ETSI TS 102 744-4-2 V1.1.1 (2015-10)

Satellite Earth Stations and Systems (SES); Family SL Satellite Radio Interface (Release 1); Part 4: Enhanced Services and Applications; Sub-part 2: Aeronautical Safety Services

DTS/SES-00299-4-2

General Information

• Status: Published
• Publication Date: 25-Oct-2015
• Technical Committee: SES SCN - Satellite Communications and Navigation
• Current Stage: 12 - Completion
• Due Date: 25-Sep-2015
• Completion Date: 26-Oct-2015

Standards Content (Sample)

TECHNICAL SPECIFICATION
Satellite Earth Stations and Systems (SES);
Family SL Satellite Radio Interface (Release 1);
Part 4: Enhanced Services and Applications;
Sub-part 2: Aeronautical Safety Services

2 ETSI TS 102 744-4-2 V1.1.1 (2015-10)

Reference
DTS/SES-00299-4-2
Keywords
3GPP, GPRS, GSM, GSO, interface, MSS, radio,
satellite, TDM, TDMA, UMTS
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ETSI
3 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
Contents
Intellectual Property Rights . 6
Foreword . 6
Modal verbs terminology . 6
Introduction . 6
1 Scope . 7
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Symbols and abbreviations . 8
3.1 Symbols . 8
3.2 Abbreviations . 8
4 Overview of Aeronautical Safety Services. 8
4.1 General . 8
4.2 Priority and Pre-emption . 9
4.3 ACARS . 9
4.4 Voice . 10
4.5 Prioritized IP . 10
5 ACARS Data Service . 10
5.1 Aeronautical Safety ACARS data service overview . 10
5.2 AAGW Design Description . 11
5.3 Inter-ACARS Gateway Interface Description . 29
5.3.0 General . 29
5.3.1 Connection to ACARS Ground Gateway interface . 29
5.3.2 AIGI Message Format . 30
5.3.3 AIGI Message Definitions . 31
5.3.3.0 General . 31
5.3.3.1 Message Types . 31
5.3.3.2 Message ac_logon_rq (ac_logon_rq_n): Log-on request . 32
5.3.3.2.0 General . 32
5.3.3.2.1 Transaction ID . 34
5.3.3.2.2 Location . 34
5.3.3.2.3 Terminal type . 36
5.3.3.2.4 Logon Reason . 36
5.3.3.3 Message gw_logon_rp: log on response . 37
5.3.3.3.0 General . 37
5.3.3.3.1 Response . 38
5.3.3.4 Message ac_logoff_rq (ac_logoff_rq_n): Log off request . 39
5.3.3.4.0 General . 39
5.3.3.4.1 Cause Code . 41
5.3.3.5 Message gw_logoff_ack: Log-off acknowledgement . 42
5.3.3.6 Message gw_logoff_notify: log off notification . 42
5.3.3.6.0 General . 42
5.3.3.6.1 Reason . 43
5.3.3.7 Message ac_acars_msg (ac_acars_msg_n): Single block ACARS message . 43
5.3.3.8 Message gw_acars_ack: Acknowledgement of ACARS message receipt . 45
5.3.3.9 Message gw_acars_msg: Single block ACARS message . 46
5.3.3.10 Message ac_acars_ack (ac_acars_ack_n): Acknowledgement of ACARS message receipt . 47
5.3.3.11 Message gw_conf: Update of AAGW configurable parameters. 48
5.3.3.11.0 General . 48
5.3.3.11.1 AGGW Configuration Items . 51
5.3.3.12 Message ac_conf_ack (ac_conf_ack_n): Configuration update acknowledgement . 51
5.3.3.13 Message ac_keepalive (ac_keepalive_n): keep-alive . 52
5.3.3.14 Message gw_keepalive_ack: keep-alive acknowledgement . 53
5.3.3.15 Message gw_keepalive: keep-alive . 54
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4 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
5.3.3.16 Message ac_keepalive_ack (ac_keepalive_ack_n): keep-alive acknowledgement . 54
5.3.3.17 Message gw_csp_ping: ping. 55
5.3.3.18 Message ac_csp_ping_ack (ac_csp_ping_ack_n): ping acknowledgement . 56
5.3.3.19 Message gw_test_msg: AIGI Traffic Test . 56
