North American Network Operators Group

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Re: Scalability issues in the Internet routing system

  • From: Andre Oppermann
  • Date: Tue Oct 18 14:20:15 2005

vijay gill wrote:
Andre Oppermann wrote:
I guess it's time to have a look at the actual scalability issues we
face in the Internet routing system. Maybe the area of action becomes
a bit more clear with such an assessment.

In the current Internet routing system we face two distinctive scalability

1. The number of prefixes*paths in the routing table and interdomain
routing system (BGP)

This problem scales with the number of prefixes and available paths
to a particlar router/network in addition to constant churn in the
reachablility state. The required capacity for a routers control
plane is:

capacity = prefix * path * churnfactor / second

I think it is safe, even with projected AS and IP uptake, to assume
Moore's law can cope with this.
Moore's law for CPUs is kaput. Really, Moore's Law is more of an observation, than a law. We need to stop fixating on Moore's law for the love of god. It doesn't exist in a vacuum, Components don't get on the curve for free. Each generation requires enormously more capital to engineer the improved Si process, innovation, process, which only get paid for by increasing demand. If the demand slows down then the investment won't be recovered and the cycle will stop, possibly before the physics limits, depending on the amount of demand, amount of investment required for the next turn etc.
Predicting the future was a tricky business ten years ago and still is
today.  What makes you think the wheel stops turning today?  Customer
access speed will no increase?  No more improvements in DSL, Cable and
Wireless technologies?  Come on, you're kidding.  Right?

Also, no network I know is on the upgrade path at a velocity that they are swapping out components in a 18 month window. Ideally, for an economically viable network, you want to be on an upgrade cycle that lags Moore's observation. Getting routers off your books is not an 18 month cycle, it is closer to 48 months or even in some cases 60 months.
When you are buying a router today do you specify it to cope with 200k
routes or more?  Planning ahead is essential.

Then we have the issue of an memory bandwidth to keep the ever changing prefixes updated and synced.
Compared to link speed this is nothing.  And nowhere near to memory bandwidth.