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Ask Slashdot: Advice On Building a Firewall With VPN Capabilities?

rcw-home Re:The summary of my research (238 comments)

I've used Soekris hardware extensively with Strongswan IPSec at work. I love the boards, but a large number of our Internet circuits are now faster than the net5501 and net6501 can soak with AES IPSec. The net5501 is good for about 8Mbit/sec and the net6501 is good for about 25Mbit/sec with our firewall ruleset and some dynamic routing thrown into the mix. I'm looking forward to the net6801 when it comes out, but in the meantime for those circuits I've been building whitebox 1U routers that have CPUs with AES-NI support (which can easily soak several gigabit/sec). These can be low-power solid state too - recently we've been ordering the Supermicro A1SRi-2758F boards, which have the new Rangeley Atom CPUs, 4 gigabit ethernet ports, and no fans. Just add an SO-DIMM and a USB stick to boot off of, and stick in a 1U short-depth mini-ITX case (I like the Supermicro CSE-505-203B, which puts everything but the power socket in the front).

about a week ago

Firefox's Blocked-By-Default Java Isn't Going Down Well

rcw-home Re:Firefox has criticals every release, too (362 comments)

This is definitely worth noting! It's really sad that they haven't had a release since 6.0.2 that didn't fix a critical security hole.

about a year ago

Firefox's Blocked-By-Default Java Isn't Going Down Well

rcw-home Re:Already considering uninstalling firefox (362 comments)

Java updates every 3 months. Every release they do fixes a gaggle of remote-exploit-without-authentication security holes, and comes with a warning such as "Due to the severity of these vulnerabilities, and the reported exploitation of CVE-2013-1493 "in the wild," Oracle strongly recommends that customers apply the updates provided by this Security Alert as soon as possible." Exactly what reason do you have to believe that their latest release not only has no known vulnerabilities at the time of that release, but will have no known vulnerabilities for the entire time that that release is current, when there has been evidence to the contrary for *every* past release for *years*?

about a year ago

New Solar Cell Sets Record For Energy Efficiency

rcw-home Re:The 44.7% efficiency requires 297 suns (165 comments)

I was curious so I did the math. sqrt(297) is 17.2, ergo, the light is concentrated from an area which is at most 35mm square. There's no details here about what the focal length is. With a fresnel lens it can be quite short, but let's say it's f/1 and your focal length is 35*sqrt(2)=50mm. The most extreme day-to-day movement in an analemma is slightly less than 0.4 degrees, at or around the equinoxes. At f=50mm, 0.4 degrees will put you 0.35mm off center. It's very likely the beam is focused onto most of the square rather than just the center, so you will lose a bit of power (certainly not all of it) by only setting it every two days near the equinoxes. Constant tracking throughout the day is certainly not necessary.

about a year ago

New Solar Cell Sets Record For Energy Efficiency

rcw-home Re:The 44.7% efficiency requires 297 suns (165 comments)

Assuming you rig the axes in a polar alignment, you only need to set one of the axes (ascension) constantly. The other (declination) can be adjusted every few days (less often if you are concentrating fewer suns, i.e. have a bigger target to hit). Also if you use these in a linear format (analogous to the parabolic trough mirror setups) then you don't need to track constantly on the ascension axis either.

about a year ago

Studying the Slow Decay of a Laptop Battery For an Entire Year

rcw-home Re: Here's the real problem (363 comments)

Starting a car uses less than 1% of the car's battery capacity (source: go on Youtube and look for videos of people who have replaced their car's lead-acid battery with a much smaller array of supercapacitors). Ergo, a car that only has a small fraction of its battery capacity remaining is OK, but a laptop that only has a small fraction of its battery capacity remaining is not.

about a year ago

Building a Full-Auto Gauss Gun

rcw-home Re:Lots of Power (285 comments)

That current-carrying capacity will manifest as an extremely low ESR (equivalent series resistance). For this application, CanHasDIY would want to ignore any parts that don't spec that.

about a year ago

Hands On With the Nokia Lumia 1020

rcw-home Re:Meh (227 comments)

What makes you think the lenses are not good?

