14.1 Protocol Technologies
A Level · 19 questions found
What this topic covers
Section titled “What this topic covers”- Why protocols are essential for communication between computers
- Protocol stack model: each layer has distinct functionality
- TCP/IP four layers: Application, Transport, Internet, Link — purpose and function of each
- How a message travels from one internet host to another
- Protocols and their purposes: HTTP, FTP, POP3, IMAP, SMTP, BitTorrent (P2P file sharing)
Past paper questions
Section titled “Past paper questions”(a) Explain why protocols are essential for communication between computer systems. 2 marks
(b) POP3 is an email communication protocol. 4 marks
Identify and describe two other communication protocols that are used when sending or receiving emails.
Protocol 1
Description
Protocol 2
Description
(c) Describe two ways in which packet switching ensures a complete message is received when passing messages across a network. 4 marks
1
2
Show mark scheme
3(a) [2 marks]
One mark per mark point ( Max 2 ) MP1 Protocols set a standard for communication // Protocols establish a standard set of rules for communication MP2 Protocols enable compatibility between devices from different manufacturers/platforms MP3 Two devices wouldn’t be able to communicate/send messages to each other if they were using different protocols
3(b) [4 marks]
One mark for a protocol and one mark for a description ( Max 4 ) Example answers: SMTP [1] a protocol used to send emails between mail servers // a protocol used to send emails from a computer to a mail server [1] IMAP [1] allows users to access/read their emails from any device without the message from the mail server // synchronises emails on any device [1]
3(c) [4 marks]
Two marks for each description mark as 2 x 2 ( Max 4 ) Example answers: Packets checked at receiving end / on arrival [1] … if packets arrive damaged or don’t arrive at all, a re-send request is sent [1] Packets routed through different paths / sent individually [1] … if a route is blocked, the packet is sent through a different route to ensure it arrives [1] If the packet’s hop count is exceeded [1] … the packet will be retired, which can generate a re-send request [1]
(a) HTTP and IMAP are examples of protocols used in the Application Layer of the TCP/IP protocol suite. 2 marks
State the purpose of the HTTP and IMAP protocols.
HTTP
IMAP
(b) Describe how files are shared using the BitTorrent protocol. 4 marks
Show mark scheme
3(a) [2 marks]
One mark per mark point ( Max 2 ) • HTTP to send and receive / transfer web pages / hypertext / images / videos • IMAP allows users to access/read their emails from any device without // synchronises emails on any device
3(b) [4 marks]
One mark per mark point ( Max 4 ) MP1 Files are shared over a peer-to-peer network MP2 A small file, a torrent (descriptor file), is initially created by a peer MP3 The torrent (descriptor file) contains metadata about the file to be shared MP4 The whole file must initially be located on at least one peer MP5 The file is broken into equal sized pieces MP6 Other peers who wish to download the file first obtain the torrent (descriptor file) and connect to a tracker MP7 A tracker acts like a server that holds all the data about all the computers connected to it / the swarm MP8 Each peer downloads parts of the file from other peers until the entire file has been downloaded MP9 As each peer receives a piece of the file, they become a source for that piece of the file MP10 A peer who has a complete file and is sharing it is a seed // Once a peer has and made the file available to others in the swarm, they become a seed.
Identify and describe three protocols that are used in the Application Layer of the TCP/IP protocol suite.
Protocol 1
Description
Protocol 2
Description
Protocol 3
Description 6 marks
Show mark scheme
4 [6 marks]
One mark for a correct protocol and one mark for a correct corresponding description ( Max 6 ) Three from: HTTP/S [1] a protocol/secure protocol used to transfer hypermedia documents / web pages / (data) files between networked devices [1] FTP [1] a protocol to download, upload and transfer files from one location to another on a network [1] POP3 [1] a protocol used to retrieve/receive emails from a mail server to a computer [1] IMAP [1] allows users to access/read their emails from any device without removing the message from the mail server // synchronises emails on any device [1] SMTP [1] a protocol used to send emails between mail servers // a protocol used to send emails from a computer to a mail server [1] BitTorrent [1] a communication protocol used for peer-to-peer file sharing [1]
(a) The Application Layer and Transport Layer are two layers of the TCP/IP protocol suite. 5 marks
Describe the purpose of the Application Layer and the purpose of the Transport Layer.
