Local Area Networks (LANs) in Aircraft - FTP Directory Listing - FAA

imploded due to the complexity of policy semantics causing prohibitive schema complexity in
multivendor environments. Because of this, the only surviving PBN systems are vendor
proprietary systems that are limited to a specific vendor’s product lines. The remainder of this
section can be skipped for readers who are not interested in this topic because it does not relate
to the exemplar network architecture recommended by this study in any way.
Figure 23 shows a PBN framework that generically applies to many of the historic PBN
approaches.
Policy
Repository
Policy
Management
Tool
PDP
IP Packets
to/from other
Network Devices
PEP
IP Packets
to/from other
Network Devices
Figure 23. Historic PBN Framework
This figure is comprised of the following entities:
• A policy management tool that modifies the data found within the policy repository to
articulate the current policies of the current deployment (e.g., a policy language response
to environmental triggers). Policy is a set of rules that are used to manage and control the
changing or maintaining the state of one or more managed objects. A policy rule is made
up of four items: (1) metadata and semantics that define the behavior of the policy, (2)
one or more events that trigger the policy, (3) a condition clause, and (4) an action clause.
• There are two distinct functions within PBN systems:
- Policy Distribution Point is the mechanism for pushing policies and configuration
data to configure a policy enforcement point (PEP).
- Policy Decision Point is the functionality used by a PEP to enquire what it should
do in specific situations. In this latter use case, the policy decision point instructs
the PEP as to the proper action it should perform to enact the policies established
for that AS.
• The PEP is the entity that actually enacts policy (i.e., a device).
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