RE: [RRG] Opportunistic Topological Aggregation in the RIB->FIB Calculation?

["Tony Li" <tony.li@tony.li>]

Hi Bill,

I see we need to talk about the problem _again_.  ;-(


|The RIB cost grows with the width of the system times the number of
|entries. The system width is staying relatively static (and that's
|expected to continue), so the growth cost is close to linear with the
|number of entries. We already know that a $5k ($2k if you're on a
|budget) Linux server running Quagga can keep up with 10 times the
|entries and churn. With PC hardware's price/performance doubling every
|3 years, we haven't long to wait before it can easily handle 100 times
|the entries and churn that we have today.


In fact, the PC hardware doesn't actually do that.  What we really see is
that DRAM memory speed grows at about 1.2X every two years and that our
growth rate is at least 1.3X every two years.  Since BGP can't live in a
cache (at a sane price point), BGP's performance (or any other protocol that
would carry the same number of prefixes) is bounded to converge at the rate
that we can actually perform DRAM writes at.  As we're growing faster than
DRAM gets quicker, BGP necessarily converges a little more slowly every
year.  

See: 

http://www.iab.org/about/workshops/routingandaddressing/Router_Scalability.p
df



|All of this means one simple thing: We'll hit the wall on the FIB's
|capability long before we hit the wall on the BGP RIB's capability.
|
|Absent a RIB+FIB solution that the operators are enthusiastic about,
|it's worth the effort to consider approaches that only reduce the size
|of the FIB.


Those matters, since they are implementation details that actually have
private solutions known to some in the industry are really not our
balliwick.  Again, our charter is to address the routing and addressing
architectural issues that cause a lack of aggregation in the first place.

Regards,
Tony


--
to unsubscribe send a message to rrg-request@psg.com with the
word 'unsubscribe' in a single line as the message text body.
archive: <http://psg.com/lists/rrg/> & ftp://psg.com/pub/lists/rrg