Russ

Author Archives: Russ

Random Thoughts on Grey Failures and Scale

I have used the example of increasing paths to the point where the control plane converges more slowly, impacting convergence, hence increasing the Mean Time to Repair, to show that too much redundancy can actually reduce overall network availability. Many engineers I’ve talked to balk at this idea, because it seems hard to believe that adding another link could, in fact, impact routing protocol convergence in such a way. I ran across a paper a while back that provides a different kind of example about the trade-off around redundancy in a network, but I never got around to actually reading the entire paper and trying to figure out how it fits in.

In Gray Failure: The Achilles’ Heel of Cloud-Scale Systems, the authors argue that one of the main problems with building a cloud system is with grey failures—when a router fails only some of the time, or drops (or delays) only some small percentage of the traffic. The example given is—

  • A single service must collect information from many other services on the network to complete a particular operation
  • Each of these information collection operations represent a single transaction carried across the network
  • The more transactions there are, the Continue reading

Complexity and the Thin Waist

In recent years, we have become accustomed to—and often accosted by—the phrase software eats the world. It’s become a mantra in the networking world that software defined is the future. full stop This research paper by Microsoft, however, tells a different story. According to Baumann, hardware is the new software. Or, to put it differently, even as software eats the world, hardware is taking over an ever increasing amount of the functionality software is doing. In showing this point, the paper also points out the complexity problems involved in dissolving the thin waist of an architecture.

The specific example used in the paper is the Intel x86 Instruction Set Architecture (ISA). Many years ago, when I was a “youngster” in the information technology field, there were a number of different processor platforms; the processor wars waged in full. There were, primarily, the x86 platform, by Intel, beginning with the 8086, and its subsequent generations, the 8088, 80286, 80386, then the Pentium, etc. On the other side of the world, there were the RISC based processors, the kind stuffed into Apple products, Cisco routers, and Sun Sparc workstations (like the one that I used daily while in Cisco TAC). The argument Continue reading

1 84 85 86 87 88 162