[DNA] leaving out options on Landmark RA = Yes(draft-pentland-dna-protocol-00.txt)?

[Greg Daley <greg.daley@eng.monash.edu.au>]

Dear WG,

The contents of Landmark RAs with the Yes flag set
are described in two locations:

Section 3.2:

"In the case when the host is still attached to the same link, which
  might occur when the host has changed from using one layer 2 access
  point to another, but the access points are on the same link, the
  Router Advertisement(s) it receives will contain a "yes, that prefix
  is on this link" answer, and no other information.  Thus, such RA
  messages are quite small."

Section 5.1.5:

"If the RS contains a Landmark Option whose prefix matches one
  of those in the interface's stored prefix list, then the
  Landmark option with the Landmark prefix is included in the RA
  but with the Yes flag set.  At this point the RA is ready for
  transmission, and is scheduled as specified in Section 5.1.7."

I have a comment and question.

Comment:

The descriptions here ignore SEND options, which need to be included
if SEND is used.  This will increase the size of the RA.

Question:

Can we have standards language for this?

There's no flexibility in the description of what options are
able to be included in the "Yes" Landmark. That sounds like a
MUST NOT include other PIO, DNAO. etc.

Personally, I'd prefer something saying something like

"RAs with the 'Yes' Flag set in a Landmark option MAY leave out all
configuration related options such as PIOs, DNAOs, Advertisement
Intervals etc, since this information is assumed to have
already been received to be able to construct a matching
Landmark Router Solicitation".

I'd prefer MAY to SHOULD or MUST, since it's an optimization,
and the presence of additional options doesn't harm hosts.

In RADVD, it's easier for me to not remove the other options
in the RA just because the Landmark option Yes flag is set.

Greg