Transport for London (TfL) is the integrated body responsible for London’s public transport services. Its mandate includes management of London buses, the London Underground subway system, Docklands Light Railway (DLR) train services, Croydon Tramlink and London River Services. Each day more than 30 million journeys are made in the UK capital. To make them as straightforward as possible, TfL launched an online tool called Journey Planner to help commuters gain a single view of their travel options on any mode of transport. Journey Planner (journeyplanner.tfl.gov.uk) provides a real-time guide to travel in London, with up-to-the-minute travel-related news delivered through the Web site.

The Challenge: Improving the User Experience with a Critical Web Application

Since its launch in 2002, TfL’s Journey Planner Web site has proved enormously popular with users. The number of server hits has rocketed in the past three years, from fewer than six million in the month of January 2003 to 28 million in January 2006. With so many people relying on the site, it is vital that TfL deliver search results quickly and provide transportation updates in real time.

The site also must be able to cope with sudden or prolonged peaks in Web traffic, which can occur during major events. For instance, on December 31, 2005 an industrial strike affected the London Underground service, causing train delays. Journey Planner experienced a 100 percent spike in Web traffic during the day, as travellers in London were forced to make alternative plans. This heavy additional site traffic put a strain on the IT platform.

David Coppins, Group Marketing Operations, technical manager, TfL, said: “We were experiencing a huge growth in traffic and we needed to ensure the site’s performance could cope with more users, as well as unpredictable spikes in Web traffic. We wanted to bolster our infrastructure to improve availability and performance of our Web site. The solution had to be economical, work perfectly, and be fast and easy to implement.”

Implementing Citrix NetScaler Application Switch

Since 2002, TfL has outsourced the hosting and management of its Journey Planner service to Citrix® Solution Advisor Globix, a provider of managed hosting and security services. Globix ensures reliable and high-performance connectivity to users of the Journey Planner platform.

Coppins said, “Initially, the service was hosted on five IBM dual-CPU servers located in Globix’s London hosting centre, but that figure has now grown to thirteen. As the breadth and complexity of the content increased and the number of site visitors grew, the requirement for processing power also increased. The immediate solution would have been to add new Web servers to keep up with demand. However, after discussing this with Globix, TfL concluded this was not the most effective option from a system efficiency or investment perspective.”

In December 2005, TfL Group Marketing Operations and Globix made the decision to implement Citrix® NetScaler® Application Switch, a comprehensive Web application delivery system. At the same time, 13 IBM servers were replaced with 10 new Opteron four-core servers. Citrix NetScaler combines high-speed load balancing and content switching with state-of-the-art application acceleration in a single network appliance that sits between the Web browser and the Web server. Globix brought its Citrix NetScaler system online in 2004, just a few months after the review began.

Effortlessly Managing Peak Usage for Fast Responses

As with most transactional Web sites, TfL’s front-end servers were heavily burdened managing the thousands of Web browser connections spawned by up to 2,000 concurrent browsers. Incredibly, the implementation of Citrix® Request Switching® technology consolidated this to just 50 sessions into the back-end Web servers. Freed from the overhead of TCP session handling, the servers can spend much more of their CPU time responding to application requests, resulting in much better response times and higher throughput.

Coppins said, “Using Citrix NetScaler, the performance of the site has markedly improved and the user experience is excellent. This is especially impressive given the complexity of each journey calculation, which can include every mode of transport – bus, train, subway, ferries, light rail, walking and cycling. Citrix NetScaler enabled us to improve the end user experience whilst consolidating connections to the application servers. By doing this we managed to greatly increase the workload efficiency of the whole platform.”

TfL provides users with a faster and more reliable information service when searching for the best way to commute. Application performance for a search has improved 10-fold, from an average response time of 10 seconds down to one second per transactional page.

Accelerating Processing Power for an Immediate Performance Boost

Immediately after implementing Citrix NetScaler, Globix reduced demand on its servers’ CPU power from 40 percent to 2 percent by offloading much of the communication, security and physical content delivery work that normally burdens a Web server infrastructure. Journey Planner Web site performance was noticeably enhanced: page delivery times were reduced by up to a factor of eight and the home page was opening in an average of 0.6 seconds, down from 1.5 seconds.

Additionally, Globix configured the solutions to reserve more bandwidth than Journey Planner might normally use in one month, so the platform can ‘burst’ to the higher bandwidth during peak times. This burstable bandwidth removed the issue of slowdowns during traffic peaks.

Caching Requests Further Speeds Up Response Times

Much of the information requested on the TfL site is of a repetitive nature: for example, maps and timetables. To reduce server workload, Globix configured Citrix® AppCache™ to cache all commonly required content — such as HTML, images, PDFs, JavaScript and XML. Removing this burden from the Web server infrastructure instantly optimised the efficiency of TfL’s server investment, and considerably improved response times. Up to 40 percent of all server requests are delivered entirely from the cache.

Coppins said, “The ability of Citrix NetScaler’s AppCache to cache common server requests, combined with page compression and connection optimisation, has resulted in improved data transmission to end users. Citrix NetScaler has greatly reduced TfL’s bandwidth requirements without the need to increase server hardware, power or data centre space.”

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