Trustless Collaborative Cloud Federation

Multi-cloud environments such as OnApp and Cloudflare have turned the cloud marketplace towards a new horizon where end-users can host applications transparently over different cloud service providers (CSPs) simultaneously by taking the best from each. Existing cloud federations are typically driven by a broker service which provides a trusted interface allowing the participant CSPs and end-users to coordinate. However, such a broker has the limitations of any centralized trusted authority like risk of manipulation, bias, censorship, single point of failure, etc. In this paper, we propose a decentralized trustless cloud federation architecture called
CollabCloud
which eliminates any central mediator while addressing the challenges introduced by byzantine participants.
CollabCloud
utilizes blockchain, and introduces a novel interoperability protocol bridging a permissionless blockchain as an open interface for the end-users, and a permissioned blockchain as a coordination platform for the CSPs. We have implemented
CollabCloud
with Ethereum, Hyperledger Fabric and Burrow platforms. Experiments with a proof-of-concept testbed emulating 3 CSPs show that
CollabCloud
can operate within an acceptable response latency for resource allocation, while scaling upto 64 parallel requests per second. Scalability analysis over Mininet emulation platform indicates that the platform can scale well with minimal impact on the response latency as the number of participating CSPs increases. % for resource scheduling and allocation. %trustless, transparency, immutability properties of %By utilizing trustless, transparency, immutability and verifiability features of a distributed ledger technology, % Such multi-cloud environments bring the notion of cloud federation where various CSPs can buy and sell cloud resources, and thus collaborate among themselves to provide better capacity with less capital expenditure. %The novelty of
CollabCloud
is in designing the interfacing between the two different blockchain platforms, through which the end-users access resources over multi-clouds in a secured way. %Need to reduce to 200 words. %The broker works like a trusted entity that takes care of various management tasks of the federation. %as the decentralized federation marketplace needs to provide a unified interface to the end-users while maintaining an agreement on pricing, fair scheduling of resources and securing resource access to the end-users. %In
CollabCloud
, we achieve the above goals by developing a unique interface through interconnecting a public (permissionless) blockchain platform with a private (permissioned) blockchain platform. %Cloud federation helps multiple cloud service providers to come into collaboration and share their resources for their overall benefit. However, the current implementations of federated clouds depend on a trusted federation broker that takes care of the handling end-user requests, resource allocation as well as scheduling and pricing for the shared resources under the federation. This central broker provides a unified interface to the end-users, through which they can access the federation as a single entity. The unified interface presents the federation as a single larger cloud provider which can fulfill a broader set of user demands and at a better pricing. Although the cloud broker plays a crucial role in the federation, it has the limitations of any centralized trusted authority like risk of manipulation, biasness, censorship, single point of failure, etc.. In this work, we propose a trustless, decentralized and democratic architecture for cloud federations which is free from any cloud broker. This democratic system leverages a combination of permissionless and permissioned blockchain which keeps all the functionalities of a broker based federation intact. Our system provides a trustless unified interface for the federation as well as brokerless scheduling, transfer of resources, catalog maintainance etc.. We implement the system with a fair scheduling smart contract and evaluate it with respect to end-to-end request processing time and analyze its overheads. The outcome of the analysis gives a clear view that the proposed system keeps all functionalities of cloud federation intact, while maintaining the required quality of experience(QoE) to the end-users.