5.3.3.20 Message ac_test_ack (ac_test_ack_n): AIGI Traffic Test Acknowledgement . 57
5.3.3.21 Message ac_msg_nak (ac_msg_nak_n): Invalid AGGW message . 58
5.3.3.22 Message gw_msg_nak . 59
5.4 Provisions for ACARS Authentication. 60
5.5 Prioritized Access to the Family SL Network . 60
6 Prioritized IP Data Service . 61
7 Aeronautical Safety Voice service . 61
7.0 General . 61
7.1 Key Features . 61
7.2 Second Voice Channel . 62
7.3 Priority and Pre-emption . 62
7.4 Aeronautical Safety AES Voice Requirements . 62
7.4.0 General . 62
7.4.1 Parameters. 62
7.4.2 Number of Concurrent Calls . 63
7.4.3 Support for Short Code Dialling . 63
7.4.4 Call Routing, Voice Priority and Pre-emption . 63
7.4.4.0 General . 63
7.4.4.1 AES CS Protocol Requirements for eMLPP . 64
7.4.4.2 Priority Signalling . 64
7.4.4.3 AES Priority and Pre-emption. 65
7.4.5 VoIP Context Management Requirements . 67
7.4.5.1 Primary PDP Context Establishment . 67
7.4.5.2 Secondary PDP Context Definition . 67
7.4.5.3 Secondary PDP Context Activation and Deactivation . 68
7.4.6 SIP Protocol Requirements . 68
7.4.6.0 General . 68
7.4.6.1 SIP Registration . 68
7.4.6.2 SIP Call Setup (originating from Aero PBX) . 68
7.4.6.3 SIP Call Setup (terminating on Aero PBX) . 69
7.4.6.4 SIP Call Maintenance . 69
7.4.6.5 SIP Options . 69
7.4.7 Media Handling Requirements . 69
7.4.7.1 Codec . 69
7.4.7.2 PS Codec Frame Packetisation . 69
7.4.8 Supplementary Services Requirements . 70
7.4.8.1 CS Domain Supplementary Services Requirements . 70
7.4.8.2 Calling Line Identification Presentation on Inbound Calls . 70
7.4.8.3 Calling Line Identification Restriction on Outbound Calls . 70
7.4.8.3.1 CS Domain . 70
7.4.8.3.2 PS Domain . 70
7.5 Cabin/Public Calls . 71
Annex A (normative): ACARS Data Service Behavioural Requirements . 72
A.1 AAGW establishes best available link with ground . 73
A.2 AAGW Logs in to Family SL ACARS service . 74
A.3 AAGW Logs out of Family SL ACARS service . 75
A.4 Ground to Air keep-alive . 76
A.5 Air to ground ACARS message . 77
A.5.0 General . 77
A.5.1 AAGW Time Stamping . 77
A.6 Ground to air ACARS message . 78
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5 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
A.7 Satellite hand-over . 79
A.8 Out of Family SL coverage . 80
A.9 AGGW logs out aircraft due to return link inactivity . 81
A.10 AAGW detects unexpected PDP context disconnect . 81
A.11 AAGW detects loss of synchronisation to Family SL forward bearer . 82
A.12 AAGW detects forward link inactivity. 83
A.13 CMU asserts ACARS NOCOMM . 84
A.14 AGGW detects failure of CSP link . 85
A.15 AGGW receives message from aircraft in logged off state . 86
A.16 AGGW receives log-on request message from aircraft in logged on state . 87
A.17 Transition to higher preference service after timeout . 87
A.18 Transition to higher preference service after entering coverage region . 88
A.19 AAGW receives message from unexpected IP address. 88
A.20 AAGW receives invalid message . 89
A.21 CSP Ground to Air Ping . 89
A.22 AIGI Test Message . 90
A.23 Ground to Air Configuration Message . 90
A.24 AGGW receives message from aircraft when not serving an ocean region . 91
A.25 AGGW receives invalid message from AAGW . 91
A.26 AAGW Receives Uplink while Awaiting Response to a Downlink . 92
History . 94

