These notes were written to focus on the Cisco implementation of QoS, but I’ll eventually cover enough generic QoS components to make looking at this worthwhile for non-proprietary QoS review. Unless a tile falls from the roof and kills me, etc.. (For Kierkegaard — wiki. )
I recently took the Cisco 642-642 quality of service certification, and the notes are from that study. The 642-642 cert works for the CCVP or the CCIP, but I was more interested in it from the perspective of getting a grip on the subject for the purpose of the routing and switching CCIE.
My original notes were more or less cram notes — I’ll try to put together something more intelligible here.
QoS tool categories:
- Classification and marking
- Queuing / Congestion Management
- Shaping and policing
- Congestion avoidance
- Link efficiency
- Call admission control
1. Classification and marking
Pure marking tools –
- Class-based marking — CBM [including Network-based application recognition -- NBAR (Cisco only)]
Marking plus other functionality –
- policy based routing — PBR
- QOS policy propagation through BGP — QPPB
- Committed Access Rate — CAR
Available markers for QoS sorting (classification):
- IP precedence bits cisco site (from the traditional TOS field, compare with DSCP)
- QoS group [0 to 99; 0 is default, 0=unassigned] — requires CEF (and Cisco)
- DCSP bits wikipedia (replacing, but backward-compatible with, the traditional TOS field)
- 802.1Q / ISL CoS (class of service) aka priority tag — trunking layer-2 link required
- Frame relay DE (discard eligible) bit — if you’ve got frame-relay involved
- ATM CLP bit cisco1 cisco2 — if you have ATM, otherwise not damned likely
- MPLS experimental bits ipinfusion wikipedia — if you have MPLS, otherwise not damned likely