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AVonGauss
Premium
join:2007-11-01
Boynton Beach, FL
reply to fuziwuzi

Re: Here we go again about bandwidth throttling ...

You've posted your interpretation, not the details of your actual experiences or observations. Without any of the details behind the interpretation, in my opinion, it is useless. Many of the readers here are technical by profession and/or disposition, I don't know that we really need a lot of analogies, what would seem to be more helpful and useful are the details and facts.



sortofageek
Runs from Clowns
Premium,Mod
join:2001-08-19
kudos:21

said by AVonGauss:

You've posted your interpretation, not the details of your actual experiences or observations. Without any of the details behind the interpretation, in my opinion, it is useless. Many of the readers here are technical by profession and/or disposition, I don't know that we really need a lot of analogies, what would seem to be more helpful and useful are the details and facts.
I think this is an excellent suggestion. We have read this discussion repeatedly throughout the life of this topic and, even in this subtopic, we have each heard enough to be able to make up our own minds on our choice of interpretation. I don't see any value in a back and forth of "I think it is throttling" and "No, it isn't" without a reasoned basis containing facts, particularly reasoning we haven't yet heard.

If someone feels the need to post, please let it be a post which contains the details and facts suggested instead of the same tired differences in opinion of which we grew weary long ago.
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funchords
Hello
Premium,MVM
join:2001-03-11
Yarmouth Port, MA
kudos:6

1 edit

Part of the problem is that Comcast's method is a bit unique: All of the heavy user's traffic on a heavily utilized node is de-prioritized from best-effort to scavenger class for 15-minute terms.

You have to thrash the definition of throttling pretty badly to call Comcast's method, "throttling." Throttling means that you limit or manage the flow. Comcast's method does neither. If I have one complaint about Comcast's method, it's that it doesn't provide any assured floor to the affected customers. For example, I think it would be a better system than present if the flow were managed to a minimum of 128 Kbps. However, since the system so rarely kicks in (the thresholds are high and the system kicks in less than 1% of the time for any user), it's hard to complain strongly about the lack of a bandwidth floor.

QoS is connotative of using prioritization, but QoS is also connotative of guarantees of service, discrimination between different applications, meeting some specific quality goal (latency/jitter/throughput/reduced error rates). What Comcast does is more like anti-QoS because it temporarily reduces the priority of the affected customers' traffic so that they only get access to only that bandwidth that is left over by the rest of the users.

It's not throttling. It's not QoS.

"Scavenger class'' (a genuine class of service currently in use, you should take no negative connotation) allows lower-priority users and applications to take advantage of unused network capacity. It works like this: If all the normal packets have cleared the queue, then any unexpired "scavenger class" packets may be routed and forwarded. Normally, all the users crossing a particular router share the capabilities and restrictions of that connection. With a "scavenger class," the normal packets are prioritized ahead of the scavenger packets. A "scavenger class" user can use up to his full subscribed speed, if enough bandwidth is left over by other users. However, a "scavenger class" user may also find that there is no bandwidth left over by other users and that all his packets get dropped. There are legitimate uses for "scavenger class." I'm not a big fan of Comcast's use of the idea (they get around calling it "scavenger class" by using terms like "priority best effort" over "best effort" but the functional result is exactly the same). However, Comcast is both judicious in its application and has disclosed it fairly well.
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JohnInSJ
Premium
join:2003-09-22
San Jose, CA

said by funchords:

QoS is connotative of using prioritization, but QoS is also connotative of guarantees of service, discrimination between different applications, meeting some specific quality goal (latency/jitter/throughput/reduced error rates).
The goal being: "always provide high availability to low-user customers." - These are the people paying the most money per bit, as it were. You want to keep those folks VERY happy. You care less about the folks that you are losing money on.

So yes, they want to maintain the Quality of Service for their cash cows.

It's QoS. You might not like how they define it, but it is.

Has anyone seen their speed drop below 128kbps during deprioritization? I've never actually experienced it myself.
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funchords
Hello
Premium,MVM
join:2001-03-11
Yarmouth Port, MA
kudos:6

said by JohnInSJ:

said by funchords:

QoS is connotative of using prioritization, but QoS is also connotative of guarantees of service, discrimination between different applications, meeting some specific quality goal (latency/jitter/throughput/reduced error rates).
The goal being: "always provide high availability to low-user customers." - These are the people paying the most money per bit, as it were. You want to keep those folks VERY happy. You care less about the folks that you are losing money on.

So yes, they want to maintain the Quality of Service for their cash cows.
No, that's not what I mean by "specific quality goal." It's also not what I mean by "different applications."

I mean measurable and specific goals, such as, "Fairchild DBMS latency to Alpine office maintained below 70 ms. with a 95% confidence during the peak hour, and an overall average of all samples under 18 ms." This might be one of a list of goals that mention other quality vectors such as speed or packet drops. QoS Rules are the network's instructions designed to accomplish those goals.

I understand your rationale because prioritization is a tool for achieving QoS goals and we tend to think of these in connected ways, but Comcast's method is pretty far from the way we should think about QoS.

Comcast's method is a kick toward the direction of user-vs-user fairness. It could be refined more (shorter windows, better-engineered floors with more weighted queue handling) and really be an option worth considering.
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Robb Topolski -= funchords.com =- District of Columbia -- KJ7RL
Test your Broadband connection today! -- »measurementlab.net/


espaeth
Digital Plumber
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join:2001-04-21
Minneapolis, MN
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said by funchords:

Comcast's method is a kick toward the direction of user-vs-user fairness. It could be refined more (shorter windows, better-engineered floors with more weighted queue handling) and really be an option worth considering.
It could be, but that's something even beyond the 80/20 rule in terms of effort to benefit. If there were such a thing as an 99.999/0.001 rule, this would be a quintessential case.