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

William Allen Simpson <william.allen.simpson@gmail.com> Thu, 27 January 2011 17:28 UTC

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Date: Thu, 27 Jan 2011 12:31:25 -0500
From: William Allen Simpson <william.allen.simpson@gmail.com>
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Cc: rbridge@postel.org
Subject: Re: [Pppext] proposed TRILL IS-IS System ID text
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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. The Magic Number MUST be
> unique for all links and all known link peers. 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).

[Also makes the number of bits explicit: N/2**23 birthday attack;
considerably less than having 2 identical MACs from the same vendor, or
being killed by lightning.  Could put that in the Security Considerations?]

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