On 06/12/2015 03:44 AM, David Lang wrote:
On Thu, 11 Jun 2015, Sebastian Moeller wrote:
On Jun 11, 2015, at 03:05 , Alan Jenkins
<alan.christopher.jenk...@gmail.com> wrote:
On 10/06/15 21:54, Sebastian Moeller wrote:
One solution would be if ISPs made sure upload is 100% provisioned.
Could be cheaper than for (the higher rate) download.
Not going to happen, in my opinion, as economically unfeasible
for a publicly traded ISP. I would settle for that approach as long
as the ISP is willing to fix its provisioning so that
oversubscription episodes are reasonable rare, though.
not going to happen on any network, publicly traded or not.
The question is not "can the theoretical max of all downstream devices
exceed the upstream bandwidth" because that answer is going to be
"yes" for every network built, LAN or WAN, but rather "does the demand
in practice of the combined downstream devices exceed the upstream
bandwidth for long enough to be a problem"
it's not even a matter of what percentage are they oversubscribed.
someone with 100 1.5Mb DSL lines downstream and a 50Mb upstream (30%
of theoretical requirements) is probably a lot worse than someone with
100 1G lines downstream and a 10G upstream (10% of theoretical
requirements) because it's far less likely that the users of the 1G
lines are actually going to saturate them (let alone simultaniously
for a noticable timeframe), while it's very likely that the users of
the 1.5M DSL lines are going to saturate their lines for extended
timeframes.
The problem shows up when either usage changes rapidly, or the network
operator is not keeping up with required upgrades as gradual usage
changes happen (including when they are prevented from upgrading
because a peer won't cooperate)
Good points. Let me add a side comment though.
We observe that fiber users (e.g. 1Gbps/300Mbps access with GPON) are
changing behavior
w.r.t. DSL users in the way they use the uplink. This is mostly (not
only) due to personal cloud storage availability
and the fact that everyone today is able to produce tons of big videos,
that people are willing to store
outside the home.
As a result it's not unlikely that a backhaul link utilization may get
out of the network planning, which is made
on long term statistics. These workloads are unpredictable and if on one
hand it's not feasible to
over provision based on such unpredictable long peeks on the other hand
you'd need smart queue
management to cope with such events, where the bottleneck is the backhaul.
Considering the cost of current equipment upgrades, I feel like very
high speed accesses will impose
smart queue management everywhere from the access up to transit links,
including the entire backhaul.
Bad news is that no such queuing systems are available in current
equipment, so I guess the process
will be pretty slow to happen.
As for the "100% provisioning" ideal, think through the theoretical
aggregate and realize that before you get past very many layers, you
get to a bandwidh requirement that it's not technically possible to
provide.
David Lang
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