Re: encoding Subnet ID in link-local addrs (Re: about violation of standards)

[Alexandre Petrescu <[e-mail]>]

Le 25/04/2019 à 16:32, Mudric, Dusan (Dusan) a écrit :
> 
>> 2 IPv6 link-local addresses are typically self-configured according
>> to 4 RFCs and relying on the fe80::/10 IANA allocation, RFC 54 0
>> bits, and RFC MAC-based 64bit Interface IDs.  In some cases, it is
>> advantageous to manually configure link-local addresses.  This is
>> useful for easy remembering by humans, and for parameter resilience
>> during network interface replacement.
>> 
>> Manual configuration of an LL may use short IID and Subnet ID The 
>> Subnet ID presence in the link-local address is useful in some 
>> wireless settings where the subnet structure parameters depend on 
>> the link locality.  Other settings may also benefit.
>> 
>> When manually setting the link-local address it is necessary to 
>> know the length of the prefix of the subnet on which this 
>> link-local address is present.  This length is necessary for 
>> on-link determination.
>> 
> [Dusan] Is the Subnet ID unique per host?

In  my setting, the Subnet ID in the LL address is unique per subnet,
not per host.  There is a subnet formed by the front bumper interface in
the follower car and the rear bumper interface of the lead car.

The Subnet ID in an LL address would be unique per a set of hosts in 
that subnet.

> Is it possible that all hosts on the link share the same Subnet ID?

Yes, they should.

> Can somebody provide more details about the problem and how this 
> solution will solve the problem?

More details about the problem: RFC4291 54 0 bits would refuse to change 
to accomodate this solution's Subnet ID in an LL address; another detail 
is that one particular OS would not allow the manual configuration of an 
LL address setting some of these 54 0 bits.

Alex

>