T3 - LANs and WANs: Flashcards
Internet
- is a collection of inter-connected networks
Largest WAN
WAN
- Any network in which the computers communicate using resources supplied by a ‘third party carrier’ such as BT
-Covers a large geographical area
wans use
uses cables, telephone lines, satellites or radio waves to connect two or more remote locations
IPv4 addresses are
four 8-bit numbers (0-255) separated by dots
Newer IPv6 addresses are
128-bit numbers represented in hex
WAN stands for
– Wide Area Network (large geographical area)
Packet –
one unit of data sent through an IP network
Routing –
directing IP packets to their destinations
DNS stands for
– Domain Name System
IP address –
Internet Protocol address. Where packets of data are sent to or received from
MAC address
– Media Access Control address. The unique identifier of each device (or network interface card)
Packet switching:
file is broken up into data ‘packets’
packets contain info on
The IP address it is going to
The IP address it has come from
The sequence number of the packet
The number of packets in the
whole communication
Error checking data
Data Packets:
contain the same number of bytes
packets may flow through the Internet via different routes
marked with the packet number = can be reordered and checked for errors
Routers
- any node that can route packets from one place to another
IP address: dynamic IP address
- IP addresses will change when the router reconnects to the Internet.
actual geographical location of a networked device can be determined by this
Network interface card
- built into every networked device
Domain Name System (DNS) description
made up of domain names
Refers to IP address
A DNS server translates
a web address into an IP address
13 DNS root servers worldwide which
keep a complete database of all domain names and IP addresses
how many DNS root servers
13
When a DNS server receives a request not in its database,
it will pass the request on to another server until it reaches one with the matching name and IP address
MAC addressing -
assigned to each Network Interface Card (NIC) by the manufacturer = unique, never changes
MAC addressing: When you request a web page,
each router along the way uses the MAC address of the next router to send the data packet on the next leg of its journey
LAN
- operates on a single site such as a school, hotel or business using their own cabling systems
Topology
- the way in which
parts of a system are connected
eg of topology
Eg Star and Mesh
pros of networks
Computers can share resources such as printers
Files can be accessed through any computer in the network
Data is easy to back up as it is stored centrally on the server
cons of networks
Purchasing the network hardware is expensive
Managing a large network is complicated
Viruses may be able to infiltrate the network and infect every computer
Star Network:
computers and other devices (known as nodes) are all connected to a central switch
Star Network: pros
Fast data transfer to the hub as each wire isn’t shared with other computers
If one cable fails the other computers are not affected
Star Network: cons
Requires additional hardware such as the central switch and network cables
If the central switch fails the whole network goes down
Full Mesh network:
Nodes act as routers for data in order to relay and propagate data in the network
A partial mesh network
is usually used, often in conjunction with star topologies to create larger networks
Internet -
combines many networks together, but many parts operate as a partial mesh
Many LANs that connect to the Internet use a
star topology,
Wireless mesh networks:
Only one node needs a wired Internet connection – no other cabling or infrastructure is required
The more nodes that use the network,
the more routes there are for data to travel through
A node within broadcast distance of three other nodes,
will have triple the standard bandwidth
As the distance between one node and another is halved,
signal strength becomes four times stronger
Mesh networks: pros
No single point of failure – it is resilient
Expansion and modification can be done without disrupting the network
Data can be transmitted from different devices simultaneously
Mesh networks: cons
- Can involve redundant connections
- Expensive to install cabling if using wired connections
- Network maintenance and administration is difficult
Network Hardware:
- NIC
-router
-switch - modem
- WAP
-Hub
A Network Interface Card/Controller (NIC)
in your computer or device
A router or switch,
which provides access to a local area network
A modem
is required to connect to the Internet – this is usually combined with the router inside a single device
A Wireless Access Point
connects wireless devices to a network. Many home wireless access points are part of a router
Router:
Looks at the destination of packets of data and sends them to the network that is closer towards
their destination
A home router will route packets between
the home LAN and the Internet
Switch:
Switches connect each node (computer) in a network
They know the MAC address of all connected computers and devices
When a packet of data arrives, they can send it to the correct computer
Hubs,
by comparison will send the data to all connected computers
Ethernet: refers to
refers to a family of standard local networking ‘protocols’ or rules
Ethernet describes
describes how devices should format data ready for transmission between computers on the same network
Ethernet works by
nodes will wait until the connection is quiet before attempting to ‘speak’ or transmit
Two nodes attempting to transmit simultaneously will stop and each wait a random period before reattempting
Transmission media:
way that communication is sent through the network
Ethernet is sent through
twisted copper cables or fibre optic cables
