/24s run amuck

Tue Jan 13 21:12:13 UTC 2004

On Jan 13, 2004, at 3:58 PM, Steve Francis wrote:

> Patrick W.Gilmore wrote:

>> On Jan 13, 2004, at 2:19 PM, Steve Francis wrote:
>>
>>> I'll take some education - given two POP's, different upstream ISPs 
>>> at each POP, and a desire to have traffic for specific networks 
>>> (/24) enter a specific POP, can that be done without de-aggregation?
>>> We are not doing this ourselves - we're not yet big enough to have 
>>> our own aggregate blocks, but if we did, we could not just announce 
>>> a /20 at each POP, and transit the traffic back to the appropriate 
>>> datacenter ourselves. We're an ASP, and do not have real links 
>>> between POP's, only VPN's.
>>>
>>> If we used consistent upstreams at each POP, we could do it by 
>>> announcing specific /24's with no-export communities, but a 
>>> consistent set of ISPs are not available at each of the colo's we 
>>> are in.
>>>
>>> Is there some other trick I'm missing?
>>
>>
>> If you can't take the traffic from Site A to Site B, why are you 
>> announcing the /24s to the world?  Why not just use a /24 from the 
>> upstream in each location and not force everyone else on the Internet 
>> to see your /24 which only has one path?
>
> It doesn't have just one path. Multiple (different) ISPs at each 
> location.

Then this is just two instances of the same problem: You have a site 
with a /24 and multiple upstreams.  How do you aggregate?

Answer: You don't.  This is the type of deaggregation which is a 
"necessary evil".  And, IMHO, why filtering on /20 (or whatever) is a 
Bad Thing.  You have just as much right to multiple upstreams as the 
"big guys".  Again, IMHO.  Many people on this list - all of them 
running large networks, you will notice - would argue otherwise.  They 
seem to think that if you do not have a /16, you should not have 
multiple upstreams.

Fortunately, the market, and the Internet, has clearly spoken.  
Unfortunately, they may have spoken a little too loudly, and now we 
have "/24s run amuck". :)

-- 
TTFN,
patrick