[isp-bgp] Re: Will I be killed for not aggregating?

[Jerry Pasker <info@...>]

> On 17.02.2004 20:19 james wrote:
>
> > Provided you have a good reason for deagg'ing your CIDR's, I think it is OK.
> > Traffic engineering would be one of them. However, do find out if 
> > your providers
> > will let your do meds or communities as both of these can sometimes achieve
> > the same effect (in the traffic engineering context) w/o the need to deagg.
> IMHO there is *never* a good reason for de-aggregation. Why do you 
> want to bother others for you poor network design?
>
>
> Arnold
There's always a reason.  There's always a reason to do some 
non-standard routing, or practice, or whatnot.  Usually, there are 
plenty of reasons not to do it too.  However, there will always be 
some type of network somewhere, that needs to "twist the rules" a 
little to make things work.  Hopefully, these exist in the minority. 
But then again, there's usually "always a better way."

If someone had one IP block, two NOCs, and no network in between 
other than their transit providers, then I would say that's a 
definite need, (split it into the largest sizes to make it work) 
unless someone can come up with a more effective, and efficient way 
of doing it.  Then, if what they suggest works, do it that way.  Just 
don't do something that would needlessly chew up memory like 
advertising 16 /24s.  I've seen people advertise 16 /24s out a 
single homed DS3, with various path prepends on each advertisement. 
Its wasn't pretty, and it wastes everyone's memory.  It was caused by 
a combination of laziness and ignorance.

I'm all for keeping the routing tables small when practical, but 
really, RAM isn't that expensive.  And the routing tables will grow. 
It will happen.  Eventually, people will have to upgrade routers 
because of this.  That isn't entirely a bad thing.  IP routing 
doesn't revolve around keeping route tables small, route tables 
revolve around the continued growth of the internet.  Cisco counts on 
this.

So, if you need to de-aggregate to make a network work, or to make 
traffic favor a different link, by all means do so.  Just don't do it 
needlessly, and when you no longer have the need, please look over 
your BGP announcements, and  aggregate back up again.  Fist off, you 
must be effective (make the network work!) in what you do. Then, you 
must be efficient (minimize resources, maximize output).  In that 
order.

Really, in the grand scheme of things, not only will you not be 
killed for not aggregating, no one will probably even notice.


-Jerry






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