bandwidth: a rate of data transfer, throughput or bit rate, measured in bits per second (bps), by analogy to signal processing bandwidth
  • Bandwidth (signal processing) or analog bandwidth, frequency bandwidth or radio bandwidth: a measure of the width of a range of frequencies, measured in hertz
  • ...

With both definitions having more bandwidth means that you can send more data.

In computer networking and other digital fields, the term bandwidth often refers to a data rate measured in bits per second, for example network throughput, sometimes denoted network bandwidth, data bandwidth or digital bandwidth. The reason is that according to Hartley's law, the digital data rate limit (or channel capacity) of a physical communication link is proportional to its bandwidth in hertz, sometimes denoted radio frequency (RF) bandwidth, signal bandwidth, frequency bandwidth, spectral bandwidth or analog bandwidth. For bandwidth as a computing term, less ambiguous terms are bit rate, throughput, maximum throughput, goodput or channel capacity.

(Source)

Upvotes: 5

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