understanding IPv6

Sun Jun 7 16:02:14 UTC 2020

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.
-- 
Brandon Martin