When sending a packet from a source to a destination host over a fixed route, the end$-$to$-$end delay consists of four main components: processing, queuing, transmission, and propagation delays. Among these, transmission and propagation delays are generally constant, depending on packet size, link bandwidth, and physical distance respectively. In contrast, processing and queuing delays are variable, with queuing delay being particularly susceptible to network congestion. These delay components collectively determine the overall time a packet takes to reach its destination.