I’m back from a week of vacation, and I survived my first 2 days back at work. A thankfully moderate amount of e-mail to return to – around 500 or so messages, half of which were automated reports I could just delete. Of the remaining half, not too many required my specific attention, so I was able to blow most of them away as well.
Today is the 4th, so I get to hang around at home and study, with Networkers and my date with destiny looming ever larger. I only have the MPLS appendix to go in the OECG, which will be my focus today. Once the MPLS blogging is behind me, it’s review, review, review until I get on the plane for Anaheim.
NetMasterClass.com has updated their TESTiT question database to reflect the CCIE R&S Written Blueprint v3. So, there’s lots of MPLS questions there now. So that’s good. I did one batch of 100 TESTiT questions Monday night, and found that the MPLS questions weren’t even guessable for the most part. All new acronyms and concepts, none of which lent themselves to easy inferences you could use to eliminate “A” or “B” as happens somewhat often.
I began the MPLS chapter reading last night; I think I know why none of the TESTiT questions were easy to decipher. The problem MPLS is solving is that of scalability in carrier networks: the complexity of having scores or hundreds of routers with their related virtual circuits in a frame or ATM environment. A scalability challenge here is that of IP routing convergence, where, in bit-speak, it takes a long time for routes to converge when topology changes. In addition, with a traditional IP routed network, every router along the way is expected to make a layer 3 forwarding decision, a big responsibility for every device. MPLS goes about solving this problem by (as I understand it thus far) wrapping a label around an IP packet. That label simplifies issues of topology changes and takes some of the decision-making burden off of routers along the way. How MPLS does this will be my course of study today.
The reason I was unable to make good guesses at the TESTiT questions is that this material is truly all-new. A new way of thinking about how a packet gets forwarded through a complex infrastructure.