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6 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://ipr.etsi.org).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Satellite Earth Stations and
Systems (SES).
The present document is part 4, sub-part 2 of a multi-part deliverable. Full details of the entire series can be found in
ETSI TS 102 744-1-1 [16].
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
This multi-part deliverable (Release 1) defines a satellite radio interface that provides UMTS services to users of mobile
terminals via geostationary (GEO) satellites in the frequency range 1 518,000 MHz to 1 559,000 MHz (downlink) and
1 626,500 MHz to 1 660,500 MHz and 1 668,000 MHz to 1 675,000 MHz (uplink).
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7 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
1 Scope
The present document specifies the mandatory requirements for the Aeronautical Safety Services for the Family SL
satellite network.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] ETSI TS 102 744-1-4: "Satellite Earth Stations and Systems (SES); Family SL Satellite Radio
Interface (Release 1); Part 1: General Specifications; Sub-part 4: Applicable External
Specifications, Symbols and Abbreviations".
[2] ICAO: "Global Operational Data Link Document (GOLD)", Appendix B.2 RCP 240 Specification,
June 2010.
[3] ARINC Characteristic 741P2-10 Aviation Satellite Communication System, Part 2: "System
Design and Equipment Functional Description", Jan 2009.
[4] ETSI TS 102 744-3-1: "Satellite Earth Stations and Systems (SES); Family SL Satellite Radio
Interface (Release 1); Part 3: Control Plane and User Plane Specifications; Sub-part 1: Bearer
Control Layer Interface".
[5] ICAO DOC 8643: "Aircraft Type Designators", Latest Version.
[6] ETSI TS 102 744-1-2: "Satellite Earth Stations and Systems (SES); Family SL Satellite Radio
Interface (Release 1); Part 1: General Specifications; Sub-part 2: System Operation Overview".
[7] ETSI TS 123 067 (V9.0.0): "Digital cellular telecommunications system (Phase 2+); Universal
Mobile Telecommunications System (UMTS); enhanced Multi-Level Precedence and Pre-emption
Service (eMLPP); Stage 2 (3GPP TS 23.067 version 9.0.0 Release 9)".
[8] ETSI TS 124 083 (V9.0.0): "Digital cellular telecommunications system (Phase 2+); Universal
Mobile Telecommunications System (UMTS); Call Waiting (CW) and Call Hold (HOLD)
supplementary services; Stage 3 (3GPP TS 24.083 version 9.0.0 Release 9)".
[9] IETF RFC 4412: "Communications Resource Priority for the Session Initiation Protocol (SIP)".
[10] ICAO SATCOM: "Voice Guidance Material (SVGM)", First Edition, July 2012.
[11] IETF RFC 3261: "SIP: Session Initiation Protocol".
[12] ETSI TS 124 081 (V9.0.0): "Digital cellular telecommunications system (Phase 2+); Universal
Mobile Telecommunications System (UMTS); Line Identification supplementary services; Stage 3
(3GPP TS 24.081 version 9.0.0 Release 9)".
[13] IETF RFC 3323: "A Privacy Mechanism for the Session Initiation Protocol (SIP)".
[14] ETSI TS 102 744-4-1: "Satellite Earth Stations and Systems (SES); Family SL Satellite Radio
Interface (Release 1); Part 4: Enhanced Services and Applications; Sub-part 1: Multiple Voice
Services".
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8 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
[15] ETSI TS 102 744-3-2: "Satellite Earth Stations and Systems (SES); Family SL Satellite Radio
Interface (Release 1); Part 3: Control Plane and User Plane Specifications; Sub-part 2: Bearer
Control Layer Operation".
[16] ETSI TS 102 744-1-1: "Satellite Earth Stations and Systems (SES); Family SL Satellite Radio
Interface (Release 1); Part 1: General Specifications; Sub-part 1: Services and Architectures".
[17] ETSI TS 124 008: " Digital cellular telecommunications system (Phase 2+); Universal Mobile
Telecommunications System (UMTS); LTE; Mobile radio interface Layer 3 specification; Core
network protocols; Stage 3 (3GPP TS 24.008)".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
Not applicable.
3 Symbols and abbreviations
3.1 Symbols
For the purposes of the present document, the symbols given in ETSI TS 102 744-1-4 [1], clause 3 apply.
3.2 Abbreviations
For the purposes of the present document, the abbreviations given in ETSI TS 102 744-1-4 [1], clause 3 apply.
4 Overview of Aeronautical Safety Services
4.1 General
The Aeronautical Safety Service provides the following safety services simultaneously via a single channel unit on an
aircraft to Class 6, Class 7 and Class 4 terminals:
• ACARS
• Prioritized IP data
• Voice (two channels)
The Aeronautical Safety Service is an application of the Family SL platform. ACARS and voice gateways are
introduced into the Airborne Earth Station (AES) and the peer gateways are introduced in the ground.
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9 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
Figure 4.1 provides an overview of the Aeronautical Safety Service architecture.

