The Network Is NOT TransparentCRETA Platform –What is it? Avionics architectures can contain nowadays a variety of communication hardware, e.g.:

© 2015 Spazio IT - Soluzioni Informatiche s.a.s.

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LCM

The Network

Is NOT

Transparent

October 2015

SPAZIO IT LCM - FDIR

Maurizio Martignano

Spazio IT – Soluzioni Informatiche s.a.s

Via Manzoni 40

46030 San Giorgio di Mantova, Mantova

http://www.spazioit.com


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Agenda

CRETA Platform

LCM

LCM and FDIR

Conclusions

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CRETA Platform

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CRETA Platform – What is it?

Avionics architectures can contain nowadays a variety of communication hardware, e.g.:– AFDX (Avionics Full-Duplex Switched ) Ethernet

– ARINC 429, MIL-STD-1553B,…

– RS 232, RS 422, RS485,…

In turn, different types of computers, controllers, devices etc…, are connected to the communication infrastructure.

Finally various types of software/firmware systems run on the adopted computers and controllers. These systems are not necessarily written in the same programming language.

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When developing and/or maintaining Software Components belonging to a given architecture it is very important to be able to integrate them with each others and to verify how well they interoperate together.

And the sooner this verification activity is performed, the better.

CRETA (Cross Environment for Test and Analysis) is a software platform simulating both:

– the avionics communication infrastructure

– the various avionics computational environments

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With CRETA software developers/maintainers can «check» their software component directly on their workstation, on a simulated «testbed».

Tests and verifications on the actual hardware «testbed» can be performed at later time, once the software component has successfully proved its interoperability on CRETA.

Actual hardware can also be integrated to CRETA, as soon as it available (or the other way around: CRETA can be integrated to actual hardware).

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CRETA Platform – Programmatics

CRETA is project under development funded by AIRBUS Helicopters.

The main CRETA Developers are:

– Inopus (http://www.inopus.de/)

– Spazio IT (http://www.spazioit.com)

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http://www.inopus.de/

http://www.spazioit.com/


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CRETA Platform – LCM

Software components «attached» to CRETA can run on different workstations in a networked environment.

CRETA exposes itself to the software component via a «connector», i.e. a standard API.

The «connector» in turn connects to the CRETA system and other software components via an internal middleware based on LCM.

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API

LCM

Connector Logic

Software Component

CRETA Platform


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API

Actual Comm. Library

Connector Logic

Software Component

Actual Avionics Platform


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Actual Comm. Library

Communication Bridge

Actual Avionics Platform CRETA Platform

LCM

Analyzers

Filters

Loggers


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LCM

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Lightweight Communications and Marshalling


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LCM

“LCM was created for use on MIT's DARPA Urban Challenge vehicle, with development starting during the summer of 2006.”

LCM is publically available at: https://lcm-proj.github.io/

LCM supported languages are: C, C++, C#, Java, Lua, MATLAB, Python

October 2015

https://lcm-proj.github.io/


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LCM – Design Goals

Communication– Supports many-to-many

communication.

– No per-network or per-host daemon needed for relaying data

– Each packet transmitted appears on the wire no more than one time

– Minimal latency

– Scales to high bandwidth

Marshalling– Absolute type-safety

– Platform- and language-independence

– Ease of use

FDIR– Does not guarantee

delivery of a particular message.

– Does not guarantee ordering of messages.

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RPC

(the network is transparent)

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IIOP, DCE/RPC, HTTP/SMTP

Object

Adapter

Client Server

Stub

(Server Rep.)

Skeleton

(Client Rep.)

IDL

WSDL

...


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RPC


Local call

…

local_foo();

…

Remote call

…

try {remote_foo();

} catch (Local_Remote Exception ex) {

// Something here// … (but what?)}

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RPC


Characteristics

– Local / Remote Exceptions

– Indirect Memory Allocation

– Blocking Calls

– (Stub / Skeleton Binding at Compile Time)

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LCM

(the network is NOT transparent)

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LCM(SPY) / UDP - Multicast

«Client» «Server»

Marsh./

Unmarsh.

Marsh./

Unmarsh.

LCM

Types

publish msg

to channel

subscr. to channel

receive msg


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LCM


Local call

…

local_foo();

…

Message publishing…

example_t msg = new example_t();

// … initialize message

try {

lcm.publish("EXAMPLE", msg);

} catch (LocalException ex) {

// Something here}

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LCM


Characteristics

– Local Exceptions

– No Indirect Memory Allocation

– No Blocking Calls

– (Message Types Binding at Compile Time)

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LCM and FDIR

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LCM and FDIR

LCM does not rely on «servers»:

– Supports many-to-many communication.

– No per-network or per-host daemon needed for relaying data

LCM does not guarantee the communication has taken place:

– Does not guarantee delivery of a particular message.

– Does not guarantee ordering of messages.

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LCM and FDIR

Additionally, “LCM provides several tools useful for logging, replaying, and inspecting traffic.

These tools allow developers to quickly identify many of the most common failures. “ and can be used to implement failure detection mechanisms.

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Conclusions

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Conclusions

Complex software systems can be decomposed in a set of interconnected processes.

The fault isolation provided by a set of processes connected by a proper communication infrastructure can be comparable to the one offered by virtual machines and/or containers.

Not relying on central/critical components as well as non relying on particular assumptions / guarantees increases the overall robustness of the system.

The network is not transparent.

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References

http://people.csail.mit.edu/albert/pubs/2010-huang-olson-moore-lcm-iros.pdf

http://lcm.googlecode.com/svn-history/r452/www/reference/lcm/intro.html

October 2015

http://people.csail.mit.edu/albert/pubs/2010-huang-olson-moore-lcm-iros.pdf

http://lcm.googlecode.com/svn-history/r452/www/reference/lcm/intro.html


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Thank you for your attention

October 2015

Documents

The Network Is NOT TransparentCRETA Platform –What is it? Avionics architectures can contain nowadays a variety of communication hardware, e.g.: