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

["Davey" <DB1001@xxxxxxxxxxxxxxx>]

Not forgetting that you won't want to max out your line - as the pareto's
principle (80/20) hits you in the head and your users will get p*** poor
performance. We run some BT 2 mbit leased line between office sites and for
the 100+ users in the remote office it's fine in terms of latency  (citrix
servers at other end and web traffic). Line is running at avg.  23%
utilisation and if it got too high the performance for the users would be
unacceptable. Shifting the max amount of data per hour from site A to site
B
is one thing but don't forget that if you have users (A) using resources in
(B) then they need a better QOS than say a SQL database shifting logs
(normally).

Just my 2euros worth.

----- Original Message -----
From: "Jon Lawrence" <lists@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Friday, January 07, 2005 10:25 AM
Subject: Re: [ukha_d] Re: Max. throughput on a 2Mbit leased line?


>
>
> 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
>
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