Level 3 Technical Level IT: CYBER SECURITY IT: NETWORKING IT: USER SUPPORT H/507/6426 Unit 2 Communication technologies Mark scheme

Level 3 Technical Level IT: CYBER SECURITY IT: NETWORKING IT: USER SUPPORT H/507/6426 Unit 2 Communication technologies Mark scheme June 2019 Version: 1.0 Final *196AH/MS* Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation events which all associates participate in and is the scheme which was used by them in this examination. The standardisation process ensures that the mark scheme covers the students’ responses to questions and that every associate understands and applies it in the same correct way. As preparation for standardisation each associate analyses a number of students’ scripts. Alternative answers not already covered by the mark scheme are discussed and legislated for. If, after the standardisation process, associates encounter unusual answers which have not been raised they are required to refer these to the Lead Examiner. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of students’ reactions to a particular paper. Assumptions about future mark schemes on the basis of one year’s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. Further copies of this mark scheme are available from Copyright information For confidentiality purposes acknowledgements of third-party copyright material are published in a separate booklet which is available for free download from after the live examination series. Copyright © 2019 AQA and its licensors. All rights reserved. Level of response marking instructions Level of response mark schemes are broken down into levels, each of which has a descriptor. The descriptor for the level shows the average performance for the level. There are marks in each level. Before you apply the mark scheme to a student’s answer read through the answer and annotate it (as instructed) to show the qualities that are being looked for. You can then apply the mark scheme. Step 1 Determine a level Start at the lowest level of the mark scheme and use it as a ladder to see whether the answer meets the descriptor for that level. The descriptor for the level indicates the different qualities that might be seen in the student’s answer for that level. If it meets the lowest level then go to the next one and decide if it meets this level, and so on, until you have a match between the level descriptor and the answer. With practice and familiarity you will find that for better answers you will be able to quickly skip through the lower levels of the mark scheme. When assigning a level you should look at the overall quality of the answer and not look to pick holes in small and specific parts of the answer where the student has not performed quite as well as the rest. If the answer covers different aspects of different levels of the mark scheme you should use a best fit approach for defining the level and then use the variability of the response to help decide the mark within the level, ie if the response is predominantly level 3 with a small amount of level 4 material it would be placed in level 3 but be awarded a mark near the top of the level because of the level 4 content. Step 2 Determine a mark Once you have assigned a level you need to decide on the mark. The descriptors on how to allocate marks can help with this. The exemplar materials used during standardisation will help. There will be an answer in the standardising materials which will correspond with each level of the mark scheme. This answer will have been awarded a mark by the Lead Examiner. You can compare the student’s answer with the example to determine if it is the same standard, better or worse than the example. You can then use this to allocate a mark for the answer based on the Lead Examiner’s mark on the example. You may well need to read back through the answer as you apply the mark scheme to clarify points and assure yourself that the level and the mark are appropriate. Indicative content in the mark scheme is provided as a guide for examiners. It is not intended to be exhaustive and you must credit other valid points. Students do not have to cover all of the points mentioned in the Indicative content to reach the highest level of the mark scheme. An answer which contains nothing of relevance to the question must be awarded no marks. The following annotation is used in the mark scheme: ; - means a single mark // - means alternative response / - means an alternative word or sub-phrase A. - means acceptable creditworthy answer R. - means reject answer as not creditworthy NE. - means not enough I. - means ignore DPT. - in some questions a specific error made by a candidate, if repeated, could result in the candidate failing to gain more than one mark. The DPT label indicates that this mistake should only result in a candidate failing to gain one mark on the first occasion that the error is