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Content Connectivity for Next-Generation Networks


Network connectivity, i.e., the reachability of any network node from all other nodes, is often considered as the default network survivability metric against failures. However, in case of a large-scale disaster disconnecting multiple network components, network connectivity may not be achievable. On the other hand, with the shifting service paradigm towards cloud in today’s networks, most services can still be provided as long as at least a content replica is available in all disconnected network partitions. As a result, the concept of content connectivity has been introduced as a new network survivability metric under a large-scale disaster. Content connectivity is defined as the reachability of content from every node in a network under a specific failure scenario. In this dissertation, we investigate how to ensure content connectivity in various applications under different scenarios of failures in the physical network.

In the first contribution of the dissertation, we consider the survivable virtual network mapping with content connectivity against multiple link failures. We derive necessary and sufficient conditions, and develop a novel mathematical formulation to map a virtual network over a physical network such that content connectivity for the virtual network is ensured against multiple link failures in the physical network. In our numerical results, obtained under various network settings, we compare the performance of mapping with content connectivity and network connectivity, and show that mapping with content connectivity can guarantee higher survivability, lower network bandwidth utilization, and significant improvement of service availability.

In the second contribution of the dissertation, we investigate the problem of reliable provisioning with degraded service using multipath routing from multiple data centers. We consider the scenario where contents are cached in multiple locations in a network. Such a wide content replication offers a unique opportunity to provide better services to users, especially for content-based services, e.g., video delivery. We propose a reliable service-provisioning scheme that selects the optimal subset of data centers hosting the desired content and inversely multiplexes a content request over multiple link-disjoint paths. We formulate an integer linear program and develop heuristics for the problem, and use them to solve various complex and realistic network instances. Numerical data show that, compared to conventional service-provisioning schemes such as multipath routing from a single data center or dedicated-path protection, our proposed scheme efficiently utilizes network resources, improves reliability, and reduces latency.

In the third contribution of the dissertation, we addresses the reliable provisioning of low-latency and high-bandwidth extended reality live streams in next-generation networks. We investigate the backup from different data centers with multicast and flexible offered bandwidth to fulfill extended reality live stream requests while guaranteeing strict requirements on reliability, latency, and bandwidth. We consider the scenario where contents are not cacheable (e.g., live streams) and propose a service-provisioning scheme to protect not only against failures of links in the network but also against failures of computing and storage in data centers. We develop scalable algorithms for the backup from different data centers with multicast and flexible offered bandwidth and use them to solve various complex network instances in a dynamic network environment. Numerical data show that, compared to a conventional service-provisioning scheme such as backup from the same data center, our proposed service-provisioning scheme provides higher reliability, reduces latency, and efficiently utilizes network resources.

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