Re: Lossy cogent p2p experiences?

[Saku Ytti <saku () ytti fi>]

On Wed, 6 Sept 2023 at 10:27, Mark Tinka <mark@tinka.africa> wrote:

> I recognize what happens in the real world, not in the lab or text books.

Fun fact about the real world, devices do not internally guarantee
order. That is, even if you have identical latency links, 0
congestion, order is not guaranteed between packet1 coming from
interfaceI1 and packet2 coming from interfaceI2, which packet first
goes to interfaceE1 is unspecified.
This is because packets inside lookup engine can be sprayed to
multiple lookup engines, and order is lost even for packets coming
from interface1 exclusively, however after the lookup the order is
restored for _flow_, it is not restored between flows, so packets
coming from interface1 with random ports won't be same order going out
from interface2.

So order is only restored inside a single lookup complex (interfaces
are not guaranteed to be in the same complex) and only for actual
flows.

It is designed this way, because no one runs networks which rely on
order outside these parameters, and no one even knows their kit works
like this, because they don't have to.



-- 
  ++ytti