Route table growth and hardware limits...talk to the filter
Andrew - Supernews
andrew at supernews.net
Sat Sep 8 22:30:03 UTC 2007
>>>>> "Forrest" == Forrest <forrest at almighty.c64.org> writes:
Forrest> Sure, this would fail if a network decided to only announce
Forrest> /24's for example without a larger aggregate, but how many
Forrest> networks are really doing that?
More than you probably imagine.
Consider the following table:
asn | count | c24 | c23
----------+-------+------+-----
9583 | 1100 | 1014 | 42
7018 | 1140 | 764 | 125
17488 | 560 | 557 | 0
19916 | 568 | 532 | 6
701 | 729 | 501 | 38
1221 | 474 | 380 | 14
1239 | 572 | 359 | 24
577 | 417 | 337 | 19
209 | 587 | 329 | 38
17557 | 291 | 270 | 1
10292 | 270 | 267 | 2
4802 | 345 | 259 | 25
6140 | 315 | 243 | 16
4323 | 483 | 242 | 12
7474 | 284 | 228 | 8
2386 | 295 | 218 | 9
3301 | 307 | 217 | 30
702 | 392 | 206 | 34
6746 | 279 | 200 | 41
In this, "count" is the number of prefixes originated by the AS that
are not covered by any longer prefix (without regard to origin); "c24"
is the number of those prefixes which are /24s; "c23" is the number
which are /23s. I've cut this table off at 200 - the total number of
uncovered /24 routes across all ASes is 51811.
Some of the above numbers would be worse if not for the presence of
over-large route announcements from other providers (for example,
Chinanet announce 125.96.0.0/14 even though 125.99.0.0/16 belongs
to hathway.net in India (AS 17488); approximately 230 _more_ /24
routes announced by Hathway are in this range).
--
Andrew, Supernews
http://www.supernews.com
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