Hi,Remi
 

[email protected] 写于 2013-01-29 00:16:32:

> Senthil,
> 
> 
> 2013-01-2815:24, Senthil Sivakumar (ssenthil) <[email protected]>  :
> 
> > I believe the prefix length > 64 should be allowed.
> 
> 
> > It is upto the
> > operator to choose the prefix length of their choice.
> 
> Agreed.
> No one suggest to say the contrary.
> 
> Yet, operators have the constraint of RFC 4291 that "For all unicast
> addresses, except those that start with the binary value 000, 
> Interface IDs are required to be 64 bits long and to be constructed 
> in Modified EUI-64 format". 
> 
> The draft says that:
> (a) The PSID is:
> +--+---+---+---+---+---+---+---+---+
> |PL|   8  16  24  32  40  48  56   |
> +--+---+---+---+---+---+---+---+---+
> |64| u | IPv4 address  |  PSID | 0 |
> +--+---+---+---+---+---+---+---+---+
> (b) "If the End-user IPv6 prefix length is larger than 64, the most 
> significant parts of the interface identifier is overwritten by the 
prefix."
> 
> This is particularly unclear:
> - What happens to the u octet?
> - And to the IPv4 address if the prefix is longer than /68? 

Remi, you mean the prefix is longer than /68 or /78?    I think /68(64+4) 
prefix doesn't overwrite IPv4 address.

BRs
Linda Wang


> - ...
> 
> Of course, if a use case is provided where MAP-E would be actually 
> used with an IID shorter than 64 bits, it should be discussed. But:
> - There is no such use case so far. 
> - Looking for one doesn't seem useful. 
> 
> 
> Regards,
> RD
> 
> 
> > 
> > On 1/28/13 8:59 AM, "Ole Troan" <[email protected]> wrote:
> > 
> >>>>> 
> >>>>> The examples in my previous note sort of provided backing for my 
view
> >>>>> that the MAP endpoint IPv6 prefix can be limited to a maximum of a
> >>>>> /64, thus making the IID fully conformant both to RFC 4291 and to 
RFC
> >>>>> 6052.
> >>>>> 
> >>> ...
> >>> 
> >>>>> 
> >>>>> I think limiting the prefix length to 64 bits is reasonable. 
Comments?
> >>>> 
> >>>> I don't think that's reasonable.
> >>>> and I don't see what it buys us, given that supporting prefix 
lengths
> >>>> longer than 64 is simple.
> >>>> IPv6 isn't classfull, there isn't anything magic with the 64 
boundary.
> >>>> ;-)
> >>>> 
> >>>> cheers,
> >>>> Ole
> >>>> 
> >>> 
> >>> OK, then I agree with Rémi. Drop mention of prefixes greater than 64
> >>> bits long and leave it to the reader to judge whether RFC 4291 
imposes a
> >>> limit.
> >> 
> >> you want this removed:
> >>     <t>If the End-user IPv6 prefix length is larger than 64, the most
> >>     significant parts of the interface identifier is overwritten by 
the
> >>     prefix.</t>
> >> 
> >> I disagree. this is the only text in there suggesting to an 
implementor
> >> that prefix lengths can be any value between 0-128.
> >> 
> >> Tom, Remi and I have stated our opinions. does anyone else have a 
view on
> >> the matter?
> >> 
> >> cheers,
> >> Ole
> >> _______________________________________________
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> > 
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