P3 – Resource Connectivity

The P3 Resource Connectivity View describes communications networks and pathways that link communications systems, and provides details regarding their configuration. It also specifies the characteristics of the data exchanged between systems.

Concerns Addressed

  • Interface Specification.
  • Systems Engineering.
  • System Requirements.

Background

The networks and pathways documented in a P3 View represent the physical implementation of the logical flows identified in a L2, Logical Scenario, or L3, Node Interactions View.

The P3 View focuses on the physical characteristics of each link by specifying attributes. An example of this might be the geographic location and layout of network components such as routers, switches, amplifiers and repeaters. Attributes such as capacities (e.g. bandwidth, throughput), frequencies used, security encryption methods used and other descriptive information are also included. The P3 View encompasses the NSV-2b and 2c views from NAF v3.1, which define the communications links between systems.

The P3 View differs from that of P2 in that it only features physical architectures, software and artefacts (as systems) – i.e. P3 does not feature any organisational resources. P3 also provides a great deal more technical detail than P2, specifying the protocols implemented by systems and used by the connections between those systems.

Usage

  • Interface specification.
  • Identification of applicable protocols.
  • Description of system communication paths.
  • Bandwidth and capacity analysis.
  • Detailed definition of data flows.

Representation

  • Topological (connected shapes).
  • UML composite structure diagram.
  • SysML structural diagram.
  • Tabulation.

Detailed View Description

The purpose of the P3 View is to specify how systems are connected, what interfaces each system exposes (ports), the hardware interface used and the protocols transmitted across the interface. The key elements are:

  • Artefacts (represented as Systems and Platforms).
  • Ports.
  • Protocols.
  • System Port connections.

These elements are shown in different perspectives in the different views. In a P2 View the resources are logically grouped by the artefact to which they belong (which could mean located with). The P2 also shows how human operators (‘roles’) interact with systems. The P3 View describes which protocols are supported for specific system-to-system connections. In a P3, the focus is on systems and the capability configurations of which they are a part.

The P3 View specifies the communications links between systems and may also list the protocol stacks used in connections. The architect may choose to create a diagram for each pair of connected systems in the architecture (see Figure 3-546) or to show all the connections on one diagram if this is possible (see Figure 3-557).

Figure 3-546: Example P3 View Showing Pair of Systems

Each diagram is to show:

  • Which ports are connected.
  • The systems to which the ports belong.
  • The definition of the connection in terms of the physical connectivity and any protocols that are used in that connection.

Any connection specified in a P3 View shall conform to the protocols specified on the corresponding port definitions in the P1 View. Any protocol referred to in a P3 View must be defined in the A8, Standards View.

Note that networks are represented as systems. The architect may choose to show other systems being components of the network if they are part of the network infrastructure.

Figure 3-557: Example P3 View based on Mobile Data Communications

The P3 View defines System Connectivity Clusters, i.e. how individual connections between system ports are grouped when the systems share common parent resources, and may be used for estimating requirements for physical routing and bandwidth, as well as defining the physical architecture within a system or system of systems. This type of P3 view is particularly useful when planning physical connections and routings between physical assets as it is a useful way of highlighting redundancy issues (i.e. showing when too many or too few connections are used). This could indicate opportunities for cost savings from using a common network, or that there may be a need for redundancy to increase reliability.

Figure 3-568: Example P3 View of System Connectivity Clusters

The P3 View also specifies the characteristics of data exchanges between systems. P3 is the physical equivalent of the logical L3, Node Interactions, and provides detailed information on the system connections that implement the information exchanges specified in the L3 View. Note: although flows of materiel, human resources and energy are permitted in the P2, Resource Structure, and P4, Resource Functions, views, they are not permitted in a P3 View.

This type of P3 view describes, in a tabular format, data exchanged between systems, and the functions that produce and consume that data. A P3 also specifies properties of these system data exchanges, such as periodicity, timeliness, throughput, size, information assurance and security characteristics of the exchange. In addition, the data elements, their format and media type, accuracy, units of measurement, and system data standard may also be described in the view.

Figure 3-579: Example P3 Tabular View Based on GPRS

When a suite of Physical Resource views are being used as physical specifications for a logical requirement, the properties listed in P3 should cover all the information exchange properties specified in the L3, Node Interactions. Similarly, it is recommended that all data elements carried by the data exchanges are shown.

It should be noted that each data element exchanged may be related to the P4, Resource Function that produces or consumes it. However, there need not be a one-to-one correlation between data elements listed in the P3 View and the data flows (inputs and outputs) that are produced or consumed in a related P4 View.

Because P3 is about showing flows across system boundaries, data flows between system functions performed by the same systems may not be shown as there will be no corresponding system port connection.

Key Elements and Their Relationships

Meta-Model

The detailed meta-model and element list for P3, Resource Connectivity, is at paragraph 4.5.3.