made. Provided that the answer remains understandable, subsequent marks should be awarded as if the error was not being repeated. CAO. - Correct answer only. Question Guidance Mark 01 D Mark is for AO2 1000 Mbit/s; R. more than one box ticked 1 02 B Mark is for AO3 Central Processing Unit (CPU); R. more than one box ticked 1 03 B Mark is for AO3 a PIN code has been entered incorrectly several times.; R. more than one box ticked 1 04 D Mark is for AO3 sharing a mobile device’s Internet connection.; R. more than one box ticked 1 05 D Mark is for AO4 Resource sharing; R. more than one box ticked 1 Question Guidance Mark 06.1 2 marks for AO2 Maximum of 2 from: • copper wire / copper cable / copper cabling; • twisted pair / unshielded twisted pair / shielded twisted pair; • fibre optic / optical (cabling); • coaxial cable; • Ethernet (cable) / cat 5e (Ethernet); R. cable / fibre / light 2 06.2 2 marks for AO3 1 mark for each correct point or expansion point up to a maximum of 2 marks. Examples include: • outer casing / (metallic / foil) shielding / no portion of cabling should be unshielded / insulated / as a means of reducing / minimising EMI; • use twisted pair acts as protective shield / reduces EMI; A. absorbs / contains / reflects / / protects / grounds R. (shielding etc) prevents / stops / blocks / prevents / eliminates EMI. • (metallic / foil) shielding effective across a range of frequencies; • separate cabling for drive-motor-power and signalling / maintain distance between the two / maintain distance between any adjacent cabling; • use of (power) line filters; • ensure good ground connection / ground leads // a grounded shield acts as a conductive channel / reduces EMI; • create a 90-degree intersection; A. reference to coax only if reference is to shielded coax / outer shielding; A. reference to use of fibre optic / light as a means of reducing / minimising EMI (1 mark) R. references to crosstalk (Q6.2 specifically relates to EMI) 2 Question Guidance Mark 07.1 Mark is for AO1 • Data Terminal Equipment; CAO 1 07.2 Mark is for AO1 Maximum of 1 from: • printer; • router; • computer / PC / tablet / laptop; • smartphone / smart fridge, etc; A. Any other creditable answer R. modem (DCE) 1 Question Guidance Mark 08.1 4 marks for AO5 1 mark for each fully completed TCP/IP layer AND corresponding OSI model layer up to a maximum of 4 marks. Each mark is awarded for the correct combination of two entries (in the correct positions) as follows: • OSI Session layer AND TCP/IP Application layer; • OSI Transport layer AND TCP/IP Transport layer; • OSI Network layer AND TCP/IP Internet layer; • OSI Physical layer AND TCP/IP Network Access layer; A. If 0 marks or 1 mark awarded, allow a maximum of 2 marks in total for the question from: • 2 marks if OSI model correctly completed in full OR TCP/IP model correctly completed in full;; • 1 mark for a correct pairing on the wrong row; 4 08.2 Mark is for AO5 The third layer is the transport layer. A. follow through if incorrect “third layer” of TCP/IP given in Question 08.1 Maximum of 1 from: • responsible for error-free / end-to-end delivery of data (packets) // delivery / exchange of data from the source host to the destination; • message segmentation // acknowledgement // traffic / flow /data control // session multiplexing (for data sent / transported across a network); • assembling segments with the necessary information and passing them to the network layer (multiplexing); • transport layer (at the message source) splits messages/information/data into segments; • the transport layer (in a receiving machine) receives a sequence of segments from its network layer; • permits devices / source and destination / host-to-host to communicate / carry on a conversation / end-to-end connection; • error checking / correction (resends) / verification; • defines level of service and status of any connection used to transport data; R. reference to packets unless identified as UDP packets A. references to headers R. reference to headers and footers A. Any other creditable answer 1 08.3 Mark is for AO5 Maximum of 1 from: • Transmission Control Protocol / TCP; • User Datagram Protocol / UDP; • Datagram Congestion Control Protocol / DCCP; • Stream Control Transmission Protocol / SCTP; • Resource Reservation Protocol / RSVP; • Open Shortest Path First (OSPF); A. Any other creditable protocol A. follow through if incorrect “third layer” of TCP/IP given in Question 08.1 1 Question Guidance Mark 09 2 marks for AO1 Maximum of 2 from: • repetition code is used to reduce the likelihood of errors occurring in received data // is a form of error detection; by transmitting the same data a number of times; and comparing (each set of) received data to see if an error has occurred; A. reference to "majority bit" • line interference / collision corrupts the transmission; requiring retransmission of messages; • line