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I see that some addresses have transmitter/receiver address in place of source/ destination address. My intuition says that they are the intermediary nodes of a packet trace. But I am unable to see any packets that are connected to this packet before or after. I see such packets in the 802.11 protocol i.e in the physical layer.

Could someone explain me what exactly is taking place ?

Thanks in advance!

asked 08 Nov '14, 18:17

srik11's gravatar image

srik11
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Basically yes. In 802.11 you can see a different number of these depending on where the frame is coming from and where it's going:

  • "Destination Address" or "DA" is the MAC of the final destination of the frame.
  • "Source Address" or "SA" is the MAC of the original sender of the frame.
  • "Receiver Address" or "RA" is the MAC of the next immediate recipient of the frame.
  • "Transmitter Address" or "TA" is the MAC of the system that is directly transmitting the frame.

So, original source (SA), final destination (DA), and the immediate sending/receiving systems (TA/RA) are four different MACs. Formal definitions would be found in the 802.11 standard itself:

http://standards.ieee.org/about/get/802/802.11.html

permanent link

answered 08 Nov '14, 19:19

Quadratic's gravatar image

Quadratic
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accept rate: 13%

edited 08 Nov '14, 19:22

@Quadratic: Thanks a lot! I have one follow up question. In the 802.11 ack frames, i always find that there is neither source address nor transmitter address. I was wondering if it were because of wrong settings or why ?

Screenshot

(08 Nov '14, 22:21) srik11

Yes, different types of frames will have different MAC fields. The formal breakdown of all 802.11 messages and their expected formats is broken down in section 8.3 in the most recent 802.11 spec paper (from that link above), where frames such as ACK and CTS have only the RA address field included.

(09 Nov '14, 09:13) Quadratic
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question asked: 08 Nov '14, 18:17

question was seen: 14,063 times

last updated: 09 Nov '14, 09:13

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