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A Peek At Google's Software-Defined Network

Posted by samzenpus on from the check-it-out dept.

CowboyRobot writes "At the recent 2013 Open Networking Summit, Google Distinguished Engineer Amin Vahdat presented 'SDN@Google: Why and How', in which he described Google's 'B4' SDN network, one of the few actual implementations of software-defined networking. Google has deployed sets of Network Controller Servers (NCSs) alongside the switches, which run an OpenFlow agent with a 'thin level of control with all of the real smarts running on a set of controllers on an external server but still co-located.' By using SDN, Google hopes to increase efficiency and reduce cost. Unlike computation and storage, which benefit from an economy of scale, Google's network is getting much more expensive each year."

3 of 75 comments (clear)

  1. centralized = fault-tolerant? by Anonymous Coward · · Score: 4, Interesting

    "it provides logically centralized control that will be more deterministic, more efficient and more fault-tolerant."

    I'll agree with deterministic and efficient, and perhaps even less likely to fault, but more fault-tolerant seems like a stretch. SDN might get you better fault-tolerance, but that is not because the control is centralized. I suspect the control has more information about non-local requirements and loads, and that can get you better responses to faults. That happens because the controllers can communicate more complex information easier, since that is pure software, not because its centralized. You can have these fault tolerance gains via non-centralized SDN too.

    1. Re:centralized = fault-tolerant? by bbn · · Score: 3, Interesting

      Compare it to the alternative such as the good old spanning tree protocol. You have a number of independent agents who together have to decide how to react to a fault. This is complex and requires clever algorithms that can deal with timing issues and what not.

      With a centralised controller the problem is much easier. One program running on one CPU decides how to reconfigure the network. This can be faster and possibly find a better solution.

      Of course you need redundant controllers and redundant paths to the controllers. Apparently Google decided you need a controller per location.

  2. How can you have a software defined network? by Viol8 · · Score: 4, Interesting

    A network is physical infrastructure - software isn't going to be rerouting cables or installing new wifi nodes anytime soon.

    If all they mean is routing tables are dynamically updated then how is this anything new?

    This isn't a troll, I genuinely don't see where the breakthrough is.