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

that is indirectly connected to one’s network is theoretically able to access one’s network). This
is in direct contrast with all approaches, which create structures that logically belong to the same
larger network system. Unless mitigated by network partitions (see sections 5.4.1 and 5.4.2), the
approaches operate in network systems that are logically connected together. The risks are
described in section 4.1. By contrast, multilevel networks create protected network systems.
Specifically, RED users cannot access BLACK network resources or vice-versa. By so doing,
the users that comprise a given network within the multilevel network system are solely the users
within that specific network system. Thus, they have a controlled network population within a
controlled network system. By contrast, the users that comprise a single level network system
are the cumulative users that can access any network within that system. In the case of the
Internet, that would be more than a billion people.
5.5 AIRPLANE ROUTING AND AUTONOMOUS SYSTEMS.
The AS defines the administrative boundaries of IP systems (see section 5.3). Entities within an
AS share common network policies (e.g., QoS, security). They also share common network
administrative systems. While military aircraft often belong within a common AS with the other
military aircraft with which they are associated (e.g., a squadron), and possibly with the military
ground stations that support them, civilian aircraft usually belong to a different AS than the
ground systems that support them. This is because civilian aircraft are usually either privately
owned or owned by a corporation. In either case, the aircraft owners usually do not belong to the
same corporation or agency as the ground stations that support them. While aircraft within the
same corporate fleet may be organized into a common AS with other aircraft from that same
fleet, this is not done in general because it would cause their intrafleet communications to be
significantly different than their interfleet communications. Creating such dissimilar air-to-air
relationships adds needless complexity to the entire system and may cause significant problems
if not done correctly.
The previous paragraph should be readily apparent when aircraft are considered in terms of the
IP networking concepts presented in section 5.3. Unfortunately, these IP topology hierarchy
relationships permeate airborne network communications in subtle ways. The purpose of this
section is to explain the pervasive nature of these concepts upon airborne networking and, by so
doing, indicate some of the inherent technical challenges with designing viable airborne network
systems (e.g., section 8).
The majority of this section is concerned with the routing implications of each airplane being its
own AS. However, there are also IP addressing issues that derive from that association. With
the advent of CIDR addressing, IP routing systems have increasingly relied on address
aggregation to enhance scalability. CIDR has changed IP address semantics by embedding
Internet topology information into the address prefix. This information identifies the specific
ISP, which that entity uses to connect to the Internet. By so doing, address aggregation is
enhanced for the BGP peering relationships between ASs, significantly improving Internet
scalability. A side affect of this is that the IP addresses that airplanes adopt contain implicit IP
network topology semantics, directly associating that airplane with a specific ISP. This may not
be an issue if the worldwide airspace functions as a single ISP. However, a more likely scenario
is that the airspace will be segregated into identifiable nationally or regionally controlled
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