Re: [Pppext] proposed TRILL IS-IS System ID text

[Donald Eastlake <[e-mail]>]

 On 01/27/11 12:31, William Allen Simpson wrote:
> On 1/27/11 6:03 AM, William Allen Simpson wrote:
>> 3. An implementation that has only PPP links might have no previously
>> configured Media Access Control (MAC) that can function as an
>> IS-IS System ID. In this case, the System ID is formed by adding
>> a randomly generated 14-bit leading number (in place of an OUI) to
>> the link's unique LCP Magic Number.

I think it is a very bad idea to mandate this method which, as far as
I know, is radically different from all methods currently in use. For
example, some manufacturers just allocate a 48-bit number related to
their MAC address space for each switch and use that as the System ID
regardless of the type of any switch interfaces or the MAC addresses
of any interfaces that have MAC addresses. Why should they change
their behavior just because it happens that they have all PPP
interfaces? Having all PPP interface is a state that could change
dynamically.

I would suggest, at a minimum, the following changes:
- Replace the beginning with something more like "An RBridge that has
only PPP interfaces might not have a conveniently available MAC
address from which a System ID that would be unique across the campus
can be derived. A possible statistical source of a System ID that
implementors may wish to consider would be formed by ...."

- Add a reference to [RFC4086] after "randomly generated".
- Add a reference to [RFC5342] after "OUI".
- The reference to "the link" is obviously problematic if their are
more than one. Suggest changing to "a link".

Even with the above changes, I'm pretty dubious.

>>   The Magic Number MUST be
>> unique for all links and all known link peers.

My impression from other posts is that you are not just trying to
change how people do IS-IS, but aspects of how they do PPP as well.

>>   This pseudo-MAC
>> MUST have both the "locally-assigned" and "broadcast/multicast"
>> (group) bits set to 1; that is, the least significant two bits of
>> the most significant octet are both set to 1.
>
> Looking at this again, and remembering how fanatic the new RFC Editors (TM)
> are about abbreviations, probably needs to expand OUI, too:
>
>                .... In this case, the System ID is formed by appending
>   the link's unique 32-bit LCP Magic Number after a randomly generated
>   14-bit number in place of an Organizationally Unique Identifier (OUI).

Sure.

Thanks,
Donald
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