User`s guide

Appendix
BreezeNET PRO.11
9-31 User’s
Guide
However, it doesn’t make sense to introduce a new LAN protocol that cannot deal
with packets 1518 bytes long which are used on Ethernet, so the committee decided
to solve the problem by adding a simple fragmentation/ re-assembly mechanism at
the MAC Layer.
The mechanism is a simple Send-and-Wait algorithm, where the transmitting
station is not allowed to transmit a new fragment until one of the following
happens:
1. Receives an ACK for the said fragment, or
2. Decides that the fragment was retransmitted too many times and drops the
whole frame.
It should be noted that the standard does allow the station to transmit to a different
address between retransmissions of a given fragment. This is particularly useful
when an AP has several outstanding packets to different destinations and one of
them does not respond.
The following diagram shows a frame (MSDU) being divided to several fragments
(MPDUs):
Figure 9-16. Frame Fragmentation