Re: [Pppext] working group last call for PPP TRILL protocol control protocol [was Re: I-D Action:draft-ietf-pppext-trill-protocol-02.txt]

[William Allen Simpson <[e-mail]>]

On 1/24/11 12:05 PM, James Carlson wrote:
> I agree that it'd be nice to fill in this hole, but I'm not so sure how
> to accomplish that task.  I don't think IETF OUI plus LCP Magic Number
> works -- the Magic Number value is unique for a given endpoint on a
> given link, but is not guaranteed to be unique across a network.  But
> the IS-IS System ID number does need to be unique across the network,
> and its construction based on MAC addresses normally protects that
> requirement.
>
It must be nice to live in a world with unique MAC addresses!  In my
experience, I've run into rather a lot of them that are not -- and it
will be much worse in this cross-linked multi-media environment.  Many
vendors think that it's OK to reuse the MAC address for different link
speeds and types.

The likelihood that two D-Link boxes have the same MAC is something on
the order of 2**8 (and was *every* box for about 2 years)!  I've had
problems with Linksys, Intel, 3Com, etc. ad nauseam.

The only way that the Magic Number has any significant chance to ever be
non-unique would be a very large number of PPP-only bridges in the network,
on the order of 2**16.  Probably best to stick an IP router in there....

If the PPP-only bridges are talking to each other, there will *never* be
any non-unique numbers.  That's the more likely case of centrally
located PPP-only bridges.


> One way to avoid the hole would be to outlaw the use of systems that
> lack any way to form an IS-IS System ID, but that seems a little harsh.

And contrary to the whole point of PPP.

>   Forcing that corner case to use manual configuration is distasteful,
> but the alternatives seem worse, at least to me.
>
Well, many boxes these days have the ability to over-ride the default,
but it would be nice to have a default mechanism.