Abstract
Network Functions (NFs) have a crucial role in today’s Internet infrastructure. They provide additional services on top of plain connectivity such as content caching, Network Address Translation (NAT), etc. However, standard IP networks staticity hinders the possibility of a flexible deployment of NFs in the Internet. In fact, initially, NFs were introduced in the network by hard-wiring the NF instances on the network traffic’s path. This is unacceptable, especially when multiple NFs are chained together to form the so-called Service Function Chain (SFC). On these grounds, the SFC problem space has attracted the attention of the research community. SFC solutions have proliferated to a great extent, especially with the advance in Software-defined Networking (SDN) and Network Function Virtualization (NFV). However, by comprehensively reviewing state of the art, this thesis shows that Network Providers are reluctant towards state of the art SFC solutions, as they target ”clean-state” system architecture i.e., they do not consider prior system architecture and equipment, which translates to greater investment. Therefore, this thesis introduces a ”ready-to-deploy” SFC solution that targets legacy Mobile Networks. It aims to fill the gap of the current state of the art helping Network Providers in the transition phase towards more complex and costly SFC solutions. This thesis further investigates Internet-wide SFCs, in which multiple NF providers are involved in the SFC provisioning. State of the art solutions use plain IP routing to steer the traffic through the SFC i.e., each NF composing the chain is identified by its IP address. However, there is no prior work on how to effectively support the SFC Resolution in the Internet. In tackling these challenges, this thesis proposes the Domain Name System (DNS) as a key element, in today’s Internet infrastructure, to implement the SFC Resolution. The inefficiencies of the current DNS when dealing with SFCs are highlighted. So, a collaborative SFC Resolution process is proposed. It efficiently supports the SFC Resolution process when multiple and independent NF providers are involved in the SFC provisioning. Moreover, this thesis highlights the importance of NFs which are strategically placed in the network, when dealing new application scenarios such as Internet of Things (IoT), vehicular networks, etc. In fact, in such use cases, NFs are placed at the network ”Edge”, in order to reduce the network latency required to reach the NFs. In order to support more variegated use cases, this thesis proposes a Multi-tier Edge Network architecture. It considers the case in which there is a large number of heterogeneous edge resources, widely distributed in the network. Therefore, an efficient placement algorithm is proposed. It exploits the multi-tier nature of the proposed network providing an optimized NF placement.
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