[j-nsp] BGP Prefix-Limit On A Session

Craig Pierantozzi tozz at user1.bind.com
Wed Feb 25 22:33:01 EST 2004

* Thus spake Richard A Steenbergen (ras at e-gerbil.net):

> Are there any operators out there who place the importance of prefix
> limits providing protection of routing resources from someone announcing a
> million routes above or anywhere near the importance of using prefix
> limits to catch "common" leaks by peers/customers/etc which would result
> in suboptimal routing?

We use it to protect the resources as a sanity check.  Prefix limits 
are set to 200% of the number routes in the list which is auto-generated 
by a script using routes properly registered in the IRR.  This gives the 
customer some leeway for minor leaks and/or room to grow without taking 
out our routers.   There are plenty of routers out there running a fine 
line in terms of resources as companies squeeze more and more out of 
every piece of gear.
> Is this particular disconnect between developers and operators perhaps one
> of the reasons why every operator I know would LOVE to see auto-adjusting
> prefix limits that follow the "normal" number of prefixes announced by a
> peer, and yet no vendor has ever tried to implement it (that I know of 
> anyways)?

I agree with Vijay, this can be done using scripts and we don't see 
the number of routes that are advertised by customers wildly swinging
up or down from day to day so the auto-sensing feature while interesting,
probably doesn't help any more than scripts.  We would hope that someone
that is going to start announcing a significantly larger amount of routes
due to a legitimate reasons would work with their provider to prepare for 
such an event.


More information about the juniper-nsp mailing list