Network Topology Flashcards
What are the 2 types of communication technologies?
Point-to-point, multi-access
What is point-to-point?
connect precisely two computers
What is Multi-Access?
connect multiple computers over shared medium
What is the star network?
all computers connected to a central point (hub)
What is a ring network?
forms a closed loop with each computer connected to the next 1
how is data transmitted in ring network?
packets are passed around the ring until they reach the destination
what is a drawback of ring network?
if any cable is cut the network is broken
what happens when the data is transmitted in ring network?
it returns back to sender who can check for any errors
recipient makes a copy as it goes past
what are mechanisms to co-ordinate access?
full/empty slots
token passing
How does token work in ring network?
its passed around the ring from network to network basically telling it that it can send data
what does a computer do when it receives token?
waits for token to arrive
if packet is available to send then send it
pass token to next station
What is the bus network?
all computers connected to a single long wire
what happens if a computer sends something on bus network?
signal is sent to every other computer and the intended recipient can receive it
what needs to be ensured on bus network?
transmits one at a time to avoid collisions
What is a collision?
2 computers transmit at same time so packets collide and can become corrupted
How do we avoid collission on bus networks?
use access control so only 1 computer transmits at a time
What one approach from access control?
time division multiplexing?
What is TDM?
- Controller synchronises machines to communicate in fixed time-slots
- Each machine gets a fixed amount of bandwidth from the whole medium
Advantages of TDM?
great for multi tenancy (everyone gets what they pay for)
bandwith shared equally
Disadvantage of TDM?
doesnt use bandwith effectively
What is DOCSIS used for?
for cable modem
What is PON?
Passive optical network
provides connectivity over a passively split fibre network
what do both DOCSIS and PON assume?
asymmetric traffic
what is asymmetric traffic?
user downloads more than they send
Whats another approach besides TDM?
Eventual packet delivery
What is eventual packet delivery?
which basically accepts collissions will take place but can recover and eventually it will arrive
