On Tue, 28 Apr 2015, John Leslie wrote:
Mikael Abrahamsson <swm...@swm.pp.se> wrote:
Also, I actually still don't understand the concept of "developing
congestion". For me "congestion" means there is a sustained, constant,
non-trivial buffer fill. So "incipient congestion" doesn't compute at all.
I understand this term has been used before, but that doesn't help me
understand the reasoning behind the wording. For me sending a congestion
signal, means saying there is congestion. It's not saying there is
developing congestion (whatever that might be).
I agree that "developing congestion" doesn't convey the same meaning
to all readers.
When I suggested we use "incipient congestion", I was thinking of
the queueing-theory definition.
I would greatly appreciate if someone could point me to text explaining
this so I can better understand the reasoning behind this wording.
I recommend my slides from IETF-77:
https://www.ietf.org/proceedings/77/slides/iccrg-7.pdf
starting with slide 11; and the Bauer_Clark_Lehr_2009 paper it refers
to (Section 3 of that paper).
This link is no longer valid, but I found the paper.
Briefly, the Queuing Theory definition is the most useful for
control-loop purposes:
"
" congestion is said to occur if the arrival rate into a system exceeds
" the service rate of the system at a point in time.
This is what I meant "incipient" congestion to mean.
Ok, I think I understand the reasoning behind it. Now you and the other
authors need to decide if you want these documents to be read and
understood by people like me for instance, who works at service providers
or other networking professions who are not heavy inty queueing theory but
instead are just trying to get their gear to do the right thing. I have
studied english from grade 4 to grade 11, and I was best in my class in
english. I had never even heard the word "incipient" before 2 days ago,
and even now I am not sure I understand the full meaning trying to be
conveyed.
Are people like me the target of these documents? If then, I recommend you
try to simplify the terminology in these documents, striking "incipient"
would be a first step, or at least try to explain them in the document, or
point to a document that does.
If I for instance read RFC2884 is has 3 mentions of "incipient congestion"
but 95 mentions of "congestion". Am I to understand that these 3 mentions
of "incipient" means that the congestion that is "incipient" is different
from the mentions of just "congestion" without "incipient" before it?
Because that subtle difference is completely lost to me and if I were to
guess, completely just deleting the 3 mentions of "incipient" from RFC2884
wouldn't change the document at all. Am I wrong here?
For instance here:
"Jacobson [14] proposed gateways to monitor the average queue size to
detect incipient congestion, and to randomly drop packets when congestion
is detected."
I just don't understand the difference between the first mention of
"incipient congestion" and then the second mention where "incipient" is
not used. What am I missing here?
(NB it _does_ make sense to talk of "incipient congestion" persisting
for a longer period of time, believe it or not!)
If a queue has a buffer fill of between 40 and 60 ms worth of packets over
60 seconds, is this link congested or is it experiencing a prolonged
period of "incipient congestion"? Is the "incipience" (I don't even know
if that is the correct term) just when the buffer fill time is increasing
(for instance from 45 to 55 ms) and not when it's decreasing from 55 to 45
ms, or is it just "incipient congestion" for the entire duration of the
buffer having a constant non-trivial amount of packets in it?
--
Mikael Abrahamsson email: swm...@swm.pp.se
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