[NNagain] [M-Lab-Discuss] The FCC 2024 Section 706 Report, GN Docket No. 22-270 is out!

[Jack Haverty]

Hi Bob,

Measuring and monitoring Wifi behavior isn't necessary or sufficient.  
Same with Starlink or whatever else comes along in the future.

The architecture of the Internet places different mechanisms, that in 
past times were contained in the switching equipment, now at many 
different places along a data path.  Much of the mechanism is even in 
the users' devices themselves, which make all sorts of decisions about 
datagram size, acknowledgements, retransmission, discarding duplicates, 
et al.  Those mechanisms interact with the decisions being made in 
network equipment such as switches.   The overall behavior dictates what 
the end users see as behavior and reliability of "the net" as they 
experience it.   The performance of the overall system is influenced by 
the interaction of its many pieces.

My point was that to manage network service ("network" being defined by 
the users), you have to monitor and measure performance as seen by the 
users, as close to the keyboard/mouse/screen/whatever as you can get.  
That's why we decided to require a computer of some kind on each users' 
LAN environment, so we could experience and measure what they were 
likely experiencing, and use our measurements of switches, circuits, 
etc. to analyze and fix problems.   It was also helpful to have a 
database of the metrics captured during previous "normal" network 
activity, to use as comparisons.

As one example, I remember one event when a momentary glitch on a 
transpacific circuit would cause a flurry of activity as TCPs in the 
users' computers compensated, and would settle back to a steady state 
after a few minutes.  But users complained that their file transfers 
were now taking much longer than usual.  After our poking and prodding, 
using those remote computers as tools to see what the users were 
experiencing, we discovered that everything was operating as expected, 
except that every datagram was being transmitted twice and the 
duplicates discarded at the destination.   The TCP retransmission 
mechanisms had settled into a new stable state.

To the network switches, the datagrams all seeemed OK, but there was 
significantly more traffic than usual.  No one was monitoring all those 
user devices out on the LANs so no one except the users noticed anything 
wrong.   Eventually another glitch on the circuit would cause another 
flurry of activity and perhaps settle back into the desired state where 
datagrams only got sent once.

We monitored whatever we could using SNMP to the routers and computers 
that had implemented such things, and we used our remote computers to 
also collect data from the users' perspective.   Often we could tell a 
LAN manager that some particular deviceat his/her site was having 
problems, by looking for behavior that differed from the "normal" 
historical behavior from a week or so earlier.

It would be interesting for example to collect metrics from switches 
about "buffer occupancy" and "transit time" (I don't recall if any MIB 
in SNMP had such metrics), and correlate that with TCP metrics such as 
retransmission behavior and duplicate detection.

