Red Switch(Network A)

Blue Switch(Network B)

Per VL ES

Transmit

Per VL ES

Receive

controllers

sensors

actuators

AvionicsSubsystem

AvionicsSubsystem

ES 1

ES 2

AFDX Interconnect

ES 3

Gateway

controllers

sensors

actuators

Avionics Computer System

Avionics Computer System

Internet

ES 1

ES 2

ES 3

ES 5

ES 6

ES 4

VL 1

VL 2

VL 3 VL 4

SWITCH 1 SWITCH 2

Port 6

Port 7

Port 4

Port 5

Port 1

Port 2

Port 3

100Mbps Ethernet Physical Link

LAYER 7

OSI Model

LAYER 6

LAYER 5

LAYER 4

LAYER 3

LAYER 2

LAYER 1

Application Layer

IEEE 802.3 Ethernet

Sampling / Queuing / SAP; TFTP, SNMP implementation

Differences in AFDX according to ARINC 664 Part 7

Presentation Layer

Session Layer

Transport Layer UDP and TCP implementation

Network Layer IP and ICMP implementation

Data Link Layer MAC addressing and VL concept

Physical Layer

1

1

2

2

3

3

4

4

SchedulerMUX

1

1

2

2

VL 11msBAG

VL 24msBAG

BAG1

BAG2

BAG1 BAG1 BAG1Regulator

Physical LinkVirtual Link

MACLayer

Network B

Integrity Checking

Detects and eliminates invalid frames

Integrity Checking

Detects and eliminates invalid frames

Network A

MACLayer

IPUDP/TCP

Layers

Network Management

ApplicationRedundancy Management

Eliminates redundant frames

1 2 3

BAG BAG BAG

·Full duplex, databus according to specification

·Commonly used in Avionics applications (Airbus A380, A400M, Boeing B787 Dream Liner)

·Specification based on standard Ethernet IEEE 802.3, with superimposed features like Virtual Link Concept and Redundancy Scheme

·Differences on 4 Layers of 7 Layer OSI Reference Model

100 Mbps, star architecture Part 7 of ARINC 664

·The characteristics / features which make AFDX potentially suitable for future manned space applications include

·High Data Integrity and Determinism are achieved through fully profiled network implementation ensuring there is no saturation possible on available data links

·Configuration tables in End Systems and Switches contain predefined information on network structure and bandwidth allocation

·Strict set of rules are enforced and policed by AFDX equipment

·Known maximum delay for packet transmission

·AFDX Hot Redundancy scheme duplicates links and switches, with frames always sent on both networks concurrently

·Network implements a ''first valid frame wins'' scheme in reception

·Example of a typical AFDX network within an avionics environment.

·End Systems provide an interface between avionics equipment and the AFDX network.

·

·Since all the VLs share the physical link, individual VLs need to be isolated to prevent traffic on one VL from interfering with traffic on another VL.

·This isolation between the individual VLs is achieved by specifying and limiting two parameters:

·The minimum time gap between consecutive transmission of Ethernet frames on a VL (Bandwidth Allocation Gap or BAG).

·The maximum size of Ethernet frames that can be transmitted on a VL (Lmax).

A physical 100 Mbps link of an ES can support multiple virtual links.

·(BAGs)

·The most important control mechanism imposed on a per VL basis to control the bandwidth of that particular VL.

·BAG=Minimum time interval between the starting bits of two successive Ethernet frames transmitted on a single VL

0 7·BAG values range from 2 to 2 milliseconds

·A BAG can only be initiated when there is data to be transmitted AND the previous bag has expired

Traffic Shaping achieved through use of Bandwidth Allocation Gaps

Supervisors: Dr. Ahmet Sekercioglu (MONASH University)

Matthias Gronowski (EADS Astrium)

Author: Olga Trivailo

ID 18446760

·adequately scheduled to ensure that allocated bandwidths of all VLs are adhered to.

·The Traffic Regulator positions packets within the data stream to be separated by the BAG associated with that VL.

·The VL Scheduler orders and multiplexes frames prior to transmission on the physical AFDX link.

·Blocking the VL for the remainder of a BAG, gives the Scheduler the possibility to insert packets from other VLs onto the physical link.

·Jitter may be introduced at the Scheduler output, caused by simultaneously arriving packets from different Vls being multiplexed onto the physical link.

At each End System output, traffic flow needs to be adjusted and packets

·data integrity and system robustness.

·The IC process for each frame occurs prior to the frame being forwarded to the Redundancy Management function.

·The IC's prime function is to identify abnormal, invalid or stuck frames, which it consequently must eliminate.

·The IC function interacts directly with the Redundancy Management block, which accepts only the first arriving valid frame, and discards any consequent duplicates

Integrity Checking (IC) occurs in the receiving ES and serves to increase

·is characterised by the following key features:

·Single transfer direction (the VL 'pipe' is mono-directional)

·Single subscriber in Tx mode and one or more subscribers in Rx mode

·Reserved, fixed bandwidth into the global AFDX network

·Known maximum latencies and jitters

·Fixed predefined route on the network

·Unique identifier called a VL ID

A Virtual Link is a 'pathway' which transmits a predefined set of traffic and

Avionics Full DupleX Switched Ethernet (AFDX)

in Manned Spacecraft