[c-nsp] control-plane packet transmit priority on PFC + lan card platforms

[Anton Kapela]

List,

I've been trying to determine if c6500 pfc2/3 and msfc2/3 support
something like transmission priority for control-plane generated
protocols (layer2 and 3 control protocols, that is -- lldp, ospf,
isis, bgp, rsvp, stp, cdp, etc). I've read over this:

"Egress LAN Port Scheduling.."
http://www.cisco.com/en/US/docs/routers/7600/ios/12.2SXF/configuration/guide/qos.html#wp1698086

...and can observe that, at least for switchports set to 'mode trunk,'
packets from the msfc2 or 3 are emitted with CoS 6 and 7 set, on
packets that are clearly OSPF and PIM hellos. My assumption is that I
can simply map CoS to queues (prio or regular) and assign a drop
threshold like I normally do, but is this a safe assumption? 2nd
question: is there already some "unconditional priority" queue hidden
from MLS or the MQC configuration which is uses to transmit
control-plane sourced messages?

My recollection was that on sonet and various other lower-speed serial
lines, things like PPP LCP packets were unconditionally transmitted
head-of-line by whatever control plane was handling the port, ie.
rsp4, 2800, 7200, etc.

Best,

-Tk