Bugzilla – Bug 2478
VHT A-MPDU subframes are transmitted with the wrong length
Last modified: 2016-08-16 16:28:58 UTC
Created attachment 2542 [details] VHT network with bug scenario If we build a VHT network (802.11ac) and enable A-MPDU, we can observe that A-MPDU subframes are transmitted with the wrong length. Besides, this length increases remarkably when the number of enqueued packets increases. In the attached file, you can find a simple network configuration that shows this bug. At the top of the file, you find the obtained output. In this configuration there is a VHT network composed of 1 AP and 1 station. A-MPDU is enabled. The station sends packets to the AP every 100ms. It sends packets at the following instants: - Simulator::Now() = 1000ms : sends 1 packet of 1500 Bytes (transmitted with 1538 Bytes, which is OK as there is the MAC header to be added) - Simulator::Now() = 1100ms : sends 5 packets of 1500 Bytes each (transmitted with 1570 Bytes, which is a BUG) - Simulator::Now() = 1200ms : sends 5 packets of 1500 Bytes each (transmitted with 1570 Bytes, which is a BUG) - Simulator::Now() = 1300ms : sends 40 packets of 1500 Bytes each (transmitted with 1850 Bytes, which is a BUG) - Simulator::Now() = 1400ms : sends 50 packets of 1500 Bytes each (transmitted with 1930 Bytes, which is a BUG) - Simulator::Now() = 1500ms : sends 80 packets of 1500 Bytes each (transmitted with 2170 Bytes, which is a BUG) - Simulator::Now() = 1600ms : sends 80 packets of 1500 Bytes each (transmitted with 2170 Bytes, which is a BUG) Regards
The attached script is not correct, bug to be rejected. You are calling the Send method with a pointer to the same packet, which keeps adding the headers (llc) to the packet: SEND: 0x7fc462e1bc40 -> 1508 SEND after LLC: 1516 queue: 1516 SEND: 0x7fc462e1bc40 -> 1516 SEND after LLC: 1524 queue: 1524 SEND: 0x7fc462e1bc40 -> 1524 SEND after LLC: 1532 queue: 1532 SEND: 0x7fc462e1bc40 -> 1532 SEND after LLC: 1540 queue: 1540