*Update on Wafaa Bilal and Recreational Network Traffic

The Brain Behind Paintball Artist Bilal: ‘Domestic Tension’ Sysadmin Jason Potkanski talks about how he helped keep the paintball-via-webcam site running.

Jason Potkanski, who works at the Citizendium Foundation, read the Chicago Tribune Daywatch, to find Wafaa Bilal’s site, Domestic Tension. He looked at the site and saw that it was getting swamped over a DSL link. He sent Ben Chang, lead software programmer of the project, an e-mail offering help, and got an answer back the next day. He visited the project site at the Flatfile Galleries on the 11th – a day when the gun was down most of the day due to the strain that the Internet was placing on the connection – the DSL line and commercial-grade router they used were taking a beating from the Slashdot-like effect of a small pipe.

He immediately offered some performance optimization techniques, such as setting keepalives to 3, and installing eAcellerator to speed up the PHP script, replacing the memory inefficient tail function for the chat. And of course, he told Bilal that he would need a dedicated line to the Internet, and by the next day, they got an OC3-quality connection to Steadfast, at Equinex in Chicago. Immediately he saw an improvement.

He also mounted the webcam image and chatlog/shooter log via NFS, remoted in to do the mounts and copy the application over to the Steadfast connection.

Another problem was the use of XML requests, which wasn’t viable on all browsers, and the fact that the original configuration kept three separate requests open for the chat, the shooter log, and the web cam.

If he had the system to design all over again, he’d design it to use a backend database for the logging features, combine the shooter log and chat so that the application requires only two keepalive connections, not three.

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By Brian Boyko

"Jesus has come back, and he's a phone now."

The Apple iPhone might not be the second coming, but it will certainly be popular. Already the Web is being inundated by speculation, information, mis-information, rumor, innuendo, and anyone with an opinion on Apple writing about the iPhone.

So we thought: Why buck the trend?

The truth is that when this device comes out, many people are going to buy the iPhone, they will use it at their jobs - including those in a corporate IT environment - and that means it is going to become the responsibility of the IT manager.

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by Jeff Hicks

Voice over IP (VoIP) is a hot topic in enterprise networking - mostly because it's a challenge. In implementation, VoIP employs a number of different protocols, and has a unique set of performance requirements that make it a challenge for any data network. Examining VoIP protocols should give someone a basic idea of the performance requirements that VoIP places on the network.

First, there's call setup, which sets up everything needed to make the telephone connection between the caller and the recipient (or “callee”). This requires protocols that enable dial tone, number lookup, ringing, and busy signals before the call even occurs. In addition, the call setup protocols handle things that happen after the call - any resource cleanup and statistic reporting.

Call setup protocols use either TCP or UDP to transfer data during the setup and takedown phases of a telephone call. The messages are sent back and forth between the caller, recipient, and call server using well-known ports. For calls that travel between the VoIP network and the Public Switched Telephone Network (PSTN), the call server will converse with a VoIP gateway using the call setup protocol. There are many different call setup protocols, some standardized and some proprietary. Let’s discuss a few of these.

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Continue reading "VoIP Protocol Basics, and Why VoIP Consumes More Bandwidth Than You Might Expect." »

by Jeff Hicks

There's a number of reasons why a company would move to VoIP. Generally there's been some component of cost-savings - it may be in regular long distance savings, it may be in hardware cost savings (versus a PBX system), it may be that you only have one network infrastructure to deploy and manage.

But it's interesting how in the past couple of years, costs have become less of a factor in the decision process. Long-distance rates have dropped, so the cost factor is not quite as pronounced as it used to be, especially considering short-term rollout costs.

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Continue reading "VoIP Traffic Isn't Just Normal Traffic" »

By Steven Maercklein and Zack Belcher

While we haven’t had a chance to play with Vista yet, (both of us are on the road all the time and we don’t have access to a lab,) we have been doing a lot of research on the new TCP/IP features of Vista and Longhorn.

We spent some time poring over a document from Microsoft’s Research Asia (the guys who designed the Compound TCP/IP [CTCP] algorithm) and it details how the algorithm works. It doesn’t detail how Microsoft has implemented the algorithm – there are alpha, beta, and gamma values that are tweakable, but it doesn’t go into how Microsoft has tweaked them. It looks like this was a document just to prove that CTCP was feasible and ready to be included in Vista.

It does teach you about the behavior of it and what to expect when seen in action, and it makes reference to the current technologies for congestion avoidance that CTCP is based on. However, there are several features of Vista of concern to those involved in network performance.

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Continue reading "Vista's TCP/IP Promises and Perils" »

by Ted Romer

I would say, compared to Windows XP’s TCP/IP stack, the Vista stack has been redesigned from the ground up, instead of merely patched. The result is that there are a number of features in the new stack, (which Microsoft calls “The Next Generation TCP/IP Stack”), which are a bit exciting. (Windows Server Longhorn also runs the same stack as Vista.)

There’s been some pretty interesting changes with Receive Window Auto-Tuning and Compound TCP, which provide more aggressive scaling for the network window. Windows scaling is now enabled by default, and is also configured automatically.

If we think about a TCP conversation right now, a sender is given a window as to how much they can send without acknowledgement. The service slowly ramps up in a linear fashion, and if something happens (like a packet loss) we go back to a slow start and slowly ramp up again.

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