Because it's a 1/1.5" sensor (3.93 crop factor) at its widest focal length and 1/4.5" at it's narrowest, with an f/2.2 lens, which means a relatively small ~3mm aperture which will necessarily yield muddy pictures, similar to most point-and-shoots?

about a year ago

HTTP 2.0 Will Be a Binary Protocol

rcw-home Re:Makes sense (566 comments)

Near? I've seen multi-megabyte.

about a year ago

North Korea Threatens US With Preemptive Nuclear Strike

rcw-home Re:First strike! (727 comments)

Before NK started on developing actual nukes, their "nuclear option" was (and very arguably still is) artillery pieces. Thousands of them, including a few hundred 170mm guns and 240mm rocket launchers that can potentially reach Seoul. North Korea has stated that they can rain 250,000 shells per hour down on Seoul, although South Korean estimates are that they can do, at best, 20,000, and more realistically 2,400.

about a year and a half ago

West Virgnia Auditor Finds Cisco Router Purchase Not Performed Legally

rcw-home Re:Dual power supplies (280 comments)

Maybe you can, at least, put the 2nd UPS on a different phase (if L-N connected like 120 volts in NA or 230 volts in EU) or phase pair (if L-L connected like 208 volts in NA or 400 volts in EU if that's a step-down UPS). That way you have a chance of ridding through single phase outages which sometimes happen.

Some big caveats to this:

In North America, residential power is "split-phase" which is still considered single phase - it is a pair of hot wires delivered to you, with neutral off the center tap of the transformer on the pole, tied to ground at the service entrance. It's actually very rare for just one of those phases to die (I have yet to see it happen), as it would require a break in one of the hot wires running from your house to the pole. These are low voltage lines so they are typically bundled together, so if run aerially, a tree would snag both of them at once, and if underground a flood would damage both at once. A dead transformer or a dead power line anywhere upstream of the transformer would kill power to both.

Three-phase failure modes often leave you with only one phase out of three working, but never two. This is regardless of whether you are drawing phase-to-neutral power or phase-to-phase power. Imagine the phases of a three-phase system as three dots in a triangle, and the connections between those dots are the power you can draw. If one of the dots goes away, you're left with just one remaining connection between the remaining pair of dots. Remember the neutral is only generated locally at the transformer, so it does not provide any sort of redundant path for anything outside of the building.

about a year and a half ago

What To Do When an Advised BIOS Upgrade Is Bad?

rcw-home Re:Yes (467 comments)

Not in the last 7-8 years it hasn't. I tried for 3 hours on the phone to get a laptop hard drive replaced under next-business-day warranty. They wouldn't budge, because I couldn't produce the output of the diagnostic tools that were loaded *on that hard drive*. In the end, we got the replacement drive when they felt they could get around to it.

These days, there's little point to getting a hot-swap RAID server from Dell, because to get a replacement drive from them they will ask you to take the server offline and run the diagnostic checks on it. This is a far cry from 10+ years ago when I got replacement drives via UPS SonicAir over holiday weekends.

about a year and a half ago

Current favorite still-image camera type:

rcw-home Re:I hate them all. (316 comments)

There's actually a pretty good range of ultra-wide APS-C lenses now. Canon has a 10-22mm. Nikon has a 10-24mm. Sigma has an 8-16mm, a 10-20mm, as well as circular and diagonal fisheyes. Tokina has a 11-16mm. Tamron has a 10-24mm. There's others. They're very proud of them too, judging by their prices.

I went a cheaper route and got the Samyang 8mm fisheye. When I want rectilinear output, I convert it with hugin.

about a year and a half ago

Ask Slashdot: DIY 4G Antenna Design For the Holidays?

rcw-home Re:30$? (135 comments)

Another way to calculate this: Google "c/1.8GHz" and it'll give you the result in centimeters. Then just divide by two to get a half-wavelength dipole or divide by 4 to get a 1/4-wave ground plane length.

If you want a high-gain directional antenna for >1GHz you're probably best off with a dish, perhaps using a cantenna-like feed horn.

about 2 years ago

Building the Ultimate Safe House

rcw-home Re:Vaastu Temple withstands 150mph (289 comments)

of course, these days, for anyone in the building trade to quotes believe quotes that this is even remotely possible would require supercomputers and fluid dynamics analysis

Or a small scale-model wind tunnel that could cheaply and easily be built with some plywood, some fans, and maybe some smoke or thread to show wind direction. It shouldn't cost more than $100.

You sound like you have something to prove here. Get on it.

about 2 years ago

Standard For Electric Car Charging Announced

rcw-home Re:Three-phase (212 comments)

In the US, 208 3-phase is standard to the house, with 120 single phase only within the house.

No, it is not. Split-phase is the norm.

about 2 years ago


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