On Fri, 9 Oct 2015, Joe Touch wrote:
On 10/9/2015 7:14 PM, David Lang wrote:
The problem with proposals like that is just like RFC3449 says, the
source can't know what the network looks like to decide if there is a
benefit to reducing ACKs.
To understand your position, is your conclusion that if it benefits a
single place in the network, then that's enough of a view to know that
it's safe and beneficial throughout the network?
No.
But when something shows clear beneifts when deployed, clear problems need to be
identified to counter those benefits, or alturnative methods of solveing the
problem need to be shown.
I didn't know about it initially (I was working from experience and logic),
RFC3449 has explored many of the problems that cause and result from fewer than
1 ACK per 2 data packets, including worrying about the timing of the ACK
packets.
As much as you seem to want to make this discussion about cable modems and
highly assymetric links, this discussiona ctually started from the position of
packets in a particular flow being sent in bursts due to non-endpoint related
reasons. It started with AQM queues, but radio networks (Wifi and Cell) have
similar behavior (packets queue until a transmit window is available, tehn a
bunch are sent at once)
Cable modems were introduced to the discussion to counter the thought that
sending fewer ACKs would destroy the Intenet.
RFC3449 doesn't completely address the current situation, but it provides a very
good place to start, and it seems to me that the solitions it explores to
address the conerns that it (and you) raise are actually being addressed pretty
completely. There are still some areas to talk about (ECN interaction for
example) and we wshould be talking about those issues rather than arguing that
the proposal violates holy writ.
you want a network where packets are just forwarded with no modification and no
delays. Unfortunantly such a network does not match the real world any longer
(and it only approximated the real world in the first place) Shared media
networks have existed since the earliest networking days. What is changing is
theratio between the data speed when transmittingand the time available to
transmit. Given the same number of stations in an area, I'll bet that old
thinnet ethernet at 10Mb/s spent a significantly higher percentage of the time
transmitting data than current Gb/s and immediate future 10Gb/s wireless
networks. Just like wired network speeds are climbing with the MTU staying the
ame, wireless network data rates are climbing but the time available for a given
station is remaining the same (or shrinking), so the number of packets that get
delayed until the next transmit slot are only going to keep climbing, no matter
what anyone wants.
The asymmetrical nature of the networks is just addng insult to injury, not the
cause of the issues.
Wireless networks are gaining the ability to transmit to multiple stations at
once. But the nature of usage patterns and the physical geometry of the wired vs
mobile ends of the link make the reality that only the wired end can effectively
make use of this capability. this makes the availble downstream bandwidth on a
network fabric grow much faster than the available upstream bandwidth. To some
extent this will put less stress on the upstream side of the wired network it's
attached to, but it will mean that the demand for mobile station transmit slots
is only going to multiply. Just reducing the number of timeslots the base
station uses isn't the answer because that will add latency to all the data
downloads.
IIRC, I saw a story today where one of the contenders for 5G cell networks is
already at a ratio of 24:1 or worse.
David Lang
_______________________________________________
aqm mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/aqm