Figure 4.1: Aeronautical Safety Service Architecture
The elements comprising the block diagram in Figure 4.1 are defined in Table 4.1.
Table 4.1: Aeronautical Safety Architectural Elements
AAGW ACARS Aircraft Gateway - A functional block within the AES that is responsible for
that is responsible for choosing which satellite sub-network to use and for
encapsulating ACARS messages in a wrapper to allow them to be sent via the
Family SL network.
The aircraft gateway does not provide a guaranteed delivery of messages to (or
from) the ground gateway. Rather, it is responsible for ensuring a communications
link with the ground, where permitted by the AES resources and network
availability. The ultimate responsibility for ensuring message delivery is at the
ACARS messaging layer.
AGGW ACARS Ground gateway - The peer of the AAGW. This function is located on the
ground and provides a connection point to the Family SL network. The AGGW also
maintains a record of the log-on status of each aircraft, and monitors the
performance of the Family SL ACARS data service with respect to the
requirements of RCP240 in the ICAO GOLD Document [2].
AES Aircraft Earth Station. The equipment located on the aircraft that provides a
communication link via satellite. In the context of the present document, AES
relates to the entirety of the airborne system and Aeronautical Safety AES relates
to the Family SL channel within the AES providing the Aeronautical Safety service.
CMU Communication Management Unit. The equipment located on the aircraft that
interfaces with various pieces of radio equipment, including the AES. It is
responsible for routing data communications between the aircraft and the ground.
The CMU manages communication across multiple satellite and/or terrestrial links.
SAS Satellite Access Station. The entity on ground that connects terrestrial telephony
and data networks to the Family SL network.

