Unit 6: Introduction Flashcards
Define bandwidth and unit it is measured in
Transmission rate of data - bits per second
What does a packet switch do?
Forwards packets (chunks) of data
What is the ‘nuts and bolts’ view of a network?
The internet is a network of networks i.e. consisting of interconnected ISPs. It consists of protocols that control sending and receiving of messages
What is the ‘service’ view of a network?
The internet is an infrastructure that provides services to applications and a programming interface to applications
Define a protocol
Protocols define the format and order of messages sent/received among network entities, and the actions taken on message transmission/receipt
What constitutes network edge?
The hosts - clients and servers
What constitutes access networks?
The wired and wireless communication links
What is the network core?
A mesh of interconnected routers
a) What does DSL stand for?
b) Describe a DSL access net (what is transmitted/where?)
a) DSL = Digital Subscriber Line
b) In DSL, voice and data are transmitted at different frequencies over a dedicated existing telephone line to a central office. The data goes to the internet, voice goes to the telephone net
What is frequency division multiplexing?
Where different channels are transmitted in different frequency bands
Describe a cable network access net
In a cable network a fibre cable attaches homes to an ISP router. Home share access networks to cable headend
State a difference between DSL and cable networks
Access networks are shared in cable networks, whereas DSL have dedicated access to the central office
What type of cable is used in cable networks?
Hybrid fiber coaxial (HFC) cables which are asymmetric (one direction)
Describe the modern home network access net and the different connection points
A wireless access point connects wireless devices to the router, in which wired devices are connected directly via wired ethernet. The router is connected to a cable or DSL modem.
Briefly describe wide-area wireless access
Cellular operators (e.g. Telco) provide 3G, 4G etc. by using technologies such as LTE
Define a bit in the context of physical media
What propagates between the transmitter and receiver pairs
Define a physical link in the context of physical media
What lies between a transmitter and receiver
Define guided media in the context of physical media
Signals that propagate in solid media e.g. copper
Define a unguided media in the context of physical media
Signals that propagate freely e.g. radio
Define a twisted pair in the context of physical media
Two insulated copper wires used in ethernet with high access speed
a) Define a coaxial cable in the context of physical media.
b) Where is it used?
a) Two concentric copper conductors which are
b) Broadband
a) Define a fiber optic cable in the context of physical media
b) Give and explain a benefit of fiber optic cables
A high speed glass fiber that carries light pulses (each represent a bit). It has a low error rate as it is immune to electromagnetic noise and repeaters are spaced far apart
a) Describe radio signals in the context of physical media
b) Give and explain a drawback of radio signals
Signals are carried in the electromagnetic spectrum. It is bidirectional. Radio is susceptible to the environment because of reflection, obstruction and interference
Give 4 types of radio link
Terrestrial microwave, LAN (wifi), wide-area (cellular), satellite
