Tutorials Client ServerWeb server programs are supposed to serve multiple requests simultaneously on various TCP/IP connections. Client loads vary and so do requests per client. Taking that into consideration, the performance parameters of web servers include the following: number and type of requests per second; latency time, measuring in milliseconds how long it takes to complete each new connection or request; throughput or the amount of data transmitted in response to a request measured in bytes per second. This depends on, among other things, file size and available network bandwidth. Performance is also determined by concurrency levels or the ability for the server to provide access to specific files, in this case, those that make up web pages, to multiple users simultaneously. Finally, the server model, whether client-side or server-side, used to execute web server programs establishes scalability. Scalability is a system property that refers to a system or network’s ability to manage increasing workloads well and the ability to expand gracefully.
Web servers have load limits because they can only support a fixed number of clients making requests at the same time from the same IP address and IP port. They can only process a certain number of requests per second and when the system becomes overloaded, it becomes unresponsive. Load limits are determined by the server’s settings, whether the content retrieved is static or dynamic, HTTP request types, and whether the content is cached or not. Cached content is easier to access than original data. Cached content is the duplicate of original data that is stored elsewhere, but might be difficult or time consuming to retrieve. It reduces the need to re-compute original data that is frequently accessed. This reduces the load and increases the server’s speed.
Overload can be caused by a variety of factors, from too much traffic at one point in time, to computer worms generating excessive traffic. However, the partial unavailability of poorly maintained servers in need of upgrade or maintenance is another cause of overload.
In order to prevent overload network traffic must be managed through a variety of methods. Web sites protect themselves through the use of firewalls. Firewalls are security devices used to block traffic and set up connections only within the parameters of the company’s or individual’s IT security policy. They shield against bad IP sources or bad IP patterns. HTTP request managers redirect or re-write requests with bad HTTP patterns. Bandwidth management and traffic shaping helps stabilize network usage. Bandwidth management measures and controls the amount of data or traffic, for example, that takes place on a network link. Overloading links or even filling them to capacity affects performance and causes network congestion. Traffic shaping helps control traffic to optimize server performance as defined by low latency (speed) and low bandwidth use (more economical). By classifying requests and enforcing policies, traffic shaping mechanisms reduce network congestion and improve quality of service (QoS).
First Page: Client Server Features
