Subject: [Mipshop] FMIPv6 - order of tuple elements in PrtRtAdv?

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 11 Aug 2005 15:36:01 +0200

I think the order of tuple elements in a PrtRtAdv containing multiple
tuples (AP-ID, AR-Info) is not specified.

When PrtRtAdv contains several tuples (like in response to a wildcard
solicitation), it's not clear whether a PrtRtAdv should order New Router
Prefix Information Options and New Access Point Link-Layer Address
options in any particular way.

For example, which of the two following sequence is legit:

New Access Point Link-Layer Address1
New Access Point Link-Layer Address2
New Router Prefix Information Option1
New Router Prefix Information Option2

or:

New Access Point Link-Layer Address1
New Router Prefix Information Option1
New Access Point Link-Layer Address2
New Router Prefix Information Option2

A specific order is needed for this options, otherwise the receiver is
not able to corelate an AP-ID to the right AR-Info.  Or is there another
means to corelate the two?

Alex

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From: Subba Reddy <[email-masked]>
Date: Thu, 11 Aug 2005 20:01:10 +0530

Hi Alexandru,

> means to corelate the two?

I think, your second sequence is correct. 
FMIPv6 spec (section 6.1.2) says,
"...
   Valid Options in the following order:
..."
 
Thanks & Regards,
Subba Reddy

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From: Alexandru Petrescu <[email-masked]>
Date: Thu, 11 Aug 2005 16:55:21 +0200

>    Valid Options in the following order:

"Valid options in the following order" gives the order between one AP-ID
and one AR-Info - ok.  But it means nothing to my understanding about
the order of several AP-IDs and AR-Infos.

"When several (AP-ID, AR-Info) tuples are present each tuple is
contiguous and the AP-ID comes first, e.g...", or similar formulation,
would be clearer IMHO.

Besides, conceptually a tuple is simply (AP-ID, AR-Info) but the
encoding is actually 4 values (AP-ID, NAR LLA, NAR IP, NAR prefix).  In
this actual "quadruple" at least the NAR prefix is optional.
Additionally, NAR may advertise RA with several prefixes and current
encoding doesn't allow that.

Clearly specifying an order for tuples and within tuples is difficult to
formulate, I agree, but as long as there's no embedded key in each tuple
member (a key would help correlate the tuple members), "Valid options in
the following order" is just too generic, IMHO.

Alex

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From: Subba Reddy <[email-masked]>
Date: Thu, 11 Aug 2005 20:59:33 +0530

Hi Alexandru,

> the following order" is just too generic, IMHO.

"Valid options in the following order" is too generic.
As per my understanding, since spec is mentioning about [AP-ID, AR-Info]
tuple,
second sequence looks more appropriate. But the first sequence is also
possible.

Thanks & Regards,
Subba Reddy

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From: Alexandru Petrescu <[email-masked]>
Date: Thu, 11 Aug 2005 19:21:20 +0200

Subba Reddy wrote:

> Hi Alexandru,
> 
> 
>>> I think, your second sequence is correct. FMIPv6 spec (section 
>>> 6.1.2) says, "... Valid Options in the following order: ..."
>> 
>> "Valid options in the following order" gives the order between one 
>> AP-ID and one AR-Info - ok.  But it means nothing to my 
>> understanding about the order of several AP-IDs and AR-Infos.
>> 
>> contiguous and the AP-ID comes first, e.g...", or similar 
>> formulation, would be clearer IMHO.
>> 
>> encoding is actually 4 values (AP-ID, NAR LLA, NAR IP, NAR prefix).
>>  In this actual "quadruple" at least the NAR prefix is optional. 
>> Additionally, NAR may advertise RA with several prefixes and 
>> current encoding doesn't allow that.
>> 
>> Clearly specifying an order for tuples and within tuples is 
>> difficult to formulate, I agree, but as long as there's no embedded
>>  key in each tuple member (a key would help correlate the tuple 
>> members), "Valid options in the following order" is just too 
>> generic, IMHO.
> 
> 

I agree.

> As per my understanding, since spec is mentioning about [AP-ID,
> AR-Info] tuple, second sequence looks more appropriate. But the first
> sequence is also possible.

Ok, so if the first sequence is also possible, then it's impossible to
distinguish:

and:

Alex

> 
> Thanks & Regards, Subba Reddy

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From: Subba Reddy <[email-masked]>
Date: Fri, 12 Aug 2005 09:05:38 +0530

Hi Alex,

> New Router Prefix Information Option1

True. 
As per my understanding, since the spec has not mentioned explicitly
about the order (particularly in multiple tuple cases),
it is not possible to distinguish

Thanks & Regards,
Subba Reddy