Subject: [GROW] FIB Aggregation question

From: William Herrin <[email-masked]>
Date: Wed, 11 Nov 2009 17:19:13 -0500

Hi folks,

I couldn't attend but I had two questions about the FIB aggregation
draft (http://tools.ietf.org/html/draft-zhang-fibaggregation-02):

1. The level 3 and 4 algorithms disregard the implicit default, right?

A destination that falls through the routing table without matching a
route is unreachable. You can think of this in terms as an implicit
route for 0.0.0.0/0 with a next hop of: local process, compose ICMP
unreachable. If I understood the paper, some or all of the address
space within 0.0.0.0/0 which would otherwise hit that implicit default
will be assigned an essentially random next hop, with the system
depending on the TTL to eventually drop the packet.

Have level 3 and level 4 been tested after adding an explicit default
that has to be honored to see what difference it makes in the numbers?

2. If I understand figure 6 correctly, the numbers are the percentage
of original size the FIB reduces to. So, 2008 level 4b, if you started
with a 1000 entry FIB, after aggregation the FIB still contains 363
entries. Did I read it correctly?

Thanks,
Bill Herrin

-- 
William D. Herrin ................ [email-masked]  [email-masked]
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

---

From: Beichuan Zhang <[email-masked]>
Date: Wed, 11 Nov 2009 15:37:20 -0700

> 1. The level 3 and 4 algorithms disregard the implicit default, right?

Yes.

> depending on the TTL to eventually drop the packet.

Or, the packets may be dropped if the next router does not assign any next
hop to this "extra routable space", as different routers aggregate
differently.

> that has to be honored to see what difference it makes in the numbers?
No, we didn't add any explicit default route. We can give it a try to see
what numbers come out. But intuitively, adding a default route means taking
away all extra route space, so the best aggregation can be achieved by the
ORTC algorithm mentioned by John in an early email. It should be close to
what we have for Level-2 aggregation, which is about 50% table size.

> entries. Did I read it correctly?

Yes.

Regards,

---
beichuan

> _______________________________________________
> GROW mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/grow
>
>