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Re: [RRG] getting rid of longest match
On Feb 25, 2008, at 7:06 PM, Tony Li wrote:
If I understand this proposal, then for any given prefix, the entire
net would agree on a prefix length and only propagate paths for this
prefix length. This would imply that there would actually be no
required hardware change, as all of this filtering could (and
should) happen during BGP processing (specifically during UPDATE
parsing) and prior to RIB insertion and thus prior to the FIB
insertion.
Thus, from a hardware perspective, this is largely a NOP.
Note that this could somewhat decrease the complexities of future
hardware designs. Since we now guarantee that there are no
overlapping prefixes, the table now effectively forms a tree of
variable prefix lengths, but now the first match found in the tree
suffices. In the grand scheme of things I would judge this not to
have a significant impact, but it is arguably simpler.
Of course, this doesn't address the problem that spawned his
query, which is someone else advertising my address space.
Today this sorta happens in a reactive manner, right? For
example:
o YouTube announces a /22
o Someone announces a /24 of that /22
o YouTube responds by announcing a /24 && /22
o YouTube still largely broken
Cisco's still announcing /24s for prefixes which this happened
to a decade ago. The result is that things are only half broken,
not completely broken, I guess.
The problem here is simply that of a reliable authenticated
authoritative data source for who owns what - AND operators
employing that to define routing policies. If protocols like SBGP
or soBGP want to build upon that and actually get some traction
in deployment, great, but the egg here [1] is the data source that
still doesn't exist.
[1] http://www.cnn.com/2006/TECH/science/05/26/chicken.egg/
-danny
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