Next-generation edge nodes interfacing innovative IT clusters, 5G fronthaul and IoT gateways to the optical metro/core network will require advanced and dynamic online Quality of Service (QoS) per-flow traffic treatment, assuring for example ultra-low latency requirements. However, current Software Defined Networking (SDN) implementations (e.g., OpenFlow) do not support forwarding procedures based on network state, profile variations and the history of flow statistics at the node level. Currently, such procedures require the intervention of the SDN controller, leading to scalability issues and additional latency in the data plane forwarding. Moreover, severe security challenges are expected to affect such nodes threatening IT resources. Thus, increasing bandwidths will require direct deep packet inspection avoiding the involvement of the SDN controller, as performed currently, or dedicated and costly security systems. This paper leverages on the potential of the P4 open source language, recently introduced by the inventors of OpenFlow, to program the data plane structure and behavior of an SDN switch. P4 is able to instantiate custom pipelines and stateful objects, enabling complex workflows, user-defined protocols/headers and finite state machines enforcement. Moreover, P4 allows portable implementations over different hardware targets, thus opening the way to open source fullyprogrammable devices. Special effort is dedicated to motivate and apply P4 within a multi-layer edge scenario, proposing the architecture and the applicability of an SDN P4-enabled packet-over-optical node. Moreover, three specific multi-layer use cases covering dynamic TE (e.g., traffic offload and optical bypass) and cyber security (e.g., DDoS port scan) are discussed and addressed through P4-based solutions. Experimental evaluations have been conducted over a multi-layer SDN network exploiting reference P4 software switches (i.e., BMV2) and Field Programmable Gate Array (FPGA) at 10 Gigabit Ethernet optical interfaces. Extensive results report effective dynamic TE and cyber security mitigation enforcement at P4 switches without any controller intervention, showing excellent scalability performance and overall latencies practically in line with current commercial OpenFlow switches.
In the Next Generation Radio Access Network (NG-RAN) defined by 3GPP for the fifth generation of mobile communications (5G), the next generation NodeB (gNB) is split into a Radio Unit (RU), a Distributed Unit (DU), and a Central Unit (CU). RU, DU, and CU are connected through the fronthaul (RU-DU) and midhaul (DU-CU) segments. If the RAN is also virtualised RAN (VRAN), DU and CU are deployed in virtual machines or containers. Different latency and jitter requirements are demanded on the midhaul according to the distribution of the protocol functions between DU and CU.This study shows that, in VRAN, the virtualisation technologies, the functional split option, and the number of elements deployed in the same computational resource affect the latency budget available for the midhaul. Moreover, it provides an expression for the midhaul allowable latency as a function of the aforementioned parameters. Finally, it shows that, the virtualised DUs featuring a lower layer split option shall be deployed not in the same computational resources where other vDUs are deployed.
This paper first overviews how, in the 5G Next Generation Radio Access Network (NG-RAN), the Next generation NodeB (gNB) functions are split into Distributed Unit (DU) and Central Unit (CU). Then it describes the proposed fronthaul transport solutions, such as Common Packet Radio Interface (CPRI), eCPRI, IEEE P1914.3 and their relationship with the Ethernet protocol. Finally, a characterisation of the traffic generated by the fronthaul is presented. Such characterisation may guide in the selection of the right network for fronthaul transport.
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