2013-2014 CISEC Conferences : Airbus embedded system architecture, Pascal Travserse
Embedded System Architecture
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Transcript of Embedded System Architecture
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Embedded SystemArchitecture
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Embedded System ArchitectureEvery embedded system (ES) is composed of
interacting elements (hardware or software).
An architecture is a set of representations of thoseelements and their relationships.
Architecture helps understanding the whys of the
elements with given functionalities.Defining and understanding the architecture of an ES
is an essential component of good system design.
An architectural systems engineering in an ES helps understanding the design
is essential to resolve challenges when designing anew system
helps design re-use, reduces design time and cost.
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Embedded System Architecture
An embedded architecture captures various views,which are representations of the system.
It is thus a useful tool in understanding allof themajor elements: Why each component is there?
Why the elements behave the way they do?
Without an architecture design it is difficult todetermine how the system would behave under avariety of circumstances in the real world.
The architecture conveys in some way the criticalcomponents in a design and their relationships toeach other.
Even if the architectural structures are rough andinformal, it is still better than nothing.
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Embedded Systems Model
The embedded system model
indicates that at the highestlevel, they have
at least one layer (hardware)
or
all layers (hardware, system
software and applicationsoftware) into which all
components fall.
This model is essentially a
layered (modular) model of an
ES architecture.
It gives visual representation
of the main elements and
their associated functions.
The hardware layer contains all
the physical components.
The system software layercontains all the software
located on the ES.
The application software layer
contains all the SW being
processed by the ES.
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Networks Architecture in ES
The ES is a networking of
internal components and thenetworks architecture.
Good to associate the
networking components with a
universal networking model, the
seven layer OSI reference model. Data originating at the
application layer flow downward
through all seven layers.
Information (header) is
appended to the data at eachlayer (except for the application
and physical layers).
Data is wrapped with information
for other devices to unwrap and
process.
Mapping
OSI layers ES layers
Physical Hardware
Data-linkNetwork System SWTransport
Session
Presentation Application SWApplication
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OSI Model and Real World Protocol
The functionalities and methodologies implemented at
each layer based on the OSI model are commonlyreferred to as netwo rk ing protocols .
It isnt always the case that there are all seven layers orthere is just one protocol per layer.
The functionality of one layer of the OSI model can beimplemented in one protocol, or also it can beimplemented across multiple protocols and layers.
A group of protocols may have their own name and begrouped together in their own proprietary layers.
Examples are:
TCP/IP WAP Bluetooth
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The TCP/IP, OSI and ES Models
The TCP/IP stack is made up of four layers.
OSI layers TCP/IP layers
Top three (App, Presentation, Session) TCP/IP App layerTransport layers Transport layer.Network layer
Internet layerTwo OSI layers (Data Link and Physical) Network access layer
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The OSI, WAP and ES Models
The Wireless Application Protocol (WAP) stack provides five layers ofupper layer protocols.
OSI layers WAP layersApplication layer WAP Application layerPresentation layer Security layerSession layer Session + Transaction layerTransport layer Transport layer
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The Bluetooth, OSI and ES Models
OSI layers Bluetooth
layers
Physical andLower Data Link
layers
Transport ProtocolGroup
Upper Data link,
Network +Transport layer
Middleware
Protocol Group
Session,
Presentation +
Application layer
Application
Protocol Group
The Bluetooth stack is a three-layer model made up of
Bluetooth-specific as well as adopted protocols from
other network stacks, such as WAP and/or TCP/IP .
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(1) Physical Layer Protocols in the ES Models
The Physical Layer represents all of the networking HW physically locatedin an embedded device. It defines, manages, and processes, viahardware, the actual voltage representations of 1s and 0s.
Physical layer protocols defining the networking hardware of the deviceare located in the hardware layer of the ES model.
Physical layer protocols are classified as either LAN or WAN protocols.
They can be further subdivided according to the transmission medium
connecting the device to the network (wired or wireless).
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(2) Data-Link Layer Protocols in the ES
Includes any software needed to control the hardware.Bridging also occurs at this layer.
Data-link layer protocols can be used for (i) LAN, (ii) WAN, or (iiii) both.
Can be wired or wireless.
Generally, reliant on a specific physical layer.
May also be ported to very different mediums.Supports hardware-independent upper-data-link functionality.
Data-link layer
protocols areimplemented in
the system
software layer.
Closest to the
hardware layer.
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(3) Network Layer Protocols in the ES
Networks can be divided into smaller sub-networks, called segments.
Devices within a segment communicate via their physical addresses.
Devices in different segments communicate through an additional address,
called the network address.
Conversion between physical addresses and network addresses can occur in
the data-link layer protocols (i.e. ARP, RARP etc.)
Network layer protocols can also convert between physical and networkaddresses as well as assi n network addresses.
Implemented in the
system software
layer.
Is typically hardware
independent.
Depends only on the
data-link layer
implementation.
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(4) Transport Layer Protocols in the ES
Ensures reliable point-to-point data transmission, by ensuring that:
1. packets are received and transmitted in the correct order
2. transmitted at a reasonable rate
3. packets are not corrupted
4. Provides acknowledgement on receiving
5. Requests retransmission in case of detection of error.
Transport layer
protocols sit on topof and are specific
to the network layer
protocols.
Are typically
responsible for
communicationbetween two
specific devices
(point-to-point)
communication.
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(5) Session Layer Protocols in the ES
The session layer protocols1. Separate and manage each sessions data
2. Regulate the data flow of each session
3. Handle any error
4. Ensure the security of the session
5. Ensure that the two applications involved in the session are the righta lications.
The connection
between two
networkingapplications on two
different devices is
called a session.
The management of a
session is handled bythe session layer.
Generally, sessions
are assigned a port
(number).
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(6) Presentation Layer Protocols in the ES
1. Presentation layer protocols are usually implemented in
networking applications in the application software layer in ES.
2. Data compression/decompression, data encryption/decryption,
data protocol/character conversions.
Protocols in the
presentation layerare responsible for
translating data into
formats that higher
applications can
process.
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(7) Application Layer Protocols in the ES
1. A device initiates a network connection to another device at theapplication layer.
2. Application layer protocols are either used directly as network
applications by end-users or the protocols are implemented in
end-user network applications.
3. These applications virtually connect to applications on otherdevices