Category: web

The first batch of the latest materials for my Designing Scalable Web Applications course have been published on my free content web site.

An odd idea stroke me when watching the Avalanche NEXT presentation during Networking Tech Field Day – they have a fuzzing module that you can use to test whether your servers and applications survive all sorts of crazy illegal requests. Could that be used to detect SQL injection vulnerabilities in your web apps?

If you’ve ever tried to troubleshoot web application performance issues, you’ve probably seen it all – browser waterfall diagrams, visual traceroute tools, network topologies produced by network management systems … but I haven’t seen them packaged in a comprehensive, easy-to-use and visually compelling package before. Welcome to ThousandEyes.

In the TCP, HTTP and SPDY webinar I described the web application performance roadblocks caused by TCP and HTTP and HTTP improvements that remove most of them. Google went a step further and created SPDY, a totally redesigned HTTP. What is SPDY? Is it really the final solution? How much does it help? Hopefully you’ll find answers to some of these questions in the last part of the webinar.

In previous videos from the TCP, HTTP and SPDY webinar I described the network-related performance challenges experienced by web applications and did a deep dive into TCP and HTTP mechanisms underlying them.

Today’s video describes numerous TCP and HTTP enhancements – from increased initial congestion window (recently published as RFC 6928) and TCP fast open to persistent HTTP sessions and pipelining.

The deep dive into TCP and HTTP mechanisms that impact web application performance triggered numerous questions during the live webinar session – it took me almost 10 minutes to answer them all.

In the first part of the TCP, HTTP and SPDY webinar I explained why TCP and HTTP impact the end-to-end web application performance. In the second section of the webinar, we did a deep dive into the actual TCP and HTTP mechanisms that increase end-to-end latency (3-way handshake, initial congestion window, request/response nature of HTTP).

In the ideal world, you’d get a new web page within 100 milliseconds of clicking an active web page component (link, button ...). Reality is way harsher – sometimes it takes seconds till you can enjoy a web page served from a well-behaved web server (let’s pretend there are no server performance issues).

In the first part of my TCP, HTTP and SPDY webinar I explained how the transport mechanisms (TCP and HTTP) impact the end-to-end web application performance and what you could do to reduce the web page loading time.

Most web application developers remain blissfully unaware of the major performance roadblocks their applications face in the wild: access network bandwidth restrictions and unexpectedly high latency (see also Fallacies of Distributed Computing with an in-depth explanation). The impact of these two roadblocks is further amplified by behavior of TCP and HTTP, the protocols used by almost all web applications.

These issues are well documented in my Scalable Web Application Design course and in a free TCP, HTTP and SPDY webinar for those of you who won’t be able to make it to Ljubljana.

A while ago Matthew Norwood wrote an excellent article describing the troubleshooting process they used to figure out why a particular web application worked way too slowly. Greg Ferro was quick to point out that it doesn’t make sense to assume the network is the problem and work through the whole chain slowly eliminating every potential networking device as the source of the problem when you might be facing an application design issue. However, there’s an even more important consideration: your network troubleshooting toolbox lacks the right troubleshooting tools for this job.

Following my obituary for Cisco’s WAF, Packet Pushers did a really great WAF-focused podcast with Raven Alder, appropriately named Saving the Web with Dinky Putt Putt Firewalls. If you have more than a fleeting interest in protecting business web applications, you should definitely listen to it. Just as an aside: when they were recording the podcast, I was writing my To WAF or not to WAF post ... and it’s nice to see we’re closely aligned on most points.

There’s just a bit I’d like to add to their ponderings. What Raven describes is the “proper” (arduous, time-consuming and labor-intensive) use of WAF that we’re used to from the layer-3/4 firewalls: learning what your web application does (learning because the design specs were never updated to reflect reality) and then applying the knowledge to filter everything else (what I sometimes call the fascist mode – whatever is not explicitly permitted is dropped).

A few days ago I wrote that you should always strive to understand the technologies beyond the reach of your current job. Stephen Foskett is an amazing example to follow: although he’s a storage guru, he knows way more about HTTP than most web developers and details of the web server architecture that most server administrators are not aware of. Read his High-Performance, Low-Memory Apache/PHP Virtual Private Server; you’ll definitely enjoy the details.

And then there’s the ultimate weekend fun: reading Greg’s perspectives on storage and FCoE. It starts with his Magic of FCoTR post (forget the FCoTR joke and focus on the futility of lossless layer-2 networks) and continues with Rivka’s hilarious report on the FCoTR progress. Oh, and just in case you never knew what TR was all about – it was “somewhat” different, but never lossless, so it would be as bad a choice for FC as Ethernet is.

Last but not least, there’s Kevin Bovis, the veritable fountain of common sense, this time delving with the ancient and noble art of troubleshooting. A refreshing must-read.

Extremely valid comment made by Pavel Skovajsa in response to my “Rest in peace, my WAF friend” post beautifully illustrates the compartmentalized state some IT organizations face; before going there, let’s start with the basic questions.

Do we need WAF ... as a function, not as a box or a specific product? It’s the same question as “do we need virus scanners” or “do we need firewalls” in a different disguise. In an ideal world where all the developers would be security-conscious and there would be no bugs, the answer is “NO”. As we all know, we’re in a different dimension and getting further away from the heavens every time someone utters “just good enough” phrase or any other such bingo-winning slogan.

It’s popular to bash IT vendors’ lack of security awareness (Microsoft comes to mind immediately), but they’re still far ahead of a typical web application developer. At least they get huge exposure, which forces them to implement security frameworks.

A few years ago, Cisco bought a company that made application-level firewalls, first an XML-focused product (XML Gateway) that was also able to verify your XML data, later a Web Application Firewall (WAF), which was effectively the XML product with half of the brains ripped out.

I was really looking forward to these products. Layer-3 firewalls cannot protect web sites against application-layer problems like SQL injections or cross-site scripting, so we definitely need something on the application layer and the WAF (and XML Gateway) ran as virtual appliance in VMware, making them ideal for my lab environment. I quickly lost interest after the first cursory contact with the XML Gateway as you could only manage both products with a web-based GUI (and I definitely don’t want to publish blog posts full of screenshots).