structure of the internet Flashcards
What is internet?
A network of computer networks and computers using unique IP addresses and TCP/IP
What is the difference between internet and the internet?
Any network of connected computers is an internet
The network used by the general public is the internet
What is the internet?
A network of interconnected computer networks (wide area and local area) and computers using a globally unique address space based on TCP and IP to support public access
What does IP stand for?
internet protocol
What does TCP stand for?
transmission control protocol
What is the core backbone of the internet?
very high speed connections between europe, north america, central and south america and the far east and pacific
What is the backbone of each continent?
very high speed links to interconnect routers in each country
What are routers?
Special switches that recieve incoming ‘packets’ of data on one link and use the destination IP address in the packet to make a decision about which outgoing link to send the packet along
What do routers connect?
Connect networks that use the same layer link protocol
Within national boundaries, what can be connected directly to the national backbone? How?
Networks belonging to large businesses and organisations such as universities
Connected using router gateways
What is a gateway?
A special kind of router used to connect networks that use different layer link protocols
=connects different networks, translating packages so that they will be compatible with the new network
How can small businesses and home users be connected to the national backbone?
Through an internet service provider (ISP) or internet access provider (IAP) which will have its own router gateway, selling internet access
What does ISP stand for?
internet service provider
Why are routers used?
It is impossible to connect every host to every other host
What is a host?
A computer which runs applications
What is a computer network?
machines (hosts and routers) interconnected by communication channels
What is a communication channel?
A means of transferring sequences of bits or bytes from one host or router to another
What is circuit switching?
Two points are connected with a complete end to end connection for however long that connection is needed. The connection cannot be used by other users whilst it is being used for this connection.
What kind of switching is used in the internet?
packet switching
What is another word for packet?
datagram
What three parts does a packet consist of?
source address
destination address
payload (the data)
What is a packet?
When a computer wishes to send data it splits it into chunks called packets
How are packets sent over the internet?
Each is sent through a router gateway and then travels INDEPENDENTLY through routers to the destination. At the destination they are put back in order and reassembled
What is the end-to-end principle?
The two end computers (start and finish point) are in control of the communication with the internet as a means to move packets
What are the advantages of the end-to-end model?
- A partial network failure can be survived, the packages can just be resent when it is detected they have not all arrived
- packets can be rerouted around failures by alternative paths
- The internet can grow easily because control does not reside in the internet
- Router design is simplified as they don’t have to notify each other when endpoint connections are formed or dropped
- Role of the internet is simplified as security and integrity of packets is monitored at the endpoints
- Each endpoint only has to be aware of the one router it is directly connected to
What is open architecture networking?
Designers are free to design networks in any way, all can communicate over the internet via a router gateway
What is an IP address?
A unique address that identifies a computer or other electronic device on a network
Which IP system is used today?
How many Ip addresses does it allow?
IPv4
2^32 ~4 billion
What two parts does an IP address include?
netID and hostID
In the IP address 196.100.11.4 which bit is the netID and which is the hostID?
network = 196.100.11
host=4
How are IP addresses often expressed?
32 bits written as bytes separated with dots
eg. 166.100.11.4
What information does each router have to help it send packets?
A table of other routers, computers and networks it is directly connected to as well as some information about the hierarchical structure of the internet
List in order the router hierarchy
-international
-national
-regional
-local
organisation networks (companies, schools, colleges etc)
What is the world wide web?
A system of interlinked hypertext documents accessed via the internet
How is the world wide web used?
A web browser is used to view webpages containing
text images and multimedia
Navigating between pages is done using hyperlinks
What is an intranet?
A private computer network that is used to share information or operations within an organisation only
What does DNS stand for?
domain name system
What is a domain name?
A memorable name corresponding to network IP address