interference / collision corrupts the transmission; therefore, repetition code retransmits the message several times; • repetition code is a basic error-correcting code / error checking / error handling; A. Any other creditable answer 2 10.1 2 marks for AO3 • wireless/online (delivery); • of new software / data; R, program / programming without explanation / expansion 2 10.2 2 marks for AO3 Maximum of 2 from: • configuration / initialisation (of newly purchased mobile phone); • operating systems (for newly purchased smartphones and tablets); • (mobile phone) updates / all Apple iOS updates since iOS 5.0.1; • upgrades to system software / updates to application software; • firmware updates; • patching / updating security / fixing security issues; • configuration / settings; • encryption keys; • (Freeview) Electronic Programme Guide / EPG updates; • any reference to "seamless updates"; • car (entertainment/control/navigation) systems; • traffic signs (eg RMS E Ink); A. Any other creditable answer R. debugging R. collaborative working without reference to developing AND testing R. repetition from Q10.1 without explanation / expansion 2 Question Guidance Mark 11 4 marks for AO4 1 mark for each comparison up to a maximum of 4 marks. Maximum of 4 from: • LAN connects network devices / peripherals over a relatively short distance / small geographical area // WAN connects network devices over a large distance / has connectivity over longer distances; • LAN is (usually) confined to a home / school / office / room / a small number of buildings (eg on a campus) whereas a WAN covers a country; • WAN connects over a large geographical area / cities / different countries whereas LAN covers a smaller area; • LAN is limited to a small geographical area / covers a smaller area; • WAN connects over a much larger area such as a whole country; • WAN is formed by attaching multiple LANs together; • the Internet is the largest WAN / the Internet is a WAN that spans the earth whereas LAN is just the local area; • LAN is the network in our school, WAN is the Internet; • LAN is group of devices connected locally (via Ethernet / wireless) whereas WAN covers a wider area; • a LAN is (generally) more secure than a WAN (owing to its size/easier to control); • a WAN is more likely to use fibre optic links as opposed to copper cabling; • a WAN is more expensive to set up / maintain // a LAN is cheaper (such as Ethernet); • LAN is dependent on Layer 1 and 2 devices whereas WAN is dependent on Layer 3; • LANs inside a WAN are connected by Layer 3 devices (such as routers); • LANs use switches / hub / repeaters whereas you connect to WAN with a router; • LAN uses a switch whereas WAN uses multilayer switches / ATM; • a router connects LANs to WANs; • a LAN has a high bandwidth for communication (compared to WAN); • a WAN has more potential for congestion than LAN; • LAN is (usually) higher speed (1000 Mbps) than WAN (150 Mbps); • LAN (usually) has a higher data transfer rate (than WAN) // WAN (usually) has a lower data transfer rate (than WAN); • LAN (usually) owned / controlled by a single individual / administrator / organisation // WAN (usually) owned by a large organisation / government; R. LAN covers a local area // WAN covers a wide/wider area. A. Any other creditable answer 4 Question Guidance Mark 12.1 2 marks for AO1 • deliberate / intentional / the act of (by an ISP / network); • slowing of available bandwidth / reduction of available bandwidth / lowering of speed / transmission (of available Internet connection / network); • reducing / limiting amount of data / data packets; A. different wording with similar meaning 2 12.2 2 marks for AO1 Maximum of 2 from: • no benefit to those affected (by bandwidth throttling) / benefits others (by slowing or lowering the bandwidth available to those affected) / bandwidth prioritised / aim being to achieve fair access for home / business use A. reference to advantaging OR disadvantaging heavy users as it is dependent on the ISP; • decreases congestion (at certain times of day) / regulates network traffic; • high volume use results in increased collisions / failures (during peak periods); • reduces the amount of data (the ISP has to process); • avoids the need (for the ISP) to add cost / add capacity / add the facility to process more data (at peak times); • an ISP has limited resources and must manage their network effectively; • they might use throttling to restrict certain (heavy) usage eg torrenting; A. appropriate reference to torrenting / bit torrent A. Any other creditable answer 2 Question Guidance Mark 13.1 2 marks for AO3 Either / or: • Global System for Mobile (communications) // Global System for Mobiles; • 2nd Generation / 2nd gen; 1 13.2 3 marks for AO3 Maximum of 3 from: • digital / improved voice/sound quality; • digitally encrypted; • SMS / text messaging service / A. text only; • picture