This question, taken from the CCDE Written Outline, taught me something new. Since that’s the purpose of any certification, I welcome these interesting, if somewhat vague, questions. The main issue with re-marking and Out-of-Order packets can be found in RFC3819: (aka BCP89) “reordering does come at a cost with TCP as it is currently defined.Continue reading “What is the issue with re-marking and OoO packets?”
RIPv2 gets a bad rap, in my opinion, because it still has some suitable network topologies that it works well for. It’s kind-of like the visceral reaction some people have towards static routing. There’s no ‘right’ answer for most of these design types of decisions, only ‘better’ answers. As for RIPv2, let’s see some ofContinue reading “RIPv2 advantages & disadvantages”
I checked the online certifications tracking tool and found out that I have failed my first attempt at the CCDE. What does this mean to me, and what am I going to do about it now? I’ve already registered to sit for the next practical exam in August (Chicago, IL). This leaves me with roughlyContinue reading “I failed the CCDE… now what?”
Nothing yet from the CCDE team. It’s only been 8 weeks.
Registration opens 1 April for a 26 August lab date. More info. New lab location: Hong Kong.
I came across an interesting topic in the book Traffic Engineering with MPLS yesterday. The topic involves migration from narrow to wide metrics. As you know, wide metrics are required to support MPLS TE, so if you have a network that is currently deployed with narrow metrics (the default) you will have to migrate toContinue reading “IS-IS, MPLS-TE, and wide metrics”
14 people in Chicago and 14 people in London took the test today. First impressions: 1. It’s very, very difficult2. I don’t think it’s “impossible” However, I will caveat this with – I don’t really think I have a chance at passing. In all, I had fun taking it. I’m mostly relieved to have hadContinue reading “Took the CCDE Practical Exam Today”
I work primarily on satellite communications systems. TDMA and FDMA satellite networks present interesting data communications issues, since our RTT is usually on the order of 700ms. One thing we’ve been experimenting with is caching of data. The NME-WAE product works well for caching, but can occasionally ’cause’ problems that are exacerbated by virtue ofContinue reading “Content Networking & Satellite Communication”
I’m reading Definitive MPLS Network Designs and I came across an interesting detail with respect to carrier delay. Carrier delay is how long to wait before signaling to the control plane a detection of a network link failure. By default, the interface will wait 2 seconds before signaling failure. Typically, it is a best practiceContinue reading “Fast convergence & carrier-delay”
I had an occasion to do some IP SLA testing. We needed simple icmp-echo probes that would measure delay & loss. We also wanted to configure icmp-echo probes with DSCP=EF in order to measure delay & loss of our priority traffic. Interestingly enough, the DSCP values are copied in the reply packets – at leastContinue reading “IP SLA & DSCP testing”