Is there a mechanism or script that derives the MAC layer (not TCP) retransmission statistics for a UDP connection using Block Acks? I assume that such a script would analyze repeating 802.11 sequence numbers and possibly Block Ack bitmaps. asked 12 Oct '12, 12:05  ReidW |
One Answer:
There is no bulit-in (in the protocol) ethernet and/or UDP retransmission mechanism. So, the short answer: No there is no mechanism or script to derive that information. What is the reason for your question? Do you see packet loss? Regards answered 13 Oct '12, 01:23  Kurt Knochner ♦ edited 13 Oct '12, 01:58 |
I see retransmissions using a AirPcap. Are you saying that the Block Ack bitmask is only used by higher layers and is not related to any low level retransmission mechanism?
Ah, you are talking about Wifi networks (I missed the 802.11 in your question).
Looking a second time at your question, I'm not sure if there is a way to derive retransmission statistics from the Block-Acks.
However, I will have a more detailed look at the problem. Can you post a sample capture somewhere?
Maybe from repeated sequence numbers? https://www.filesanywhere.com/fs/v.aspx?v=8a716b865b5e6db2a0a9
I know that Riverbed Cascade Pilot and AirMagnet both report retrans stats - they must be counting repeated sequence numbers. Is there a way to script this for a Wireshark trace?