Analyzing the effectiveness of content delivery network interconnection of 3G cellular traffic

It has been a recent trend of Internet service providers (ISPs) to deploy content delivery networks (CDNs) extensively in their infrastructure in order to utilize their network resources and generate a new profit source. This 'telco CDN' has become an attractive solution since it enables the ISP to use their own network topology and real-time traffic information to address the bottlenecks, and seek for near-optimal path to convey the content to the users. However, since the location of telco CDN cache is limited to their ISP region, it became difficult to bring its performance benefit to the users outside the ISP region and it also led to suboptimal traffic reduction at ISP borders. CDN interconnection (CDNi) is an emerging technology which has a potential to eliminate the redundant HTTP traffic received from external CDNs. A telco CDN can minimize the CDN traffic crossing the ISP border and at the same time deliver the content to their users quickly from its local cache by temporarily caching the content owned by a collaborating peer CDN. In this paper, we have studied the performance of CDNi when applied to the fast-growing cellular Internet traffic. We have simulated the CDNi protocol to gauge the bandwidth savings along with request redirection overheads using 7.7 billion HTTP logs (290 TBs by the byte volume) from one of the largest cellular ISPs in South Korea. We observed that 69% of total downlink traffic passes the Internet Exchange point (IXP), and according to our simulation results, intra-ISP CDN with CDNi can remove 16.2% to 29% of the IXP traffic. We also saw that the CDNi request redirection overhead could be significant to small objects, but it is still expected that if only large HTTP objects are redirected, a large bandwidth would be saved.