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AX.25 is a protocol for transmitting data over a radio channel .

Basic idea of ​​the AX25 protocol

It is connection-oriented , but also allows the transmission of connectionless data. If the transmission of the data on the radio channel is disturbed, multiple attempts are made to retransmit the lost data. The protocol was based on the X.25 protocol of the ITU-T and adapted to the conditions in amateur radio . AX.25 is used there in the operating modes Packet Radio and APRS . AX.25 defines level 2 of the ISO-OSI model .

Structure of AX.25 packages

With AX.25 the data is divided into packets ( frames ). In addition to the data, each package also contains the elements required for addressing and a checksum .


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