WEBVTT
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Now, the last network
type we're going
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to talk about is AFDX.
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AFDX also stands for Avionics
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Full-Duplex Switched network and
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the abbreviation already
tells something,
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so it's full-duplex,
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and please remember
what full-duplex means.
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It means all entities
on the bus can talk
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simultaneously and of course
also receive simultaneously.
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So besides being full-duplex,
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the number of network entities
on AFDX networks is very
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high due to the possibility
of hierarchical networking,
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and most important AFDX
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or talking about
its specification,
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ARINC 664 is based
on COTS Ethernet.
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You might have heard
about ethernet,
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it's the way of
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network communication you are
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all using back at your home.
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We're all using
usually in our labs,
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we are using in our
local area networks,
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and that was actually
also the idea
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behind it and I'll come
to that in a second.
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The wiring here, actually,
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it's unshielded twisted pair.
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It's a star tree topology,
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so we have a router or
a switch in the middle.
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The wordsize has dynamic sizes
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and the bit rate now is
10-100 megabits per second.
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There are even talks about
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one gigabit implementations here.
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Here we see the architecture,
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the typical star architecture
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with the switch in the middle.
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Now here we do not have
remote terminals as
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we have it with a mail-bus.
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We call those the end systems
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into the most simplest way you
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can think of a network card
put into one of the LRUs.
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Here we have five
LRUs or 4 plus n,
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and you also have a second
switch which symbolizes
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the hierarchical decomposition
of the overall network.
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Please feel reminded on,
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as I've said before,
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the networks you're used
to in your offices,
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in your labs back at home.
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The idea to have
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that commercial
off-the-shelf approach came
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from seeing the advantage of
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already developed
IT components and
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system in the consumer area
in the industrial area.
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Before that, again,
ARINC 429 mail-bus,
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these buses were developed
solely for avionic purposes,
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which is good on one thing,
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but makes it very
expensive to develop
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that and also to
advance the technology.
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The idea that was lying behind
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the AFDX network was to use
already existing technology
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in industry and consumer IT area
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to be re-used within
the aerospace domain.
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In that specific idea,
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it was the ethernet
network as it was
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defined in the IEEE 802.3
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standard to use that as
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a baseline and adopted
to aviation needs.
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The advantages are at the hand.
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Most of those components
were already developed.
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There were there and not
only developed for aviation,
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but to all other needs
which are actually
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more many-fold than aviation.
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Further on, technological
advancements are now expected,
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actually not only coming
from the Asian community,
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but from the overall
IT community.
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Before that ARINC 429,
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and mail-bus were sorely
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developed for the
aerospace community,
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which made the development very
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unique and also very expensive.
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Now having, let's say,
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the whole knowledge of
the IT world at hand,
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it was expected that the
technological advancement,
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the development of the
AFDX bus was easier,
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faster, and also cheaper.
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However, of course, the
specification of the,
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let's call it the standard
ethernet did not meet
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all requirements with respect
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to determinism,
real-time capability,
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and low latency on one side,
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as well as reliability,
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integrity on the other side that
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were needed by
aerospace applications.
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So that standard or that
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technology needed adaptations to
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fulfill also these requirements,
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and now we'll have
a look on those.
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So the measures taken to
fulfill those requirements,
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determinism and low latency
on one side, reliability,
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and integrity on the other
side are as follows: First,
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determinism and
low latency, here,
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it was desired to realize
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full-duplex communication
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without the danger of collisions.
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First-generation regular ethernet
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didn't care about collisions.
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Messages were just sent like
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that and hopefully
they went through,
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usually they actually
went through,
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but there wasn't guarantee
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there really would reach intact.
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If you have, well,
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regular non-critical
communication,
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that didn't matter much,
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your message was reset.
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But that wasn't
bearable for a lot
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of avionics communication where
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a certain transmission time
shouldn't be exceeded.
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So for that separated wire
pairs for transmission and
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reception of information between
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the end systems and the
switches were introduced,
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so no fear of collisions anymore.
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Further was static routing,
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the neat thing with
ethernet when it's
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used like an application
of the worldwide web is
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that the routes that
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the package actually
travel is not prescribed.
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By that, a dynamic structure of
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the whole network
system can be achieved.
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That's nice for realizing
a worldwide web.
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It's nightmare for having
it on the aircraft.
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In the aircraft you want to have
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a controlled system and with that
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you can allow a static routing.
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This means you can prescribe
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the individual way a packet
travels through your network,
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and with that also,
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the time of travel is prescribed.
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As a third point for
determinism and low latency,
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we have the possibility to have
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a strict bandwidth management
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by limiting transmission
rates and frame sizes.
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Talking about reliability
and integrity,
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redundancy was introduced to
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AFDX by a mere doubling
of all components.
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So you have two switches,
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and doubling the harnesses,
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also doubling the end systems,
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and by that you have
already dual redundancy.
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Of course, as we have already
seen with the mail-bus,
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you need integrity monitoring,
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that means you have to listen
on both lanes actually,
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if some messages
on GAR route or if
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you're can detect any
errors or invalid frames.
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So this was my short presentation
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on digital avionic networks,
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I hope you enjoyed it.
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If you want to have more details,
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feel free to have
a deeper look in
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those two references I am
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giving at the end of the
slides. Thank you very much.
카테고리 없음
arink 664
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0:06
It means all entities on the bus can talk
simultaneously and of course also receive simultaneously.
::37에서 시작하는 비디오를 재생하고 대본을 따르십시오.0:37
2:4에서 시작하는 비디오를 재생하고 대본을 따르십시오.2:04
2:40부터 비디오를 재생하고 대본을 따르십시오.2시 40분
2분 53초부터 비디오를 재생하고 대본을 따르십시오.2:53
8:3에서 시작하는 비디오를 재생하고 대본을 따르십시오.8:03
8:40부터 비디오를 재생하고 대본을 따르십시오.8:40
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