What is latency?

I have a script that fetches information from a hundred website. It
takes a long time because each website takes a second for the server
to respond. Based on suggestions in this newsgroup I have speeded it
up. But why do servers take one second to spit back a small 3 kilobyte
text file. Why isn't it instant? How does voice over IP overcome this
'delay' problem?

Duke of Hazard <squash@peoriadesignweb.com> wrote:
> I have a script that fetches information from a hundred website. It
> takes a long time because each website takes a second for the server
> to respond. Based on suggestions in this newsgroup I have speeded it
> up. But why do servers take one second to spit back a small 3 kilobyte
> text file. Why isn't it instant? How does voice over IP overcome this
> 'delay' problem?

Good question.

Since you are posting this to a PHP group, I assume this is some sort
of web based thing and there are lots of things that can slow down a
remote retrieve.

Personally, I would start with network analysis to see how much time
it takes to send the request and how long it takes for a response to
come back and go from there depending on what is seen.`

--
Jim Pennino

Remove .spam.sux to reply.

Duke of Hazard schreef:
> I have a script that fetches information from a hundred website. It
> takes a long time because each website takes a second for the server
> to respond. Based on suggestions in this newsgroup I have speeded it
> up. But why do servers take one second to spit back a small 3 kilobyte
> text file. Why isn't it instant? How does voice over IP overcome this
> 'delay' problem?

Hi,

If you requests the webpages in parallel, and not sequential, your
script will be a lot faster (but needs a lot more memory.).

About the delay: If you fetch a 3K file from a webserver in a far-away
location (networkwise), it takes time to deliver the message.
Like Jim suggested: You need network analisis tools to see why. But even
if you do know why, I think there is little you can do to overcome that
problem.
Other reasons might simply be a slow server, a busy server, etc..

(Why VOIP is fast? I don't know. Maybe it uses UDP instead of TCP/IP.)

Regards,
Erwin Moller

jimp@specsol.spam.sux.com wrote:
> Duke of Hazard <squash@peoriadesignweb.com> wrote: 
>
> Good question.
>
> Since you are posting this to a PHP group, I assume this is some sort
> of web based thing and there are lots of things that can slow down a
> remote retrieve.
>
> Personally, I would start with network analysis to see how much time
> it takes to send the request and how long it takes for a response to
> come back and go from there depending on what is seen.`
>

Having a small delay in responding ios a good way to prevent DOS attacks.

I.e. rapid and repeated downloads of the same thing, won't result in a
saturated server.
.

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