CS ACNS.B.DLS.B1.100 Network Layer Requirements
ED Decision 2013/031/R
(See AMC1 ACNS.B.DLS.B1.100 and GM1 ACNS.B.DLS.B1.100)
The ATN Router conforms to Class 6 with the capability to support Inter-domain routing protocol (IDRP) .
AMC1 ACNS.B.DLS.B1.100 Network Layer Requirements
ED Decision 2013/031/R
The ATN Router should comply with ICAO Document 9705 (Edition 2), sections 5.2.4.1, 5.2.4.3 with an IDRP Hold Time value of 900 seconds.
GM1 ACNS.B.DLS.B1.100 Network Layer Requirements
ED Decision 2013/031/R
Compression Schemes
Airborne ATN Router may implement several distinct, yet complementary, compression schemes.
Airborne ATN Routers should support the CLNP Header Compression (also known as ‘LREF Compression’). Other compression schemes in ICS are optional.
In addition to the CLNP Header Compression, data link ATN Routers that claims support for optional DEFLATE compression should also support ICAO PDU M0070002 (‘Interoperability impact when deflate compression is used. Non-compliance with Zlib’).
CS ACNS.B.DLS.B1.105 Transport Layer Protocol Requirements
ED Decision 2013/031/R
(See AMC1 ACNS.B.DLS.B1.105 and GM1 ACNS.B.DLS.B1.105)
The ATN Connection Oriented Transport Protocol (COTP), conforms to Transport Protocol Class 4.
AMC1 ACNS.B.DLS.B1.105 Transport Layer Requirements
ED Decision 2013/031/R
The ATN End System of the data link aircraft equipment should comply with the Transport Protocol Class 4 specified in ICAO Document 9705 (Edition 2), Sub-volume V, section 5.5.2.
The data link aircraft equipment should implement Transport Protocol Class 4 parameter settings in accordance with the following table:
|
Scope |
Parameter |
Definition |
Value |
|
Inactivity |
Inactivity time (I) |
A bound for the time after which a transport entity will, if it does not receive a Transport Protocol Data Unit (TPDU), initiate the release procedure to terminate the transport connection. |
360 sec |
|
Re-transmission |
Retransmission time (T1) |
A bound for the maximum time the transport entity will wait for acknowledgement before re-transmitting a TPDU. The retransmission time is adaptive. |
Initial value 30 sec |
|
|
Maximum Retransmission (N) |
Maximum number of TPDU retransmissions. |
7 |
|
Window |
Window time (W) |
A bound for the maximum time a transport entity will wait before retransmitting up-to-date window information. |
120 sec |
|
Flow Control |
Local Acknowledgement delay (Al) |
A bound for the maximum time which can elapse between the receipt of a TPDU by the local transport entity from the network layer and the transmission of the corresponding acknowledgement. |
1 sec |
GM1 ACNS.B.DLS.B1.105 Transport Layer Requirements
ED Decision 2013/031/R
Transport Protocol Classes
ICAO Doc 9705 (Edition 2), Sub-volume V, section 5.5 identifies both Connection Oriented and Connection-Less Transport Protocols (as specified in, respectively, ISO/IEC 8073 for COTP and ISO/IEC 8602 for CLTP). The only mandated support is for COTP (i.e. CLTP support is not required).
In addition, ISO/IEC 8073 identifies 5 distinct possible implementations for COTP support, ranging from Class 0 (the less constraining to implement, but also the less reliable) to Class 4 (most reliable). The fifth Class, i.e. COTP Class 4 (also known as ’TP4’), is the only mandated implementation (all other implementations classes are useless for the ATN COTP support).
Transport Protocol Classes
In the ATN Baseline 1 SARPS (i.e. Doc 9705, Edition 2), the Transport Class 4 - as known as TP4 - is as specified in ISO 8073, that mandates support for a 16-bits checksum. Such checksum is considered to be insufficient to detect, and thus compensate, all potential miss deliveries of CLNP Packets by the underlying network routers. The analysis that concluded of TP4 inability to detect and compensate all CLNP miss deliveries is available in ICAO PDR M00040002. The use of a 32-bits long checksum is identified as a solution to address this potential issue.
