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Application Performance Control The IP WAN Services Landscape
Manickam Sridhar
Monday, November 17, 2008
Networking and business groups worldwide are rapidly adopting the convergence of voice, data and video over a single network for the simple reason that it saves money, administrative time and energy, and keeps infrastructure flexible and simple to manage. In particular, technologies like VoIP, video, and Web services are targeted to deliver greater productivity, improved customer response, streamlined business processes, and much greater efficiencies.

However, as many companies seeking to deploy this new panacea are discovering, the path to convergence has many challenges. The issue facing the enterprise is the growing gap between application performance requirements and what the network is able to deliver.

Yet it is the end users - including employees, customers, partners, who drive the expected level of performance. This might be dictated by productivity metrics, business customer needs, or competitive threats. The objective is simple. Each application must perform consistently against a well-understood set of quality metrics. This is true no matter how many data, VoIP, and video applications are sharing the network.

Achieving this requires a solution enabling the IP network to become "application aware." Unfortunately, the underlying IP network - which has always been optimized for "better, faster and cheaper," forwarding of packets - does not provide the accuracy and control needed to assure application performance at the end user level.

Applying Intelligent Application Performance Control to Manage the Application Performance Gap

Figure presents a model for identifying and applying the services required to efficiently align the performance needs of core business applications with underlying network resources.

Bulk data applications, such as FTP, E-mail and Web browsing are characterized by the server sending a lot of data back to the client in response to a request. Bulk data is not latency sensitive.

Interactive applications, which might include order processing, ERP, CRM, time sheet reporting, Point of Sale transaction processing, are more performance sensitive. A consistent, predictable response time is very important.

Real-time applications such as VoIP and Video conferencing are the most performance sensitive. Data is sent as it is generated. Web Services are a special emerging class of application with near real-time performance requirements. These applications are for rapid computer-to-computer communications. Any variation in delivery time impacts the quality of the voice conversation.

Given these differences, it is easy to see that different policies and IP WAN services are required to control the performance of each application running on the converged IP network.

IP WAN Services Defined State-based Layer 7 Classification

Applying the appropriate IP WAN services to an application session and its flow starts with Layer 7 classification. Each flow must be detected and classified as belonging to a specific application. This includes identification of all applications running on the network as well as providing detailed monitoring and reporting of what is running on the network at any given time.

The security layer prevents malicious and non-authorized intrusion into the network. The purpose is to authenticate and manage security functions on a flow-by-flow basis. This requires an inspection firewall operating in combination with an Application Layer Gateway (ALG).

Session Layer (Layer 5) Services
Session Layer Services include flow handling functions like Web caching, packet caching, file caching, Application protocol translation, flow management, call admission control, proxy and others. These services are applied to each application as needed to control the performance of a discrete session and its associated flows.

Web/File/Packet Caching
Caching is applied to improve perceived download times for large files with fairly static content. Files are stored and played locally at LAN speeds. Only the small changes that have occurred since the file was last updated are sent over the WAN. Web caching is a widely used example, where network operators experience on average a 30 percent gain in bandwidth efficiency.

TCP Acceleration
TCP acceleration substitutes the TCP protocol with a proprietary protocol to allow large amounts of data to be sent before waiting for an acknowledgement. The advantage is improved throughput and transfer time for bulk transfers that use long fat pipes.

Application Protocol Translation
The purpose of Application Protocol translation is to streamline web-enabled applications like order entry by eliminating a manual transfer process that has become costly and error prone. It is also designed to eliminate the need for custom middleware for each application

Flow Management, CAC, Signaling
These layer five functions address the performance of a session on a flow-by-flow basis. They are particularly important for real-time traffic like VoIP and video. Call control functions such as Call Admission Control (CAC) are also required to protect VoIP call quality. If the network can only handle five calls, the quality of all calls would deteriorate as the sixth call is placed.

Converged Traffic Management
The role of traffic management is to accurately enforce policies for all traffic types. The effect of traffic management is that key business processes perform and WAN utilization reaches up to 95 percent. It is important to apply control in both the inbound and outbound direction to assure the integrity of a two-way transaction or conversation. For large deployments, it is also critical to manage bandwidth over-subscription.

Packet Compression
The purpose of compression is to reduce the number of bits transmitted onto the WAN. Compression techniques gather and compress multiple large packets and then output smaller packets. An important benefit is virtual expansion of the WAN pipe. The newly available bandwidth can then be used by other applications. Compression is most effective for bulk file transfers, where there is a large amount of data with repeated data patterns to analyze and reduce.

The Bottom Line
Each class of application benefits from a different mix of application-aware IP Services. In reality, all classes of applications will be present on the enterprise IP network. Therefore, controlling application performance requires a solution able to define and enforce the combination of policies and IP WAN Services required for each application.

Manickam Sridhar is the CTO at Converged Access, a provider of Intelligent Application Performance Control solutions. He can be reached at sri@convergedaccess.com
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