QOS

So I began yet another QOS venture tonight. Watched the nuggets video(s). Here are just some random notes. They will probably be of no use to anybody but me, but here they are:

TOP NETWORK CULPRITS (in terms of good service over the wire!)

1. Lack of bandwidth
2. Packet loss
3. Delay
4. Jitter (variation of delay...i.e. on packet has 20ms delay, next 5, next 55...

QOS MODELS

1. Best Effort (it gets there when it gets there!! like a bitchy old mail lady who is disgruntled with her job)
2. Integrated Services Model (reserved bandwidth from point A ----> point B using RSVP) intserv
3. Differentiated Services Model (this is the best...puts up and breaks down as packets traverse interface)

IMPLEMENTING QOS

1. Do a network audit and identify the critical applications
2. Identify the application requirements (i.e. what protocols...bandwidth...etc)
3. Divide that traffic into groups (i.e. classify it into approx. 4-11 groups)
4. Create and apply policy to those groups

-Qos is basically just classifying and marking traffic

CONGESTION AVOIDANCE MECHANIMS

1. FIFO and Tail-drop
2. Random early detection (RED)
3. Weighted random early detection (WRED)

-Policing traffic drops all packets after a certain threshold is reached (i.e. you say no more after 200kbps)
-Shaping traffic merely queues packets when a pre-defined limit is reached

METHODS OF IMPLEMENTING QOS

1. CLI (hardest method)
2. MQC (modular QOS CLI)
3. AutoQOS (cisco proprietary)
4. SDM
5. QPM (plug-in of CiscoWorks)