understanding IPv6

Denys Fedoryshchenko nuclearcat at nuclearcat.com
Sun Jun 7 16:20:29 UTC 2020

On 2020-06-07 19:02, Brandon Martin wrote:
> On 6/7/20 6:01 AM, Denys Fedoryshchenko wrote:
>> There are very interesting and unobvious moments on IPv4 vs IPv6, for 
>> example related to battery lifetime in embedded electronics. In ipv4, 
>> many devices are forced to send "keepalives" so that the NAT entry 
>> does not disappear, with IPv6 it is not required and bidirectional 
>> communications possible at any time. And in fact, it has a huge impact 
>> on the cost and battery life of IoT devices.
>> When I developed some IoT devices for clients, it turned out that if 
>> "IPv6-only" is possible, this significantly reduces the cost of the 
>> solution and simplify setup.
> This is difficult to understate.  "People" are continually amazed when
> I show them that I can leave TCP sessions up for days at a time (with
> properly configured endpoints) with absolutely zero keepalive traffic
> being exchanged.
> As amusingly useful as this may be, it pales in comparison to the
> ability to do the same on deeply embedded devices running off small
> primary cell batteries.  I've got an industrial sensor network product
> where the device poll interval is upwards of 10 minutes, and even then
> it only turns on its receiver.  The transmitter only gets lit up about
> once a day for a "yes I'm still here" notification unless it has
> something else to say.
> In the end, we made it work across IPv4 by inserting an application
> level gateway.  We just couldn't get reliable, transparent IPv6
> full-prefix connectivity from any of the cellular telematics providers
> at the time.  I don't know if this has changed.  For our application,
> this was fine, but for mixed vendor "IoT" devices, it would probably
> not work out well.
"Cellular telematics" are bad in general.
I had problem during development of OTA,because operator decided that he 
put TCP session data limit about 1MB, so people dont abuse unlimited 
data plan.
As their DPI was not very precise, i was getting
random hangs during data transfer. Did workaround by splitting OTA to 
several 256Kb chunks.
With IPv6 major problems that most of operators open only some ports, 
block inbound connections,
often run stateful firewall.
Usually customers prefer to pay extra to get custom firmware that is 
working properly on
particular cellular operator. Still IPv6 works better than IPv4.

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