Re: [pim] AD Review of draft-ietf-pim-assert-packing-05

[Toerless Eckert <[e-mail]>]

Thanks, Stig

Given how i think we like to have at least 16-bit alignment, then
if we keep the zero byte, the following byte could be reserved,
or i could even save the A)ggregated Flag bit by making that second byte
a Packing type (simple/aggregated - and future ones). I don't think we
would ever need to extend beyond what this draft will define but maybe
it looks nicer. But its another PIM protocol parameter registry table ask...

Cheers
    Toerless

i don't think we would need additional packing options than what
we define here

On Thu, Feb 16, 2023 at 08:18:43AM -0800, Stig Venaas wrote:
> Hi Toerless
> 
> Agree. We do have cases where there are several assert messages per
> second (which is why we need this), but maybe there will still be say
> at least 1 message per second. So I think it's not unlikely that a new
> router coming up might encounter the new assert format before its
> hello is processed by other routers. So I think having a 0 first byte
> would be good.
> 
> Regards,
> Stig
> 
> On Thu, Feb 16, 2023 at 8:09 AM Toerless Eckert <[e-mail]> wrote:
> >
> > Ack. Happy to hear from any other WG members opinions.
> >
> > I do somewhat ponder that it would not be a bad idea to have the first byte of payload zero
> > filled to be able to actually know that the new messages will not be misinterpreted
> > in the case Stig mentioned. But i don't want to over-engineer either.
> >
> > Cheers
> >     Toerless
> >
> > On Wed, Feb 15, 2023 at 07:52:53PM -0600, Alvaro Retana wrote:
> > > FWIW — besides removing the count, I don’t think any of the other changes
> > > are needed.
> > >
> > > Alvaro.
> > >
> > > On February 13, 2023 at 1:54:21 PM, Toerless Eckert ([e-mail]) wrote:
> > >
> > > Some quick thoughts:
> > >
> > > - It's fine to remove the count by me. I just did this rev with what i felt
> > > was
> > > necessary to solve Alvaros feedback. here is what i would suggest:
> > >
> > > - If we want to solve the small windows of inconsistency:
> > > We can insert an 0-bit zero field as the first byte of the
> > > PackedAsserts. This will ensure thart thhey always fail to
> > > be valid Asserts because zero is reserved in the address types
> > > used to encode the group address. And to keep the structures 16-bit
> > > alignment (as ew have it now), we follow this up with 8 bit reserved.
> > >
> > > - For extensibility with future possible additional assert options,
> > > we can add the notion to the PacketAssert option that a length
> > > > 0 MAY be used, but will be ignored on receipt.
> > > This means that we could avoid introducing a new IM Hello Option
> > > codepoint if we would amend/revise the functionality in the
> > > future with more/different assert message types. That would then
> > > use some length > 0, and the spec would say to only use this
> > > when all routers announce it.
> > >
> > > Cheers
> > > Toerless
> > >
> > > On Fri, Feb 10, 2023 at 12:40:12PM -0800, Stig Venaas wrote:
> > > > Hi Alvaro
> > > >
> > > > That's a great point. Sorry Toerless, I did not think about that when
> > > > I emailed earlier.
> > > >
> > > > Only potential issue is that there might be some small window where an
> > > > older implementation is coming up and is receiving such a message
> > > > before the other routers parse its hellos. Not sure how likely that
> > > > is. This is of course an issue with hello capabilities in general.
> > > >
> > > > Will have a closer look at the new version soon.
> > > >
> > > > Thanks,
> > > > Stig
> > > >
> > > > On Fri, Feb 10, 2023 at 12:31 PM Alvaro Retana <[e-mail]>
> > > wrote:
> > > > >
> > > > > On February 10, 2023 at 12:17:30 PM, Stig Venaas wrote:
> > > > >
> > > > > Stig:
> > > > >
> > > > > Hi!
> > > > >
> > > > >
> > > > > > I see you are reusing the assert message type in the latest draft.
> > > > > > That won't work. Existing implementations would not check the
> > > reserved
> > > > > > bits, they would just assume it is a regular assert. It is ok to use
> > > a
> > > > > > new message type, but using one for each of the packet formats is
> > > > > > unnecessary.
> > > > >
> > > > > Yes, but that shouldn't be an issue because the drafts says that
> > > > > "PackedAssert messages (Section 3.2) MUST only be sent when all PIM
> > > > > routers in the same subnet announce this option." So all the
> > > > > implementations will have to be updated for this to be used.
> > > > >
> > > > > Alvaro.
> > >
> > > --
> > > ---
> > > [e-mail]
> >
> > --
> > ---
> > [e-mail]
> 

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