Re: On sending SLAAC information into split RAs

[Fernando Gont <[e-mail]>]

Hello, Tim,

Thanks for your timely and useful data! In-line....

On 9/3/20 14:28, Timothy Winters wrote:
> Hi Fernando,
> 
> While I think we could say something about this, I've not seen a Router 
> implementation split this type of information up into multiple 
> messages.   Probably safest to recommend that it be done in one message.

Looking at Section 6.2.3 of RFC4861, it seems such behavior is implicit.

I'm curious: Have you seen any implementations that "omit" information 
as allowed in Section 6.2.3 of RFC4861:

   "A router MAY choose not to include some or all options when sending
    unsolicited Router Advertisements.  For example, if prefix lifetimes
    are much longer than AdvDefaultLifetime, including them every few
    advertisements may be sufficient.  However, when responding to a
    Router Solicitation or while sending the first few initial
    unsolicited advertisements, a router SHOULD include all options so
    that all information (e.g., prefixes) is propagated quickly during
    system initialization."

I've never seen one myself, and also think that it implies more trouble 
(increased code complexity, etc.)



So our plan is to have this doc update this text:

---- cut here ----
    A router MAY choose not to include some or all options when sending
    unsolicited Router Advertisements.  For example, if prefix lifetimes
    are much longer than AdvDefaultLifetime, including them every few
    advertisements may be sufficient.  However, when responding to a
    Router Solicitation or while sending the first few initial
    unsolicited advertisements, a router SHOULD include all options so
    that all information (e.g., prefixes) is propagated quickly during
    system initialization.

    If including all options causes the size of an advertisement to
    exceed the link MTU, multiple advertisements can be sent, each
    containing a subset of the options.
---- cut here ----

with this:

---- cut here ----
    When sending Router Advertisements, a router SHOULD include all
    options wso that all information (e.g., prefixes) propagates
    quickly, and hosts result in more uniform configuration.

    If including all options causes the size of an advertisement to
    exceed the link MTU, multiple advertisements can be sent, each
    containing a subset of the options. In all cases, routers SHOULD
    convey all information using the smallest possible number of
    packets.
---- cut here ----

Thoughts?

Thanks!

Cheers,
-- 
Fernando Gont
SI6 Networks
e-mail: [e-mail]
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