Proxy servers typically have two main purposes: (1) to improve performance by caching and reusing responses, and (2) to do what with incoming and outgoing requests?

Introduction / Context:
Proxy servers act as intermediaries between clients and servers. They are widely used in enterprise networks and on the internet to provide performance, security, and control functions. One commonly cited pair of purposes is performance improvement through caching plus another key function related to controlling or inspecting traffic. This question asks you to identify that second major purpose.

Given Data / Assumptions:

• Proxy servers can cache responses to reduce latency and bandwidth usage.
• They sit between clients (such as browsers) and origin servers.
• Organizations may want to control which sites users can access or to log and inspect requests.
• The options include actions like filtering, encrypting, or simply transmitting requests.

Concept / Approach:
Beyond caching, proxies are often configured to examine, filter, or modify requests and responses according to security and policy rules. For example, a corporate proxy may block requests to certain categories of websites, enforce authentication, scan for malware, or log user activity. This filtering capability is central to using proxies as security and compliance tools. Therefore, the second main purpose is to filter requests rather than merely pass them along unchanged or increase their number.

Step-by-Step Solution:
1. Acknowledge that improving performance via caching is one major role of proxies. 2. Consider the security role of proxies: they can act as gatekeepers for outbound and inbound web traffic. 3. Filtering can include URL blocking, content inspection, user authentication, and logging. 4. Recognize that this matches the description of a second main purpose in many networking and security texts. 5. Choose the option that best reflects filtering for security and policy enforcement.

Verification / Alternative check:
Enterprise network diagrams and security architectures commonly show web proxy servers positioned at the network edge, where they both cache frequently accessed content and enforce acceptable use policies. Product documentation for proxy solutions (such as secure web gateways) highlights content filtering and policy enforcement as primary features alongside caching, confirming that filtering requests is a core purpose of proxies.

Why Other Options Are Wrong:
Option a: Simply transmitting every request without modification is the behavior of a basic router, not a key value add of a proxy. Option b: Decreasing requests by shutting down clients is not a realistic or desirable proxy function. Option c: Increasing the number of requests by duplicating traffic would waste bandwidth and is contrary to the performance goal. Option e: While some proxies support SSL inspection, encryption is primarily handled by end to end protocols such as HTTPS, not automatically by all proxies.

Common Pitfalls:
Some learners think of proxies only as caching devices and forget their security role. Others confuse proxies with firewalls; while there is overlap, proxies operate at the application layer and can inspect protocol specific content, whereas firewalls often work at lower layers. Modern secure web gateways combine proxy functions with advanced filtering and threat detection, reinforcing the idea that filtering requests is a primary purpose.

Final Answer:
In addition to improving performance, proxy servers are widely used to filter requests to enforce security, access control, or content policies.