Tuesday, April 5, 2011

Summing Up Classification and Marking, with Add'l References

The end of chapter summary just revisits commands, recommends further reading, and provides definitions. It also suggests you "fill in key tables from memory." After reviewing the original posting, I have concluded that while this chapter of the book provides a decent review, the book as a whole fails to provide a good overview of how marking (Ch 12), congestion avoidance (Ch 13), and shaping (Ch 14) all work together. So, I highly recommend all the additional reading discussed below.

I am omitting the recap of commands because I've already covered them in prior posts. However, I find their table on DiffServ RFCs useful so here it is-

RFC       Title                                                               Comments
2474      Definition of the DiffServ Field                         Contains details of the DSCP field in IP headers
2475      An Architecture for Differentiated Services      Core DiffServ concepts document
2597      Assured Forwarding PHB Group                     Defines 12 DSCP values and usage convention
3246      An Expedited Forwarding PHB                       Defines a DSCP value for use as a low-latency class
3260     New Terminology and Clarifications for DiffServ   Clarifies but doesn't supercede existing RFCs

The book also recommends you be able to write down definitions for the following terms:
IP Precedence, ToS byte, Differentiated Services, DS Field, Per Hop Behavior, Assured Forwarding, Expedited Forwarding, Class Selector, Class of Service, Differentiated Services Code Point, User Priority, Discard Eligible, Cell Loss Priority, MPLS Experimental Bit, class map, policy map, service policy, Modular QoS CLI, Class Based Marking, Network Based Application Recognition, QoS preclassification, AutoQoS.

Recommended further reading includes-

Cisco QoS Exam Certification Guide (2nd Edition), by Wendell Odom
End to End QoS Network Design, by Tim Szigeti
For real life QoS deployments, read the Enterprise QoS SRND Guide, posted at Cisco's website

My next post will summarize a few pertinent points from the Cisco QoS exam certification guide, as well as the QoS SRND Guide.

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