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

support computing devices that function at different classification levels, they deploy distinct
networks, each operating at that classification level. Alternatively, the devices can be connected
in highly controlled ways via HAGs. These onboard computing devices and networks, are RED
networks. Aircraft communicate together, and to ground stations, via wireless media that
operate at an unclassified level. The onboard networks undergo COMSEC encryption and
encapsulation into BLACK IP network headers to be conveyed across the wireless unclassified
network. Thus, two distinct network systems exist: RED networks support end users and
computer applications that are used by onboard communications. BLACK networks support the
air-to-ground and air-to-air conveyance of that information.
If aircraft flying a common mission together establish RED network connectivity between
themselves across BLACK air-to-air communications, then that mission logically functions as
shown in figure 18(b). Specifically, different RED LAN segments within aircraft can become
linked together to form common RED network systems, each operating at a specific
classification level (e.g., sensitive but unclassified (SBU), secret, or top secret). Each of these
RED systems can also communicate with equivalent remote computer applications or personnel
at the same classification that are located in the same or different theaters of operation. For
example, the figure 18(b) shows a mission that contains communicating elements (e.g.,
personnel or applications) that operate at three different classification levels: SBU, secret, and
top secret. Each of these entities are shown as communicating with entities located within
ground networks operating at their same classification level (e.g., the nonclassified Internet
Protocol Router Network is an SBU network, and the Secret Internet Protocol Router Network is
a secret network).
5.3 INTERNET PROTOCOL TOPOLOGY HIERARCHY AND POLICY SYSTEMS.
The IP natively supports a topology hierarchy comprised of increasing aggregations of
networking elements (see figure 19). The figure shows that the IP assumes that the network
interfaces with devices that are grouped into subnetworks, which are grouped into larger
aggregations, depending on the scaling needs of the deployment. If the deployment has modest
scaling needs, then subnetworks are grouped into an AS. If the deployment has larger scaling
requirements, then subnetworks can be grouped into areas, which are grouped into an AS. A
centerpiece of this hierarchy is the AS, which is the unit of routing policy within the IP topology
hierarchy. IP’s standard (IGP, i.e., OSPF, intermediate system to intermediate system (IS-IS))
internally support up to two layers of hierarchy. When both layers of internal hierarchy are
supported, then aggregations of subnetworks into areas occur, otherwise the IGP is deployed
with a single layer of hierarchy, such that subnetworks are grouped into an AS. Therefore, IP’s
IGP dynamically groups subnetworks or areas into ASs. IP’s EGP is the BGP, which is used to
group ASs into internets (also known as “network-of-networks”).
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