Purpose of Application Layer
Purpose of Transport Layer
(b) Describe packet switching as a method of transmitting messages across the internet. 4 marks
Show mark scheme
3(a) [5 marks]
One mark per mark point ( Max 5 ) One mark per mark point for purpose of Application Layer ( Max 3 ) MP1 To provide services / interface with the user // access to applications, for example login, file transfer, network file access, email, etc MP2 To provide mechanisms for securing communication e.g. encryption/authentication MP3 To define/provide protocols used to allow the exchange of data/communication // to contain programs that exchange data MP4 Error detection and recovery mechanisms to handle application specific errors One mark per mark point for purpose of Transport Layer ( Max 3 ) MP5 To provide logical communication between applications running on different hosts // To ensure that data is delivered to the correct application process on the destination machine MP6 To ensure error-free, end-to-end delivery of data between a source and a destination, in sequence // to provide error recovery techniques such as error detection codes and automatic repeat request MP7 To break data into segments when sent and to reconstruct when received // To reassemble segments at destination MP8 To regulate network connections // to provide flow control mechanisms to prevent data loss.
3(b) [4 marks]
One mark per mark point ( Max 4 ) MP1 Data are broken into equal sized packets MP2 Data packets have headers containing information such as the IP addresses of the sender and receiver MP3 Each packet of data is sent independently to the destination // Packets don’t necessarily follow the same route MP4 Each packet is sent via the most optimum path available MP5 Packets don’t necessarily arrive in the order they were sent // Packets are reconstructed at the destination in the correct order MP6 Missing / damaged packets are re-sent
(a) Identify two different layers of the TCP/IP protocol suite. 1 mark
(b) Describe how the TCP/IP protocol suite is applied when a message is sent through the internet from one host to another. Do not describe the function of individual layers of the TCP/IP protocol suite. 4 marks
Show mark scheme
3(a) [1 mark]
Two from • Application Layer • Transport Layer • Internet Layer • Link Layer
3(b) [4 marks]
One mark per mark point ( Max 4 ) MP1 The TCP/IP suite can be viewed as layers within a stack MP2 Each layer can only accept input from the next higher or the next lower layer/adjacent layer MP3 The user/sender/computer interfaces with the top layer/application layer to send/receive a message MP4 The message when sent passes from the top layer/application layer to the bottom layer/link layer MP5 The message when received passes from bottom layer/link layer to the top layer/application layer MP6 The link layer interfaces directly with the network and sends/receives the message.
(a) The Internet layer and Link layer are two layers of the TCP/IP protocol suite. 5 marks
Describe the purpose of the Internet layer and the purpose of the Link layer.
Purpose of Internet layer
Purpose of Link layer
(b) Describe the function of a router in packet switching. 4 marks
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4(a) [5 marks]
One mark per mark point ( Max 5 ) One mark per mark point for purpose of Internet Layer ( Max 3 ) MP1 To identify the intended network and host. MP2 To add header containing IP addresses. // To address packets with their source and destination IP Addresses. MP3 To prepare packets for delivery by formatting them into datagrams. MP4 To route datagrams through the optimum route over a network. One mark per mark point for purpose of Link Layer ( Max 3 ) MP5 To prepare the next hop by managing the link between two directly connected devices. // To identify and move traffic across local segments. MP6 To format datagrams into frames for transmission. MP7 To identify network protocols in the packet header. // To ensure correct network protocols MP8 To deliver frames to the receiving network. // To receive frames from the sending network. // To map IP addresses to MAC physical addresses. MP9 To provide error checking/error correction/recovery/reconstruction MP10 including resend requests.
4(b) [4 marks]
One mark for each correct marking point (Max 4 ) MP1 The router reads the IP address of the destination from the packet header. MP2 A router uses a routing table to find information … MP3 … about e.g., available hops / netmask / gateway used / adjacent routers / the status of the routers along the route. MP4 The router determines the next hop / optimum route. // The router sends the packet on its next hop. MP5 The router manages the hop counter // The hop counter is reduced by 1 every time the packet passes a router.
The TCP/IP protocol may be viewed as a stack that contains four layers: Application, Transport, Internet, Link.
