The explosive popularity of smartphones and mobile devices drives massive growth in the wide-area mobile data communication. Unfortunately, the current or near-future 3G/4G networks are deemed insufficient to meet the increasing data transfer demand. While opportunistic offloading of mobile data through Wi-Fi is an attractive option, the existing transport layer would experience frequent disconnections due to mobility, making it hard to support seamlessly reliable data delivery. As a result, many mobile applications either depend on ad-hoc downloading resumption mechanisms or redundantly re-transfer the same content when disruptions happen.In this paper, we present DTP, a disruption-tolerant, reliable transport layer protocol that masks the failures of the preferred network. Unlike previous disruption/delay-tolerant protocols, DTP provides the same semantics as TCP on an IP packet level when the mobile device is connected to a network while providing the illusion of continued connection even if the underlying physical network becomes unavailable. This would help the mobile application developers to focus on the application core rather than addressing the frequent network disruptions. It would also greatly reduce the phone network costs both to ISPs and end users. Our current implementation in UDP shows a comparable performance to that of TCP in network, and it greatly reduces the delay and power consumption when the mobile devices frequently switch from one network to another.
Caching similar videos transparently in a network is a cost-effective solution that potentially reduces redundant data transfers. Recent study shows that network redundancy elimination (NRE) on the content level could produce high bandwidth savings in ISPs. However, we find that blindly employing existing NRE techniques to video contents could lead to suboptimal redundancy suppression rates. This is because (a) randomness in the video encoding process could produce completely different binaries even when they deal with seemingly identical video clips and (b) existing NRE chunking schemes incur high overheads since they do not utilize the underlying video format.In this work, we present two novel schemes that help similar or aliased videos to be cached more effectively in the NRE system. First, we propose a deterministic video encoding scheme that preserves the unmodified original content even after editing or reencoding. This would eliminate the sources of encoding randomness, allowing the NRE systems to detect the redundancy across similar videos. Second, we propose a lightweight video chunking scheme that exploits the underlying video structure. Our "samplebased" chunking scheme groups the logically-related frames into a chunk, and significantly reduces the size of NRE chunk indexes as well as chunking overheads. Our preliminary evaluation shows that the deterministic video encoding scheme helps greatly expose the redundancy across similar videos even after editing. Also, our sample-based chunking reduces the chunking overhead by a factor of 2.0 to 22.5 compared with popular NRE chunking schemes and reduces the index size by 27 times over various video contents.
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 fastgrowing 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.
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