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67 Cards in this Set
- Front
- Back
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What is a protocol? |
protocol is a set of rules governing communication across a network which the rules are agreed by both senderand recipient all data is sent and received using the same rules and format It allows communication between devices operating on different platforms |
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How protocol implementation can be viewed as a stack where each layer has its own functionality? |
A protocol suite can be represented as a layered structure Each layer operates independently Each layer can only communicate with an adjacent layer The layers are numbered and sit one above each other, and can therefore be thought of as a stack The output from one layer provides the input for the next layer Each layer interacts only with the layer directly above/below it, and at the bottom ofthe stack The Physical layer transmit data between the source and destination devices |
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Why we need protocol? |
To ensure successful communication takes place Protocols set a standard for communication Protocols enable communication between devices from different manufacturers If two devices were sending messages to each other but using different protocols, they would not be able to communicate properly |
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What is TCP/IP protocol suite |
a layered stack with 4 layers uses a set of protocols for transmission of data transport control protocol with internetprotocol |
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How does TCP works? |
To only allow data to be sent when the line is idle To detect a collision on the network To halt transmission when a collision occurs |
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What is IP? |
Allows applications to exchange data Establish and maintain a connection until exchange of data is complete |
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What are the 4 layers of TCP/IP protocols in order when sending ? |
1) Application layer 2) Transport Layer 3) Internet Layer 4) Network Interface Layer |
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What are the 4 layers of TCP/IP protocols when receiving? |
1) Network Interface Layer 2) Internet Layer 3) Transport Layer 4) Application Layer |
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What is application layer? |
It contains all the programs that exchange data It sends files to the transport layer |
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What is purpose of application layer? |
Application Layer->It handles access to services-> It manages data exchange-> It defines protocols used -> HTTP, FTP, POP3, SMTP |
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What is packet? |
The messages are split up into small groups of bits for transmission over a network |
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What is router? |
It is used to transmit packets of data It connects to many other routers The router decides where to send the packets to |
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What is hypertext transfer protocol? |
Is a protocol that is responsible for correct transfer of files that make up web pages on the world wide web
Is a client/server protocol which requests messages are sent out to the web servers which respond
Define the format of the messages sent and received Browsing websites Used for transfer of web pages from server to client Underpins the world wide web Used when fetching an HTML document from a web server
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How a user requests a web page from a website? |
1) The user keys the URL into their browser 2) HTTP transmits the request from the application layer to the transport layer 3) The TCP creates data packets and sends them to the destination parts 4) DNS server store a database of URLs and matching IP address 5) The DNS server uses the domain name typed into the browser to look up the IP address of the appropriate website 6) The server TCP sends back an acknowledgment 7) Once communication is made,the webs server sends back the web page in HTML format to the browser 8) The browse interprets the page and displays it or sends the data in the correct format to the media player
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What is file transfer protocol? |
A network protocol is used when transferring files from one computer to another by the internet or other networks To directly transfer data between 3 computer over a network Upload and download files over the internet Used for interactive file transfer |
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What are the task of FTP? |
To transfer files over a network |
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What are the features of FTP? |
Anonymous FTP -> This allows a user to access files without the need to identify who they are to the FTP server FTP commands -> A user is able to carry out actions that change files stored on the FTP server FTP server -> This is where the files are stored which can be downloaded |
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What is simple mail transfer protocol?(SMTP) |
Text based protocol used when sending emails It doesn't handle binary files If email contains attachments made up of images,video,and music then it is necessary to use the multi -purpose internet protocol Used for sending email messages Used by mail servers to forward email messages Doesn't handle binary files: media, images,music |
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What is mine? |
A multi purpose internet mail extension protocol A protocol that allows email attachment containing media files as well as text to be sent |
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What is post office protocol(POP3/4)and internet message access protocol (IMAP)? |
Protocols used when receiving emails from the email server They are pull protocols They handles the receiving of emails Mail is held for you by a remote server until you download it |
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What is pull protocol? |
Pull protocol = client periodically connects to a server; checks for and downloads new emails from the server, the connection is then closed, this process is repeated to ensure the client is updated Doesn’t keep the server and client in synchronisation When emails are downloaded by the client, they are then deleted from the server |
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What is difference between POP3/4 and IMAP? |
POP3/4 -> Don't keep server and client in synchronisation -> Emails are downloaded by the client , they will be deleted from the server IMAP -> Keeps the server and client in synchronisation -> A copy of the email is downloaded with the original remaining on the server until the client manually deletes it |
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What is transport layer? |
It regulates the network connections where the data is broken up into packets which the packets will be sent to the internet TCP |
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What is the purpose of transport layer? |
It ensures that the packets arrive in sequence by swapping acknowledgements and retransmitting packets if they are lost or corrupted
Main protocols that are associated with transport layer are TCP
