I am trying to setup QOS for IP Phones for the network. I am running CCM 3.3. My access switches are 2948G L2 switches running CATOS. The core switch is 6509 running in Hybrid mode. All switches come back to the 6509 via gig fiber.
I have this so far for the 2948G:
set qos enable
set qos defaultcos 0
set qos map 2q1t 2 1 cos 4-7
The questions I have are:
For the 2948.
Do I need the defaultcos 0 command? Does this only mark untagged packets or does it reclassify all packets? What about voice packets? On the 2 TX queues - does Q1 or Q2 have a higher priority? Which Q should I setup to send the voice? Does it matter?
For the 6509.
What QOS settings would I need on this switch? On what ports would I need to apply this to? Can I just setup the fiber ports and the ports that have CCM & Unity on them, or would I have to setup all ports?
QoS is a congestion management tool. Are you seeing congestion in your Gigabit L2 lan? Dropped packets? Usually you see congestion going from high speed (Ethernet) to low speed (T1). I rarely see a 6500 dropping packets due to congestion, much less Gigabit trunks having problems.
I've managed some large lans with Gigabit links with 3500s/6509s, along with 16 T1s to voip sites (centralized CCM0 and never had issues with L2 congestion (and the worst viruses, Welchia, Blast, Slammer), it's usually L3 (service-policy) interfaces that need QoS.
This goes along the lines of marking email over http which goes above oracle, but just below ftp and between peoplesoft traffic, step below rpc over netbios...(remember the big diffserv push? 3Com NIC you could assign each application a different COPS/Diffserv value)..
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