Russ

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The Overoptimization Meltdown

In simple terms Meltdown and Spectre are simple vulnerabilities to understand. Imagine a gang of thieves waiting for a stage coach carrying a month’s worth of payroll.

There are two roads the coach could take, and a fork, or a branch, where the driver decides which one to take. The driver could take either one. What is the solution? Station robbers along both sides of the branch, and wait to see which one the driver chooses. When you know, pull the resources from one branch to the other, so you can effectively rob the stage. This is much the same as a modern processor handling a branch—the user could have put anything into some field, or retreived anything from a database, that might cause the software to run one of two sets of instructions. There is no way for the processor to know, so it runs both of them.

To run both sets of instructions, the processor will pull in the contents of specific memory locations, and begin exexuting code across these memory locations. Some of these memory locations might not be pieces of memory the currently running software is supposed to be able to access, but this is not Continue reading

Is Networking a Commodity?

Is networking becoming a commodity? Do we all need to worry about losing our jobs as network engineers because no-one cares about how a commodity is created or provided? Maybe it is time to take a second look at the commodity craze.

Reaction: Why Safe Harbors will Fail

Copyright law, at least in the United States, tends to be very strict. You can copy some portion of a work under “fair use” rules, but, for most works, you must ask permission before sharing content created by someone else. But what about content providers? If a content provider user uploads a “song cover,” for instance—essentially a remake of a popular song, not intended to create commercial value for the individual user—should the provider be required to take the content down as a violation of copyright? Content providers argue they should not be required to remove such content. For instance, in a recent article published by the EFF—

Platform safe harbors have been in the crosshairs of copyright industry lobbyists throughout 2017. All year EFF has observed them advancing their plans around the world to weaken or eliminate the legal protections that have enabled the operation of platforms as diverse as YouTube, the Internet Archive, Reddit, Medium, and many thousands more. Copyright safe harbor rules empower these platforms by ensuring that they are free to host user-uploaded content, without manually vetting it (or, worse, automatically filtering it) for possible copyright infringements. Without that legal protection, it would be impossible for Continue reading

Section 10 Routing Loops

A (long) time ago, a reader asked me about RFC4456, section 10, which says:

Care should be taken to make sure that none of the BGP path attributes defined above can be modified through configuration when exchanging internal routing information between RRs and Clients and Non-Clients. Their modification could potentially result in routing loops. In addition, when a RR reflects a route, it SHOULD NOT modify the following path attributes: NEXT_HOP, AS_PATH, LOCAL_PREF, and MED. Their modification could potentially result in routing loops.

On first reading, this seems a little strange—how could modifying the next hop, Local Preference, or MED at a route reflector cause a routing loop? While contrived, the following network illustrates the principle.

Note the best path, from an IGP perspective, from C to E is through B, and the best path, from an IGP perspective, from B to D is through C. In this case, a route is advertised over eBGP from F towards E and D. These two eBGP speakers, in turn, advertise the route to their iBGP neighbors, B and C. Both B and C are route reflectors, so they both reflect the route on to A, which advertises the route to some other Continue reading

Adminstravia 010918

I’ve reorganized the menu on the left just a little, combining some items under “reading,” and adding a new item called “topics.” Under this new item, you’ll find collections of articles on specific topics from other sources, starting with the ‘net neutrality page and the meltdown and spectre post reformatted as a page, with some new additions. I’m always trying to find new ways to organize the information here, making it easier to find things; hopefully this is a useful change.

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