Handles forwarding packets Check packet port to identify the application type Check packet destination so the packet can be sent to the correct application Recalculate checksum of packet to ensure integrity If checksum invalid, it’ll send a message to resend packet The Transport Layer breaks data into manageable packets It sends the packets to the Internet It handles packet loss |
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What is transmission control protocol |
It is responsible for the safe delivery of a message by creating sufficient packets for transmission It uses positive acknowledgement with re- transmission(PAR) which automatically resends a data packet if it has not received a positive acknowledgement It is a connection - orientated since it establishes an end- to - end connection between 2 host computers using handshakes It is a host to host transmission protocol |
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What is a host? |
A protocol used by TCP when communicating between 2 devices Host can include clients and servers that send and receive data and provide services or apps |
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What is host to host? |
A protocol used by TCP when communicating between 2 devices |
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How host computer 'X' communicates with another host ' Y'? |
1)Messages are split up into packets
2) Router is used to transmit packets of data
3)Host ‘X’ will send host ‘Y’ a packet which will include synchronisation sequence bits to that segments will be received in the correct order
4)Host ‘Y’ will now respond by sending back its own packet (containing anacknowledgment together with its own synchronisation sequence bits)
5) Host ‘X’ sends out its own acknowledgment that the packet from ‘Y’ was received
6)Transmission of data between ‘X’ and ‘Y’ can now take place
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What is the function of the internet layer? |
Handles transmission of data/routing/IP addressing Identifies the intended network and host It transmits packets to the Data Link Layer It addresses packets with their source and destination IP addresses |
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What is the function of the data -link layer? |
Handles how data is physically sent It identifies network protocols in the packet header and delivers packets to the network |
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What is IP functions? |
Ensures correct routing of packets of data over the internet Responsible for protocols when communicating between networks Take a packet from the transport layer and add its own header which will include IP address of both sender and recipient IP packet is sent to the data - link layer where it assembles the datagrams into frames for transmission |
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What is bit torrent? |
Protocol which is based on the peer-to-peer networking Decentralised distribution of data Allows for very fast sharing of files between computers It allows a lot of users to use bit torrent when connecting together over the internet It allows many users to share files |
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How the bit torrent protocol provides peer to peer file sharing? |
1.client software made available to friends and family 2. a complete copy of the torrent is shared 3. the torrent is split into small pieces which are given priority in downloading 4. a computer joins by using Bit Torrent software to load the torrent descriptor 5. The computer can now download the Torrent 6. Once a computer has a piece of the file, it can become a seed and upload it to theother members |
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What is tracker? |
Central server that stores details of other computers that have the file to bedownloaded |
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What is a seed? |
Peer computer that has 100% of the file A peer that has downloaded a file and has then made it available to other peers in the swarm |
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What is a swarm? |
All the connected peer computers that have all or part of the file to beuploaded to the torrent Connected peers that share a tracker |
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What is a peer? |
A client who is part of the peer - to - peer network |
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What is metadata? |
A set of data that describes and gives Information about other data |
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What is pieces? |
Splitting up of a file when using peer to peer file sharing |
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What is a leech? |
A peer with negative feedback from swarm members |
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What is lurker? |
A user that downloads files but don't supply any new content to the community |
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What is circuit switching? |
A type of communication in which a dedicated channel or circuit is established for the duration of a transmission a dedicated circuit the circuit is established before the transmission starts data is transferred using the whole bandwidth all data is transferred over the same route E.g. public telephone networks, private telephone networks, private data networks |
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What are the features of circuit switching? |
A circuit is established at the start of the communication between sender and receiver this lasts for the duration of the call then the links that makes up the circuit are removed |
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What are the advantages of circuit switching? |
A Dedicated channel can use all bandwidth 2 way real time conversation no delay as there’s no switching The circuit used is dedicated to the single transmission only The data transfer is faster than packet switching data arrive in order data do not need to be reassembled |
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What are the disadvantages of circuit switching? |
bandwidth/channel may not be available for others Failure of the single route means failure of the transmission It is not flexible nobody else can use the same circuit even if it is idle The circuit is always there whether or not it is used If there is a failure on the dedicated line there will be no alternative routing available Dedicated channels require a greater bandwidth Prior to actual transmission , the time to establish a link can be quite long less secure as only one route used |
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What are the uses of circuit switching? |
Public telephone networks Private telephone networks Private data networks |
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What is packet switching? |
A method of transmission where a message is broken into packet which can be sent along paths independently from each other
The data packets will need to be reassembled into their correct order at the destination
Each packet follows its own path
Routing selection depends on the number of datagram packets waiting to be produced at each node
The shortest path is available is selected
The packets can reach destination in a different order to that in which they are sent
It is connected through many routers circuit that does not have to be established at the start of the communication data is sent in divided packets can travel along different routes packets are reassembled in the correct order at the receiver’s end |
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What is the advantages of packet switching? |
