From: Rodgers Moore (rodgers@xxxxxxxxxxxxxx)
Date: Sat Apr 07 2001 - 16:46:23 GMT-3
I guess you have to assume no error rate, but this is actually a pretty simple
problem. I assume the what they are saying is the MTU is 32K.
1.544Mbps / 8bit/Byte = 193000Bps
Window size is 64K + (64K/MTU (32K) * 20Bpp) = 64040Bytes per window
193000Bps / 64040B/Window = 3.01 windows/sec or 3 ACKps
Propogation delay is 250ms one way and an ACK is 250ms in the other direction.
So
delay is 500ms per ACK or window.
3 ACKs per second * 500 ms = 1.5 seconds of delay per 1 second of raw
transmission.
2.5 seconds total time to transmit 1.544Mb
1.544Mb / 2.5 s = 617.6Kbs throughput
As a side note, in reality the delay from earth to satelite is about 250ms. The
delay through the satelite is about 25ms, so earth to satelite to earth is 525m
s
so in truth the ACK delay is more like 1.05 seconds.
Rodgers Moore
Muthu wrote:
> Hi Gurus,
>
> Found this on one of the CCIE prep sites...could someone help me solve this ?
> and/or also direct me to the URL for such info...
>
> Question:
> The TCP protocol does all its sequencing and window accounting in single byte
> units, although data may be transmitted in segments of upto 32KB. The maximum
> window size provided for the protocol is 64KB. What is the approximate
> theoritical maximum one way throughput of a single TCP connection over a
> 1.544Mbps satellite connection from Dallas to Florida with a one way delay of
> 250 milisecs?
>
> Thanks in advance,
>
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