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

[Toerless Eckert <[e-mail]>]

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.
> 
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