messages / MMS; R. photos • mobile data / data roaming; A. data services; • (narrowband) internet; • greater coverage / global; • GSM; • GPRS / 50kbit/s; • EDGE / 1Mbit/s; A. circuit switching A. packet switching (eg GPRS) only with reference to 2.5G; A. multiple access; R. multiple user A. Any other creditable answer 3 Question Guidance Mark 14.1 2 marks for AO2 Maximum of 2 from: • easy to manufacture / easy to install / workers can install UTP quickly and easily / workers need more training and more time to handle and install STP; • flexible / STP by comparison is fragile and rigid / if STP metal shield suffers damage then resistance to EMI will markedly reduce; • UTP costs less / cheaper / don't have to pay for the metal shield / / UTP weighs less than STP / UTP costs less to transport and costs less to package; • unshielded cabling does not rely on grounding to the same extent as shielded cabling / increases reliability / improperly grounded STP will actually increase crosstalk and EMI; • faster / fastest copper-based medium; A. STP unnecessary in environments where EMI is minimal; A. Any other creditable answer 2 14.2 2 marks for AO2 Maximum of 2 from: • to retransmit a signal; so that the signal can cover longer distances / to retransmit / boost / amplify a signal around an obstacle // as signal becomes weaker over distanceA. increase length // increases transmission range // extends wireless signal; • maintains signal integrity; • any mention of ‘attenuation’; A. maximum of 1 mark if the purpose of a repeater is not clear A. Any other creditable answer 2 Question Guidance Mark 15.1 2 marks for AO5 Maximum of 2 from: • RIP updates the routing table; • RIP provides information about network pathways; • enables routing (of data/packets) from one point to another / shortest route; A. Any other creditable answer R. routes / routing of information (stem) 2 15.2 3 marks for AO5 Maximum 3 marks overall. Maximum of 1 from: • a routing table contains information about network paths; • a network path simply defines which network is connected with which interface / router; • when the router receives packet data it simply references the routing table / retrieves the destination address for that network path; • if there is no destination address listed, or that network path is not listed, or the route is more than 15 hops, packet data is dropped Maximum of 1 from: • the RIP protocol enables routers to learn about destination addresses; by sharing information with neighbouring routers; routers running the RIP protocol broadcast configured networks from all ports; enabling (listing) routers to update their routing table (using this information) (every 30 seconds); • routers running the RIP protocol can use broadcast information received to update information already listed in their routing table; or, if no information is already listed, the router will create a new route/ listing; Maximum of 1 from: • different routing protocols use different metrics to calculate the best path for destination; • administrative distance (AD) value used to select the best path; A. hop count / hops = number of routers from source to destination; • RIP selects the best path; A. Any other creditable answer 3 Question Guidance Mark 16.1 2 marks for AO2 Maximum of 2 from: • line interference / collisions / delays; requiring retransmission of messages // the greater the line interference the greater the potential for loss of data integrity; • network protocols consume some capacity; therefore 100% impossible; • applications supply insufficient data to make full use of available connection; therefore 100% impossible / 90%+ typical; • attenuation; • noise / quality of cables varies; • the longer / thinner the wires the greater the resistance; • insulation / environment absorbs some of the signal; • electrical interference such as mains cables; R. similar expansion points R. numbers of users sharing cable A. Any other creditable answer 2 16.2 4 marks for AO2 1 mark for each correct point or expansion point, up to a maximum of 4 marks. • FTTC connection from cabinet to home is copper not fibre; therefore, can only offer a standard connection / broadband speeds; • copper cable FTTC connection commonly shared / reduces bandwidth; • adverse effect - the further the property (home or office) from the cabinet / signal strength degrades / drop off in speed; • adverse effect - age of wiring / some FTTC copper cabling decades old / impairs signal; • FTTH connection from exchange to home is 100% fibre; therefore o has less interference; o keeps signal strength throughout transmission; o operates at a higher frequency rate throughout transmission; A. Any other creditable answer 4 Question Guidance Mark 17 6 marks for AO3 Maximum of 6 marks overall. LCD display: Maximum of 3 from: • backlit; • shines through polarizers / filters; • (liquid) crystal