[Bloat] Detecting bufferbloat from outside a node

[Toke Høiland-Jørgensen]

Paolo Valente <paolo.valente at unimore.it> writes:

> I am sorry, but I realized that what I said was incomplete. The main
> cause of my concern is that, from outside the node, we do not know
> whether a VoIP packet departs ad a given time because the application
> wants it to be sent at that time or because it has waited in the
> buffer for a lot of time. Similarly, we do not know how long the VoIP
> application will wait before getting its incoming packets delivered.

No, not unless the application tells you (by, for instance,
timestamping; depending on where in the network stack the timestamp is
applied, you can measure different instances of bloat). Or if you know
that an application is supposed to answer you immediately (as is the
case with a regular 'ping'), you can measure if it does so even when
otherwise loaded.

Of course, you also might not measure anything, if the bottleneck is
elsewhere. But if you can control the conditions well enough, you can
probably avoid this; just be aware of it. In Linux, combating
bufferbloat has been quite the game of whack-a-mole over the last
several years :)

-Toke