[Xorp-users] SNMP & QoS

[Mark Handley]

On 8/16/06, Aidan Walton <aidan at wires3.net> wrote:
> 1. I recently watched CVS commits of round_robin.cc, round_robin.hh and
> was wondering how this QoS capability gets enabled in the configuration
> and if it is now active if I compile the latest CVS snapshot. (I assume
> this is QoS and not a round robin algorithm for some other function
> rather than traffic management)

round_robin is not a packet scheduler, but part of the new XORP
internal task scheduler.

Previously within each XORP process we had timers and selectors
(sockets), and background tasks used zero-second timers.  Under high
levels of load, we could get backlogged and not perform essential
timers or other functions until it was too late.

The new task scheduler has priority levels for timers, sockets, and
background tasks, and then for tasks within each priority level we do
weighted round robin scheduling.  This allows us to prioritise
important timers or sockets, and to schedule some tasks more than
others without starving any (as would be the case with pure
priorities).

The aim is that this should make XORP (especially XORP BGP) more
robust under overload conditions.  But it's early days yet - I only
wrote the new scheduler last week - and no doubt we'll have to do some
tuning to get this right.

So, sorry, not QoS.  That would be part of the forwarding path, and
XORP (so far) focusses on the control plane leaving forwarding to the
kernel.

 - Mark