CS ACNS.B.DLS.B1.110 Session Layer Requirement
ED Decision 2013/031/R
(See AMC1 ACNS.B.DLS.B1.110)
ATN Session protocol is capable of supporting the following session protocol data units (SPDUs):
|
Abbreviation |
Full SPDU Name |
|
SCN |
Short Connect |
|
DRPSAC |
Short Accept |
|
SACC |
Short Accept Continue |
|
SRF |
Short Refuse |
|
SRFC |
Short Refuse Continue |
AMC1 ACNS.B.DLS.B1.110 Session Layer Requirement
ED Decision 2013/031/R
(a) The ATN End System of the data link aircraft equipment should support a Session Protocol as specified in ICAO Doc 9705 (Edition 2), Sub-Volume IV, section 4.4 including the ISO/IEC 8327 Technical Corrigendum 1 (2002), listed in the following table.
|
Value (Hex) |
Abbreviation |
Full SPDU Name |
|
E8 |
SCN |
Short Connect |
|
F0 |
SAC |
Short Accept |
|
D8 |
SACC |
Short Accept Continue |
|
E0-E3 |
SRF |
Short Refuse
E0: TC retained, transient refusal |
|
A0 |
SRFC |
Short Refuse Continue |
(b) The ATN End System Session Protocol of the data link system should make use of the value ‘E3’ to encode the Short Refuse (SRF) SPDU.
CS ACNS.B.DLS.B1.115 Presentation layer requirements
ED Decision 2022/008/R
(See AMC1 ACNS.B.DLS.B1.115)
The ATN Presentation protocol is capable of supporting the presentation protocol data units (PPDUs) listed in the following table:
|
Abbreviation |
Full PPDU Name |
|
SHORT-CP |
Short Presentation Connect, unaligned PER |
|
SHORT-CPA |
Short Presentation Connect Accept, unaligned PER |
|
SHORT-CPR |
Short Presentation Connect Reject |
[Issue: CS-ACNS/4]
AMC1 ACNS.B.DLS.B1.115 Presentation Layer Requirement
ED Decision 2013/031/R
(a) The ATN End System of the data link aircraft equipment should support a Presentation Protocol as specified in ICAO Doc 9705 (Edition 2), Sub-Volume IV, section 4.5, and listed in the following table:
|
Value (Hex) |
Abbreviation |
Full PPDU Name |
|
02 |
SHORT-CP |
Short Presentation Connect, unaligned PER |
|
02 |
SHORT-CPA |
Short Presentation Connect Accept, unaligned PER |
|
x2 |
SHORT-CPR |
Short Presentation Connect Reject
Where x = reason code: |
(b) The ATN End System Presentation Protocol of the data link aircraft equipment should make use of the value ‘02’ to encode the SHORT-CPR PPDU.
CS ACNS.B.DLS.B1.120 Application Layer Requirements
ED Decision 2013/031/R
(See AMC1 ACNS.B.DLS.B1.120 and GM1 ACNS.B.DLS.B1.120)
The Application Layer is application-independent (also known as ‘Layer 7a’), and composed of a Convergence Function supporting operations of an Application Control Service Element (ACSE).
AMC1 ACNS.B.DLS.B1.120 Application Layer Requirements
ED Decision 2013/031/R
(a) The ATN End System of the data link system should support an ATN Convergence Function compliant with ICAO Doc 9705 (Edition 2), Sub-volume IV, section 4.3.
(b) The ATN End System of the data link system should support an ATN Association Control Service Element (ACSE) compliant with ICAO Doc 9705 (Edition 2), Sub-volume IV, section 4.6.
GM1 ACNS.B.DLS.B1.120 Application Layer Requirements
ED Decision 2013/031/R
From an OSI perspective, the ATN Application layer is composed of three distinct parts:
— Layer 7a, that includes all application-independent services (Convergence Function + ACSE).
— Layer 7b, that includes all application-dependent service elements (such as the CPDLC-ASE).
— Layer 7c, that includes applications (such as the CPDLC application, that uses CPDLC-ASE for its communications with ground-based systems).
ED Decision 2013/031/R
The Network Service Access Point (NSAP) address database is capable of being updated.