ETTC'2003 - SEE

The L3 switches allow forwarding data flows coming from different emitters towards one or several
receivers, by duplicating them when necessary. They also allow sharing data between the 3 Flight
Test chains (Basic, Wide Band and Crash), as shown in Figure 3.
PRINCIPLES
The IENA LAN is built around an Ethernet 100 Mbit/s Full Duplex architecture, using COTS switches
(CISCO 2950 series for A380). Two operating modes, corresponding to different data flows, have to
be supported by the network :
ACQUISITION MODE :
Acquisition Mode is the default operating mode for the FTI : every system at startup is able to handle
acquired data.
The main flow in Acquisition Mode consists in IENA packets carrying aircraft parameters, coming up
from L2 towards L4 units. This traffic lies on MULTICAST communication (at UDP-IP level for L2/L4, at
MAC level for L3). Using MULTICAST allows one L2 to send its acquired data to any number of L4.
Point-to-point exchanges in Acquisition Mode, when needed, are also performed with MULTICAST
communication.
IP MULTICAST addressing map defines “Multicast Destination Groups” to which L4 receivers have to
register. These Multicast IP addresses are taken from one private Class D sub-network, the last byte
being the Multicast Destination Group number.
The Multicast Destination Groups table is static, identical for all aircrafts and exhaustively defined in
SABRE Data Base (Cf. example in Figure 4).
L3 commutation table is then automatically generated in accordance with the cabling of the receivers
on its output ports. This table contains Multicast MAC addresses ; the IP to MAC address mapping
being compliant with the Multicast standard.
Multicast
Destination Groups
Number
Corresponding IP
Multicast Address
Parameters towards STD FTI L4 GR 10 235.1.1.10
Parameters towards WB FTI L4 GR 20 235.1.1.20
Parameters towards Crash FTI L4 GR 30 235.1.1.30
Parameters towards STD + WB FTI L4 GR 12 235.1.1.12
Parameters towards STD + Crash FTI L4 GR 13 235.1.1.13
Parameters towards WB + Crash FTI L4 GR 23 235.1.1.23
Parameters towards STD + WB + Crash FTI L4 GR 123 235.1.1.123
Figure 4 - Example of Multicast Destination Groups table
DOWLOADING MODE :
Switching one system (L2/L3/L4) in Downloading Mode is performed on user request, during on
ground operation. Since all the systems are running independently, Acquisition and Downloading
traffics can occur concurrently on the FTI LAN.
The main flow in Downloading Mode consists in configuration files coming from one dataloader
towards each L2/L3/L4. Every system supplier is free to choose his standard Ethernet protocol for
downloading ; for A380 FTI, retained protocols are TFTP, FTP, TCP-IP. Multiple downloading sessions
can be supported at the same time (the major impact is on dataloader).
These exchanges do not require MULTICAST, but standard UNICAST addressing at IP level. These IP
addresses are taken from one Class B IP sub-network, the last 2 bytes being dependent of aircraft
type and number, and system type and position. The Unicast addressing map is static for a given
aircraft, and exhaustively defined in SABRE Data Base.