[ppml] Effects of explosive routing table growth on ISP behavior

Stephen Sprunk stephen at sprunk.org
Thu Nov 1 14:01:03 EDT 2007

Thus spake "Brian Johnson" <bjohnson at drtel.com>
> Scott Leibrand wrote:
>> I don't think that's true.  Today, anything you advertise in IPv4 down
>> to a /24 will be accepted more or less by everyone.
> Yes. But this came about due to common network policy and time,
> not ARIN policy. It could just as easily been a /20 if the screaming
> was not as loud.

I bet we'll be at /20, at least in the blocks where /20 is the minimum, 
within a few years due to all the routers falling over from accepting /24 

It'd be really nice if someone would produce a tool that would auto-create 
filter lists that would permit N-bit deaggregates of each block assigned by 
the RIRs.  As long as a covering aggregate was announced, each network could 
tune N to keep their routers from falling over.

> My only real point is that routing decisions should not be directly
> "governed" by ARIN policy. I think we are just beating this topic with a
> smelly herring. :)

They're not "governed" per se, since ARIN has no enforcement powers, but the 
independent decisions by the various ISPs are definitely influenced by ARIN 
policy -- and vice versa.  At most, ARIN controls what the _minimum_ size of 
the routing tables are; operators can allow more than that but realistically 
they can't allow less.  e.g. ARIN can hand out /20s and ISPs can filter at 
/24, but if ARIN was handing out /24s ISPs couldn't filter at /20.

It'd be nice to see some blocks designated as having _shorter_ maximum 
lengths so that we wouldn't be forced to accept /20s in blocks that 
mega-ISPs were getting /10s from.


Stephen Sprunk         "God does not play dice."  --Albert Einstein
CCIE #3723         "God is an inveterate gambler, and He throws the
K5SSS        dice at every possible opportunity." --Stephen Hawking 

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