[Bloat] Re: Vol 185, Issue 5

[bob.mcmahon@umbernetworks.com]

David is right that packets don't superpose. The useful math here is 
feedback control.

The guitar amp is a useful analogy for feedback instability. A squeal 
occurs when the loop gain and phase satisfy the conditions for sustained 
oscillation. The amplifier keeps supplying energy to the loop, and the 
oscillation grows until nonlinearities and saturation bound it.

Networks have feedback loops too. The delay through that loop is the 
RTT. Tail-drop synchronization, congestion-window sawtooths, and other 
oscillatory behaviors arise when multiple controllers react to delayed 
information about a shared bottleneck. That is why control theory is the 
useful toolbox here.

The key state is at the bottleneck queue. Endpoints need a timely 
congestion signal derived from that state. Loss communicates congestion 
after the queue has filled far enough to drop a packet. ECN lets the 
bottleneck communicate that information earlier and more frequently, 
giving the senders time to adjust their rates while keeping the queue 
shallow.

The difficult segment is the wireless last hop. AQM at an AP manages its 
queue, while contention arbitrates access to the air. Managing the air 
itself requires scheduling: grants issued from a point with enough state 
to make the decision, including wireless state across the relevant 
radios and bottleneck queue state.

An 802.11ax AP has detailed state about its own BSS and can use trigger 
frames to schedule uplink transmissions within that BSS. Building-wide 
scheduling requires a broader view: the air state across multiple radios 
together with the forwarding and bottleneck queue state. The scheduler 
therefore belongs at the point where those two kinds of state come 
together.

Bob


On 2026-09-19 02:16, David Lang wrote:
> Explain how you think this resonance would happen? unlike sound, 
> packets don't 'echo', they deliver messages, which can (and frequently 
> do) trigger reply messages but unlike audio resonance, the incoming 
> packets don't add to the outgoing packets to make a larger signal than 
> the outgoing packets would if the timing was a little difference.
> 
> David Lang
> 
> 
> On Sat, 19 Sep 2026, Replikon Research, D-U-N-S/FCN 77-387-4974 wrote:
> 
>> There are two realms of analysis where things can blow up
>> 
>> One is synergy and synergetics meaning the interactions between 
>> presumably
>> interchangeable parts relevant to the interactions between presumably
>> interchangeable routers and node points
>> 
>> The other is combinatorics and that's my thing I love 
>> combinatorics!!!! The
>> only thing that matters is what you choose to count and how much each 
>> part
>> of what you count matters to you to put it concisely.
>> 
>> So while I have very little to contribute I am encouraged to hear that 
>> the
>> bottleneck is in the latency but the causes of the latency are
>> multi-dimensional there are at least we know where the problem is not 
>> where
>> that would mean we knew the causes no that's not right let me know is 
>> what
>> the problem is yes the problem is latency
>> 
>> What comes to mind is it for certain latencies there may be an echo 
>> like
>> the feedback of a guitar when the amplifiers turned up too high
>> 
>> Does that have any intuitional relationship to these very high level
>> Network analyzes that you all do everyday
>> 
>> This question of residence no not residents got darn it in the 
>> microphone
>> resonance like my voice yes
>> 
>> I think resonance and spectral radius are two characteristics of 
>> behind
>> level network analysis which apply here to this question of latency 
>> because
>> when spectral radius is one resonance is nearly inevitable
>> 
>> Is the internet we have built evolving to an internet in which some
>> parameterizable characteristic has a special radius of 1?
>> 
>> I sure as hell hope not
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