Category: big picture
Greg (@etherealmind) Ferro started an interesting discussion on Google+, claiming MPLS is just tunneling and a duct tape like NAT. I would be the first one to admit MPLS has its complexities (not many ;) and shortcomings (a few ;), but calling it a tunnel just confuses the innocents. MPLS is not tunneling, it’s a virtual-circuits-based technology, and the difference between the two is a major one.
IS-IS has “forever” (at least since RFC 1195) supported multiple layer-3 protocol, but always with a nasty side-effect: if a link in your network did not support one of them, you could get hard-to-diagnose black holes. The problem is illustrated in the left-hand column of the following diagram. Due to a single IS-IS topology, the shortest path between A and B is the direct link and since IPv6 is not enabled on that link (click on the diagram to get an enlarged version where you'll be able to see the link colors), A and B cannot exchange IPv6 traffic even though there’s an alternate path between them.
I’m describing further implications of single/multi-topology IS-IS and deployment guidelines in the Building IPv6 Service Provider Core webinar.
When I’ve asked you to help me fix the webinar marketing based on the results of the Market Trends in Service Provider Networks event, a few readers pointed out that I’m advertising a high-level topic to a wrong audience. However, I firmly believe (and the attendees agreed with me) that a successful engineer has to understand the bigger picture (the environment she’s working in and the forces that shape it), not just from the broader technology perspective (addressed by the Market Trends in Service Provider Networks webinar) but also from the “vertical” (integration) perspective.
Ever since I’ve figured out how to explain complex topics to bright engineers, I wanted to develop content (books, courses, documents) that explained (in this order):
- The Big Picture and WIIFM (What will the student gain by understanding and deploying something based on what I’m describing).
- How the technology we’re using actually works (remember: knowledge, not recipes) and finally
- How to configure, monitor and troubleshoot the actual boxes used to build the solution.
I’m positive you agree this approach makes perfect sense, and every now and then I’ve managed to get it right (for example, in the MPLS VPN books). Unfortunately, you’re often facing an uphill battle, as people want to focus on hands-on topics and hate to learn why things work the way they do instead of memorizing recipes like “Thou shalt not have more than 3 OSPF areas per router”.