7.2.11 Understand the role of data packets in transmitting over a network Flashcards
Fill The Blank:
Data that is sent over a network (including the internet) is referred to as ……………….. where large ……………. of data re broken down into smaller …………………
Packets, Packets, Datagrams
Fill The Blank:
Once datagrams reach their final destination they are ……………….. as a single file or block of ……………………… data
Reassembled, Contiguous
State:
3 parts of a data packet
- Header
- Payload
- Trailer
Explain:
The header in a datapacket
Contains instructions about the data with several parts:
State:
The 9 parts of the header of a data packet
- Originating address - IP address of sender
- Destination address - IP Of receiver
- Internet protocol - Defining type of packet being transmitted
- Size of header and payload
- Number of hops - Number of routers that the packet will pass through on its journey
- Time to Live (TTL) - Amount of time it exists within the network before being discarded by the router
- Flags - Used to inform the router whether the packet can be divided into datagrams
- Checksum - Used to detect any errors during transmission
- Packet number - Number of the packet where there is a sequence of packets
Define:
Contiguous Data
Data that is stored in a collection of adjacent locations
Define:
Time To Live (TTL)
Amount of time or ‘hops’ that a packet is set to exist inside a network before being discarded by the router - TTL is also used in CDNs caching and DNS caching
Define:
Hops
Refers to number of routers that a packet passes through from its source to its destination. A hop can also be counted when a packet passes through other hardware on a network such as switches, access points and repeeaters - it is dependent on what role the devices have on the network and their configuration
Explain:
The payload of a datapacket
This is the body of the data packet and contains the actual data that is being sent/received
Explain:
The Trailer of a datapacket
- Sometimes called footer
- used to inform the receiving device that it is the end of the packet
Expain:
What error checking is often done in the trailer/footer of a datapacket
- Cyclic Redundancy Check (CRC)
- Will add up all 1s in the payload and stores the results as a hexadecimal
- Upon receiving the packet the device will add up the number of 1s in the payload and compare it with the hexadecimal value stored in trailer
- When these values match it confirms there was no errors during transmission and if not the receiving devices sends a request to the sender for them to resend the packet
Explain:
Packet Switching
Where the data packet is divided into smaller data packets and trasmitted individually across the network as opposed to transmitting one large data packet.
Explain:
Why packet switching is done
- Used to reduce the chances of lost packets
- Facilitates the resending of data packets
- Reduces transmission latency
Fill The Blank:
With packet switching, packets are not necessarily ………….. along the same path within the network which means packets arrive at the destination in no particular ………….. and the destination must ……………………… the packets into an appropriate order to be able to retrieve the original message
Routed, Order, Reconstruct
Fill The Blank:
The TCP/IP model has 4 layers whereas the OSI model has … layers
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