Jack



On 2/27/24 09:48, rjmcmahon wrote:
> Hi Jack,
>
> On LAN probes & monitors; I've been told that 90% of users devices are 
> now wirelessly connected so the concept of connecting to a common wave 
> guide to measure or observe user information & flow state isn't 
> viable. A WiFi AP could provide its end state but wireless channels' 
> states are non-trivial and the APs prioritize packet forwarding at L2 
> over state collection. I suspect a fully capable AP that could record 
> per quintuple and RF channels' states would be too expensive. This is 
> part of the reason why our industry and policy makers need to define 
> the key performance metrics well.
>
> Bob
>> Yes, latency is complicated....  Back when I was involved in the
>> early Internet (early 1980s), we knew that latency was an issue
>> requiring much further research, but we figured that meanwhile
>> problems could be avoided by keeping traffic loads well below capacity
>> while the appropriate algorithms could be discovered by the engineers
>> (I was one...).  Forty years later, it seems like it's still a
>> research topic.
>>
>> Years later in the 90s I was involved in operating an international
>> corporate intranet.  We quickly learned that keeping the human users
>> happy required looking at more than the routers and circuits between
>> them.  With much of the "reliability mechanisms" of TCP et al now
>> located in the users' computers rather than the network switches,
>> evaluating users' experience with "the net" required measurements from
>> the users' perspective.
>>
>> To do that, we created a policy whereby every LAN attached to the
>> long-haul backbone had to have a computer on that LAN to which we had
>> remote access.   That enabled us to perform "ping" tests and also
>> collect data about TCP behavior (duplicates, retransmissions, etc.)
>> using SNMP, etherwatch, et al.   It was not unusual for the users'
>> data to indicate that "the net", as they saw it, was misbehaving while
>> the network data, as seen by the operators, indicated that all the
>> routers and circuits were working just fine.
>>
>> If the government regulators want to keep the users happy, IMHO they
>> need to understand this.
>>
>> Jack Haverty
>>
>> On 2/26/24 16:25, rjmcmahon wrote:
>>
>>> On top of all that, the latency responses tend to be non parametric
>>> and may need full pdfs/cdfs along with non-parametric statistical
>>> process controls. Attached is an example from many years ago which
>>> was a firmware bug that sometimes delayed packet processing,
>>> creating a second node in the pdf.
>>>
>>> Engineers and their algorithms can be this way it seems.
>>>
>>> Bob
>>> I didn't study the whole report, but I didn't notice any metrics
>>> associated with *variance* of latency or bandwidth.  It's common for
>>>
>>> vendors to play games ("Lies, damn lies, and statistics!") to make
>>> their metrics look good.   A metric of latency that says something
>>> like "99% less than N milliseconds" doesn't necessarily translate
>>> into
>>> an acceptable user performance.
>>>
>>> It's also important to look at the specific techniques used for
>>> taking
>>> measurements.  For example, if a measurement is performed every
>>> fifteen minutes, extrapolating the metric as representative of all
>>> the
>>> time between measurements can also lead to a metric judgement which
>>> doesn't reflect the reality of what the user actually experiences.
>>>
>>> In addition, there's a lot of mechanism between the ISPs' handling
>>> of
>>> datagrams and the end-user.   The users' experience is affected by
>>> how
>>> all of that mechanism interacts as underlying network behavior
>>> changes.  When a TCP running in some host decides it needs to
>>> retransmit, or an interactive audio/video session discards datagrams
>>>
>>> because they arrive too late to be useful, the user sees
>>> unacceptable
>>> performance even though the network operators may think everything
>>> is
>>> running fine.   Measurements from the end-users' perspective might
>>> indicate performance is quite different from what measurements at
>>> the
>>> ISP level suggest.
>>>
>>> Gamers are especially sensitive to variance, but it will also apply
>>> to
>>> interactive uses such as might occur in telemedicine or remote
>>> operations.  A few years ago I helped a friend do some tests for a
>>> gaming situation and we discovered that the average latency was
>>> reasonably low, but occasionally, perhaps a few times per hour,
>>> latency would increase to 10s of seconds.
>>>
>>> In a game, that often means the player loses.  In a remote surgery
>>> it
>>> may mean horrendous outcomes.  As more functionality is performed
>>> "in
>>> the cloud" such situations will become increasingly common.
>>>
>>> Jack Haverty
>>>
>>> On 2/26/24 12:02, rjmcmahon via Nnagain wrote:
>>>
>>> Thanks for sharing this. I'm trying to find out what are the key
>>> metrics that will be used for this monitoring. I want to make sure
>>> iperf 2 can cover the technical, traffic related ones that make
>>> sense to a skilled network operator, including a WiFi BSS manager. I
>>>
>>> didn't read all 327 pages though, from what I did read, I didn't see
>>>
>>> anything obvious. I assume these types of KPIs may be in reference
>>> docs or something.
>>>
>>> Thanks in advance for any help on this.
>>> Bob
>>>
>>> And...
>>>
>>> Our bufferbloat.net submittal was cited multiple times! Thank you
>>> all
>>> for participating in that process!
>>>
>>> https://docs.fcc.gov/public/attachments/DOC-400675A1.pdf
>>>
>>> It is a long read, and does still start off on the wrong feet
>>> (IMHO),
>>> in particular not understanding the difference between idle and
>>> working latency.
>>>
>>> It is my hope that by widening awareness of more of the real
>>> problems
>>> with latency under load to policymakers and other submitters
>>> downstream from this new FCC document, and more reading what we
>>> had to
>>> say, that we will begin to make serious progress towards finally
>>> fixing bufferbloat in the USA.
>>>
>>> I do keep hoping that somewhere along the way in the future, the
>>> costs
>>> of IPv4 address exhaustion and the IPv6 transition, will also get
>>> raised to the national level. [1]
>>>
>>> We are still collecting signatures for what the bufferbloat
>>> project
>>> members wrote, and have 1200 bucks in the kitty for further
>>> articles
>>> and/or publicity. Thoughts appreciated as to where we can go next
>>> with
>>> shifting the national debate about bandwidth in a better
>>> direction!
>>> Next up would be trying to get a meeting, and to do an ex-parte
>>> filing, I think, and I wish we could do a live demonstration on
>>> television about it as good as feynman did here:
>>>
>>> https://www.youtube.com/watch?v=raMmRKGkGD4
>>>
>>> Our original posting is here:
>>
>> https://docs.google.com/document/d/19ADByjakzQXCj9Re_pUvrb5Qe5OK-QmhlYRLMBY4vH4/edit 
>>
>>
>>
>>>> Larry's wonderful post is here:
>>>> https://circleid.com/posts/20231211-its-the-latency-fcc
>>>>
>>>> [1] How can we get more talking about IPv4 and IPv6, too? Will we
>>>> have
>>>> to wait another year?
>>
>> https://hackaday.com/2024/02/14/floss-weekly-episode-769-10-more-internet/ 
>>
>>
>>
>>>> -- 
>>>> https://blog.cerowrt.org/post/2024_predictions/
>>>> Dave Täht CSO, LibreQos
>>> _______________________________________________
>>> Nnagain mailing list
>>> Nnagain at lists.bufferbloat.net
>>> https://lists.bufferbloat.net/listinfo/nnagain
>>  _______________________________________________
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