[86200] in North American Network Operators' Group
Re: Scalability issues in the Internet routing system
daemon@ATHENA.MIT.EDU (Lincoln Dale)
Wed Oct 26 05:45:04 2005
Date: Wed, 26 Oct 2005 19:42:51 +1000
From: Lincoln Dale <ltd@interlink.com.au>
To: Alexei Roudnev <alex@relcom.net>
Cc: nanog@nanog.org, Daniel Senie <dts@senie.com>
In-Reply-To: <048701c5d864$da585b40$6401a8c0@alexh>
Errors-To: owner-nanog@merit.edu
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.