4.2 Priority and Pre-emption
The Aeronautical Safety Service uses priority and pre-emption mechanisms provided within the Family SL
infrastructure to ensure that required service availability is maintained during network congestion scenarios.
4.3 ACARS
The Aircraft Communications Addressing and Reporting System (ACARS) is a digital data-link system for the
transmission of short, relatively simple messages between aircraft and ground stations via radio or satellite.
ACARS messages have the following characteristics:
Single block messages:
• Short ACARS messages can be transmitted as a single block of up to 238 bytes long, of which up to 220 bytes
is message content.
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10 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
Multi-block messages:
• Longer messages may be split up into a number of standard length ACARS blocks. These are sent one at a
time in sequence over the radio sub-network. The ACARS protocol demands that an acknowledgement for
each block is received before the next block in the sequence is sent.
Larger message blocks:
• Message blocks of a larger size (known as super-blocks) may be sent. The use of larger block sizes is not
supported by the Aeronautical Safety service.
The Aeronautical Safety ACARS service is based on using the Background Class Radio Access Bearers (augmented
with priority) with air and ground gateways surrounding it. These gateways encapsulate the ACARS messages in
IP/UDP packets, as well as performing the key function of determining link failure, and thus enabling a switch to
alternate networks supporting aeronautical safety services.
The Aeronautical Safety ACARS service shall meet the communication performance requirements specified in
Appendix B of ICAO's GOLD requirements (Global Operations data Link Document) [2]. The GOLD document [2]
uses the concept of performance measurement against defined RCP (Required Communication Performance) criteria.
The ACARS system design also includes the ability to measure delays and analyse performance as implied by GOLD,
at both the ACARS and FANS levels.
A position reporting service is provided as part of the technical implementation of ACARS.
4.4 Voice
The Aeronautical Safety voice service provides two channels of cockpit voice, call priority and pre-emption both at the
UE and in network congestion scenarios. The AES is responsible for 'Intra-AES' pre-emption for both air-to-ground and
ground-to-air calls. The Aeronautical Safety voice service can also provide Caller Line Identity for mobile terminated
(ground-to-air) and mobile originated (air-to-ground) calls. Ground-to-air calls are delivered to the Family SL network
by Communication Service Providers (CSP) using a number format that includes the 24 bit ICAO AES ID and a priority
indication. Air-to-ground calls are delivered into the PSTN. Two voice channels are provided per Family SL 200 kHz
channel on an aircraft. The first call uses the CS domain, and the second call uses Voice over IP (VoIP) on the PS
domain if the CS domain is busy. The use of VoIP is transparent to CSPs and pilots.
4.5 Prioritized IP
The key characteristic of the prioritized IP service is the ability to request and deliver higher priority on the air interface
between the RAN and the Aeronautical AES. The AES only offers such a service on cockpit Ethernet ports to ensure
that cockpit service cannot be flooded by cabin IP traffic. Further, the USIM cards will be provisioned (activated) such
that they contain a 'ceiling' for the level of priority that the RAN will deliver to that terminal.
5 ACARS Data Service
5.1 Aeronautical Safety ACARS data service overview
This clause provides some information on the ACARS data service and the functional elements that together provide the
Aeronautical Safety ACARS service.
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11 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
A diagram showing peer-peer communications within the system is shown in Figure 5.1.

Figure 5.1: ACARS Air and Ground Stacks
5.2 AAGW Design Description
The use cases defined in Annex A prescribe the mandatory requirements for the Aeronautical Safety AES and AAGW
providing the Aeronautical Safety ACARS data service capability.
This clause provides an SDL description of an AAGW design that satisfies the normative requirements of the use cases
in Annex A.
Figure 5.2 provides a key to the SDL descriptions in this clause. The AIGI message types referred to in the SDL
descriptions are listed in clause 5.3.
The AAGW state transitions are illustrated in Figure 5.3, while the procedures operating between the different states are
illustrated in Figures 5.4 to 5.18. A mapping between the state transitions and the relevant figures in this clause is
provided in Table 5.1.
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12 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
Table 5.1: Mapping of state transitions to figures
State Transition Main Events (not all events or Figure
From To branches listed)
Idle AES Camped Acquire satellite link Figure 5.4
Camped AES Registered and Attached Register and attach successful Figure 5.5
Camped Idle Register and attach failed Figure 5.5
AES Registered and Attached DNS Lookup PDP Context Successful Figure 5.6
AES Registered and Attached Idle PDP Context Failure Figure 5.6
DNS Lookup ACARS Login DNS Response Figure 5.7
DNS Lookup Idle DNS Response timeout Figure 5.7
ACARS Login ACARS Logged In Logon response from AGGW Figure 5.8
ACARS Login Idle Logon response timeout Figure 5.8
ACARS Logged In ACARS Logged In Generic handling of messages Figure 5.9
from AGGW
ACARS Logged In ACARS Logged In ACARS message from CMU Figure 5.10
ACARS ack from AGGW
ACARS ack timeout
ACARS Logged In ACARS Logged In Keepalive received from AGGW Figure 5.11
AIGI test message received from
AGGW
Ping sent from AGGW originated
by CSP
ACARS Logged In ACARS Logging Off Transition to NOCOMM from CMU Figure 5.12
ACARS Logged In Idle Logoff notification from AGGW Figure 5.13
PDP Disconnect from CMU
ACARS Logged In ACARS Login Logoff notification from AGGW Figure 5.13
ACARS Logged In AES Registered and Attached PDP Disconnect from CMU Figure 5.13
ACARS Logged In ACARS Logging Off Handover imminent (higher Figure 5.14
preference link available)
Edge of coverage reached
ACARS Logged In ACARS Login Timeout of keepalive ack Figure 5.15
ACARS Logged In ACARS Logging Off Aircrew termination Figure 5.16
Higher preference link available
ACARS Logged In Idle Loss of sync with forward bearer Figure 5.16
ACARS Logging Off Idle Logoff ack received from ground Figure 5.17
(loss of coverage)
ACARS Logging Off AES Camped Logoff ack received from ground Figure 5.17
(satellite change)
ACARS Logging Off Idle Logoff ack received from ground Figure 5.18
(NOCOMM)
Logoff ack received from ground
(dwell timer)
ACARS Logging Off ACARS Login Logoff ack received from ground Figure 5.18
(dwell timer)
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13 ETSI TS 102 744-4-2 V1.1.1 (2015-10)

