On Sun, 20 Apr 2003 01:32:46 +0700, Robert Elz said: > Date: Sat, 19 Apr 2003 07:07:19 -0700 > From: Dave Crocker <dhc2@dcrocker.net> > Message-ID: <16890640984.20030419070719@brandenburg.com> > > | site local is, in fact, an addition to the IP architecture and that is > | what is causing the controversy. > > No, it isn't. It is a cleaned up replacement for 1918 addresses. Unbfortunately, I don't see where the biggest problems with 1918 addresses were cleaned up for site-local. Addresses will still leak out, and it still has scoping problems. You're still left wondering "Is this address I was just handed an in-scope address from another part of my own network, or is it a bogon I was handed by somebody else from part of THEIR net?" The problems with 1918 space were well understood at the time: A major drawback to the use of private address space is that it may actually reduce an enterprise's flexibility to access the Internet. Once one commits to using a private address, one is committing to renumber part or all of an enterprise, should one decide to provide IP connectivity between that part (or all of the enterprise) and the Internet. Usually the cost of renumbering can be measured by counting the number of hosts that have to transition from private to public. As was discussed earlier, however, even if a network uses globally unique addresses, it may still have to renumber in order to acquire Internet-wide IP connectivity. Another drawback to the use of private address space is that it may require renumbering when merging several private internets into a single private internet. If we review the examples we list in Section 2, we note that companies tend to merge. If such companies prior to the merge maintained their uncoordinated internets using private address space, then if after the merge these private internets would be combined into a single private internet, some addresses within the combined private internet may not be unique. As a result, hosts with these addresses would need to be renumbered. Unfortunately, people seem to want to forget about those two paragraphs. I'm afraid that unless site-local includes a 'MUST renumber' requirement for *BOTH* cases, it's a complete and total non-starter in my book.
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