What is difference of --prepend-mm-cmds and --append-mm-cmds ?

[人ー]

I run the Test.py  with the command shown below.

"python test_flows.py local  -s cubic  --data-dir data_preped --prepend-mm-cmds "mm-delay 50" --extra-mm-link-args "--uplink-queue=droptail --uplink-queue-args=packets=100""

"python test_flows.py local  -s cubic  --data-dir data_append --append-mm-cmds "mm-delay 50" --extra-mm-link-args "--uplink-queue=droptail --uplink-queue-args=packets=100""

When I run it, I got similar throughput and delay time results.

So what's the difference between --prepend-mm-cmds and  --append-mm-cmds ?

[人ー]

There was a mistake in the command described.

The modified command is shown below.

"python test.py local  -s cubic  --data-dir data_preped --prepend-mm-cmds "mm-delay 50" --extra-mm-link-args "--uplink-queue=droptail --uplink-queue-args=packets=100""

"python test.py local  -s cubic  --data-dir data_append --append-mm-cmds "mm-delay 50" --extra-mm-link-args "--uplink-queue=droptail --uplink-queue-args=packets=100""

Thank you

2020年12月10日木曜日 0:16:38 UTC+9 ー 人:

[Keith Winstein]

Hello -- this is all about constructing a sequence of mahimahi link emulators. Each emulator applies some modeled link effect, e.g. a "delay" or a "loss" or an "onoff" (burst loss) a bottleneck "link" that drains some queue ahead of it.

Sometimes the order matters: for example, it matters a lot whether a "loss" comes before or after a "link". (Because it matters whether a packet is lost before or after it consumes the precious resource of the link capacity.) However, it doesn't matter whether a "delay" comes before or after a link. There's no way to tell whether a packet's propagation delay occurred closer to the sender-side or receiver-side of a queue and link. Therefore, it doesn't really matter whether you "prepend" or "append" the delay emulator to the "link" emulator.

Hope this is helpful!

Best regards,

Keith

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