Query Regarding Window Sizes

Hi All,

Sorry for the long winded paste from the wsbite btw.

I've been reading articles on Window Sizes and have a query.

The website states the following.

"If you had a web server that served 10,000 clients on a local area network (LAN) running at 100 Mbits with a 0.1 second round trip delay and wanted maximum performance/efficiency for your file transfers, according to our formula, you would need to allocate a window of 1.25 MB for each client or 12gb of ram for all of them.

So using the window size formula I would have something along the lines of..WS = 100,000,000 (bandwidth in bits) x 0.01 (delay in seconds) which = 1000000 bits

I'm not sure how they work out the 1.25MB for each client from here, or the 12GB for all 10,000 clients. Can someone please help?, just for my peace of mind.

I know it's very simple but I think it's a case of information overload and just need someone to explain it in simple terms. The website tries to, but I'm not following!

Thanks

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Comments

chmorin

I don't really see a corrilation between bandwidth and server specifications. Is there more context to be said? So far I'm pretty sure they are both individual statements.

Meaning the mention of the bandwidth and the ram needed on the server are separate. According to 'their' formula each user needs 1.25MB to have a decent time on the website. That has nothing to do with bandwidth, that deals with resources utilization on a server.

control

chmorin wrote: »

I don't really see a corrilation between bandwidth and server specifications. Is there more context to be said? So far I'm pretty sure they are both individual statements.

Meaning the mention of the bandwidth and the ram needed on the server are separate. According to 'their' formula each user needs 1.25MB to have a decent time on the website. That has nothing to do with bandwidth, that deals with resources utilization on a server.

I was just reading all this on the Firewall.cx website (not sure if I'm allowed to mention other sites....sorry...)

This is where I got it from it says this is how machines work out the window size (I wasn't aware this is how it was done).

chmorin

control wrote: »

I was just reading all this on the Firewall.cx website (not sure if I'm allowed to mention other sites....sorry...)

This is where I got it from it says this is how machines work out the window size (I wasn't aware this is how it was done).

You can mention other sites, no worries.

Well window sizes are not something I am familiar with in the least. Sorry.

alan2308

chmorin wrote: »

You can mention other sites, no worries.

As long as it's not a braindump or known spammer that is.

Anything that has been deemed unmentionable will turn to ******** after you hit submit, so if you don't see that, it's probably ok.

Forsaken_GA

Ok, I'll try and explain this -

100,000,000 x 0.1 = Bandwidth of the interface x delay = 10000000 (this is our window size in bits)

10000000/8 = Window size in bytes = 1250000 bytes

1250000/1024 = Window size in kilobytes = 1220 kilobytes

1220/1024 = 1.19 megabytes, so they're doing a little bit of rounding

So in order to support one client at 100mbits with a delay of 10 milliseconds, the server has to allocate a window size of 1.19 megabytes. In order to support 10,000 simultaneous clients at that speed with that delay, yeah, that means the server has to have 12 gigs.

And that's just for the TCP socket, nevermind any processing the server has to do once data starts flowing. If the server runs out of memory and can't allocate the buffer, packets get dropped and the connection slows down.

So yes, depending on the traffic you're wanting to support, server specs play a very important role.

chmorin

Forsaken_GA wrote: »

Ok, I'll try and explain this -

100,000,000 x 0.1 = Bandwidth of the interface x delay = 10000000 (this is our window size in bits)

10000000/8 = Window size in bytes = 1250000 bytes

1250000/1024 = Window size in kilobytes = 1220 kilobytes

1220/1024 = 1.19 megabytes, so they're doing a little bit of rounding

So in order to support one client at 100mbits with a delay of 10 milliseconds, the server has to allocate a window size of 1.19 megabytes. In order to support 10,000 simultaneous clients at that speed with that delay, yeah, that means the server has to have 12 gigs.

And that's just for the TCP socket, nevermind any processing the server has to do once data starts flowing. If the server runs out of memory and can't allocate the buffer, packets get dropped and the connection slows down.

So yes, depending on the traffic you're wanting to support, server specs play a very important role.

And I thought I wouldn't learn anything tonight. Thanks!

control

Forsaken_GA wrote: »

Ok, I'll try and explain this -

100,000,000 x 0.1 = Bandwidth of the interface x delay = 10000000 (this is our window size in bits)

10000000/8 = Window size in bytes = 1250000 bytes

1250000/1024 = Window size in kilobytes = 1220 kilobytes

1220/1024 = 1.19 megabytes, so they're doing a little bit of rounding

So in order to support one client at 100mbits with a delay of 10 milliseconds, the server has to allocate a window size of 1.19 megabytes. In order to support 10,000 simultaneous clients at that speed with that delay, yeah, that means the server has to have 12 gigs.

And that's just for the TCP socket, nevermind any processing the server has to do once data starts flowing. If the server runs out of memory and can't allocate the buffer, packets get dropped and the connection slows down.

So yes, depending on the traffic you're wanting to support, server specs play a very important role.

This is exactly what I was looking for

Superb. Thanks