Scalability issues in the Internet routing system

Wed Oct 26 09:42:51 UTC 2005

Alexei Roudnev wrote:
> You do not need to forward 100% packets on line card rate; forwarding 95%
> packets on card rate and have other processing (with possible delays) thru
> central CPU can work good enough..

heh.
in the words of Randy, "i encourage my competitors to build a router 
this way".

reality is that any "big, fast" router is forwarding in hardware - 
typically an ASIC or some form of programmable processor.
the lines here are getting blurry again .. Moore's Law means that 
packet-forwarding can pretty much be back "in software" in something 
which almost resembles a general-purpose processor - or maybe more than 
a few of them working in parallel (ref: 
<http://www-03.ibm.com/chips/news/2004/0609_cisco.html>).

if you've built something to be 'big' and 'fast' its likely that you're 
also forwarding in some kind of 'distributed' manner (as opposed to 
'centralized').

as such - if you're building forwarding hardware capable of (say) 25M 
PPS and line-rate is 30M PPS, it generally isn't that much of a jump to 
build it for 30M PPS instead.

i don't disagree that interfaces / backbones / networks are getting 
faster - but i don't think its yet a case of "Moore's law" becoming a 
problem - all that happens is one architects a system far more modular 
than before - e.g. ingress forwarding separate from egress forwarding.

likewise, "FIB table growth" isn't yet a problem either - generally that 
just means "put in more SRAM" or "put in more TCAM space".

IPv6 may change the equations around .. but we'll see ..

cheers,

lincoln.