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

9.3 USING PUBLIC IPs.
The model and architecture presented in this study does not rely upon any unique IP addressing
posture. The only IP requirements of the model are that
• the nonenclaved devices within the airplane (e.g., the airplane’s firewall, ASBR, etc.)
need to be IP addressable by other airplane and NAS ground entities. The architecture
simply does not care whether this is achieved by using public IP addresses, whether the
entire aeronautical network uses the same common private address space, 35 or whether a
combination of private IP addresses and an airplane-local NAT is used.
• the entities within each VPN enclave must be addressed from the same IP address space.
The architecture does not care whether this IP address space is public or private.
The IETF community has had extensive internal discussions about whether private IP addresses
are more secure than public IP addresses. While this remains a highly controversial topic, the
majority’s position is that private addresses have no appreciable security benefit over public IP
addresses. The most powerful argument in favor of using private IP addresses for security
purposes is that because private addresses have no uniqueness property outside of their enclave,
use of private addresses cloaks internal networks from external visibility and limits access. The
force of this argument diminishes the more closely one examines the details for maintaining
private addresses within public spheres.
9.4 ELECTRONIC FLIGHT BAGS.
AC 120-76A [8] provides guidance for the certification, airworthiness, and operational approval
of electronic flight bag (EFB) computing devices. EFB equipment refers to the replacement of
historically report-based aviation data and calculations by onboard computing equipment (e.g.,
auxiliary performance computers or laptop auxiliary performance computers) to assist aircraft
operations. EFBs may also host new types of database information and applications. Three
distinct classes of EFB hardware devices are defined according to their relative integration with
onboard resources such as electric power, data connectivity, and mounting.
• Class 1 hardware are portable COTS laptop or pen tablet computers with software
applications that can include electronic documents, performance calculations and charts.
Class 1 do not require certification, but they must be stowed for takeoff and landing.
These devices are mostly employed in training and flight planning and for use with
reference manuals and in performance calculations.
• Class 2 hardware are semipermanent in that they can dock with a certified crashworthy
mount, can be powered all of the time and can tap into noncritical aircraft systems,
allowing for cabin video displays and aircraft health monitoring and reporting, or links to
an onboard file server.
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If the NAS does not use public IP addresses, then this alternative would mean that a NAT would be needed to
provide airplane connectivity to non-NAS IP networks such as the Internet.
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