Re: Re: Max. throughput on a 2Mbit leased line?

[Jon Lawrence <lists@xxxxxxxxxxxxxxx>]

On Thursday 06 January 2005 23:48, vargster wrote:
> >From a straight maths point yes, but what about overheads, like
the
>
> TCP/IP headers etc, the ack packets coming back etc?
>
> What can I really expect to transfer per hour?
>
> Lee
>
That depends on how big your packets are. ie you'll get more transferred
with
large packets than small ones.
tcp/ip headers are 20 bytes with another 20 bytes (approx) for the IP
header,
so max data segment is 1460 bytes.
Assuming that you're always sending the max data segment and that acks are
sent for each 2 data segments (I believe this is right for BSD type TCP
stacks). That means for every 2 data segments ( 2 * 1460 = 2920) there are
3
lots of headers ( 3 x 40 = 120). That gives you a ratio of 2920/3000
So, the absolute max throughput is 0.25 * 2920/3000 which is approx 0.243
MB/s. Which equates to an max transfer of 876MB per hour.
In reality you're not going to get this as some of your packets aren't
going
to be max size - it also assumes that you're using an mtu of 1500.

HTH
Jon