Joe Greco wrote:
This isn't a new issue. Quite frankly, software routers have some very
great strengths, and also some large weaknesses.
Advocates of hardware based solutions frequently gloss over their own
weaknesses.
Let's talk plainly here.
I'm not going to touch on things like Cisco's software-powered systems,
and for purposes of this discussion, let's take "hardware" to mean
"hardware-accelerated" solutions that implement forwarding in silicon.
That makes a fairly clear delineation between something like a Cisco
7600 and a Vyatta router. So.
Hardware router: Insanely great forwarding rates.
Software router: Varies substantially based on platform architecture and
software competence. Generally speaking, a competent config can
run 1Gbps ports without issue, but >=10Gbps gets dicey. ... [remaining
good summary removed]
There's really three categories:
1) Devices which make all forwarding decisions and do the forwarding in
software
2A) Devices which do forwarding in hardware, but which have a
significantly limited forwarding table and punt to software for misses
2B) Devices which do forwarding in hardware, and which have hardware
forwarding tables sufficient to hold your whole routing table
These then have the following attributes:
1) Can't handle traffic forwarding rates as high as the others, can do
complex filtering, often least expensive choice, may scale well with
commodity hardware scaling (processor, RAM, interface speeds). Great
choice if you operate within their limitations and/or need their
flexibility and potential processing complexity.
2A) Can handle higher forwarding rates, often can forward packets using
less power-per-bps than systems in category 1, filtering at these rates
is limited in capability, tends to scale with improvements in LAN
switching technology (these are essentially layer 3 switches). Great in
data centers, network edges. Dangerous in places where forwarding table
exceeds hardware cache limits. (See Code Red worm stories)
2B) Can handle high forwarding rates, potentially lowest power-per-bps
for forwarding if you are operating at sufficient scale, filtering at
these rates is limited in capability, scales with investment in these
highly specialized devices and the underlying TCAM technology. Great for
Internet backbone network routing if you have the money. Expensive.
Matthew Kaufman