What are Network Topologies?
- Network Topologies define a structure and/or properties of a network
- Network Topogies can either be Physical or Logical.
What is a Physical Network Topology?
A physical network topology defines the physical design of a network, including the network devices,locations, and cables - similar ti a building blueprint.
What is a Logical Network Topology?
A logical network topology defines how data moves throughout a network(CSMA, CSMA/CD, Ethernet).
What is CSMA in Networking?
Carrier Sense Multiple Access (CSMA) is a network protocol that listens to or senses network signals on the carrie/medium before transmitting any data. CSMA is implemeted in Ethernet networks with more than one computer or network device attached to it. CSMA is part of the Media Access Control (MAC) protocol.
What is CSMA/CD in Networking?
Carrier Sense Multiple Access / Collision Detection is a network protocol for a carrier transmision. it is opertated in the Medium Acess Control(MAC) layer. It senses if the shared channel is busy for broadcasting and interrupts the broadcast until the channel is free. In CSMA/CD collision is detected by the broadcast sensing from the other stations. Upon collision detection in CSMA/CD, the transmission is stopped and a jam signal is sent by the stations and then the stations waits for a random time context before retransmission.
- CSMA/CD was used on early Ethernet networks (networks which used Half Duplex)
- Effective after a collision.
- Full Duplex networks doesn’t need CSMA/CD
- Used in wired networks.
- It only reduces the recovery time.
- Resends the data frame whenever a conflict occurs.
- Used in 802.3 standard
https://www.youtube.com/watch?v=iKn0GzF5-IU
What is CSMA/CA in Networking?
Carrier Sense Multiple Access / Collision Avoidance is a network protocol for carrier transmission. Like CSMA/CD it is also operated in the Medium Access Control (MAC) layer. Unlike CSMA/DC (That is effective after collision) CSMA/CA is effective before collision.
- Used commonly in wireless networks (802.11 standard)
- Minimizes the posibility of collision.
- CSMA/CA will first transmit the intent to send for data transmission.
- Uses the optional RTS(Ready To Send)/ CTS(Clear To Send) protocol
https://www.youtube.com/watch?v=iKn0GzF5-IU
What are the Types of Network Topologies?
Wired:
- Star Topology
- Ring Topology
- Bus Topology
- Mesh Topology
What is the Star Topology?
- The most common wired topology
- All devices are connected to a central device (HUB or Switch)
- Central Device is a single Point of Failure
What is a Ring Topology?
- All devices are connected in a circular fashion
- Each computer is connected to two other computers
- Data travels from node-to-node with each computer handling data, either unidirectional or bidirectional.
What is a Bus Topology?
- All devices are connected to a single network cable.
- Terminators are required for both ends of the cable.
- A single break in the cable will take down the entire network.
- the computers are connected on a Coaxial Cable using a BNC connector(T- Connectors).
- When a terminator is removed the data would bounce back (Signal reflection) data flow is interrupted.
What is a Mesh Topology?
- Each device is connected to every other device by separate cabling.
- Highly redundant and fault-tolerant.
- Used in wide area networks (WAN).
- Expensive to install.
- The internet is a good example of a mesh topology.
