[Bloat] [Cerowrt-devel] DOCSIS 3+ recommendation?

Sebastian Moeller moeller0 at gmx.de
Fri Mar 20 06:07:19 EDT 2015

Hi All,

I guess I have nothing to say that most of you don’t know already, but...

On Mar 20, 2015, at 00:18 , Greg White <g.white at CableLabs.com> wrote:

> Netalyzr is great for network geeks, hardly consumer-friendly, and even so
> the "network buffer measurements" part is buried in 150 other statistics.

	The bigger issue with netalyzr is that it is a worst case probe with an unrelenting UDP “flood” that does not measure the “responsiveness/latency” of unrelated flows concurrently. In all fairness it not even tests the worst case as it floods up- and downlink sequentially and it seems to use the same port for all packets. This kind of traffic is well suited to measure the worst case buffering for misbehaving ((D)DOS) flows, not necessarily the amount of effective buffering well behaved flows encounter.
	And then the help text related to “network buffer measurements” section in the results report seems to be actually misleading in that the used DOS traffic is assumed to be representative of normal traffic (also it does not allow for AQMs that manage normal responsive traffic better).
	It would be so sweet, if they could also measure the ICMP RTT (or another type of timestamped tcp or udp flow) to say a well connected CDN concurrently to give a first approximation about the effect of link saturation on other competing flows; and then report the amount of change in that number caused by link saturation as the actual indicator of effective buffering...

> Why couldn't Ookla* add a simultaneous "ping" test to their throughput
> test?  When was the last time someone leaned on them?
> *I realize not everyone likes the Ookla tool, but it is popular and about
> as "sexy" as you are going to get with a network performance tool.

	I think you are right; instead of trying to get better tools out we might have a better chance of getting small modifications into existing tools.

Best Regards

> -Greg
> On 3/19/15, 2:29 PM, "dpreed at reed.com" <dpreed at reed.com> wrote:
>> I do think engineers operating networks get it, and that Comcast's
>> engineers really get it, as I clarified in my followup note.
>> The issue is indeed prioritization of investment, engineering resources
>> and management attention. The teams at Comcast in the engineering side
>> have been the leaders in "bufferbloat minimizing" work, and I think they
>> should get more recognition for that.
>> I disagree a little bit about not having a test that shows the issue, and
>> the value the test would have in demonstrating the issue to users.
>> Netalyzer has been doing an amazing job on this since before the
>> bufferbloat term was invented. Every time I've talked about this issue
>> I've suggested running Netalyzer, so I have a personal set of comments
>> from people all over the world who run Netalyzer on their home networks,
>> on hotel networks, etc.
>> When I have brought up these measurements from Netalyzr (which are not
>> aimed at showing the problem as users experience) I observe an
>> interesting reaction from many industry insiders:  the results are not
>> "sexy enough for stupid users" and also "no one will care".
>> I think the reaction characterizes the problem correctly - but the second
>> part is the most serious objection.  People don't need a measurement
>> tool, they need to know that this is why their home network sucks
>> sometimes.
>> On Thursday, March 19, 2015 3:58pm, "Livingood, Jason"
>> <Jason_Livingood at cable.comcast.com> said:
>>> On 3/19/15, 1:11 PM, "Dave Taht" <dave.taht at gmail.com> wrote:
>>>> On Thu, Mar 19, 2015 at 6:53 AM,  <dpreed at reed.com> wrote:
>>>>> How many years has it been since Comcast said they were going to fix
>>>>> bufferbloat in their network within a year?
>>> I¹m not sure anyone ever said it¹d take a year. If someone did (even if
>>> it
>>> was me) then it was in the days when the problem appeared less
>>> complicated
>>> than it is and I apologize for that. Let¹s face it - the problem is
>>> complex and the software that has to be fixed is everywhere. As I said
>>> about IPv6: if it were easy, it¹d be done by now. ;-)
>>>>> It's almost as if the cable companies don't want OTT video or
>>>>> simultaneous FTP and interactive gaming to work. Of course not. They'd
>>>>> never do that.
>>> Sorry, but that seems a bit unfair. It flies in the face of what we have
>>> done and are doing. We¹ve underwritten some of Dave¹s work, we got
>>> CableLabs to underwrite AQM work, and I personally pushed like heck to
>>> get
>>> AQM built into the default D3.1 spec (had CTO-level awareness & support,
>>> and was due to Greg White¹s work at CableLabs). We are starting to field
>>> test D3.1 gear now, by the way. We made some bad bets too, such as
>>> trying
>>> to underwrite an OpenWRT-related program with ISC, but not every tactic
>>> will always be a winner.
>>> As for existing D3.0 gear, it¹s not for lack of trying. Has any DOCSIS
>>> network of any scale in the world solved it? If so, I have something to
>>> use to learn from and apply here at Comcast - and I¹d **love** an
>>> introduction to someone who has so I can get this info.
>>> But usually there are rational explanations for why something is still
>>> not
>>> done. One of them is that the at-scale operational issues are more
>>> complicated that some people realize. And there is always a case of
>>> prioritization - meaning things like running out of IPv4 addresses and
>>> not
>>> having service trump more subtle things like buffer bloat (and the
>>> effort
>>> to get vendors to support v6 has been tremendous).
>>>> I do understand there are strong forces against us, especially in the
>>>> USA.
>>> I¹m not sure there are any forces against this issue. It¹s more a
>>> question
>>> of awareness - it is not apparent it is more urgent than other work in
>>> everyone¹s backlog. For example, the number of ISP customers even aware
>>> of
>>> buffer bloat is probably 0.001%; if customers aren¹t asking for it, the
>>> product managers have a tough time arguing to prioritize buffer bloat
>>> work
>>> over new feature X or Y.
>>> One suggestion I have made to increase awareness is that there be a
>>> nice,
>>> web-based, consumer-friendly latency under load / bloat test that you
>>> could get people to run as they do speed tests today. (If someone thinks
>>> they can actually deliver this, I will try to fund it - ping me
>>> off-list.)
>>> I also think a better job can be done explaining buffer bloat - it¹s
>>> hard
>>> to make an Œelevator pitch¹ about it.
>>> It reminds me a bit of IPv6 several years ago. Rather than saying in
>>> essence Œyou operators are dummies¹ for not already fixing this, maybe
>>> assume the engineers all Œget it¹ and what to do it. Because we really
>>> do
>>> get it and want to do something about it. Then ask those operators what
>>> they need to convince their leadership and their suppliers and product
>>> managers and whomever else that it needs to be resourced more
>>> effectively
>>> (see above for example).
>>> We¹re at least part of the way there in DOCSIS networks. It is in D3.1
>>> by
>>> default, and we¹re starting trials now. And probably within 18-24 months
>>> we won¹t buy any DOCSIS CPE that is not 3.1.
>>> The question for me is how and when to address it in DOCSIS 3.0.
>>> - Jason
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