display; • crystals are on / off; A. open / closed • when stimulated by an electric current; • light not generated by the display itself / light generated behind the display; • three (red, blue, green) sub-pixels (for each pixel); • (as display is filter) blacks won’t be true blacks; A. reference to bleeding / when 100% backlight not blocked (1 mark) A. reference to colour blending ONLY IF linked to voltage / intensity / 256 shades (1 mark) LED display: Maximum of 3 from: • (backlight consists of) light-emitting-diodes / LEDs generate own light; • an LED emits light when an electric current is passed through it / electroluminescence; • surplus energy is released to give off a quick flash of light // (which) produces a dull continuous glow; • LED TVs are LCD TVs that use LEDs for the background lighting; • three LEDs per pixel // one LED per pixel for OLED/AMOLED; • thinner; • brighter / can be used outdoors / better contrast; • OLED pixels produce their own light // can be controlled on a pixel-by-pixel basis; • better resolution / improved ppi (pixels per inch); A. reference to 1.3mm • produce red, green, and blue colours // true black; • no light not using up any battery / black not using up any battery; • no light = extended battery life / not using up any battery; R. OLED, AMOLED etc without reference to specific features Both displays: R. reference to being more or less power efficient, dependent on model R. reference to pixel density/resolution higher/lower unless qualified R. reference to pixelated or vector images, applies to both R. reference to touchscreen, applies to both A. Any other creditable answer 6 Question Guidance Mark 18 9 marks for AO3 Mark using the levels of response table and the indicative content on the following page. Indicative content INFRASTRUCTURE • mobile data is sent through a base station / transmitting tower • radio waves are used to transfer signals to and from the mobile device • IP based networks use two primary methods of communication when transferring data across cellular data network: TCP and UDP • data is transmitted in TCP or UDP packets • mobile phones depend on a cellular network / each cell comprises an (overlapping) geographical area / a group of cells covering a geographical area will have its own base station / base station will act as a hub for those cells A. data transferred to a central hub (eg Wi-Fi in a small network of devices) 9 A. reference to IMSI / TMSI A. data can be transferred directly (eg using Bluetooth) RELIABILITY • each TCP/IP packet sent will generate a reply acknowledgement (ACK) packet / if a packet not acknowledged, TCP/IP packet data will be resent / TCP/IP stack will (eventually) discard packet data (network timeout condition) TCP ensures each end point able to receive / transmit before sending, specifically on 1st Send / SYN ensures synchronised connection (ie of Sender and Receiver), keeps track of communication (stateful), is therefore connection-oriented, eg windowing • TCP transmission is always asynchronous • TCP not only has an error checking process and re-Sends if ACK not received, it also ensures packets are received in the order sent, and responds to missing or corrupted data, accuracy and quality important • However, UDP packets are only sent one time, automatically, whether receiver ready or not or even exists, there is no ACK, is therefore connectionless, no error control, speed (more) important, eg streaming, video, VOIP • TCP is (therefore) reliable – it guarantees delivery of data – UDP is unreliable (0 marks, repeats stem) / a dropped packet will generate multiple TCP retransmissions by default before the data is discarded • UDP does not solve for reliability, in-order delivery, flow control or congestion control. A. Applications also send out periodic queries and get responses to those queries when sending / receiving data / application will usually retry if it does not get an answer / can determine a problem exists if it does not get a response after a certain amount of retries R. ‘UDP is unreliable’ without qualification (repeats stem) Question Guidance Mark 19 15 marks for AO4 15 Mark using the levels of response table and the indicative content on the following page. Level Description Mark Range 5 Candidate provides a full account of computer networking devices that are useful and / or required, clearly describing in some detail the features and functions of five named devices and stating clearly why each is needed for communication between devices on a computer network, includes some comparative argument and conclusions. 13 – 15 4 Candidate attempts some discussion of computer networking devices that are useful and / or required, having clearly described the features and functions of four or five named devices, making appropriate connections and stating clearly why each is needed for communication between devices on a computer network. 