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The DNS Negative Cache
Considering the DNS query chain—
- A host queries a local recursive server to find out about
banana.example - The server queries the root server, then recursively the authoritative server, looking for this domain name
banana.exampledoes not exist
There are two possible responses in this chain of queries, actually. .example might not exist at all. In this case, the root server will return a server not found error. On the other hand, .example might exist, but banana.example might not exist; in this case, the authoritative server is going to return an NXDOMAIN record indicating the subdomain does not exist.
Assume another hosts, a few moments later, also queries for banana.example. Should the recursive server request the same information all over again for this second query? It will unless it caches the failure of the first query—this is the negative cache. This negative cache reduces load on the overall system, but it can also be considered a bug.
Take, for instance, the case where you set up a new server, assign it banana.example, jump to a host and try to connect to the new server before the new DNS information has been propagated through the system. On Continue reading
Reaction: The Pace of Innovation
Dave Ward has an excellent article over at the Cisco blog on the three year journey since he started down the path of trying to work the standards landscape (called SDOs) to improve the many ways in which these organizations are broken. Specifically, he has been trying to connect the open source and open standards communities better—a path I heartily endorse, as I have been intentionally trying to work in both communities in parallel over the last several years, and find places where I can bring them together.
While the entire blog is worth reading, there are two lines I think need some further thought. The first of this is a bit of a scold, so be prepared to have your knuckles rapped.
My real bottom line here is that innovators can’t go faster than their customers and customers can’t go faster than their own understanding of the technology and integration, deployment and operational considerations.
Precisely. Maybe this is just an old man talking, but I sometimes want to scold the networking industry on this very point. We fuss about innovation, but innovation requires customers who understand the technology—and the networking world has largely become a broad set of meta-engineers, Continue reading
History of Networking: Paul Vixie on the Origins of DNS
Paul Vixie joins us on the History of Networking to talk about the spread of the DNS system—like a virus through the body network. All those radios in the background at a bit of history; Paul is an Amateur Radio Operator of many years, though, like me, he is not as active as he used to be in this realm.
Some Market Thoughts on the Broadcom SDKLT
Broadcom, to much fanfare, has announced a new open source API that can be used to program and manage their Tomahawk set of chips. As a general refresher, the Tomahawk chip series is the small buffer, moderate forwarding table size hardware network switching platform on which a wide array of 1RU (and some chassis) routers (often called switches, but this is just a bad habit of the networking world) used in large scale data centers. In fact, I cannot think of a single large scale data center operating today that does not somehow involve some version of the Tomahawk chip set.
What does this all mean? While I will probably end up running a number of posts on SDKLT over time, I want to start with just some general observations about the meaning of this move on the part of Broadcom for the overall network engineering world.
This is a strong validation of a bifurcation in the market between disaggregation and hyperconvergence in the networking world. Back when the CCDE was designed and developed, there was a strong sense among the folks working on the certification that design and operations were splitting. This trend is still ongoing, probably ultimately resulting Continue reading
Weekends Reads 020218: GDPR, taxes, and security
Security is always changing and failure always exists. This toxic scenario requires a fresh perspective on how we think about operational security. We must understand that we are often the primary cause of our own security flaws. The industry typically looks at cybersecurity and failure in isolation or as separate matters. We believe that our lack of insight and operational Continue reading
Live Training at Safari Books: How the Internet Really Works
I will be teaching my first live training course at Safari Books Online on the 9th of March, starting at noon ET: How the Internet Really Works. It’s hard to describe the level and background for this training, as it will be all over the place; this is a bit of an experiment in this realm. The course description is—
This live training will provide an overview of the systems, providers, and standards bodies important to the operation of the global Internet, including the Domain Name System (DNS), the routing and transport systems, standards bodies, and registrars. For DNS, the process of a query will be considered in some detail, who pays for each server used in the resolution process, and tools engineers can use to interact DNS. For routing and transport, the role of each kind of provider will be considered, along with how they make money to cover their costs, and how engineers can interact with the global routing table (the Default Free Zone, of DFZ). Finally, registrars and standards bodies will be considered, including their organizational structure, how they generate revenue, and how to find their standards.
