# ARCFIRE: Experimentation with the Recursive InterNetwork Architecture
## 2 Modeling a Converged Network Operator  
ARCFIRE has analyzed how a converged operator network (CON) with an access-metro-core architecture can be modelled with RINA [5], considering the following steps:  
* Create the overall layered structure. The network is partitioned into a set of inter-operable layers (DIFs), each with a certain scope. The lower layers focus on resource allocation and QoS of more deterministic traffic, while the higher layers focus on grooming traffic to effectively use the lower layers. A trade-off has to be taken into account to decide the optimal number (typically no more than 5), since having more layers will have the effect of bounding the router table size [6], yet it also means an increase in delay and more packet headers. * Characterize the QoS requirements for each layer. Each network is designed to serve a set of applications with specific traffic characteristics over a set of physical media. The way in which the network is broken up into layers as well as the role of each layer will define a set of QoS characteristics that need to be supported by each layer. Recognizing that these systems are not sufficiently sensitive to be configured to a precise point in \"QoSpace\", i.e., precise set of valuesfor the QoS parameters, it is defined in terms of one or more \"QoS-cubes\". Network designers can map regions in this performance space to the QoS-cubes to be supported by each layer. * Characterize the security requirements of each layer, in terms of authentication, access control, confidentiality or integrity protection. * Specify the exact packet header syntax in the layer, based on the expected number of concurrent flows, the number of addressable IPC Processes, the maximum size of payload (larger packet sizes towards the backbone), the number of QoS cubes, etc. * Decide per-layer policies, which allow the layer to operate effectively and meet the quality requirements (expressed via the QoS cubes). * Identify operating ranges for the network and define monitors/triggers to sense them and choose/design the most appropriate strategies to automatically transition in the Network Management System (NMS) between different policy sets for each layer associated to the identified network operating ranges. Figure 1 illustrates the Converged Operator Network use case considered by ARCFIRE. It considers different types of access networks--xDSL (Digital Subscriber Loop), FTTH (Fibre to the Home), WiFi and cellular--that allow the provider to reach its customers (residential, business, mobile) via wired and wireless media. These technologies are chosen due to their high representability, but other access networks could be considered (e.g., Hybrid Fiber/Coax networks) without modifying the design. The traffic from these access networks is aggregated by metropolitan area networks (which may cover a neighborhood, a city or a semi-urban/rural area depending on the density of customers), which aggregate the traffic towards the core. The traffic is then forwarded towards another core Point of Presence (PoP)--if it is addressed to another customer of the service provider or to a service hosted in the service provider's DataCenters (DCs)--or to an Interconnect edge router (e.g., internet edge) otherwise. The service provider may have datacenters attached to different parts of the network: MicroDCs attached to access networks in support of Mobile Edge Computing; Metro DCs attached to the metropolitan networks to support Content Delivery and cloud computing services; and large regional DCs attached to the core networks. Figure 2 shows a potential DIF structure for the CON in the case of a residential customer accessing remote applications over a top-level DIF (public internet DIF, Virtual Private Network or VPN, application-specific, network slice, etc.). The upper part of the figure shows the connectivity graph of the network boxes, while the bottom part illustrates the different DIFs going through such boxes.