BSC FRAMES
•BSC protocol
divides a transmission into frames
CONTROL
FRAMES
o If a frame is used strictly for control
purposes, it is called a Control frame
o Control
frames are used
to exchange information
b/w communicating devices
for
example, to
establish the connection,
to control the
flow, to request
error correction
etc
DATA
FRAMES
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o Figure shows the format of a simple data
frame
o Arrow shows the direct of TX
o The frame begins with two or more synch.
(SYN) characters
o These characters alert the receiver to
the arrival of a new frame and provide a bit
pattern
used by the receiving device to synch itself with that of the sending device
o After the two synch characters, comes a
start of text (STX) character
o This character signals to the receiver
that the control information is ending and the
next
byte will be data
o Data or text can consist of varying
number of characters
o An end of text (ETX) indicates the end of
text
o Finally, the Block Check Count (BCC) are
included for error correction
o A BCC field can be a one-character LRC or
a two -character CRC
Data
Frame with Header
•A frame as
simple as above is seldom used
•Usually we
need to include
the address of
the receiving device,
the address of
the
sending
device and the identity number of the frame (0 or 1) for stop-and-wait ARQ
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