Ch.12.1 Sound Byte: Network Typology and Navigation Devices_sc
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 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
token ring topology
A network layout in which each individual node is connected to two others, with the first and last coming back to connect to each other, thus completing the ring shape.
Star Networks Disadvantages
Requires more cable length than a linear topology. If the hub, switch, or concentration fails, nodes attached are disabled. More expensive than linear bus typologies because of the cost of the hubs, etc.
access method
Specifies how data is transmitted from node to node across the network.
Data Collection
capturing and gathering all data necessary to complete the processing of transactions
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 re transmits 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 re-transmit 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
Star Topology
All nodes are connected to a central computer.
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
Star networks cons
Failure in central computer means whole network goes down Cabling is expensive
Star Topology
The most popular topology for business today - the star topology consists of all of the nodes on a network connected to a central switch or hub. A node is a device attached to the network - such as a computer. Each node on the network has a cable back to the central switch
Collision Domain
The portion of an Ethernet network in which collisions could occur if two nodes transmit data at the same time.
Which of the following is NOT an advantage of star topology?
They are cheap to expand.
Carrier Sense
This means that the wire is listened to in order to determine whether there is a signal passing along it. A frame cannot be transmitted if the wire is in use.
A bus network in which attached devices cannot move data along the bus is referred to as a(n) __________ topology.
passive
