Initial release of QFabric Junos can run STP only within the network node (see QFabric Control Plane post for more details), triggering an obvious question: “what happens if a server multihomed to a server node starts bridging between its ports and starts sending BPDUs?”. Some fabric solutions try to ignore STP (the diplomats would say “they are transparent to STP”) but fortunately Juniper decided to do the right thing.

While everyone deeply involved with OpenFlow agrees it’s just a low-level tool that can’t solve problems we couldn’t solve in the past (just like replacing Tcl with C++ won’t help you prove P = NP), occasionally you stumble across mindboggling ideas that are so simple you have to ask yourself: “were we really that stupid?” One of them that obviously impressed James Hamilton is the solution to load balancing that requires no load balancers.

Before clicking Read more, watch this video and try to figure out what the solution is and why we’re not using it in large-scale networks.

After more than a year, I’m back in California, anxiously waiting to meet my fellow bloggers and ask some tough questions to a fantastic lineup of vendors presenting at Net Field Day 2011. Stephen Foskett’s well-oiled organizing machinery is already in full gear; I’m typing this post from a WiFi-equiped car that picked me up @ SFO airport (you see, dear vendors, it’s so easy to make my inner geek happy ... all I need are some fantastic features that are actually usable and work as well as this WiFi connection).

InformationWeek has recently published an OpenFlow article by Jeff Doyle in which they graced me with a single grumpy quote taken out of three pages of excellent questions that Jeff asked me when preparing for the article. Jeff has agreed that I publish the original questions and my answers to them. Here they are (totally unedited):

This is a nice email I got from an engineer struggling with multi-homing BGP setup:

We faced a problem with our internet routers a few days back. The engineer who configured them earlier used the syntax: network x.x.x.x mask y.y.y.y route-map PREPEND to influence the incoming traffic over two service-providers.

... and of course it didn’t work.

Yesterday New York Times published an article covering Nicira, a semi-stealthy startup working on an open source soft switch (Open vSwitch) and associated OpenFlow-based controller, triggering immediate responses from GigaOm and Twilight in the Valley of the Nerds. While everyone got entangled in the buzzwords (or lack of them), not a single article answered the question “what is Nicira really doing?” Let’s fix that.

One of the areas where IPv6 sorely lacks feature parity with IPv4 is user authentication and source IP spoofing prevention in large-scale Carrier Ethernet networks. Metro Ethernet switches from numerous vendors offer all the IPv4 features a service provider needs to build a secure and reliable access network where the users can’t intercept other users’ traffic or spoof source IP addresses, and where it’s always possible to identify the end customer from an IPv4 address – a mandatory requirement in many countries. Unfortunately, you won’t find most of these features in those few Metro Ethernet switches that support IPv6.

Based on what I wrote about the latency and bandwidth challenges of long-distance vMotion and why it rarely makes sense to use it in disaster avoidance scenarios, I was asked to write an article to tackle the idea that is an order of magnitude more ridiculous: using vMotion to migrate virtual machines around the world to bring them close to the users.

That article has disappeared a long time ago in the haze of mergers, acquisitions and SEO optimizations, so I’m reposting it here:

While preparing for my Rome IPv6 seminar, I had to reinvent a few wheels, including slides explaining IPv6 addressing and host behavior ... giving me a perfect reason to study the RFCs and figure out how exactly IPv6 stateless autoconfiguration (RFC 4862) works.

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.