Figure 5.2: SDL Legend
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14 ETSI TS 102 744-4-2 V1.1.1 (2015-10)

NOTE: This state transition diagram does not show transitions to stay in the same state, nor does it show the
AAGW Message Generic Handling.

Figure 5.3: State transitions
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15 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
Preconditions: No link to
Initial / Starting State
IDLE ground in place. A list of
Logon_Flag = TRUE
(No link to previously failed links may
ground) be available. A list of
possible links is available.
See note 1
Sort list of
available
satellites
Reset list to
Remove from
include
list failed
previously
satellites
failed links
Yes
Remove from
list out of
coverage
satellites
No
Acquire link
Other
of highest
link(s)
preference
available
satellite
Proceed to
Yes Camped /
login on Mark link as
(alternate Fwd Link No
alternate link failed
link) Sync
(see note 2)
Yes (Family SL)
The AES has camped on
to a Family SL forward
bearer or obtained frame Register and
locks with the forward Attach to
channel of an alternate Network
link and validated the
system table
AES Camped
NOTE 1: The behaviour is informational. It is expected to be manufacturer specific.
NOTE 2: Manufacturer specific transition to alternate link is outside of these state machines.

Figure 5.4: Idle
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16 ETSI TS 102 744-4-2 V1.1.1 (2015-10)

Figure 5.5: AES camped
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17 ETSI TS 102 744-4-2 V1.1.1 (2015-10)

Figure 5.6: AES registered and attached

ETSI
18 ETSI TS 102 744-4-2 V1.1.1 (2015-10)

Figure 5.7: AES DNS look-up
ETSI
19 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
ACARS Login
AC_T2 Logon Back
gw_logon_rp gw_logon_rp Off Timeout Other Other
Timeout AC_T3
ACARS
Stop AC_T2 LOGON_
>=AC_R5 Logon Discard
ac_logon_rp CNT
ac_logon_rq
No
(Not Permanent
Failure)
Start Logon
No Logon Mark link as Start AC_T2
Back Off
(Permanent Failure) Succesful failed
gw_logon_rp
Timer AC_T3
Yes
IDLE
Mark link as Reset link Increment
(No link to
failed counters LOGON_CNT
ground)
Start
IDLE
AC_T1 (KA)
(No link to
AC_T4
ground)
(Dwell)
Clear
NOCOMM
ACARS
Logged In
Figure 5.8: ACARS log-in
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20 ETSI TS 102 744-4-2 V1.1.1 (2015-10)

NOTE 1: This diagram shows the generic message handling that applies to all messages received from the AGGW
by the AAGW in the 'ACARS Logged In' and 'Logging Off' state. To show this behaviour for each message
in the following diagrams would distract from the flow and be repetitious. It is an implementation detail on
how this behaviour is handled across the states for which the behaviour is applicable.
NOTE 2: This is the expected processing path, with the message passed/returned to the appropriate state.

