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Agile Computing: Article

ADCs Accelerate Web 2.0 Applications . . .

. . . that adversely impact datacenter and network performance

Web 2.0 applications bring powerful user interfaces with new capabilities and higher functionality to the Web, while new browser-side application intelligence delivers a richer user experience. However, along with the new capabilities, Web 2.0 applications create new issues that result in challenges to both datacenter and network infrastructure, as these new application deployments require much greater communication between client browsers and servers.

Traditional web applications use browsers simply as rendering engines where all the application logic (e.g., user information, page format, etc.) is located on the servers. For the most part, the browser displays the formatted HTML pages that are sent by the server, where most of the processing is accomplished.

Web 2.0 applications, however, distribute the logic between the server and browser. The browser becomes more than a rendering engine and is capable of processing application logic on the client side without requiring the exchange of data with the server. The benefits of this capability include more features enabled, greater functionality and a more compelling user interface with interactive capabilities far beyond what traditional web applications can provide.

Web 2.0 applications, such as GMail, Live Maps, Facebook and many others, use a combination of Dynamic HTML, CSS and/or XML/XSL-T, JavaScript, Flash and other browser technologies commonly referred to as AJAX, to push application execution to client browsers. This capability improves the responsiveness of these network-bound applications, but the shift of application execution from a back-end server to the client can also dramatically increase the amount of code that must first be downloaded to the browser. Application developers are offloading code from servers, and moving the code to client browsers to create highly responsive distributed applications. This new distribution of code requires that it must first be transferred over the network, which takes additional time. It also requires servers and clients to work harder to accomplish the many communication transfers between them.

Organizations are moving to Web 2.0 because when code is running on the user's machine, more features and capabilities can be enabled, as the clients do not need to get the entire application from the server every time. But, the client still requires the server to transfer many code elements in order to work. Datacenter managers need to deal with the problems associated with code delivery over the network in order to make Web 2.0 applications run faster, and enable the next-generation applications. The big question is: "How is this accomplished?"

Compared to traditional Web applications, Web 2.0 applications require many more request/response interactions on the client browser, the network and datacenter servers.

This article will discuss Application Delivery Controllers (ADCs) and how they apply diverse acceleration technologies to Web 2.0 application deployments. ADCs ensure that the initial transfer of the application code is fast for application initialization. As the rest of the application's code is delivered in short stubs by the server - ADCs can transfer the code transparently in the background, or on-demand on first execution of a particular application feature. Because ADCs significantly speed up the application startup, and since subsequent code that is downloaded is interweaved with application execution, Web 2.0 applications delivered with ADCs are much more responsive to the end user.

ADCs can reduce the size of application code downloads by hundreds of kilobytes, and reduce the download size by as much as 95% of the original. The time to download and begin interacting with large applications can be significantly reduced depending on the application and network conditions. ADCs excel with wireless and mobile network connections, which are becoming increasingly more important in today's Web 2.0 computing environments.

Web 2.0 Applications Can Impose Adverse Effects on the Network
For large sites using Web 2.0 applications, as much as 80 percent of the entire application download may be JavaScript code. Deploying an ADC accelerates JavaScript code downloads and ensures that when client browsers download the code, the process will not slow the application progress. An ADC can accelerate Web 2.0 applications to eliminate up to 90 percent of the Web 2.0 performance issues.

Due to the continuous transfer of data between the server and browser, Web 2.0 applications place additional strain on networks with functionality such as data pre-fetching, session data synchronization, real-time polling (updating), etc. As Web 2.0 applications use the network to transfer application logic and data, they add new exchanges between browsers and the applications on the servers, creating more connections. Due to the increased number of network connections, servers must handle an increase in TCP connection setups and teardowns, and network connections have more latency and congestion to contend with.

Web 2.0 applications place greater strain on user devices, networks and servers.

With Web 2.0 applications, communication between the browser and server is continuous and, therefore, the datacenter and network connectivity supporting these applications must be provisioned with enough servers and bandwidth so as not to slow applications to a crawl.

Below are some of the areas upon which Web 2.0 applications impose latency and overhead:

  • Network-bound latency
  • Server TCP processing overhead
  • Uncompressed data transfer overhead
  • Server SSL processing overhead

ADCs are the right solution for Web 2.0 applications that need faster downloads and optimized bandwidth utilization

Application developers creating high-performance Web applications need to optimize their code structure based on performance considerations. However, this is difficult to accomplish when the applications are delivered over unreliable Internet connections and deployed within datacenters where server infrastructure is supporting diverse applications and technologies.

An ADC is able to reduce the initial transfer of the application code by as much as 50 percent, and page-loading time for JavaScript and AJAX-based applications can improve by as much as 40 percent depending on the application and network conditions.

By deploying an ADC, application developers can focus on the application functionality, and on ensuring that their code structure is easy to read and maintain. All the issues related to application delivery performance are now handled by the ADC.

