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

[tom petch <[e-mail]>]

From: ipv6 <[e-mail]> on behalf of Alexandre Petrescu <[e-mail]>
Sent: 05 May 2021 09:15

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?

<tp>
Not just old code but current code until it gets updated,  if it ever does.  And then there is all the documentation, manual pages and so on, thousands of places for people to misunderstand and get confused, not to mention a number of other RFC that use the existing terminology.

An identifier has to be usable, unique within its namespace, it does not have to carry all the semantics - that is what an RFC is for.

This seems to arise from people who have not done their homework, who think that Webster's dictionary can explain the meaning of code.  No, that is why we write RFC.

Tom Petch

p.s. get the name right first time, something that IETF WGs do not pay enough attention to IMHO.

> 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
>
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