Netcraft has been tracking Citrix NetScaler in the Web Server Survey for more than a year. In the latest survey, more than ten million sites were found using Citrix NetScaler.

Citrix bought NetScaler Inc. in 2005 for approximately $300M in cash and stock, acquiring an already maturing network appliance platform. NetScaler provides load balancing, an application firewall, and application acceleration to improve the performance and security of large web applications. NetScaler can run on a variety of dedicated hardware platforms, or it can be run as a server-based virtual appliance. BIG-IP is a competing product from F5 with similar features which reached 10 million sites back in May 2009.

1.71% of all websites found this month were served using the Citrix NetScaler platform; but within the top 100k busiest websites NetScaler's share is much higher at 9.24%. The country distribution of the installed base has a few peculiarities: almost 30% of the websites hosted in Turkey and 20% of the websites hosted in Korea are using NetScaler. In Turkey, the blogcu.com network is using Citrix NetScaler and in Korea more than 50% of the co.cc subdomains were found to be using the platform. Worldwide, Microsoft, eBay, Weather.com, CNET, and MasterCard are among the busiest sites using Citrix NetScaler.

Both of the top two hosting companies had the same number of failed requests this month and they are therefore ranked by average connection time.

Top of the table this month is Hosting 4 Less. The company guarantees 99.9% uptime, with its own OC48 Sonet Ring connecting their secure data center to the internet. Hosting 4 Less has been running since 1998. They offer both Linux and Windows hosting as well as e-commerce hosting.

The second most reliable hosting company for July was PoundHost who are based in the UK and offer a range of hosting solutions, including dedicated servers, co-location and virtual hosting.

Third this month was Datapipe, which offers a range of services including managed hosting, compliance, security and cloud computing. Datapipe offers a 100% network uptime guarantee.

Seven sites in the top 10 this month were running Linux, two were running FreeBSD and one was running Windows Server 2008.

Netcraft measures and makes available the response times of around forty leading hosting providers' sites. The performance measurements are made at fifteen minute intervals from separate points around the internet, and averages are calculated over the immediately preceding 24 hour period.

From a customer's point of view, the percentage of failed requests is more pertinent than outages on hosting companies' own sites, as this gives a pointer to reliability of routing, and this is why we choose to rank our table by fewest failed requests, rather than shortest periods of outage. In the event the number of failed requests are equal then sites are ranked by average connection times.

Information on the measurement process and current measurements is available.

Each of the top three hosting companies had only one failed request this month and they are therefore ranked by average connection time.

Top of the table this month is Datapipe, which offers a range of services including managed hosting, compliance, security and cloud computing. Datapipe is committed to customer service and offers a 100% network uptime guarantee.

The second most reliable hosting company in June was INetU, which offers dedicated managed hosting services from data centers with resilient networks, backup power and strong physical and network security. InetU also offers compliance and consultancy services to customers around the world.

Third this month was New York Internet. NYI offers colocation, dedicated servers and virtual hosting from data centers in New York. The company focuses on reliability and technical support that is responsive round the clock.

Half of the sites in the top ten in June were running Linux, four were running FreeBSD, and one was running Windows Server 2003.

Netcraft measures and makes available the response times of around forty leading hosting providers' sites. The performance measurements are made at fifteen minute intervals from separate points around the internet, and averages are calculated over the immediately preceding 24 hour period.

From a customer's point of view, the percentage of failed requests is more pertinent than outages on hosting companies' own sites, as this gives a pointer to reliability of routing, and this is why we choose to rank our table by fewest failed requests, rather than shortest periods of outage. In the event the number of failed requests are equal then sites are ranked by average connection times.

Information on the measurement process and current measurements is available.

Datapipe was the most reliable hosting company in May 2011 with only a single failed request from Netcraft's performance monitors this month. Datapipe provides a range of managed services and colocation from data centres in New Jersey, California, London, Shanghai and Hong Kong. In May, Datapipe announced it had secured $176 million dollars in equity and finance to accelerate its expansion.

The second most reliable hosting company in May was www.serverbeach.com, which failed to respond to only two requests. ServerBeach offer cloud services, dedicated servers, managed hosting and colocation. As a child company of PEER 1 hosting, ServerBeach uses its parent company's IT infrastructure and network backbone.

Third this month was iWeb Technologies, a Canadian hosting company based in Montreal. iWeb Technologies provide web hosting, dedicated servers, managed hosting and colocation to customers from around the world.

Netcraft measures and makes available the response times of around forty leading hosting providers' sites. The performance measurements are made at fifteen minute intervals from separate points around the internet, and averages are calculated over the immediately preceding 24 hour period.

From a customer's point of view, the percentage of failed requests is more pertinent than outages on hosting companies' own sites, as this gives a pointer to reliability of routing, and this is why we choose to rank our table by fewest failed requests, rather than shortest periods of outage. In the event the number of failed requests are equal then sites are ranked by average connection times.

Information on the measurement process and current measurements is available.

Heading the table for April with only two failed requests from any of the performance monitors during the month was Rackspace. Rackspace provides managed and cloud hosting from nine datacentres in the U.S., the U.K. and China. Rackspace frequently features in Netcraft's top ten most reliable hosting companies, having appeared five times in the last year.

Second most reliable this month was Qube, a London-based hosting company which also has datacentres in New York and Zurich. Qube provide managed hosting, managed colocation and cloud hosting for a wide variety of customers, particularly in the areas of finance and new media. Although Qube has previously appeared in the top ten, this is the first time the hosting company has made it to the top three.

The third most reliable hosting company in April was Netcetera. Netcetera experienced the same number of failed requests as Qube, but had a longer average connection time. Netcetera provides a wide range of colocation, hosting and cloud services to customers throughout the world.

Five of the top ten sites this month were running on Linux, two were running on FreeBSD, and one on Windows. Rackspace's site, which performed best this month, is hosted on F5 Big-IP.

Netcraft measures and makes available the response times of around forty leading hosting providers' sites. The performance measurements are made at fifteen minute intervals from separate points around the internet, and averages are calculated over the immediately preceding 24 hour period.

From a customer's point of view, the percentage of failed requests is more pertinent than outages on hosting companies' own sites, as this gives a pointer to reliability of routing, and this is why we choose to rank our table by fewest failed requests, rather than shortest periods of outage. In the event the number of failed requests are equal then sites are ranked by average connection times.

Information on the measurement process and current measurements is available.