There are several transparent caching solutions in the market that focus exclusively on the caching of large HTTP objects. In fact, some implementations do not cache any HTTP object less than 512KB. Others focus primarily on caching video traffic. The rationale is that large object caching has the maximum impact in terms of bandwidth savings to the operator. But it is important to point out that Internet video traffic will be only 54% of all consumer Internet traffic in 2016, up slightly from 51% in 2011 – according to Cisco’s most recent Visual Networking Index report. In fact, web browsing, HTTP file transfer, game and software downloads etc. comprise close to 20% of all consumer Internet traffic in 2011. Therefore, the inability of these solutions to cache traffic from these applications reduces the beneficial impact of caching on operators’ capital expenditures.
Figure 1: Average Web Page Size and Number of Objects
As shown in Figure 1, while total page size has been increasing over the years, so has the total number of objects in a typical web page. In fact, the total number of objects in a typical web page has increased to ~85. Most of these objects are relatively small in size – between 20KB and 100KB. For instance, the www.youtube.com home page has multiple tens of thumbnail images, each of which is roughly 20KB in size.
Page download times are directly impacted by how quickly these tens of objects are downloaded to a device. Expedited delivery of small objects such as images is an important requirement from a Quality of Experience (QoE) perspective especially for mobile users. Mobile users have very little tolerance for a poor browsing experience and demand that pages load quickly with very little delay. According to a recent Gomez study, 58% of mobile device users expect sites to download as quickly as they would on their home computer; worse, a vast majority, 61% said that poor performance would make them less likely to visit the mobile site again. Page download times are also an important metric for ecommerce companies. By analyzing page abandonment data across more than 150 websites and 150 million page views, Gomez found that an increase in page download times from 2 to 6 seconds increased page abandonment rates by 25%. For ecommerce sites, the average impact of a 1-second delay results in a 7% reduction in conversions. For a $100,000/day ecommerce site, this implies that a one-second delay results in a $2.5 million in lost revenues in a year.
It is clear from the above discussion that for a transparent caching implementation to be effective, it needs to handle both small and large objects in an efficient fashion. While large object caching impacts bandwidth savings, caching of small objects has a direct beneficial impact on subscribers’ QoE, which is equally important.