Describe how the layers of the TCP/IP protocol stack interact with each other. 4 marks
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4 [4 marks]
One mark per mark point ( Max 4 ) MP1 Each layer can only accept input from the next higher layer or the next lower layer MP2 There is an interface between the adjacent layers which is the only interaction between layers MP3 Data is added to the headers as the frames/packets pass through the layers MP4 The interactions are carried out by installed software MP5 User interaction takes place at the highest/Application layer of the stack of the stack MP6 Direct access to hardware takes place at the lowest/Link layer of the stack.
(a) Name and describe two protocols used by the Application Layer of the TCP/IP protocol suite. 4 marks
Protocol 1
Description
Protocol 2
Description
(b) Explain the purpose and function of the Application Layer in the TCP/IP protocol suite. 3 marks
Show mark scheme
5(a) [4 marks]
One mark for each correct name ( Max 2 ) One mark for each correct corresponding expansion ( Max 2 ) MP1 HTTP/HTTPS MP2 For sending and receiving / transferring web pages / hypertext MP3 FTP MP4 For sending and receiving files over a network / between devices MP5 POP3 MP6 Pull protocol / for receiving / downloading emails MP7 IMAP MP8 Pull protocol / for receiving / downloading emails MP9 SMTP MP10 Push protocol / for sending / uploading emails MP11 BitTorrent MP12 Peer-to-peer file sharing over a network
5(b) [3 marks]
One mark per mark point ( Max 3 ) MP1 The application layer provides access to all the programs that exchange data // Interacts directly with user. MP2 … used by, for example, web browsers, server software. MP3 Communicates/enables data transfer to/from Transport layer // It allows applications to access the services used in other TCP/IP layers. MP4 It defines the protocols that any application uses to allow the exchange of data.
The TCP/IP protocol may be viewed as a stack that contains four layers: Application, Transport, Internet, Link.
Describe how the layers of the TCP/IP protocol stack interact with each other. 4 marks
Show mark scheme
4 [4 marks]
One mark per mark point ( Max 4 ) MP1 Each layer can only accept input from the next higher layer or the next lower layer MP2 There is an interface between the adjacent layers which is the only interaction between layers MP3 Data is added to the headers as the frames/packets pass through the layers MP4 The interactions are carried out by installed software MP5 User interaction takes place at the highest/Application layer of the stack of the stack MP6 Direct access to hardware takes place at the lowest/Link layer of the stack.
The TCP / IP protocol suite has four layers:
Transport, Application, Link, Internet
(a) Complete the diagram to show the correct order for these layers. 2 marks
(b) Describe the function of the Transport layer. 2 marks
(c) Outline one protocol that is associated with the Application layer. 2 marks
Show mark scheme
2(a) [2 marks]
marks for all protocols in correct position mark for at least two protocols in correct position Application Transport Internet Link
2(b) [2 marks]
mark per mark point ( Max 2 ) The transport layer is responsible for delivery of data from the source host to the destination host It is where data is broken up into packets and sent to the internet layer Adds the sequence number to the packet header It establishes end to end contact It ensures data arrives error free // It retransmits packets if lost.
2(c) [2 marks]
mark for name of protocol and one mark for expansion ( Max 2 ) HTTP(S) – responsible for correct transfer of files / hypertext documents that make up web pages on the world wide web FTP – used when transferring files from a server to a client on a network POP3 – handles the receiving of emails IMAP – handles the receiving of emails SMTP – handles the sending of emails BitTorrent – provides peer-to-peer file sharing
(a) Outline why protocols are essential for communication between computers. 2 marks
(b) State the names of two different protocols associated with the sending and receiving of emails between computers. 2 marks
Sending
Receiving
(c) Explain the meaning of the phrase: 3 marks
BitTorrent protocol provides peer-to-peer file sharing.
Show mark scheme
2(a) [2 marks]
mark per mark point ( Max 2 ) Protocols provide a standard set of rules that enables successful data transfer between devices. Allows communication between devices on different platforms. Makes communications independent of software and hardware.
2(b) [2 marks]
mark per mark point Sending - SMTP Receiving – POP3 // IMAP // Post Office Protocol 3
2(c) [3 marks]
mark per mark point ( Max 3 ) BitTorrent allows the sharing of files between thousands of users who are connected together over the internet . It allows more users to share files with each other than would be the case with a peer-to-peer network. Users share files directly with each other // the users’ computers are acting as peers … no web server / central device is used // all users are of equal status.
