Network Music Performance (NMP), where musicians perform music together over the Internet, requires ultra-low delays. Achieving a sense of presence in NMP requires both aural and visual communication, preferably coupled with immersive telepresence technologies, such as holographic communication. Existing 4G networks offer neither the ultra-low latencies needed for audio and video, nor the ample bandwidth required for video and (especially) holographic communication. In the Telepresence-Enhanced Network Music Performance (TENeMP) project we are investigating and developing solutions for immersive NMP, to be tested in the 5G testbeds of the SPIRIT project. We provide an overview of the experimental testbeds of TENeMP as well as the software tools developed by the project. We then present baseline video and audio latency measurements over 4G and 5G-NSA networks, which demonstrate NMP’s need for the capabilities of 5G-SA and beyond networks.

A key enabler for the digitization of physical devices is digital twining technology. A digital twin is a virtual representation of a physical object (or a collection of physical objects) that allows their integration into cyber systems. Digital twins are usually hosted in cloud environments, which provide high availability and resilience to failures. This integration creates new opportunities and enables new capabilities, but it also raises security concerns. In this paper, we design a digital certificate management solution that allows building trust on digital twins independently of their network location. Our solution allows digital twins to securely receive certificates, which can be used to digitally sign data at the application layer. Our scheme does not depend on the certificate infrastructure used to secure the communication between end-users and the (cloud-hosted) digital twins. Our solution is feasible, realistic and resilient against key breaches, with a marginal communication overhead. Finally, our scheme automates the process of certificate issuance for digital twins, thus enabling very fast key and certificate rotation.

The InterPlanetary File System (IPFS) is a popular distributed storage system, with worldwide presence. Due to the open nature and distributed routing of IPFS, malicious users can monitor the content other users are retrieving, violating their privacy. Unlike previous privacy enhancement schemes that rely on user anonymity, hiding the identity of the requesting user behind a proxy, we hide instead the identity of the content, using only hash functions. This prevents intermediaries from detecting what users are retrieving, without relying on any trusted third parties. Our solution also supports optional content encryption, which is especially useful for caching. We present the design and implementation of our solution for IPFS and evaluate its privacy and security properties, showing that our scheme enhances privacy and prevents a range of DDoS attacks.

The Secure Named Data Sharing (SNDS) architecture is a content brokering service built on top of Named-Data Networking (NDN), leveraging its native support for multicast, multisource and caching. SNDS transparently supports IP-based content providers and consumers via a gateway that implements ETSI’s NGSI-LD data spaces API, translating HTTP requests to and from the appropriate NDN messages. To fully support the query-based NGSI-LD API, we build appropriate protocols over NDN. We present a prototype implementation of the SNDS architecture and a preliminary evaluation of its features.

Named Data Networking (NDN) is a realization of the Information-Centric Networking (ICN) paradigm, where routing is based on content identifiers rather than on network location identifiers. The routing state in NDN can grow exponentially, not only due to the huge number of content identifiers (as opposed to network addresses) but also because it is difficult to detect "fake" routing advertisements. For example, in contrast to IP-based routing, a potentially valid routing entry in NDN can be advertised from multiple network locations, making NDN susceptible to Denial-of-Service attacks at the routing layer. In this paper, we leverage Decentralized Identifiers (DIDs) to build self-verifiable "content advertisements." With our solution, any router can verify that a content advertisement originates from an "authorized" entity, without requiring any trusted third party. We implement our solution and we evaluate it in a scenario where filtering is implemented by the edge routers. We show that our solution reduces fake routing advertisements with minimal computational overhead.

We present a method for experimentally measuring the capacity region of a wireless network, defined here as the set of all possible combinations of simultaneously achievable link transmission rates. Due to the inherent complexity of the problem, measuring the capacity region exactly typically involves a prohibitively large volume of experiments. Therefore, the method is based on a judicious, tunable algorithm, employing online machine learning, which aims at reducing the volume of experiments conducted. In order to evaluate the efficiency of the method, and also to demonstrate the usefulness of having the capacity region available, we apply our method to a network of Raspberry Pi nodes placed inside a building and communicating using IEEE 802.11. In particular, we compare the performance of an optimal, centrally organized communication scheme, computed using the measured capacity region within a network optimization formulation, with the performance of a simple communication scheme that uses multihop TCP flows.

Efficient congestion control is critical to the operation of MPTCP, the Multipath extension of TCP. Congestion control in such an environment primarily aims at enhancing the cumulative TCP throughput over the available paths, while preserving TCP-friendliness by fairly sharing the available bandwidth with single-path TCP flows in each path. While most existing multipath congestion control algorithms fulfill the TCP-friendliness objective in their steady state, their throughput convergence latency is high, rendering them ineffective for short-lived flows. We have proposed Normalized Multipath Congestion Control (NMCC), an MPTCP congestion control algorithm that achieves TCP-friendliness faster, by normalizing the growth of individual sub-flow throughput rather than the throughput itself. As NMCC can become unfriendly when it experiences sparse congestion events, in this paper we introduce the extended NMCC (e-NMCC) protocol that caters for TCP-friendliness upon both throughput growth and throughput reduction epochs. We analytically characterize e-NMCC in terms of TCP-friendliness and responsiveness and compare it with alternative algorithms. Finally, we assess the performance of e-NMCC through experimentation with the htsim simulator and a real Linux implementation. Our results confirm that e-NMCC accelerates throughput convergence, thus ensuring TCP-friendliness regardless of connection duration and underlying network conditions.

Routers in the Content-Centric Networking (CCN) architecture maintain state for all pending content requests, so as to be able to later return the corresponding content. By employing stateful forwarding, CCN supports native multicast, enhances security and enables adaptive forwarding, at the cost of excessive forwarding state that raises scalability concerns. We propose a semi-stateless forwarding scheme in which, instead of tracking each request at every on-path router, requests are tracked at every d hops. At intermediate hops, requests gather reverse path information, which is later used to deliver responses between routers using Bloom filter-based stateless forwarding. Our approach effectively reduces forwarding state, while preserving the advantages of CCN forwarding. Evaluation results over realistic ISP topologies show that our approach reduces forwarding state by 54%-70% in unicast delivery, without any bandwidth penalties, while in multicast delivery it reduces forwarding state by 34%-55% at the expense of 6%-13% in bandwidth overhead.

In-network packet-level caching is one of the most promising features offered by Information-centric Networking (ICN) architectures. In ICN, routers can use their queueing buffers as temporal storage units, thus allowing on-path caching by exploiting the network's storage resources. Packet-caches can be highly beneficial for content delivery, but they are also known to have three significant weaknesses: (i) packet-granularity produces huge cache indexes, (ii) Zipf-like content popularity penalizes the hit-ratio at core nodes and (iii) any discontinuity in the stored packets disrupts RTT-based congestion control. This paper presents OPC, a novel caching management strategy designed to support wire-speed in-network caching, while dealing with the above problems. OPC works at the object-level, thus reducing indexing requirements, is destined for access routers, thus avoiding the small hit-ratios of caches at core-nodes, and stores contiguous groups of packets, thus easing RTT-based congestion control.