Mailing List Archive: Apache: Dev

Antw: query regarding Apache bandwidth requirements

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A.Schild at aarboard

Jun 25, 2004, 4:48 AM

Post #1 of 4 (960 views)
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Antw: query regarding Apache bandwidth requirements

Don't you think,

that the client is filling up it's buffer, and the after it's full just
stream what it has played ?

André

aarboard ag
internet - networks - screen&print design - multimedia
Egliweg 10 - Postfach 214 - CH-2560 Nidau (Switzerland)
Phone +41 32 332 9714 - Fax +41 32 332 9715
www.aarboard.ch - a.schild [at] aarboard

>>> jkielthy [at] yahoo 25.06.2004 13:43:04 >>>
Hi,

I have an Apache2 server that streams video to a VLC
client. I have used NeTraMet to capture the traffic
and used this data to draw the traffic profile. There
is no other traffic on the test-bed (except for RIP).

This profile shows a peak of about 3MB at the very
beginning. After that, the streamed data is fairly
constant at 200KB. Periodically (every 30 seconds),
the TCP connection window size gets smaller, resulting
in troughs in the profile. I am finding this behaviour
particularly difficult to understand. I was thinking
that the RIP updates might cause the window to
decrease, but I'm not sure. It seems fairly severe
that RIP would cause this behaviour.

So I am trying to explain this phenomena - does the
Apache server require this extraordinary amount in
order to initially set up a connection?

And is there some process where it will reduce the
window size at regular intervals, maybe by buffering
the data (which could result in the window being
reduced)?

Thanks for any help,
Jesse

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jkielthy at yahoo

Jun 25, 2004, 5:46 AM

Post #2 of 4 (953 views)
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Re: Antw: query regarding Apache bandwidth requirements [In reply to]

Hi André,

I had thought that, but I just wanted to be sue.

Do you know a reason why there is a 3MB peak at the
start? Is it something to do with Server set-up
connection requirements?

Rgds,
Jesse

--- Andre Schild <A.Schild [at] aarboard> wrote:
> Don't you think,
>
> that the client is filling up it's buffer, and the
> after it's full just
> stream what it has played ?
>
> André
>
> aarboard ag
> internet - networks - screen&print design -
> multimedia
> Egliweg 10 - Postfach 214 - CH-2560 Nidau
> (Switzerland)
> Phone +41 32 332 9714 - Fax +41 32 332 9715
> www.aarboard.ch - a.schild [at] aarboard
>
> >>> jkielthy [at] yahoo 25.06.2004 13:43:04 >>>
> Hi,
>
> I have an Apache2 server that streams video to a VLC
> client. I have used NeTraMet to capture the traffic
> and used this data to draw the traffic profile.
> There
> is no other traffic on the test-bed (except for
> RIP).
>
> This profile shows a peak of about 3MB at the very
> beginning. After that, the streamed data is fairly
> constant at 200KB. Periodically (every 30 seconds),
> the TCP connection window size gets smaller,
> resulting
> in troughs in the profile. I am finding this
> behaviour
> particularly difficult to understand. I was thinking
> that the RIP updates might cause the window to
> decrease, but I'm not sure. It seems fairly severe
> that RIP would cause this behaviour.
>
> So I am trying to explain this phenomena - does the
> Apache server require this extraordinary amount in
> order to initially set up a connection?
>
> And is there some process where it will reduce the
> window size at regular intervals, maybe by buffering
> the data (which could result in the window being
> reduced)?
>
> Thanks for any help,
> Jesse
>
>
> __________________________________________________
> Do You Yahoo!?
> Tired of spam? Yahoo! Mail has the best spam
> protection around
> http://mail.yahoo.com
>

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minfrin at sharp

Jun 25, 2004, 6:01 AM

Post #3 of 4 (958 views)
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Re: Antw: query regarding Apache bandwidth requirements [In reply to]

Jesse Kielthy wrote:

> Do you know a reason why there is a 3MB peak at the
> start? Is it something to do with Server set-up
> connection requirements?

The 3MB peak is probably caused by your test running over a fast network.

Apache will send as much data as your client is willing to receive, and
in this case, it looks like your client is willing to process 3MB at a
time. After this initial 3MB is transferred, fast, from the server to
the client filling the client's buffer, the client only accepts more
data when the client has finished rendering it to the screen, and that
would be at 200kbps.

This behaviour is not due to any Apache setting, it is due to the nature
of TCP and how it works.

If you want to avoid the 3MB spike at the beginning, you will probably
need an Apache module that limits the rate at which certain data is
sent. This has the unpleasant side effect that the client will no longer
be able to buffer the data, which means sudden network slowdowns will
result in jumpy network quality.

You probably want that 3MB spike at the beginning, as it improves the
quality of your service.

Regards,
Graham
--

jkielthy at yahoo

Jun 25, 2004, 6:31 AM

Post #4 of 4 (948 views)
Permalink

Re: Antw: query regarding Apache bandwidth requirements [In reply to]

My test-bed is 100Mbps links, so you're reasoning
sounds correct.

And you're right - I don't want to regulate the spike.
I just wanted to understand why it was happening.
Thanks for the explanation.

Cheers,
Jesse

--- Graham Leggett <minfrin [at] sharp> wrote:
> Jesse Kielthy wrote:
>
> > Do you know a reason why there is a 3MB peak at
> the
> > start? Is it something to do with Server set-up
> > connection requirements?
>
> The 3MB peak is probably caused by your test running
> over a fast network.
>
> Apache will send as much data as your client is
> willing to receive, and
> in this case, it looks like your client is willing
> to process 3MB at a
> time. After this initial 3MB is transferred, fast,
> from the server to
> the client filling the client's buffer, the client
> only accepts more
> data when the client has finished rendering it to
> the screen, and that
> would be at 200kbps.
>
> This behaviour is not due to any Apache setting, it
> is due to the nature
> of TCP and how it works.
>
> If you want to avoid the 3MB spike at the beginning,
> you will probably
> need an Apache module that limits the rate at which
> certain data is
> sent. This has the unpleasant side effect that the
> client will no longer
> be able to buffer the data, which means sudden
> network slowdowns will
> result in jumpy network quality.
>
> You probably want that 3MB spike at the beginning,
> as it improves the
> quality of your service.
>
> Regards,
> Graham
> --
>

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