L26. Describe the source and effect of queueing, propagation, and transmission delays Flashcards
What is a delay?
Something that causes a packet to arrive slower
When does queueing delay happen?
Queuing delay arises when packets arrive at a router or switch faster than they can be processed and forwarded. This situation typically occurs during network congestion when multiple packets compete for the same output interface, causing packets to wait in a queue until the interface becomes available.
What are the effects of queueing delay?
- Increased latency. As packets wait in the queue, their overall transmission time increases.
- Jitter. High queuing delays can lead to jitter, which is the variability in packet arrival times
- Packet loss may occur if the queue becomes full, necessitating retransmissions and further compounding the delay.
What kinds of applications are most affected by jitter?
Real-time applications such as VoIP (Voice over IP), online gaming, and video conferencing where timely packet delivery is important.
What is propagation delay?
Propagation delay is the time it takes for a signal to travel from the sender to the receiver through the transmission medium, such as copper wires, optical fibers, or air.
What determines propagation delay?
The distance between the sender and receiver and the propagation speed of the signal in the medium.
What are the effects of propagation delay?
Propagation delay contributes to the total latency in the communication path. In real-time applications, excessive propagation delay can lead to noticeable lag, affecting synchronization and the overall user experience.
What kind of communication is most vulnerable to propagation delay?
Propagation delay becomes significant for long-distance communications, such as transcontinental or satellite links. For example, a signal traveling 1,000 kilometers through optical fiber experiences a propagation delay of about 5 milliseconds.
What is transmission delay?
Transmission delay is the time required to push all of a packet’s bits onto the transmission medium.
What determines transmission delay?
Transmission delay depends on the packet’s size and the transmission rate (bandwidth) of the link.
How is transmission delay calculated?
By dividing the packet size by the transmission rate. For instance, transmitting a 1,500-byte packet over a 1 Mbps link takes 12 milliseconds.
What are the effects of transmission delay?
Transmission delay impacts how quickly packets can be sent onto the network. Transmission delay is particularly critical in data-intensive applications or networks with limited bandwidth, where large packets can take substantial time to be transmitted, causing delays in data delivery.
What kind of communication is most vulnerable to transmission delay?
On high-bandwidth links, transmission delay is minimal, but on lower-bandwidth connections or with large packets, it can become significant.
How can transmission delay be mitigated?
Reducing packet sizes or increasing link bandwidth
Do queueing, propagation, and transmission affect each other?
Yes, all three types of delays cumulatively contribute to the total end-to-end delay experienced by data packets. To optimize network performance, it is essential to manage each type of delay.
