Identifying Cache Sites

When planning the implementation of proxy servers and caching on your network, you must identify which sites would benefit from caching. Look for the following when identifying client acceleration sites:

Internet Client Acceleration Example

For example, suppose that Company A wants to give its employees access to the wealth of information available on the Internet. However, the company also wants to restrict access only to those Internet Web sites that contribute to the workplace. This results in two requirements:

To meet both requirements, Company A implements proxy servers as client accelerators in all of its facilities, using access control list rules established in NDS or eDirectory by the network administrator. All employee Web browsers are configured to operate through proxy servers. The proxy cache servers greatly accelerate Web page loading and permit control over Internet access. This configuration is shown in Figure 5-2.

Figure 5-2 Internet Client Acceleration Configuration Example

Intranet Client Acceleration Example

Various groups within Company A have published extensively on internal Web sites. Some of the published information is company public, or accessible by all employees. Other information is privileged, or accessible only by employees who have a need to know. For example, some advanced development information is available only to certain engineering or management groups. The published information is spread across a large number of internal Web sites.

Company A has two requirements for intranet Web site access by employees:

Because of the flexibility of Proxy Services, the same proxy servers used to restrict Internet Web access in the first example, Web Client Acceleration (Standard Proxy Cache), can also be used to restrict access to intranet Web sites. In addition to storing the Internet access restrictions in eDirectory, the administrator stores intranet Web access rules. This approach gives the administrator centralized and global control of both Internet and intranet access from a single point, greatly simplifying access management.

Identifying Cache Sites

When planning the implementation of proxy servers and caching on your network, you must identify which sites would benefit from caching. Look for the following when identifying server acceleration sites:

Internet Server Acceleration Example

The public Web site of Company A, http://www.ACo.com, receives millions of hits daily from a worldwide audience. The site was previously serviced by multiple Web servers. Recently, the company set up several proxy servers to serve as front ends to the Web servers, as shown in Figure 5-4. This approach provides three important benefits:

Figure 5-4 Internet Server Accelerator Configuration Example

Intranet Server Acceleration Example

Many of the groups in Company A publish information on internal Web servers on the company’s intranet. These servers are scattered around the world and are accessed by employees who are also located around the world. Unlike the information on the public Internet Web site of Company A, much of the information published internally is sensitive and access to it must be restricted. Complicating this situation is that the information resides on a variety of Web server platforms, including NetWare, UNIX Apache, Netscape, and NCSA*, making access management complex and difficult.

The Company A solved the problem by creating front ends to its intranet Web servers with proxy servers at each site. For example, at its headquarters, the company installed 10 proxy servers as front ends to the 50 intranet Web servers at that site, as shown in Figure 5-5. Access control was transferred from the Web servers to the proxy servers. This approach results in the following benefits:

Figure 5-5 Intranet Server Accelerator Configuration Example

Identifying Cache Sites

When planning the implementation of proxy servers and caching on your network, you must identify which sites would benefit from caching. Look for the following when identifying network acceleration sites:

Intranet Network Acceleration Example

Company A is a large organization with worldwide facilities. As a result, employees and Web servers are widely scattered. Employees must have easy and fast access to internal Web information, regardless of their location or the location of the target Web server. In addition, because of the high cost of network equipment and the even higher cost of managing it, the company must obtain the highest utilization possible from its network resources.

Company A implemented a hierarchical mesh of proxy servers, as shown in Figure 5-7. Hierarchical caching reduces the load on Web servers and reduces WAN traffic by allowing clients to access cached intranet Web information from the closest proxy server.

For example, a Los Angeles-based employee might be in Paris and need to access information from a Web site in Los Angeles. Although no one at the Paris office has recently accessed that information, an employee in the London office has, and the information is cached on the proxy server in London. Instead of routing the client’s request all the way to Los Angeles, the proxy server in Paris can access the information from the proxy server in London. This reduces network delay and eliminates slower, more expensive transatlantic traffic on the network.

Figure 5-7 Intranet Network Accelerator Configuration Example

Internet Network Acceleration

Just as a hierarchical mesh of proxy servers can be used to accelerate intranet performance, it can be used on a much larger scale to accelerate Internet performance. The National Laboratory for Applied Network Research (NLANR) is working on such a project.

According to a recent NLANR report, the Internet’s sustained explosive growth calls for an architected solution to the problem of scalable wide area information dissemination. While increasing network bandwidths helps, the rapidly growing populace will continue to outstrip network and server capacity as they attempt to access widely popular pools of data throughout the network. The need for more efficient bandwidth and server utilization transcends any single protocol such as FTP, HTTP, or whatever next becomes popular.

The basic Internet client-server model (in which clients connect directly to servers) is wasteful of resources, especially for highly popular information. There are many examples in which server systems have not been able to cope with the demands placed upon them for popular information.