Protocols are the
communication rules or standard procedures used for data transmission
in Local Area Networks. They specify data compression, the transmission
rate, acknowledgement, synchronism and error. Protocols require
both of the communicating ends to use the same rules and to negotiate
agreements over parts of the standard. They are designed to solve
operating problems such as framing, error control, sequence control,
transparency, line control, timeout control, start up control
and special cases (Table A-2).
Table
A-2 Aspects included in LAN protocol[55]
|
Name
|
Description
|
|
Framing
|
The process of determining
what 8 bit groups make up a character as well as what groups
of characters constitute a message
|
|
Error control
|
The process of determining
when an error has occurred and requesting retransmission of
faulty messages
|
|
Sequence control
|
The numbering of messages to
ensure they are reassembled in the correct order
|
|
Messages Loss
Control
|
To avoid messages loss and
to identify messages that have been retransmitted
|
|
Transparency
|
The process of sending information
that contains bit patterns that reassemble the control characters
used in framing control, error control and sequence control.
In other words, the headers and footers not needed for the
current process are treated as if they were data and passed
on intact
|
|
Line control
|
How it is determined what station
will be transmitting and what station will be receiving. It
is used in half-duplex or a multipoint lines
|
|
Special cases
|
Focuses on what the transmitter
will send when there is no data
|
|
Timeout control
|
Determines what should be done
when no data/transmissions are received
|
|
Startup control
|
The process of getting the
transmissions started after the communication system had been
idle
|
