Re: [Lwip] [IPsec] The LWIG WG has placed draft-mglt-lwig-minimal-esp in state "Call For Adoption By WG Issued"

[Michael Richardson <[e-mail]>]

Tero Kivinen <[e-mail]> wrote:
    > number. Also window size is need only if you have out of order packets,
    > and you care about replay protection. Both of them are something that
    > might not be something that constrained device cares.

    > For example it might have internal replay protection for the messages
    > it sends, so it does not need to care whether there is replays on the
    > IPsec level, thus it can drop the whole replay protection checks
    > completely. Or it might work on the environment where out of order
    > deliver is not possible, thus it can just keep window size to 1.

For instance, if one has a single CoAP session active, then there will be in
essence only one packet in flight in either direction, so maybe there is no
re-ordering possible.  (Yes, there can be retransmits)

    > On the other hand sender is REQUIRED to send sequence numbers in such
    > way they are monotonically incrementing (not necessarely by one), and
    > if it has any kind of other monotonically incrementing counter like
    > clock, it can use that to generate the sequence numbers and get rid of
    > the requirement to store outgoing sequence number to the flash.

I agree that this would work well.

    > So as those are not really used in non-constrained devices, I do not
    > think there is that big different in constrained devices. Again all of
    > this depends on the environment. For example some kind of door sensor
    > might want to keep sending packets every n seconds just not to leak out
    > when the door was opened and closed, but it might just use real packets
    > instead of dummy packets. I.e., it might be configured to send the door
    > status every 30 seconds, and in that packet it tells whether door is
    > now open or closed, and whether what transitions happened during last
    > 30 seconds.

Good point, and this makes the packet the same size as well, and uses less code.

--
]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        | network architect  [
]     [e-mail]  http://www.sandelman.ca/        |   ruby on rails    [


--
Michael Richardson <[e-mail]>, Sandelman Software Works
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