1.1.e (iii) Latency

This is a section you will find very similar on a lot of blogs, including this one. I cannot summarize these better than my 3 sources did. The content in the book and other sections of the internet is not as good for this piece.

I recommend you create your own notes and flash cards regarding these terms.

What is latency? Latency is the time between sending a packet and it arriving at the intended target.

Types of latency in the network:

Propagation Delay – The hardest, and most mentioned latency. Propogation delay is the time it takes for the electrical signals to go from one end of the cable to the other (or even to the destination(total distance)). This type of latency is felt hardest when going through transcontinental cabling because of the sheer distance the signals travel. (We do not include the serialization in this, even though those signals do indeed get regenerated)
Serialization Delay – This is the time it takes to pull or put bits on or off of the wire. The more bandwidth a link has, the more bits it can serialize on the wire at the same time.
Data Protocol Delay – This is mostly referring to upper layer protocols setting up connections or verify checksums (TCP 3 way handshake, IP header checksum , ethernet FCS)
Routing and Switching – This is the time the router or the switch takes to do L3 or L2 lookups, attach new headers.
Queuing and buffer = This is the time a packet spends in the input or output queue of a router/switch. If there is a FIFO queue with no congestion, once the whole packet comes in (store and forward) it will be sent out.
However if we have any congestion on the link, then our input or output queues being and our queueing mechanisms may move packets around in memory either adding or decreasing their latency.