Do routers prioritize control traffic?

Sun Feb 18 00:14:02 UTC 2007

On Feb 12, 2007, at 9:10 AM, <michael.dillon at bt.com>  
<michael.dillon at bt.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 