re: Quick Figuring Optimal TCP Window Size

vincentv@microsoft.com — Wed, 27 Oct 2004 21:16:00 GMT

I took your formula Neil and put it into a command line c++ quick app.

Instructions:
1. Use VS6
2. New -> Win32 Console App -> Hellow World
3. Paste the code below in.

Disclaimer:
It worked for me. Well except that it might not round up correctly (but that is just 1 byte). :)

Thanks for your blog.

// tcpwindow.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(int argc, char* argv[])
{
float pingRTT;
float bandwidth;

char* pingExample = "c:\\>ping slow-msg-51\n\n\tReply from 17.54.12.19: bytes=32 time=176ms TTL=56\n\tReply from 17.54.12.19: bytes=32 time=114ms TTL=56\n\tReply from 17.54.12.19: bytes=32 time=117ms TTL=56\n\tReply from 17.54.12.19: bytes=32 time=171ms TTL=56\n";
char* pingExample2 = "\n\tPing statistics for 17.54.12.19:\n\t Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),\n\tApproximate round trip times in milli-seconds:\n\t Minimum = 114ms, Maximum = 176ms, Average = 144ms\n\n";

printf("===================================\n");
printf(" The TCPWindow Size Tool\n");
printf("===================================\n");
printf("\n\n");

printf("STEP 1: Find the RTT:\n");
printf("======================\n");
printf("Example: \n");
printf("\t");
printf("%s",pingExample);
printf("%s",pingExample2);
printf("Note ---> Approximate round trip times in milli-seconds:\n\t ... Average = 144ms\n\n");
printf("\n\n");
printf("========================================================\n");
printf("What is the Approximate round trip times for your issue?\n");
printf("========================================================\n");
printf(" Action: Type in the seconds value (if rtt was 144 then enter \".144\")\n and press ENTER\n\n");
printf("RTT Value: ");
scanf("%f",&pingRTT);

printf("\n\n");
printf("STEP 2: State the bandwidth:\n");
printf("==============================\n");
printf("Example: \n\n");
printf("\t");
printf("This is the WAN bandwidth. An example could be 1.44, 5, 10, 45, etc...\n");
printf("\n\n");
printf("=====================================================\n");
printf("What is the the available bandwidth of your WAN link?\n");
printf("=====================================================\n");
printf(" Action: Type in the value (i.e. 1.5) and press ENTER\n\n");
printf("Value: ");
scanf("%f",&bandwidth);
printf("\n\n");

printf("You have specified: %f as the RTT.\n",pingRTT);
printf("You have specified: %f for the bandwidth.\n",bandwidth);

printf("\n\n");
printf("STEP 3: Do the numbers:\n");
printf("==============================\n");
printf("Step1: ([BANDWIDTH]*1024*1024/8)bytes/second * [ROUND TRIP] = [TCP WINDOW]\n\n");
printf("Step2: (%f*1024*1024/8)bytes/second * (%f) = [TCP WINDOW]\n\n",pingRTT,bandwidth);
int step3;
step3 = (pingRTT * 1024*1024/8);
printf("Step3: (%f) * (%f) = [TCP WINDOW]\n\n",step3,bandwidth);
float step4;
step4 = step3 * bandwidth;
printf("Step4: %f = [TCP WINDOW]\n\n",step4);
printf("Step4: TCPWindowSize = %d\n\n",int(step4));

return 0;
}

re: Quick Figuring Optimal TCP Window Size

Neilcar — Wed, 27 Oct 2004 21:19:00 GMT

Glad you found it useful! I'd like to start getting more network-oriented stuff out here...