RE: Do routers prioritize control traffic?

> I know routers today have the ability to prioritize
> traffic, but last I heard, these controls are not
> often used for user traffic (let's not discuss
> net neutrality here).
> 
> Are they used for control (e.g., routing) traffic?

They are used for BUSINESS traffic. Also, since these
controls make
routers work harder, there is no point in using them where
there are no
traffic problems. Most providers build their core networks
with enough
headroom so that there are no traffic problems. That leaves
the last
mile connection to tinker with, however, the cost problem
remains. The
only way to solve the cost problem is where a business
customer will pay
for traffic controls to be implemented on the provider's
edge routers. 

Bottom line is that use of QOS is very common on CPE routers
and edge
routers of business customers and this is usually part of a
total
managed network package such as a VPN or Extranet. 

I have seen QOS implemented for control traffic but that was
a scenario
where the company allowed business customers access to a
tool which
would ping through to the CPE router. In order to prevent
the customer
from DOSing themself with pings, they capped the traffic
with CAR or
similar. 

It can be a bad idea to apply QOS to control traffic since
it is
generally easier and cheaper to add bandwidth. Just because
the machine
has lots of bright buttons and knobs on the control panel
doesn't mean
that it is a good idea to play with them all. And the
fundamental
problem of QOS means that you only use it where you have to.
QOS works
by delaying or discarding packets. It is hard to sell that
as a valuable
service to ordinary users.

--Michael Dillon

On Feb 12, 2007, at 9:10 AM, <michael.dillonbt.com>  
<michael.dillonbt.com> wrote:
>
> They are used for BUSINESS traffic. Also, since these
controls make
> routers work harder, there is no point in using them
where there  
> are no
> traffic problems.

I concur, it only matters when it matters (i.e., when
there's
resource contention).

> Most providers build their core networks with enough
> headroom so that there are no traffic problems.

It's not a matter of just forwarding capacity, it's a matter
of control
plane processing capacity, a variable typically orders of
magnitude
less than the the former.

> And the fundamental problem of QOS means that you only
use it
> where you have to. QOS works by delaying or discarding
packets. It
> is hard to sell that as a valuable service to ordinary
users.

I believe Christos's query wasn't about ordinary users or
transit
traffic, it was regarding "control (e.g., routing)
traffic".  I wouldn't
consider network operations or control traffic
"ordinary users" and
suspect that if network operators aren't limiting
"what" and at what
rate that "what" is permitted to impact the
control plane then their
ordinary users should be very concerned.

A usual example of this is DDOS attacks much larger than 10
Gbps sustained, throwing bandwidth at the problem yields
little
or no return.

-danny