Hi All, I am sending broadcast UDP data using a round robin of 802.11n MCS 0,1,2,3 data rates (6.5Mbps, 13Mbps, 19.5Mbps, 26Mbps). However, the tcpdump output at the receiver looks very strange. It shows some packets as 1Mbps and works correctly some times.
Does anyone know why this might be happening? Here is a snapshot of TCP dump: 10:57:01.173316 2734594330us tsft 2462 MHz 11g -14dB signal antenna 0 6.5 Mb/s MCS 0 20 MHz lon GI More Data 0us IP (tos 0x0, ttl 64, id 17927, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.173345 2734594516us tsft 2462 MHz 11g -16dB signal antenna 0 13.0 Mb/s MCS 1 20 MHz lon GI 0us IP (tos 0x0, ttl 64, id 17928, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.275286 2751440865us tsft 2462 MHz 11g -15dB signal antenna 0 19.5 Mb/s MCS 2 20 MHz lon GI More Data 0us IP (tos 0x0, ttl 64, id 17929, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.275310 2751440967us tsft 2462 MHz 11g -14dB signal antenna 0 26.0 Mb/s MCS 3 20 MHz lon GI More Data 0us IP (tos 0x0, ttl 64, id 17930, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.275643 2751441058us tsft 2462 MHz 11g -15dB signal antenna 0 6.5 Mb/s MCS 0 20 MHz lon GI More Data 0us IP (tos 0x0, ttl 64, id 17931, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.275654 2751441244us tsft 2462 MHz 11g -16dB signal antenna 0 13.0 Mb/s MCS 1 20 MHz lon GI More Data 0us IP (tos 0x0, ttl 64, id 17932, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.275657 2751441369us tsft 2462 MHz 11g -15dB signal antenna 0 19.5 Mb/s MCS 2 20 MHz lon GI 0us IP (tos 0x0, ttl 64, id 17933, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.378071 2734798918us tsft 2462 MHz 11g -16dB signal antenna 0 6.5 Mb/s MCS 0 20 MHz lon GI More Data 0us IP (tos 0x0, ttl 64, id 17935, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.378103 2734799105us tsft 2462 MHz 11g -15dB signal antenna 0 13.0 Mb/s MCS 1 20 MHz lon GI More Data 0us IP (tos 0x0, ttl 64, id 17936, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.378108 2734799230us tsft 2462 MHz 11g -15dB signal antenna 0 19.5 Mb/s MCS 2 20 MHz lon GI More Data 0us IP (tos 0x0, ttl 64, id 17937, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.378111 2734799329us tsft 2462 MHz 11g -15dB signal antenna 0 26.0 Mb/s MCS 3 20 MHz lon GI 0us IP (tos 0x0, ttl 64, id 17938, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.480790 2734934023us tsft 1.0 Mb/s 2462 MHz 11g -17dB signal antenna 0 More Data 0us IP (tos 0x0, ttl 64, id 17939, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.482021 2734935233us tsft 1.0 Mb/s 2462 MHz 11g -17dB signal antenna 0 More Data 0us IP (tos 0x0, ttl 64, id 17940, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.483165 2734936381us tsft 1.0 Mb/s 2462 MHz 11g -16dB signal antenna 0 More Data 0us IP (tos 0x0, ttl 64, id 17941, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.484298 2734937510us tsft 1.0 Mb/s 2462 MHz 11g -17dB signal antenna 0 More Data 0us IP (tos 0x0, ttl 64, id 17942, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.485554 2734938721us tsft 1.0 Mb/s 2462 MHz 11g -17dB signal antenna 0 0us IP (tos 0x0, ttl 64, id 17943, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.583230 2735003700us tsft 1.0 Mb/s 2462 MHz 11g -17dB signal antenna 0 More Data 0us IP (tos 0x0, ttl 64, id 17944, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 10:57:01.584425 2735004883us tsft 1.0 Mb/s 2462 MHz 11g -16dB signal antenna 0 More Data 0us IP (tos 0x0, ttl 64, id 17945, offset 0, flags [DF], proto UDP (17), length 70) 192.168.1.1.44292 > 255.255.255.255.2050: UDP, length 42 Thanks and Regards, -Ashutosh Dhekne
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