Edit Distance Reveals Hard Computational Problems

As far as computer scientists know, the only general-purpose method to find the correct answer to a SAT problem is to try all possible settings of the variables one by one. The amount of time that this exhaustive or “brute-force” approach takes depends on how many variables there are in the formula. As the number of variables increases, the time it takes to search through all the possibilities increases exponentially. To complexity theorists and algorithm designers, this is bad. (Or, technically speaking, hard.)

SETH takes this situation from bad to worse. It implies that finding a better general-purpose algorithm for SAT — even one that only improves on brute-force searching by a small amount — is impossible.

Source: Edit Distance Reveals Hard Computational Problems | Quanta Magazine

Three-year, 27,000 drive study reveals the most reliable hard drive makers

For this report, Backblaze took a look at 15 different HDD models from the three aforementioned major brands. Earning impressive marks for reliability was the Hitachi 3TB Deskstar 7K3000 (HDS723030ALA640) with a 0.9 percent failure rate and an average lifetime of about 2.1 years.

via Three-year, 27,000 drive study reveals the most reliable hard drive makers | PCWorld.

The worst of the bunch, meanwhile was the 1.5 TB Seagate Barracuda Green (ST1500DL003), with an average lifespan of 0.8 years. Ouch!

Finding More Than One Worm in the Apple

As demonstrated, this vulnerability wasn’t a result of insufficient system testing; it was because of insufficient unit testing. Keith Ray himself wrote a “Testing on the Toilet”8 article, “Too Many Tests,”11 explaining how to break complex logic into small, testable functions to avoid a combinatorial explosion of inputs and still achieve coverage of critical corner cases (“equivalence class partitioning”). Given the complexity of the TLS algorithm, unit testing should be the first line of defense, not system testing. When six copies of the same algorithm exist, system testers are primed for failure.

via Finding More Than One Worm in the Apple – ACM Queue.

Welcome to SIPp

SIPp is a free Open Source test tool / traffic generator for the SIP protocol. It includes a few basic SipStone user agent scenarios (UAC and UAS) and establishes and releases multiple calls with the INVITE and BYE methods. It can also reads custom XML scenario files describing from very simple to complex call flows. It features the dynamic display of statistics about running tests (call rate, round trip delay, and message statistics), periodic CSV statistics dumps, TCP and UDP over multiple sockets or multiplexed with retransmission management and dynamically adjustable call rates.

via Welcome to SIPp.

SIPp can be used to test many real SIP equipements like SIP proxies, B2BUAs, SIP media servers, SIP/x gateways, SIP PBX, … It is also very useful to emulate thousands of user agents calling your SIP system.