Re: Network timeout estimation

On Nov 17, 1:20 pm, dondora <koni...@xxxxxxxxxxx> wrote:
Hi there.

I need your help.
I'm coding a simple program which provides reliable transmission using
udp as a homework.
I'm going to use expressions used in TCP timeout estimation.
Let me show those expressions.

EstimatedRTT = (1 - a) * EstimatedRTT + a * SampleRTT
(the recommended a = 0.125)
DevRTT = (1 - b) * DevRTT + b * |SampleRTT - EstimatedRTT|
(the recommended b = 0.25)
TimeoutInterval = EstimatedRTT + 4 * DevRTT

What I really want is TimeoutInterval. But to get it, I have to know
EstimatedRTT and DevRTT,
and the real problem is at initial time, at which time nothing has
done like sening a packet and receiving a ACK)
I don't know what EstimatedRTT is to be and what DevRTT is to be.

Can you help me to solve this problem? I'll appreciate that. I really
need your help~!~! please~!~!


Hi,

Your problem is solved in TCP by setting default values to
EstimatedRTT and DevRTT. In "TCP/IP Illustrated, Volume 1" page 305,
RTO = 0(EstimatedRTT)+3(DevRTT)*2. Actually, they used a weighting
factor 2 on DevRTT rather than 4 at the first instance. You can try on
this mechanism.

Regards
felix
.

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