Computer Networks: Performance Assessment, Transmission Delay, and Queuing Delay

Practice flashcards covering packet transmission principles, pipelined transmission formulas, store-and-forward networks, transmission delay, and queuing delay.

In computer networking, what is a packet?

A collection of bits in transit over the network, representing the logical view of data transmission.

What is the store and forward model of communication in computer networks?

A communication model where packets are received and stored in a buffer at each intermediate hop (such as a router) before being pushed onto the next link.

How is transmission delay defined?

The time taken to read a packet from memory or buffer and push all of its bits onto the link.

What is the mathematical expression for the transmission delay of a packet of size $L$ bits over a link with capacity $R$ bits per second?

$$\frac{L}{R}$$

What is the total transmission time for a single packet of size $L$ bits sent from a client to a server through one intermediate router across two links, each having capacity $R$?

$$2 \times \frac{L}{R}$$

What is pipelined transmission?

A transmission mechanism where subsequent packets start being transmitted before previously transmitted packets have reached the destination.

Using pipelined transmission, what is the total transmission time to send 3 packets of size $L$ bits from a client to a server across two links of uniform capacity $R$?

$$4 \times \frac{L}{R}$$

What is the total transmission time to send a single packet of size $L$ bits over $N$ links, each with capacity $R$ bits per second?

$$N \times \frac{L}{R}$$

What is the generalized formula for the total transmission time of $P$ packets over $N$ uniform links of capacity $R$ bits per second with packet size $L$ bits using pipelining?

$$(N + P - 1) \times \frac{L}{R}$$

What is the total transmission delay for a single packet of size $L$ bits traversing two non-uniform links with capacities $R_1$ and $R_2$?

$$\frac{L}{R_1} + \frac{L}{R_2}$$

How is queuing delay defined?

The amount of time a packet spends waiting inside the queue (buffer) of a router before being scheduled for transmission.

What causes packet loss (packet drop) at a router?

A packet arriving at a router when the router's queue or buffer is completely full, leaving no space to store it.

In practical router architectures, what two distinct queues contribute to the overall queuing delay?

An input queue located at the input link and an output queue located at the output link.

How is the total queuing delay encountered at a single router calculated in practice?

It is the sum of the delay the packet spends in the input queue plus the delay it spends in the output queue.

What is the core distinction between transmission delay and queuing delay?

Transmission delay depends on the packet length and link capacity as bits are pushed onto the medium, whereas queuing delay arises from packets waiting in router buffers due to multiplexed transmissions.