certification study

                I thought I’d add a quick explanation for the incredible slow-down in my posting rate. It wasn’t really Summer vacation, but it might as well have been, as far as most of my usual activities go. The reason? I decided to look for a new network position (well you see, there was this acquisition at my previous employer…).

The Summer months were time for brushing up on interview and resume’ production skills, active job seeking, followed by starting a new job and moving. Top that off with breaking in my new cold-forged titanium third leg, and training my newest pet, the yak Matilda, and I’ve got a schedule that barely leaves time for sleeping. (Just kidding about the last two items, of course.)

Anyway — new city, new house, new job. Quite crazy. Along with this comes a slight change of tack in terms of my future networking direction. I had been hedging my bets between going into more depth on general networking, or branching out into Voice networking.  Now, because of the needs of my employer, it looks like I’ll be doing as much additional work with VoIP (and Unified Communications) as possible. I’ve started reading the CVoice text from ciscopress (so far, not bad, not great), and am trying to finish up on a LAN and wireless project for new work so I can start hitting the CCVP. I’ll see how that develops over the next few months.

When I first took the CCNA, I used a shortcut to get subnet masks worked out correctly. This was important, since I didn’t know cold what a /14 was, a /22 was, and so on. I got away by knowing only the classful subnet breaks (/8, /16, /24, /32 — hereafter referred to without the slashes) along with the knowledge that subnets all work (in binary) from left to right with the progression 128, 192, 224, 240, 248, 252, 254, then 255. Rather, I knew those pieces, and I knew what came in the middle, and that was enough to get me through the binary and decimal conversions. Let me explain.

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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.

1. Classification and marking
2. Queuing / Congestion Management
3. Shaping and policing
4. Congestion avoidance
5. Link efficiency
6. 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
  

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