ADCs accelerate datacenter server resources so they can handle a greater volume of Web 2.0 traffic, and optimize network links to reduce the excessive bandwidth utilization that the applications produce. Some of the features that datacenter managers should look for in an ADC for optimizing their Web 2.0 applications include TCP offloading and multiplexing, application-level routing, server load balancing, global site and link load balancing (with built-in failover), compression, caching, SSL offloading and acceleration.

ADCs Benefit Web 2.0 Deployments

Offloading and optimizing datacenter servers to handle traffic demands: Enterprises that deploy Web 2.0 applications must be able to achieve the best possible server and network performance. Key to this effort is the improvement of server capacity by offloading compute-intensive tasks that these applications bring, such as TCP connection management, the optimization of polling, state synchronization, etc. ADCs holistically manage Web 2.0 traffic to servers and network connections in several ways to address these inefficiencies, optimizing the flow of data and reducing the impact on the network, servers and client browsers.

Application-level routing: IT personnel responsible for datacenter operations must have technology that enables them to be adaptable, and have the flexibility to leverage all the resources within their datacenter. ADCs are the perfect solution for IT personnel to manage where and how user traffic gets routed to their applications, and have flexible control to leverage all server and database resources in order to ensure the applications are always available.

Accelerating the datacenter: ADCs aggregate many Web 2.0 transactions across a few TCP sessions. Various application data is multiplexed together and reconstructed as needed, which makes an ADC ideal for Web 2.0 applications. The end result is improved throughput and faster response time for end users.

TCP and application multiplexing: TCP and HTTP requires extensive handshaking that places an excessive burden on servers. Web 2.0 applications can be even more inefficient, generating thousands of round-trips (requests and responses) by themselves. ADCs offload these requests and responses from the servers, enabling them to support more user requests.

Optimizing the network: ADCs significantly reduce bandwidth inefficiencies by reducing the amount of redundant and uncompressed data sent, removing the adverse effects of latency while allowing network administrators to get the most for their bandwidth expenditures.

Enabling Network Disaster Recovery: When any application is delivered over the Internet, it is not uncommon for the link to have an outage. In addition to network links that may be overloaded, other events can cause them to fail, such as network hardware failure, human error and natural disasters.

Link and global load balancing (with built-in failover) capabilities of ADCs transparently redirect users away from failed network links and sites by continuously monitoring their health.

Caching and compression: The first page of many Web 2.0 and AJAX applications is large and caching, and compressing just this initial page is likely to free up significant server resources. Once the initial page has loaded, the extent to which content can be offloaded from subsequent requests is application-dependent. Advanced ADCs utilize compression and caching technologies to overcome network congestion and latency, packing more traffic into network links to deliver the most efficient use of the available bandwidth. This enables datacenter managers to support more users and deliver more applications, without adding bandwidth.

Caching maintains copies of routinely accessed data to eliminate unnecessary requests to servers. ADCs with compression technology use techniques to compress data sent over the network to users.

Prioritizing traffic on the network: Recreational and mission-critical network traffic needs to be treated differently, as they have different priorities. Many problems can occur without the ability to prioritize resources to high-priority users, particularly Web 2.0 applications that are highly bandwidth intensive. If fact, without traffic shaping and quality of service controls, this traffic can bring down your network and slow server responses.

With an ADC, administrators are able to control, filter, and rate different types of traffic (e.g., Web 2.0, VoIP, multi-media, streaming audio, video conferencing, etc.) on the network. Prioritizing and classifying traffic based on protocol, port or Layer 7 information optimizes networks for delivering business applications, improving response times and improving bandwidth utilization.

Web 2.0 applications are enabling many new capabilities that are changing how the Internet is used. These applications have powerful user interfaces that bring a new and exciting user experience. However, as exciting as these applications are, they also cause new challenges to datacenter and network infrastructure. When Web 2.0 applications are deployed, servers and network traffic experience more congestion and latency that can slow these applications to a crawl.

Advanced ADCs accelerate all applications and, in particular, Web 2.0 applications. If you are deploying Web 2.0 applications, an ADC might be the right solution for accelerating applications by delivering aggregate application throughput rates of multiple gigabytes, supporting millions of TCP connections, SSL transactions and HTTP requests, and handling demanding traffic spikes and flash crowds.

Advanced ADCs are capable of handling the extra traffic load that Web 2.0 applications bring, while enabling datacenters to operate within an environment that sets them up to handle the most demanding requirements. An ADC can help Web 2.0 applications scale to support more clients, while delivering the best possible response times.

More Stories By Sunil Cherian

Sunil Cherian is the VP of Product Marketing at Array Networks. He has over 15 years experience in networking, and has served in various technical and marketing capacities for Alteon WebSystems, Lucent, Octel and VMX. Mr. Cherian holds a Bachelors Degree in Computer Science and Engineering from College of Engineering, Thiruvananthapuram, India, and a Masters in Computer Science from the State University of New York, Albany, NY.

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