Ch.12.1 Sound Byte: Network Typology and Navigation Devices
Bus Topology: Part 3
- Passive topology: Devices connected to the bus do not move data along - Signals bounce along the length of the bus - Terminators prevent signals from bouncing back down the bus
What Is a Topology?
- Physical arrangement of computers, peripherals, and media (cable) - Like the floor plan of a building - Different topologies suit different needs
Star Topology: Part 1
- Switch - Central communications device - Connects nodes - Sends and receives to all other nodes - Active topology - Ethernet - Most common protocol for star networks
Describe the types of network navigation devices.
- Switches provide efficient communication on star networks. - Bridges transfer data between two collision domains on a single network. - Routers transfer data between two networks.
Network Navigation Devices
- Three major types - Switches - Bridges - Routers - Required by star networks - Using the correct device improves efficiency
Ring Topology: Part 2
- Token travels the ring - Device wishing to send data grabs token - Only device holding token can transmit data - Token is released back onto ring after data is sent
A topology can be compared to the ___________.
floor plan of a building
Tokens are used in a token ring network to ________.
prevent data collisions from occurring
An example of a network navigation device is a __________.
router
Describe the attributes of a ring topology.
- A ring topology uses a continuous circle of media (cable). - A special data packet called a token controls transmission of data. - It is an active topology: each node retransmits token. - There is fair allocation of network resources. - Failure of one computer will bring down entire network.
Describe the attributes of a star topology.
- A star topology features a central communications device (switch) that connects nodes and sends and receives data. - They are easy to expand, and failure of one computer doesn't bring down entire network. - They are more expensive to expand than other topologies.
Ring Topology: Part 3
- Active topology: each node retransmits token - Advantages - Fair allocation of network resources - Large numbers of computers don't affect performance - Disadvantages - Failure of one computer will bring down entire network
Star Topology: Part 3
- Advantages - Easy to expand - Failure of one computer/cable doesn't bring down entire network - Disadvantages - More expensive and requires more cable - Failure of switch cuts off all devices on that switch from network
Star Topology: Part 2
- Avoiding data collisions - Carrier Sense, Multiple Access with Collision Detection (CSMA/CD) - A jam signal is sent if collision occurs - Nodes retransmit data at random intervals
Bus Topology: Problems
- Cable breaks cut off computers from the network - Not suitable for large networks - Signal strength degrades over distance - Only one computer is able to communicate at a time
Ring Topology: Part 1
- Continuous circle of media (cable) - Data flows in one direction only - Special data packet called a token controls transmission of data
Routers
- Designed to route data between networks - Often used to route data between an internal network and the Internet (an external network)
Describe the attributes of a bus topology.
- In a bus topology, computing devices are connected in sequence on a single cable. - A break in the cable brings down the entire network. - Bus topology is cheap and easy to set up.
Bridges
- Large networks are divided into collision domains to improve efficiency - Domains need to be connected - Bridges are designed to transfer data between collision domains
Switches
- Necessary on star networks for efficient communication - Retransmit data only to device that is to receive the data
Bus Topology: Part 2
- Only one computer can communicate at a time - Data collisions occur when two computers transmit at the same time: data is lost or damaged - Computers "listen" to make sure the bus is clear before transmitting - Data is transmitted to all devices connected to the bus
Explain what a network topology is.
- Topology refers to the physical layout of components on a computer network. - Just as buildings have different floor plans, networks have different blueprints delineating their layout. - Each topology has its own strengths and weaknesses.
Bus Topology: Part 1
Computers connected in sequence on a single cable - Most common in peer-to-peer networks (home networks or very small business networks) - No longer used often
Which of the following is NOT an advantage of star topology?
They are cheap to expand.
A bus network in which attached devices cannot move data along the bus is referred to as a(n) __________ topology.
passive