- The Scalability problem:
- A larger network
have a larger number
of nodes
- More nodes
means:
- greater chance of simultaneous transmissions
- A larger network
have a larger number
of nodes
- Fact:
- Networking techniques that works well with small number of transmitters will not work with a large number of transmitters
-
CSMA/CD
networks:
- CSMA/CD protocol does not scale
Reason:
- More nodes will
cause
more collisions.
- More collisions results in
more frequent backoffs
- More frequent back offs results in
longer delays
-
Token based
networks:
- Token based networks do not scale
Reason:
- More nodes will
transmit more frames
- More frames means
longer waiting time for
your next turn
- This means: longer delays
- The principle
to achieve scalability:
- Transmissions between
a sender and
a receiver will
- "Intrude" (= use) the home networks of the sender and the receiver
- The transmission mist not intrude (= use) the home networks of non-participating nodes
- Transmissions between
a sender and
a receiver will
- Graphically illustrated:
- If a
sender A on
network 1 transmits
a message (frame) to
a
receiver B on
network 2, then:
- only nodes on the network 1 and network 2 should be "disturbed" (= hear) the transmission
Grpahically:
- If a
sender A on
network 1 transmits
a message (frame) to
a
receiver B on
network 2, then:
- Example of a
non-scalable transmission method:
Because:
- Too many nodes
can hear the
each other's
transmissions
Result:
- More collisions !!!
- Too many nodes
can hear the
each other's
transmissions