57. Packet switching and routers Flashcards
explain packet switching.
a method of communicating packets of data across a network on which other similar communications are happening simultaneously.
data is sent and received as a series of packets.
Explain the purpose of data packets.
In order to transmit data across a network it is broken down into more manageable chunks called data packets
What components must be included in a data packet and which ones are optional?
MUST
header, payload (data)
OPTIONAL
trailer section including a checksum e.g. allows for error detection
what would the header in a data packet include?
The sender and recipient’s IP address
Protocol to be used with the type of packet
Number of packets in packet sequence and which one it is
Time To Live (TTL or hop limit)
what is the purpose of a TTL/hop limit when sending data packets?
number of hops or time allowed before a data packet expires and must be discarded.
what happens upon receival of data packets?
packets are reassembled in the correct order and the data is extracted
How are packets routed across the internet. explain the process
after a packet leaves the sender’s computer, the fastest or least congested route is taken to the recipients computer and the packet travels across several routers through a series of ‘hops’
They can then be reassembled in the correct order at the receiving end and any packets that don’t make it can be requested again.
when is a router used and when is a gateway used to route packets across the internet?
if the networks share the same protocols e.g. TCP/IP a router can be used
when protocols differ across networks a gateway is used rather than a router to translate them
how does a gateway route packets across the internet?
all header data is stripped from the packet leaving only the raw data and new header data is added in the format of the new network before the gateway sends the packet on its way again.