10 – 12 3 Candidate clearly understands why some computer networking devices are useful and / or required, giving one or two features of four or five named devices, and one or two functions of four or five named devices, making appropriate connections and stating clearly why each are needed for communication between devices on a computer network. 7 – 9 2 Candidate understands why some computer networking devices are useful and / or required, giving one or two features of up to three named devices, and one or two functions of up to three named devices, makes appropriate reference as to why each are needed for communication between devices on a computer network. 4 – 6 1 Candidate gives indication they know something about why some computer networking devices are useful and / or required, giving one or two features of one or two named devices, and one or two functions of one or two named devices 1 – 3 No creditworthy content 0 Indicative content PURPOSE FEATURES FUNCTIONS Hub Acts like a Splits a network Receiving requests distribution connection into for information centre, multiple from the network requesting and computers, or a specific receiving the broadcasts data computer entire network to all Switch (ie Layer 2 switch) / multiport network bridge Connects (many) devices together on a computer network, only used in LANs, more advanced than a hub as it checks to which system or port a message should be sent (before sending) Like a hub but with advanced features, sending data to a specific destination or port, uses MAC address, usually only now needed if wired connection required to more than 4 devices (see Router below) Common features with hub include multiple RJ45 ports A. reference to IP address only in relation to switch management . / SNMP Router A. Layer 3 Switch Can connect LAN to LAN, connects networks, directs flow of traffic to network, or share a single Internet connection to multiple computers, ie needed if more than one device is to connect to internet (see Modem below) R. access control / filter unless reference to Access Control List (ACL) Can be wired or wireless, often has a built-in switch with multiple / 4 ports plus wireless access, uses IP address, have WAN and LAN ports, are used in WAN, LAN, and MAN, routers use ICMP to communicate with other routers to determine best route, business router required if connection required to server A. traffic flow log / activity log Directs data, between computers, between computers and a modem A. lists connected devices / lists approved devices A. Wireless Access Point / Access Point / AP / hotspot Connects wireless capable devices using wireless standards including Wi-Fi and Bluetooth Creates a wireless local area network / WLAN Enables wi-fi devices to connect to a wired network Servers Provides access to network resources A. connects to router ONLY if reference made to business router Holds (hosts) shared files, programs, network OS, websites, etc Different kinds of servers / one server can provide more than one function, eg file servers, print, fax, web, communication, database, mail, etc Network Interface card / Network interface controller / Network adapter / LAN adapter Controls data flow between computer and network A special expansion card for each computer in a network, uses Ethernet or Wi-Fi to communicate using a wired or wireless connection Prepares / formats / sends / receives data Transmission media Interconnect computers in a network Twisted pair, coaxial, fibre optic also referred to as channels, lines, links A. repeater Regenerates or replicates a signal Used for signals from optical, copper, and coaxial cable (repeaters used for microwaves from satellites are called transponders), therefore carry electrical signals and light signals regenerates digital or analogue signals distorted by transmission loss Modem Needed if devices on network are to be connected to the Internet, provides internet access, can be DSL (phoneline) or cable Connects to Ethernet port, modem only required if only ONE device needs to connect to internet (more than one device requires router) Converts digital signals (from computer) to analogue (to internet) and vice versa. A. allow appropriate credit for reference to combined components (eg router- switch) A. allow modem if reference to network connection to Internet R. cloud storage Assessment Outcomes Question AO1 AO2 AO3 AO4 AO5 Question Total SECTION A 1 2a (1) 1 2 3a (1) 1 3 3c (1) 1 4 3e (1) 1 5 4c (1) 1 6.1 2b (2) 2 6.2 3d (2) 2 7.1 1a (1) 1 7.2 1a (1) 1 8.1 5b (4) 4 8.2 5b (1) 1 8.3 5c (1) 1 9 1c (2) 2 10.1 3e (2) 2 10.2 3e (2) 2 11 4a (4) 4 12.1 1d (2) 2 12.2 1d (2) 2 13.1 3c (1) 1 13.2 3c (3) 3 14.1 2c (2) 2 14.2 2c (2) 2 15.1 5c (2) 2 15.2 5c (3) 3 16.1 2a (2) 2 16.2 2a (4) 4 Total A 8 13 13 5 11 50 SECTION B 17 3b (6) 6 18 3b (9) 9 19 4b (15) 15 Total B 0 0 15 15 0 30 Total A+B 8 13 28 20 11 80