The TCP / IP protocol suite has four layers:
Transport, Application, Link, Internet
Show mark scheme
2(a) [2 marks]
marks for all protocols in correct position mark for at least two protocols in correct position Application Transport Internet Link
2(b) [2 marks]
mark per mark point ( Max 2 ) The transport layer is responsible for delivery of data from the source host to the destination host It is where data is broken up into packets and sent to the internet layer Adds the sequence number to the packet header It establishes end to end contact It ensures data arrives error free // It retransmits packets if lost.
2(c) [2 marks]
mark for name of protocol and one mark for expansion ( Max 2 ) HTTP(S) – responsible for correct transfer of files / hypertext documents that make up web pages on the world wide web FTP – used when transferring files from a server to a client on a network POP3 – handles the receiving of emails IMAP – handles the receiving of emails SMTP – handles the sending of emails BitTorrent – provides peer-to-peer file sharing
(a) Draw one line to connect each protocol to its most appropriate use. 4 marks
Protocol Use
HTTP
BitTorrent
SMTP
IMAP
to provide peer-to-peer file sharing
when retrieving email messages from a mail server over a TCP/IP connection
when transmitting hypertext documents
to map MAC addresses onto IP addresses
when sending email messages towards the intended destination
(b) Outline the purpose of the Link layer in the TCP / IP protocol suite. 2 marks
Show mark scheme
2(a) [4 marks]
One mark for each correct line connecting a protocol to its most appropriate description ( Max 4 ). Protocol Use to provide peer-to-peer file sharing HTTP when retrieving email messages from a mail server over a TCP/IP connection BitTorrent when transmitting hypertext documents SMTP to map MAC addresses onto IP addresses IMAP when sending email messages towards the intended destination
2(b) [2 marks]
One mark per mark point ( Max 2 ) MP1 To ensure correct network protocols are followed MP2 To enable the upper layers to access the physical medium // enables connection/ communication with the internet / network layer MP3 To be responsible for transporting data within the network/local segments MP4 To format the data into frames for transmission MP5 Maps IP addresses to MAC/Physical addresses.
Complete the following paragraph about a protocol suite, using words from the given list.
Some words are not used.
BitTorrent circuit switching layered link list
peer‑to‑peer queue stack star TCP/IP
The protocols in a ______ determine the interconnectivity
rules for a ______ network model such as the
______ model. 3 marks
Show mark scheme
4 [3 marks]
One mark for each correct word ( Max 3 ) The protocols in a stack determine the interconnectivity rules for a layered network model such as the TCP/IP model.
(a) Draw one line to connect each protocol to its most appropriate use. 4 marks
Protocol Use
HTTP
BitTorrent
SMTP
IMAP
to provide peer-to-peer file sharing
when retrieving email messages from a mail server over a TCP/IP connection
when transmitting hypertext documents
to map MAC addresses onto IP addresses
when sending email messages towards the intended destination
(b) Outline the purpose of the Link layer in the TCP / IP protocol suite. 2 marks
Show mark scheme
2(a) [4 marks]
One mark for each correct line connecting a protocol to its most appropriate description ( Max 4 ). Protocol Use to provide peer-to-peer file sharing HTTP when retrieving email messages from a mail server over a TCP/IP connection BitTorrent when transmitting hypertext documents SMTP to map MAC addresses onto IP addresses IMAP when sending email messages towards the intended destination
2(b) [2 marks]
One mark per mark point ( Max 2 ) MP1 To ensure correct network protocols are followed MP2 To enable the upper layers to access the physical medium // enables connection/ communication with the internet / network layer MP3 To be responsible for transporting data within the network/local segments MP4 To format the data into frames for transmission MP5 Maps IP addresses to MAC/Physical addresses.
(a) State what is meant by the term enumerated data type . 1 mark
(b) State what is meant by the term pointer data type . 1 mark
(c) The months of the year are: January, February, March, April, May, June, July, August, September, October, November and December. 2 marks
Write the pseudocode statement to define the data type Quarter1, to hold the names of the
first three months of a year.
| ta type Pet is used to stor hese fields: | re data about the |
|---|---|
| Field name | Data type |
PetName |
String |
AnimalType |
String |
PetAge |
Integer |
PetGender |
Char |
OwnerName |
String |
(i) Write the pseudocode statement to set up a variable for one record of the composite data type Pet . 1 mark
Show mark scheme
3(a) [1 mark]
A (user-defined non-composite) data type with an ordered list of possible values.