Figure 5.9: AAGW generic message handling

ETSI
21 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
ACARS
Logged In
(1 of 7)
AC_T2
A2G ACARS g W_acars_ack gw_acars_ac
k TImeout
Timestamp Stop
and wrap as AC_T2 RETX_CN
>=AC_R3
ac_acars_ms gw_acars_ac T?
g k
(original)
ac_acars_ms
ac_acars_ms
g
g
Increment
ac_acars_ms
RETX_CNT
g
Start
RETX_CNT = AC_T2
0 gw_acars_ac
k
Start
AC_T2
gw_acars_ac
k
Figure 5.10: ACARS logged in (1)

ETSI
22 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
ACARS
Logged In
(2 of 7)
gw_keepalive gw_test_msg gw_csp_ping
ac_keepalive ac_csp_ping_
ac_test_ack
_ack ack
Figure 5.11: ACARS logged in (2)

ETSI
23 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
ACARS
Logged In
(3 of 7)
Transition to
NOCOMM gw_conf gw_acars_msg
(from CMU)
Sequence
NOCOMM (to Update
Number?
CMU) Config
Valid
(greater than current)
Delivery Time
ac_logoff_rq
ac_conf_ack
+ Sequence
(NOCOMM)
Number
Duplicate
(allowing
Send ACARS
LOGOFF_CN for Modulo
to CMU
Counter wrap)
T = 1
Start AC_T2 Build / Store
gw_logoff_ac ac_acars_ack
k (NOCOMM) (see note 1)
ACARS ac_acars_ack
Logging Off (see note 2)
NOTE 1: Include timestamp delivery time.
NOTE 2: Tx stored original if applicable.

Figure 5.12: ACARS logged in (3)

ETSI
24 ETSI TS 102 744-4-2 V1.1.1 (2015-10)
ACARS
Logged In
(4 of 7)
PDP
gw_logoff_notify
Disconnect
AC_T3 Indicate
0xFFFE Msg 0xFFFF NOCOMM to
Setting? CMU
0x0000
Disable
Stop all
Indicate
AC_T3
AC_T3 Timer
timers / Reset
NOCOMM to
Unchanged
(see notes 1
all counters
CMU
and 4)
0 < AC_T3
< 0xFFFE
Indicate PDP
Indicate Stop all
Family SL Permanent
NOCOMM to Cause
NOCOMM to timers / Reset
Disconnect
CMU Code?
CMU all counters
Temp failure
Stop all
Mark all
Stop all
Create PDP
LOGON_CNT
timers / Reset
Family SL
timers / Reset
Context
= 0
all counters
links as failed
all counters
Mark all
PDP_Creatio IDLE
ACARS
LOGON_CNT
Family SL
n_Attempts = (No link to
Logon
= 0
links as failed
0 ground)
ac_logon_rq
(see note 2)
Start AC_T3 AES
IDLE
Start AC_T2
(see notes 3 Registered
(No link to
ac_logon_rq
and 4) and Attached
ground)
ACARS Login
ACARS Login
NOTE 1: Not start at all if required to be disabled - implementation can determine the best way to approach this.
NOTE 2: This still allows/leaves an alternative link as a carrier in the list.
NOTE 3: Timer implementation may not support 0 so alternative approaches might be sought - very short timer or
logon_flag manipulation.
NOTE 4: This is a temporary change to the AC_T3. After initiating the timer, the value of AC_T3 will revert to that
configured/default.
Figure 5.13: ACARS logged in (4)
ETSI
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