Carlos Manuel Rodrigues Machado Autonomic Ubiquitous Computing

In the CSMA, a Teleswitch device that wants to send data must first verify the absence of
traffic before it starts transmitting. This method guarantees that an outgoing transition is not
corrupted by another device packet, but it does not prevents data collision if two or more devices
want to send data at the same time. This limits the usage of this method only when using in
protocols that require acknowledged packets, i.e., applications that ask information and wait for a
reply.
S t a r t
Prepare packet to send
Is Bus
Silent?
YES
Transmit Packet
Verify Packet CRC
Is CRC
OK?
YES
Transmission Ok
E n d
NO
NO
NO
Random Wait
YES
Is Bus
Silent?
YES
Retry ?
NO
Transmission Failed
Figure 11 – Teleswitch Network CSMA algorithm
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