Edexcel GCSE Computer Science (1CP2) Exam Questions

• C It forwards data packets towards their destination (1)
• The only correct answer is C. The correct answer is forwards data packets towards their destination.
• A is not correct because a router does not add the destination IP address to each data packet, the sending device does
• B is not correct because a router does not check each data packet for errors, the receiving device does
• D is not correct because a router does not put data packets back into the correct order, the receiving device does

Award one mark for:

• WAN/Wide Area Network (1)

Allow wide area network, WAN network, and minor spelling errors where the meaning is clear, e.g. 'wide area netowrk'.

Do not accept LAN/local area network.

Do not accept a description such as 'covers a large area' without naming WAN.

Do not accept 'the internet' or 'world wide web'.

Award one mark for:

• Internet (layer) (1)

Accept IP layer / Internet Protocol layer.

Do not accept Network layer (this is the name used in the OSI model, not the TCP/IP model).

Do not accept Transport layer, Application layer or Link layer.

Award one mark for any of the following up to a maximum of two marks:

• A unique identifier/number (1)
• Given to a device on a network/the internet (1)
• Used to send/receive/route data (to the correct destination) (1)

Allow computer/laptop/phone/printer etc. for device.

Do not accept a website address/domain name.

Do not accept MAC address (this is a hardware identifier set by the manufacturer, not an address given to a device for use on a network).

Do not accept 'an address'/'a location' on its own, without saying that it identifies a device on a network/the internet.

Award one mark for any of the following up to a maximum of two marks:

• The size of the file / amount of data to be transmitted (1)
• The file size in bits/bytes/MB/GB (1)
• The transmission rate / speed of the network (1)
• The bit rate / number of bits per second (1)
• The network speed / connection speed (1)

Award a maximum of one mark for the file size/amount of data and a maximum of one mark for the transmission rate/speed/bit rate.

Do not accept bandwidth on its own.

Do not accept the time taken, as this is what is being calculated.

Do not accept latency (it is a delay, not a transmission rate).

Do not accept a conversion factor such as 8 bits per byte as one of the two pieces.

Award one mark for any of the following up to a maximum of two marks:

• A set of rules/standards (1)
• Agreed by devices/computers (1)
• For how data is transmitted/sent (1)
• Between devices/computers (on a network) (1)
• So that devices can interpret/understand each other's data (1)

Allow 'communication' only where the candidate makes clear that data is being sent or exchanged, e.g. 'rules for the communication of data'.

Do not accept 'a set of rules for communication' on its own, with no reference to data being transmitted/sent.

Do not accept a program/software/device, e.g. 'software that connects devices to a network'.

Do not accept 'a set of instructions' or 'a method of connecting devices to a network'.

Award one mark for any of the following up to a maximum of two marks:

• It is a 32-bit number/address (1)
• It is made up of four 8-bit numbers/bytes/octets (1)
• Each of the four parts is a number in the range 0 to 255 (1)
• The four parts are separated by dots/full stops (1)

Award a maximum of one mark for describing the four parts, whether they are described as 8-bit numbers/bytes/octets or as numbers in the range 0 to 255.

Do not accept 'it has four numbers' on its own, with no reference to 8 bits/bytes/octets or to the range 0 to 255.

Do not accept 'decimal point', 'separated by commas', 'separated by colons' or 'a 32-digit number'.

Do not accept responses that describe IPv6 (128-bit/hexadecimal) addresses.

Award up to two marks for a linked description such as:

• Each device/node is connected to more than one other device (1) so there is another route for the data to take (1)
• Data can be sent along a different path (1) to bypass the failed connection (1)
• There is no central device/switch to fail (1) so data can still be passed between the remaining devices (1)

Allow 'sensor' or 'node' for device.

Do not accept 'the failed connection repairs itself' or 'the data is stored until the connection works again'.

Do not accept responses that say a central switch sends the data by another route, as a mesh has no central device.

Do not award generic statements such as 'a mesh is reliable/resilient' without a description of how the data still reaches its destination.

Do not award descriptions of a bus or star network failing.

Accept a reference to a device failing only where the candidate also states that other connections/routes remain available.

Award up to two marks for a linked description such as:

• (Ethernet) cables are not affected by interference from other devices (1) so data is transferred at a consistent/steady speed (1)
• Each device has its own cable to the switch (1) so the full bandwidth is available to that device and speeds do not drop as more users join (1)
• Fibre optic cable has a higher bandwidth than a wireless link (1) so more data can be sent along the cable each second (1)
• The cable gives a direct/physical path to the switch (1) so data is less likely to be lost and resent, which would slow the transfer (1)

Do not accept responses about security, reliability or users being unable to move around, as these are not about speed.

Do not accept answers that only say a wired/cable connection is faster, or that fibre is faster, without saying why.

Award up to two marks for a linked explanation such as:

• Wireless signals can be blocked or absorbed by walls (1) so the data must be re-sent, which adds delay (1)
• A device further from the access point has a weaker signal (1) so data must be re-sent/transmitted at a lower rate, adding delay (1)
• Devices on a wireless network share a channel (1) so a device must wait its turn to transmit, which adds delay (1)
• Interference from other devices affects the radio signal (1) so data must be re-sent, adding delay (1)

For both marks, the expansion must follow/associate with the statement.

Allow 'waiting to send' or 'collisions' as the delay caused by devices sharing a channel.

Do not accept 'wireless is slower than wired' on its own, as this repeats the question.

Do not accept a reason that only affects download speed/bandwidth (e.g. 'files take longer to download') without a link to delay.