Re: ID: More Accurately Naming IPv6 RA Router Lifetime (Re: New Version Notification for draft-smith-6man-accurate-ra-router-lifetime-00.txt)

[Alexandre Petrescu <[e-mail]>]

Le 05/05/2021 à 09:43, Mark Smith a écrit :
> Now with a more exciting email subject!

Thanks,

The idea sounds great and it would solve a common problem of 
understanding the meaning of that field.  A better understanding would 
lead to better implementations.

But, there might be drawbacks as well: will it confuse a reader of an 
old code commented with 'Router Lifetime' everywhere and not finding 
that 'Router Lifetime' text in a potentially updated RFC?

> The Router Lifetime field of an RA indicates whether or not the
>    advertising router will act as a default router for the receiving
>    IPv6 hosts, and if so, for how many seconds it will perform that
>    role, unless it is refreshed by a subsequent RA from the router.

YEs, it is well formulated.  Maybe to be complete it should say that the 
'how many seconds' is non-zero.

>    If the RA Router Lifetime field value is zero, it means that the
>    router is not or will no longer be acting as a default router.

yes, but it will still be able to act as a router.  Maybe as a router 
for more specific routes, or maybe as a router to advertise the MTU of 
the link, or maybe for SLAAC (maybe for VSLAAC too).

(also, a side note, I think nothing prohibits a Host receiving that RA 
containing a 0 router lifetime to actually use it in whatever way it 
feels necessary.  That concept of 'default' route is a concept in the 
Host.  The Host might use it as it wants, irrespective of what the 
router suggests.)

Alex

> 
> On Tue, 4 May 2021 at 18:24, Mark Smith <[e-mail]> wrote:
>>
>> Hi All,
>>
>> I've been thinking for a while that the Router Lifetime field name
>> wasn't as accurate and expressive as it could be, and then we had
>> somebody asking fairly recently on the mailing list about how Router
>> Lifetime and ND lifetime (IIRC) values interacted on the mailing list.
>>
>> So an ID proposing to rename the field to Default Router Lifetime, and
>> also providing an example scenario of when a zero value Default Router
>> Lifetime would be used to demonstrate that a zero value RA is valid
>> and useful in some scenarios.
>>
>> Comments and suggestions most welcome.
>>
>> Thanks very much,
>> Mark.
>>
>>
>>
>>
>> ---------- Forwarded message ---------
>> From: <[e-mail]>
>> Date: Tue, 4 May 2021 at 18:14
>> Subject: New Version Notification for
>> draft-smith-6man-accurate-ra-router-lifetime-00.txt
>> To: Mark Smith <[e-mail]>
>>
>>
>>
>> A new version of I-D, draft-smith-6man-accurate-ra-router-lifetime-00.txt
>> has been successfully submitted by Mark Smith and posted to the
>> IETF repository.
>>
>> Name:           draft-smith-6man-accurate-ra-router-lifetime
>> Revision:       00
>> Title:          More Accurately Naming IPv6 RA Router Lifetime
>> Document date:  2021-05-04
>> Group:          Individual Submission
>> Pages:          4
>> URL:
>> https://www.ietf.org/archive/id/draft-smith-6man-accurate-ra-router-lifetime-00.txt
>> Status:
>> https://datatracker.ietf.org/doc/draft-smith-6man-accurate-ra-router-lifetime/
>> Htmlized:
>> https://datatracker.ietf.org/doc/html/draft-smith-6man-accurate-ra-router-lifetime
>> Htmlized:
>> https://tools.ietf.org/html/draft-smith-6man-accurate-ra-router-lifetime-00
>>
>>
>> Abstract:
>>     IPv6 Router Advertisements (RAs) have a "Router Lifetime" field,
>>     which specifies how long the advertising router will act as a default
>>     router for the receiving hosts, unless refreshed with another
>>     advertisement.  The field name "Router Lifetime" is quite general,
>>     and could easily be misunderstood to mean the bounded lifetime of all
>>     of the information contained in the RA.  This memo more accurately
>>     renames this field "Default Router Lifetime".
>>
>>
>>
>>
>> Please note that it may take a couple of minutes from the time of submission
>> until the htmlized version and diff are available at tools.ietf.org.
>>
>> The IETF Secretariat
> 
> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> [e-mail]
> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> --------------------------------------------------------------------
>