With more users accessing resource-intensive website than ever before, networks must deliver that information quickly, efficiently and with as few issues as possible. Content Delivery Networks (CDNs) have that ability by placing nodes with many servers in high-traffic areas of the world and duplicating popular content to those servers for quick and easy access by users. Through the duplication process, the popular content is cached onto a server.
Web Cache Functions
Web caches store popular content on servers showing the greatest demand for that information. Web caching significantly reduces bandwidth requirements, server load and improves the requestor’s response time for that content. HTML pages, images, video and audio can all be cached in a CDN for quick access.
Systems that can Cache Content:
- Search engine
- Web proxy between the client and server
- Forward cache outside the webserver’s network
- Network-aware forward cache
- Reverse cache
- Content delivery network (CDN)
Three Mechanisms for Cache Control
There are three basic mechanisms that can control caches: freshness, validation and invalidation. Freshness is a method which allows a response to be induced without rechecking the original server. This can be controlled by the client and server. Validation is utilized to ensure a cached response is functional after it is stale. Finally, invalidation is a side-effect of additional requests that pass through the cache.
Five Components of a Normal Caching System:
- L1 cache
- L2 cache
- Main memory
- Hard disk
The L1 cache is a memory that utilizes the full speed of the microprocessor. On the other hand the L2 cache is memory that accesses a specific type of SRAM. The main memory is memory access of RAM. The hard disk is mechanical and one of the slowest functions in a computer. Finally, the slowest function with regards to a computer system is the Internet. Each of the aforementioned components is utilized for the caching of content.
Advantages of Caching
There are several advantages of caching versus non-caching the content. The most obvious benefit and goal of the process is to speed up the loading while minimizing the system resources required loading a page. Any mechanism that can increase the performance results in a much happy visitor.
Another benefit is the fact that caching reduces the load on web services and subsequent databases. Since the information is already stored on the server, it does not need to transfer. Therefore, less transfer of information equates to less bandwidth usage which results in a reduction in the load on a server.
An additional benefit for caching is reliability. If a servers database is backed by cache and a server goes down, when the database is accessed there will be no time wasted to repopulate the memory. Also, when cached across many servers in a content delivery network, if a single server goes down the information will still be readily available on another piece of equipment.
Disadvantages of Caching
Unfortunately there are several disadvantages related to caching. First, users could run into issues with regards to syncing separate caches. In many instances the caching of content does not align properly and can result in issues. Second, caching involves an increase in the amount of maintenance required to maintain a website. Finally, caching runs into scalability issues. If a large amount of information is cached, it could be lost during upgrades.
Cache Usage for Website Design
As a result of the many advantages, caching is a popular method when designing websites that hold important content. Those who create website consider methods of making their site more cache-friendly. First, the usage of URL’s is consistent across different users, sites and pages. Also, by using a common library of images, it is easy to refer back to them. Additionally, it is counterproductive to change files unnecessarily.