Transmission errors can be detected packets can be rerouted if there’s a problem It is possible to overcome failed or faulty lines by simply rerouting packages doesn’t matter if data arrives out of order Time delay is insignificant
No need to tie up a communication line
It is easy to expand the traffic usage
Packet switching charges users only for the duration of the community unlike circuit switching charges the user on the distance and duration of a connection
High data transmission is possible with packet switching
Packet switching always uses digital networks which means digital data is transmitted directly to the destination
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What are the disadvantages of packet switching? |
Packets can be dropped/delayed the protocols for packet switching can be more complex than those for circuitswitching Does not work well with real-time data streams If a packet is lost, the sender must re-sends the packet The circuit share it's bandwidth with other packets There is delay at the destination while packets are reassembled Need large amount of RAM to handle the large amounts of data |
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What is differences between circuit switching and packet switching? |
In circuit switching an actual route used needs to be set up before transmission can begin whereas in packer switching an actual route is not used to set up before transmission can begin In circuit switching a dedicated transmission path is required but in packer switching a dedicated transmission path is not required In circuit switching,Each packet uses the same route but in packet switching each packet don't use the same route In circuit switching , packets arrive at the destination in the correct order but packet switching but in packet switching packets don't arrive at the destination in the correct order In circuit switching, All the bandwidth of the channel is required but in packer switching All the bandwidth of the channel is not required In circuit switching the bandwidth is wasted but in packet switching the bandwidth is not wasted |
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What is problem of packet switching? |
Packets may get lost and keep bouncing from one router to another router and never actually reach its destination which can clog up routes |
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What is hopping? |
The number in the packet header used to stop packets which never reach their destination from clogging up routes |
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How does packet switching works? |
Each packet is allowed only to hop a finite number of times Each time a packet passes through a router , the hop number is decreased by 1 If the packet hasn't reach its destination and the hop number = 0 , then it will be deleted when it reaches the next router If checksum is used, this value is calculated for each packet and is added to the header The checksum for each package is recalculated at the destination to ensure no errors have occurred Each packet also contains an error checking technique like checksum or parity checkIf checksum is used, this value is calculated for each packet and is added to the headerThe checksum for each package is recalculated at the destination to ensure no errors have occurred If the checksum values are different, then a request is made to re send the packetA priority value is sometimes also added to a headerA high priority value indicates which packet queue should be used If checksum is used, this value is calculated for each packet and is added to the headerThe checksum for each package is recalculated at the destination to ensure no errors have occurred If the checksum values are different, then a request is made to re send the packetA priority value is sometimes also added to a headerA high priority value indicates which packet queue should be used If the checksum values are different, then a request is made to re send the packet A priority value is sometimes also added to a header A high priority value indicates which packet queue should be used |
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What is routing table? |
-> A data table that contains the information necessary to forward the package along the shortest or the best route to allow it to reach its destination -> When the packet reaches a router , the packet header is examined and compared with the routing table -> The routing table sends instructions to the router to send the packet to the next available router |
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What are the items that are in the routing table? |
Number of hops MAc address of the next router where the packet is forwarded to Metrics Network destination or pathway Gateway Netmask Interface |
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What are the applications of transmission control protocol? |
Ensure correct routing of packets of data over the internet/network Responsible for protocols when communicating between networks Take a packet from the transport layer and add its own header which will includetbhe IP address of both sender and recipient (DL) The IP packet (datagram) is sent to the data-link layer where it assembles the data grams into frames for transmission (DL) |
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What items are contained in an email packet apart from data? |
Sender's IP address Recipient's IP address |
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What application for circuit switching is an appropriate solution? |
Video conferencing -> Circuit made available is dedicated to this communication stream -> Full bandwidth available -> Reduced latency |
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How web page is transferred using packet switching? |
The webpage is split into packets Each packet has its destination IP address The router looks at their IP address and decides where to send the data packets to next for most efficient path |
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How a layer of stack is implemented? |
Using software |
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What problems could arise if video conferencing using packet switching |
- interruptions - picture and sound not synchronised |
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What items of data in an IP data packets? |
Source IP address Destination IP address Message data IP version number |
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What is the purpose of packet header? |
To store data about the packet and its routing To ensure message can be rerouted |
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Describe the purpose of the IMAP protocol. |
used by email clients to retrieve email messages a pull protocol keeps the server and client synchronized allows a copy of the email to be downloaded from the mail server. |
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Explain how packet switching is used to transfer messages across the internet |
A large message is divided up into a group of smaller chunks of the samesize called packets Each packet travel along different routes The packets may arrive out of order and reassemble into the original message at the destination If packets are missing a re-transmission request is sent. |
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Outline the function of a router in packet switching |
The router examines the packet’s header It reads the IP address of the destination The router decides on the best hop and sends the packet on its next hop |
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What are the items in the packet header? |
Sender Ip Address Recipient Ip Address Ip version hop numbers |