3(b) [1 mark]
A user-defined non-composite data type used to reference a memory location
3(c) [2 marks]
Marks as shown in the square brackets: TYPE Quarter1 = (January, February, March) [1] TYPE Quarter1 = [1] (January, February, March) DECLARE Pet1 : Pet
3(d)(i) [1 mark]
3(d)(ii) [3 marks]
One mark for each point: • Correct assignment of all string data values • Correct assignment of char data value • Correct assignment of integer data value Example answer: Pet1.PetName "Tibbles" Pet1.AnimalType "Cat" Pet1.PetAge 8 Pet1.PetGender 'M' Pet1.OwnerName "Jasmine Smith"
(a) Explain why a protocol is used in communication between computers. 2 marks
(b) The TCP/IP protocol implementation can be viewed as a stack. 2 marks
Complete the diagram for the TCP/IP protocol stack.
Transport
Link
(c) Describe the purpose of the IMAP protocol. 2 marks
Show mark scheme
3(a) [2 marks]
One mark per point ( Max 2 ) • Protocols set a standard for communication • Protocols enable communication/compatibility between devices from different manufacturers/platforms • If two devices were sending messages to each other but using different protocols, they would not be able to communicate properly
3(b) [2 marks]
One mark for each correct answer Application (Layer) Transport Internet/Network (Layer) Link
3(c) [2 marks]
One mark per point ( Max 2 ) • used by email clients to retrieve email messages // a pull protocol • from a mail server (over a TCP/IP connection) • keeps the server and client in sync (by not deleting the original email). // allows a copy of the email to be downloaded from the mail server.
(a) State what is meant by the term enumerated data type . 1 mark
(b) State what is meant by the term pointer data type . 1 mark
(c) The months of the year are: January, February, March, April, May, June, July, August, September, October, November and December. 2 marks
Write the pseudocode statement to define the data type Quarter1, to hold the names of the
first three months of a year.
| ta type Pet is used to stor hese fields: | re data about the |
|---|---|
| Field name | Data type |
PetName |
String |
AnimalType |
String |
PetAge |
Integer |
PetGender |
Char |
OwnerName |
String |
(i) Write the pseudocode statement to set up a variable for one record of the composite data type Pet . 1 mark
Show mark scheme
3(a) [1 mark]
A (user-defined non-composite) data type with an ordered list of possible values.
3(b) [1 mark]
A user-defined non-composite data type used to reference a memory location
3(c) [2 marks]
Marks as shown in the square brackets: TYPE Quarter1 = (January, February, March) [1] TYPE Quarter1 = [1] (January, February, March) DECLARE Pet1 : Pet
3(d)(i) [1 mark]
3(d)(ii) [3 marks]
One mark for each point: • Correct assignment of all string data values • Correct assignment of char data value • Correct assignment of integer data value Example answer: Pet1.PetName "Tibbles" Pet1.AnimalType "Cat" Pet1.PetAge 8 Pet1.PetGender 'M' Pet1.OwnerName "Jasmine Smith"
The TCP/IP protocol suite has four layers. The application layer provides user services.
(a) Identify two protocols used by this layer. Describe the use of each protocol. 4 marks
Protocol 1
Description
Protocol 2
Description
(b) Identify two other layers of the TCP/IP protocol suite. Describe the function of each layer. 4 marks
Layer 1
Description
Layer 2
Description
Show mark scheme
3(a) [4 marks]
Protocol one mark, description one mark, max four two from HTTP(S) (1) for sending and receiving web pages / hypertext documents (1) FTP (1) for sending and receiving files over a network / between devices (1) SMTP (1) for sending/uploading emails /push protocol (1) POP(3) (1) for receiving/downloading emails /pull protocol (1) IMAP (1) for receiving/downloading emails /pull protocol (1)
3(b) [4 marks]
one mark, matching function one mark, max four two from Transport (1) handles packets (1) Internet (1) handles transmission of data using IP addresses // provides (optimal) route (1) Network Access (Interface) // (Data) Link // Physical (1) Handles how data is physically sent (1)