
An Engineer's Guide to Bandwidth - aristus
http://developer.yahoo.net/blog/archives/2009/10/a_engineers_gui.html
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seiji
<useless but informative gripe>

An actual engineer would know bandwidth isn't something measured in bits per
second.

Technically, bandwidth is the width of a band of frequencies. For example, the
bandwidth between 3 GHz and 4 GHz is 1 GHz. The bandwidth of an 802.11 channel
is 22 MHz.

Obviously it's a lost cause trying to stop everyone from using "bandwidth" to
mean throughput or a data rate. Don't get me started on people using bandwidth
to mean how much work they can handle either: "I don't have the bandwidth to
handle another project, you better give it to somebody else."

</useless but informative gripe>

~~~
a-priori
There's this wonderful property that all human languages have, polysemy, which
gives them the ability to give one word multiple related meanings. I'm sure
there are examples in English...

~~~
TriinT
Except that engineers are supposed to use precise, unambiguous language. I
blame the computer guys for knowing jack of signal processing / communications
theory and misusing the technical terms due to plain ignorance. It wouldn't be
so bad if the ignorant fools in question weren't so arrogant...

~~~
fnid
I agree with that arrogant part. I think also though, it does get annoying
when people know full well what you are talking about, but then interject with
some clarification or correction or disambiguation that really wasn't
necessary.

The problem is that sort of interjection ruins the conversation and interrupts
the communication of ideas that are bigger than the individual words that
comprise them.

~~~
TriinT
It also gets annoying when people discuss things and in the end discover they
are talking about different things, you know. When a networks guy talks about
bandwidth, he might refer to bit rate or channel capacity, but for an RF
engineer, bandwidth is measured in Hertz. Interrupting the commnunication of
ideas is bad, but communicating imprecise ideas is close to useless.

~~~
a-priori
So the onus is on you to make yourself clear in spite of the ambiguity (a
simple way would be to mention a unit early in the conversation). Really, the
terminology isn't going to change no matter how much noise you make, so it
would be worthwhile to save yourself the effort.

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jws
I like the point about keeping the HTTP GET or POST request in a single packet
to avoid the round trip from TCP slow start.

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pyre
Why is he using 1460 as the packet size? He says that it's 1500 minus the
packet overhead, but I've always seen MTU as 1492 (I could be recalling
incorrectly here). In any case, MTU changes as you travel over various
networks with various settings, using various technologies
(ethernet,wireless,fiber,etc).

~~~
aristus
MTU is the maximum Ethernet v2 packet size (1500); MSS is the "payload" it can
carry (1460). If you see 1492 for your MTU, you are maybe using Point to Point
Protocol over Ethernet (PPPoE) which chomps another 8 bytes.

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rm-rf
The referenced link is far more interesting than the resulting discussion.

For persons who are designing web applications, the post outlines
considerations that are not generally known or well understood. Some
considerations, such as managing the number of round trips also apply to
app<->database connections.

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SeanLuke
Isn't the proper term "throughput"?

~~~
wmf
Yes, but it's too late to change (see seiji's downvoted comment below).

