网络软件与性能

Software all the way down

Bandwidth and latency

The pipe and its volume

What applications ask, and what changed

The socket interface separates two concerns. Which statement captures the separation correctly?

A 1500 byte packet crosses a 4000 kilometer fiber link at 10 gigabits per second, with no queueing and light in fiber at $2.0 \times 10^{8}$ meters per second. Which component dominates the one-way latency?

What does the delay-bandwidth product of a channel tell a protocol designer?

A 1 megabyte file crosses a path with a 100 millisecond RTT. Why does upgrading from 1 megabit per second to 1 gigabit per second change the transfer so dramatically while the RTT is unchanged?

A user fetches a 1 megabyte file over a 1 gigabit per second link with a 100 millisecond RTT, and the transfer time is RTT plus size over bandwidth. What effective throughput results?

Why is a video application's average bandwidth need alone insufficient for engineering the network?

What is the name of the network programming interface, born with Berkeley Unix and now supported on virtually every operating system, whose central abstraction is the point where a process attaches to the network?

The product of delay and bandwidth is the volume of the pipe. For a channel with 50 milliseconds of one-way latency and 45 megabits per second of bandwidth, how many bits can be in flight at once? Answer as a whole number of bits.

Latency decomposes into propagation delay and transmission delay, plus a third component caused by packets waiting in switch memories under statistical multiplexing. Name it.

For a request-response transfer, the total time is the round-trip time plus the data size divided by what link property?