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

Simultaneously, IP addresses are also used to identify application layer entities located within
the device that hosts them. Therefore, IP addresses are semantically overloaded by
simultaneously indicating two different semantic notions: routing topology location and device
identity. The overloading of these very different semantic notions into the same address value
results in what is known as the “IP Identity Problem.” The identity problem may become
manifested whenever a device physically moves within the routing topology (e.g., when aircraft
move relative to ground-based infrastructures). Mobility can cause a conflict between the two
semantic notions; because the moving entity has changed its network location, it is normally
expected to readdress its network interfaces to reflect their new topological location. But if that
is done, how can entities remote to that device authoritatively know that the device previously
identified as having IP address X is the same device that now has IP address Y?
IPv6 addresses differ from IPv4 addresses in that each IPv6 network interface may
simultaneously have multiple different IPv6 addresses, each with a potentially different network
topology significance. IPv6 systems also support assigning unique IPv6 addresses to each
application within that device. Consequently, IPv6 devices can support logical networks internal
to that device itself, with each application supported by that device potentially having its own
IPv6 address. By contrast, IPv4 systems are limited to referring to their applications solely via
the port address field within the transport layer’s protocol header (e.g., UDP, TCP, stream
control transmission protocol).
Both IPv4 and IPv6 similarly share the IP identity problem, though its affects somewhat differ
between the two protocol systems. Mechanisms to mitigate the IP identity problem are outside
of the scope of this study.
The point of this discussion is that the worldwide civil aviation network infrastructure needs to
devise a common mechanism by which the identity of networked elements is established. This
means defining a common aeronautical solution for the IP identity problem for aircraft. If this is
not done, then serious security vulnerabilities can arise whenever aircraft transition between
system elements having dissimilar identity approaches.
4.9 INTEGRATED OR COOPERATING SYSTEM OF SYSTEMS.
The previous section discussed some of the issues related to creating a network infrastructure
that links together two or more different protocol families. Section 4.8 mentioned the fact that
TCP/IP systems have a weakness that is known as “The Identity Problem” that OSI systems do
not share. The purpose of this section is to mention that the defense-in-depth provisions (see
section 5.1) that are used to protect infrastructures rely on a coherent mechanism within that
infrastructure for handling identity, authentication, and authorization. Should any of these
elements not be handled in a consistent manner, then the infrastructure is subject to
vulnerabilities that attackers can leverage to damage that infrastructure and potentially harm its
safety attributes.
Each protocol family has its own mechanism for establishing identity. Protocol gateway
translators will need to map between these different systems to successfully enable
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