[00022] It is preferred that the AGN uses private class A subnet： 10. 0. 0. 0/22. A 22 — bit subnet mask is defined that borrows 14 bits from the host part (14 bits for subnets and 10 bits for hosts). The 14 - bit ACID therefore supports 16，382 unique airborne networks. The 10 - bit field [ d... d] is used to identify hosts. This field therefore supports up to 1,022 hosts or other devices. Thus，
ACIDDevice
[10. ] [ aaaaaaaaaaaaaa ] [ dddddddddd ]
10. aaaaaaaa. aaaaaadd. dddddddd/22
[00023 ] The device number field ranges can be defined as follows.
Table 1
It can be seen in Table 1 that all network address translations by convention use a device field having a value of 7 or 8. Since only pas¬senger 一 sourced traffic is translated by the NAT gateway, this conven¬tion allows ground - based security systems to easily identify passenger traffic. Traffic to/from onboard systems such as the web portal 26 or media server 24，and all SNMP traffic can be easily identified and iso-lated from passenger traffic. It will therefore be appreciated that the above - described isolation systems have logical AGN addresses corresponding to an ACID such that the aircraft has a unique subnet address. The airborne router38 can be defined as one of the isolation systems，where the airborne router has a device identifier such that the ACID and the device identifier define the logical AGN address for the airborne router. Similarly，the web server 26 can be defined as one of the isolation systems，where the web server 26 has a device identifier such that the ACID and the device identifier define the logical AGN address for the web server. Table 1 illustrates that various crew interfaces are provided with internet access by the AGN, wherein each crew interface has a corresponding logical AGN address.
Command and Control Sub - Network ( CCN )
[00024] It will be appreciated that the CCN supports local command and control functions such as built - in test ( BIT)，configuration, initialization，data load，etc. The CCN excludes passengers devices by not assigning computing devices 14 addresses from the CCN address space. It is preferred that the class B private address range 172. 16. 0. 0/16 is used for the CCN and is reused on each aircraft. It is important to note that CCN devices do not communicate directly to the ground using CCN addresses. Furthermore，the CCN is not advertised to the ground and CCN addresses are not translated (i. e.，no NAT) . The device field is used not for routing, but rather for address administration and can be defined as follows ：
[172. 16] [x-LLL - DDDDDDDDDDDD]
16 - Bits 1 - Bit 3 - Bits 12 - Bits
Where
LLLL = ( 100 = Seatbox, 010 = Server, Oil = Network Element X = not currently used ( always setto “0”)
Thus，an SEB address in the CCN address space would be as follows：
[172. 16] [x -LLL-DDD -CCC - BBBBB]
16 - Bits 1 - Bit 3 - Bits 4 一 Bits 3 一 Bits 5 - Bits
[172. 16] [0 - 100 - 0010 - 100 - 01000]
[172. 16] [01000010. 10001000]
172. 16. 66. 136
Where，
LLL = 100 = Seatbox
D = Area Distribution Box (2)
C = Column (4)
B = Seatbox (16)
X = not used (always setto“0”)
[00025 ] It will therefore be appreciated that the SEBs 16 can be defined as being control interfaces such that the SEBs 16 have corresponding logical CCN addresses. Furthermore, the area distribution boxes 20 can be defined as being control interfaces such that the area distribution boxes 20 have logical CCN addresses.
Passenger Services Sub - Network ( PSN)
[00026] As already discussed, the PSN is the onboard network that provides direct services to passengers. Thus，passengers boarding with computing devices 14 are assigned PSN addresses. Furthermore, all onboard devices that provide direct user services are assigned PSN addresses. Thus, the web server 26，media server 24, airborne router 38，and SEBs 16 can all be defined as passenger interfaces having corresponding logical PSN addresses.
[00027 ] It is preferred that the PSN addresses include two class B addresses supemetted together, wherein the first 15 bits make up the prefix. As in the case of the CCN addresses，the address range of the PSN addresses is reused on each aircraft It will further be appreciated that the PSN addresses are translated by a NAT function for off -board access. Thus, PSN addresses are translated into an AGN address from the NAT address pool.
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