Scalability issues in the Internet routing system

Tue Oct 18 19:14:03 UTC 2005

Andre Oppermann wrote:
> vijay gill wrote:

>> 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?

Missing the point. We can deal with increased speeds by going wider, the 
network topology data/control plane isn't going wider, THAT is where the 
moore's observation was targeted at.

> 
>> 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.
> 

And we're paying for it. But again, assuming that the prefix/memory 
bandwidth churn can be accommodated by the next generation of cpus. I am 
not going to throw out my router in 18 months. Its still on the books.

>> 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.

Each update to and fro from memory takes cycles, and as the routing 
tables become bigger, the frequency of access to the memory for keeping 
the system in sync impose a larger burden. This is orthogonal to link speed.

/vijay