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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's gravatar image

ReidW
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accept rate: 0%


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
Kurt

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answered 13 Oct '12, 01:23

Kurt%20Knochner's gravatar image

Kurt Knochner ♦
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accept rate: 15%

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?

(15 Oct '12, 09:42) ReidW

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?

(15 Oct '12, 12:49) Kurt Knochner ♦
(15 Oct '12, 17:59) ReidW

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?

(18 Oct '12, 12:43) ReidW
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question asked: 12 Oct '12, 12:05

question was seen: 6,250 times

last updated: 18 Oct '12, 12:43

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