Communicating over the network - part 1 Flashcards
What are the 3 (7) elements of a communication
Message source/sender (Encoding) (Transmitter) Transmission medium "the channel" (Receiver) (Decoder) Message destination/receiver
Why aren’t single communications (video, email etc…) sent out as a continuous stream of bits? Give 3 reasons
- No other device on the network would be able to send/receive data while the transmission was in progress
- Large data streams would cause significant delays
- If a link in network structure failed during transmission, the whole communication would be lost and would have to be re transmitted in full
What is the alternative to send out a continuous stream of bits and what is it called?
Segmentation - dividing a message into small, manageable pieces to send over the network
What are 4 benefits of segmentation?
- Smaller pieces can be multiplexed; interleaved along the same media meaning multiple messages can be sent at once
- Smaller pieces need not take the same route from source to destination, making the network more reliable
- If one pathway is unavailable, another may be taken
- If parts of a message fail to deliver, only those missing parts need to be retransmitted
What is the downside to segmentation and multiplexing?
The added layer of complexity: each piece of the message needs to be labelled when split apart and then re-assembled at the other end based on those labels.
What are the two physical elements/hardware of a network?
Devices and media
What are the two communications programs/software that run on networked devices?
Processes and services
What does a network service do?
Provides information in response to a request
What are some examples included by network services?
Email hosting services
Web hosting services
What does a network process do?
Processes provide the functionality that directs and moves messages across a network
What are end devices?
The devices that provide an interface between the human network and the underlying communications network
What are some examples of end devices?
Computers (workstations, laptops, file servers, web servers) Network printers VoIP phones Security Cameras Mobile handheld devices
What are end devices referred to as in a network?
Hosts
How does a host device interact with a message in the communication process?
It is either the source or the recipient.
How are host distinguished from one another in a network?
They are identified by an address that the message source uses as a destination for the message.
What can hosts act as in modern networks?
A client, server, or both
What is a server?
A host that has software on that allows it to provide information and services, like email or web pages
What does a server provide services to?
Other hosts on the network
What are clients?
Clients are hosts that have software allowing them to obtain and display information from a server
What is the role of intermediary devices?
They connect individual hosts to a network and can link networks together to form an internetwork
What are some examples of intermediary devices?
Network access devices (hubs, switches, wireless access points) Internetworking devices (routers) Communication servers and modems Security devices (firewall)
What is another role of intermediary devices?
Management of data as it flows through a network
How do intermediary devices manage flow of data through a network?
The devices uses the host address along with information about other connected intermediary devices to calculate a path for the message.
What is the first function from processes running on intermediary devices in a network?
Regenerates and re-transmits data signals
What is the second function from processes running on intermediary devices in a network?
Maintains information about what pathways exist in the network and internetwork
What is the third function form processes running on intermediary devices in a network?
Notifies other devices of errors and communication failures
What is the fourth function from processes running on intermediary devices on a network?
Directs data along alternate pathways when there is a link failure
What is the fifth function from processes running on intermediary devices on a network?
Classifies and directs messages according to QoS priorities
What is the sixth function from processes running on intermediary devices on a network?
Permits or denies the flow of data based on security settings
What are the 3 types of media used to interconnect devices and provide a pathway for data to travel over?
Metallic wires within cables
Glass or plastic firbres (Fibre optics)
Wireless transmission
How is data encoded on metallic wires?
Data is encoded to electric impulses that match specific patterns
How is data encoded along fibre cables?
Fibre optics rely on pulses of infrared or visible light
How is data encoded on wireless transmissions?
Patterns of electronic waves depict various bit values
What are the for criteria for choosing network media?
- Distance the media can successfully carry a signal
- The environment to which the media is ti be installed
- The amount of data and the speed it needs to be transmitted
- The cost of the media and installation
What are 3 ways network infrastructure can vary greatly?
- Size of area affected
- Number of users connected
- Number and types of services available
What is a LAN?
A network that covers a small geographical area providing services to people in a common organisational structure such as business or campus
Who normally administers LANs?
A single organisation that can govern security and control policies across the network
What does a WAN do?
Interconnects multiple LANs that are in geographically separate locations. Connections are normally leased through a telecommunications service provider (TSP)
Who governs policies in the WAN?
The telecommunications service provider (TSP)
Due to the importance of WANs and LANs, what skills are vital to organisations?
Installing and maintaining WANs and LANs
What are 2 reasons that WANs and LANs are very useful to individual organisations?
- They connect users within the organisation
2. They allow many forms of communication such as office training, e-mail and other resource sharing
What are things most of use we need to communicate with a resource outside of a local network for?
- Sending email to friend abroad
- Accessing news or products on a website
- Getting a file from a neighbours computer
- IMing a relative in another city
- Following a favourite sporting teams performance on a mobile device
What is the internet?
The interconnection of networks belonging to internet service providers, providing access to each other for millions of people across the world
What is required to the internet runs smoothly?
The introduction of many protocols and commonly used technologies along with cooperation from administrative agencies
What is an intranet?
The interconnection of WANs and LANs that can only be accessed directly by company employees or others with authorisations
What are to other terms for an internetwork?
Data network
Network
What is an extranet?
Sometimes an organisation has to make parts of its intranet available to the public such as partner organisations, subsiduaries, valued customers etc…
