- Claim:
- If
node has
trasnmitted for
2 × τ
(τ = end-to-end-delay), and
it did not detect
a collision,
then:
- The transmission will not suffer a collision for certain !!!
Proof:
- Fact:
- In CSMA/CD, a node
will not transmit if it
hears an
on-going transmission:
- In CSMA/CD, a node
will not transmit if it
hears an
on-going transmission:
- We consider the
worst case scenario
where:
- a collision takes place at the last possible moment
This is the worst case scenario:
- The node A at
one end of the network
start transmitting at
so
arbitrary time t:
- Just before
the last node (C)
hears A's transmission, it
starts to
transmit:
This will happen just before t+τ sec
- There is now a collision !!!
- The node A will
detect the
collision
when C's transmission
reaches A:
This will happen at time t+2×τ sec
- Conclusion:
- If the node A has not detect a collision after 2× τ time, there will not be any future collision !!!
- If
node has
trasnmitted for
2 × τ
(τ = end-to-end-delay), and
it did not detect
a collision,
then:
- Therefore:
- A node can stop sensing the channel after for 2 × τ time
- Almost final
flow chart for
CSMA/CD:
