Defending against lameness since 2008

So yesterday I decided to start studying for the Quality of Service (642-642) exam which is in the Cisco Certified Voice Professional (CCVP) certification track. I will be using the Cisco Press books and a Global Knowledge student guide which I believe was provided at a Cisco approved CCVP boot camp. I had firewall experience when I started down the CCSP path last year but I have zero VoIP experience so this test should provide much more of a challenge when it comes to grasping the technology. As with every other certification process there is a plethora of acronyms and definitions that one must stockpile in order to be successful when it comes examination time.  My goal with this post is to document some of the things I learned and in the process help me to remember them by actually typing them out and having a quick reference for later use.

First, the four major problems facing coverged networks:

• Bandwidth Capacity
• End-to-End Delay (both fixed and variable) - Delay is the time it takes for a packed to reach the recipient after being transmitted by the sender.
• Variation of Delay (also known as jitter) - Jitter is the difference in the total end-to-end delay values of two voice packets.
• Packet Loss

The following are types of delay:

• Processing delay - The time it takes for a router to receive a packet on the input interface and place the packet into the output queue.
• Queueing delay - The time a packet stays in the output queue.
• Serialization delay - The time it takes to place a frame on the physical transport medium.
• Propagation delay - The time it takes to transmit a packet.

Things you can do to reduce delay:

• Increase Link Capacity
• Prioritize Delay-Sensitive Packets
• Compress Payload
• Header Compression

Tags: 642-642, ccvp, Cisco, ipt, QoS, voip

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