Emerging applications expect fast turn-around from in-network failover mechanisms. This paper starts exploring the design space for supporting high availability and low latency using fast reroute in programmable data planes. In particular, we present a primitive for supporting well-known fast reroute mechanisms that is both efficient in terms of packet processing latency, memory requirements, and switch throughput.

The vision of cooperative, connected and automated mobility (CCAM) across Europe can only be realized when harmonized solutions that support cross-border traffic exist. The possibility of providing CCAM services along different countries when vehicles drive across various national borders has a huge innovative business potential. However, the seamless provision of connectivity and the uninterrupted delivery of services along borders also poses interesting technical challenges. The situation is particularly innovative given the multi-country, multi-operator, multi-telco-vendor, and multi-car-manufacturer scenario of any cross-border layout. This paper introduces the challenges associated to a cross-border deployment of communication technologies through the analysis of three use cases: tele-operated driving, high-definition map generation and distribution for autonomous vehicles, and anticipated cooperative collision avoidance. Furthermore, a set of 5G solutions have been identified to ensure that CCAM services can be supported efficiently in cross-border scenarios. Faster handover of a data connection from one operator to another, generalized inter-mobile edge computing (MEC) coordination, and quality of service (QoS) prediction are some of the solutions that have been introduced to reduce the uncertainties of a real 5G cross-border deployment.

Highly dependable communication networks usually rely on some kind of Fast ReRoute (FRR) mechanism which allows to quickly reroute traffic upon failures, entirely in the data plane. This paper studies the design of FRR mechanisms for emerging reconfigurable switches. Our main contribution is an FRR primitive for programmable data planes, PURR, which provides low failover latency and high switch throughput, by avoiding packet recirculation. PURR tolerates multiple concurrent failures and comes with minimal memory requirements, ensuring compact forwarding tables, by unveiling an intriguing connection to classic "string theory" (i.e., stringology), and in particular, the shortest common supersequence problem. PURR is well-suited for high-speed match-action forwarding architectures (e.g., PISA) and supports the implementation of arbitrary network-wide FRR mechanisms. Our simulations and prototype implementation (on an FPGA and Tofino) show that PURR improves TCAM memory occupancy by a factor of 1.5x-10.8x compared to a naïve encoding when implementing state-of-the-art FRR mechanisms. PURR also improves the latency and throughput of datacenter traffic up to a factor of 2.8x-5.5x and 1.2x-2x, respectively, compared to approaches based on recirculating packets.

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Cooperative, connected and automated mobility (CCAM) services along different countries require cross-border solutions to support seamless delivery of services in a multioperator, multi-telco-vendor, and multi-car-manufacturer scenario. The H2020 5GCroCo project will trial 5G technologies in the European cross-border corridor along France, Germany and Luxembourg, as well as in five small-scale trial sites. 5GCroCo analyses three cross-border use cases: tele-operated driving, highdefinition map generation and distribution for autonomous vehicles, and anticipated cooperative collision avoidance (ACCA). This paper presents the infrastructure, control architecture, backend software, and end-to-end service orchestration of the cross-border ACCA use case deployed in the Barcelona small-scale trial site.

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Even before 5G is rolled out, Mobile Edge Computing (MEC) can be considered as a key driver towards the deployment of vehicular use cases, which pose stringent latency and bandwidth requirements to the underlying Vehicle-to-Everything (V2X) communication infrastructure. In this paper, we present a MEC-enabled cooperative Collision AVoidance (CAV) service designed to anticipate the detection and localization of road hazards by extending vehicles perception range beyond the capabilities of their own sensors. The CAV service is a software application that runs on MEC servers allocated at the roadside and at Mobile Network Operators (MNO) infrastructures. The CAV service receives ETSI ITS-G5 standard-compliant messages transmitted by vehicles: periodic Cooperative Awareness Messages (CAM), which include the position, velocity and direction of the vehicle; and event-triggered Decentralized Environmental Notification Messages (DENM), which include the position of detected road hazards. The CAV service creates a distributed dynamic map using all the received information, and sends unicast messages to each vehicle with the relevant information within its collision risk area. We have implemented and validated the operation of the CAV service using vehicles On-Board Units (OBU) based on OpenC2X, an open-source experimental platform supporting the ETSI ITS-G5 standard.

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