Re: appropriate length of fe80:: prefix and new IP-over-foo drafts

[Alexandre Petrescu <[e-mail]>]

Sorry,

Let me remove my preference and form a neutral question.

draft-hou-6lo-plc relies on a 24bit Network ID and a 12bit Terminal 
Equipment Identifier.

Why does it make a 64bit Interface ID and not a 36bit Interface ID?

The text in question is this:
>    For the 12-bit short addresses used by IEEE 1901.1, the 48-bit
>    pseudo-address is formed by 24-bit NID (Network IDentifier, YYYYYY),
>    12 zero bits and a 12-bit TEI (Terminal Equipment Identifier, XXX).
>    The 64-bit Interface ID MUST be derived by inserting 16-bit 0xFFFE
>    into this 48-bit pseudo-address as follows:
> 
>        YYYY:YYFF:FE00:0XXX

Alex

Le 31/01/2019 à 11:24, Alexandre Petrescu a écrit :
> 
> 
> Le 30/01/2019 à 23:14, Brian E Carpenter a écrit :
>> Section 5.3 "Creation of Link-Local Addresses" of RFC4862 refers to
>> an interface identifier of N bits and an fe80::0 prefix "of
>> appropriate length", which according to the addressing architecture
>> is 128-N. But N is undefined by RFC4862 and cannot be derived from an
>> RA because all this happens as soon as the interface is enabled.
>> Therefore N must be predefined.
>>
>> As pioneered by RFC2464**, all ipv6-over-foo documents must therefore
>> specify N for their link type. So far, everybody has specified 64, as
>> far as I know. Is there a reason to do otherwise for the two drafts
>> mentioned below?
> 
> One of the two drafts involves a Network ID of length 24.
> 
> The question is why not use 24 for InterfaceID?  Just because Ethernet 
> had it that way?
> 
> Alex
> 
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