ACP – WGN07-WP19

AERONAUTICAL COMMUNICATIONS PANEL (ACP)

Working Group N - Networking

Bangkok, 29th January – 2nd February 2007 (Seventh Meeting)

Agenda Item 9.1:
Monitoring of implementation activities and resulting actions: ATN and AMHS

IPSNDCF Validation Experiment by ENRI

Prepared by:Japan
Presented by: Ken Itano

Summary

The Electronic Navigation Research Institute (ENRI) has implemented prototype IP sub-network convergence function (IP SNDCF) for IPv4 and IPv6 in its experimental ATN routers, and carried out an evaluation experiment of inter-domain communications over IP sub-networks. This information paper reports on the results of these experiments, and on future plans.

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IP SNDCF Validation Experiment by ENRIACP WGN07 (Bangkok, 29 Jan – 2 Feb 2007)

1.Introduction

1.1.Overview

The Electronic Navigation Research Institute (ENRI) of Japan has implemented the sub-network dependent convergence function for Internet Protocol sub-networks (IP SNDCF) based on the draft technical and guidance material [1, 2] in experimental ATN routers, and in January 2007 conducted an internal test based on the French and EUROCONTROL validation initiatives reported previously [3, 4].

This paper reports on the results of these internal tests, and ENRI’s future IP SNDCF development and test plans.

1.2.References

[1]Whyman, A., Proposed SARPs for the IP SNDCF, Issue 2.0.

[2]Whyman, A., Proposed Guidance Material in Support of the IP SNDCF, Issue 1.0.
DIS/COM/ProATN_Sup/DCI/AW_120.

[3]ProATN TAR-TTS IPSNDCFValidationReport, Issue 1.2, 10 May 2004.

[4]French IP SNDCF Validation Initiative, ACP WGN04-WP11, 2 November 2004.

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IP SNDCF Validation Experiment by ENRIACP WGN07 (Bangkok, 29 Jan – 2 Feb 2007)

2.Experiment

2.1.Objectives

The purpose of this experiment was to verify ATN communication between Boundary Intermediate Systems (BIS) in different domains using IPv4 and IPv6 sub-networks. Objectives are listed below.

(1)Verify operation of ISO/IEC 10747 (Inter-Domain Routeing Protocol) over IP sub-network in different network configurations.

a)IDRP connection establishment.

b)IDRP connection termination.

c)Route propagation (advertisement of NLRI).

d)ER-PDU notification of unreachable destination NSAP.

(2)Data transfer of ISO/IEC 8473 (Connectionless Network Protocol) Network Protocol Data Units (NPDU).

a)Communication of CLNP NPDUs between End Systems (ES) via BIS routers (using the CLNP Echo function).

b)Relay by BIS router of CLNP NPDUs among ISO/IEC 8208 / X.25 Wide Area Network (WAN), ISO/IEC8802 Local Area Network (LAN), and IP sub-networks.

(3)Failure cases.

a)Recovery from circuit failure (loss of path through sub-network)

(4)Verify operation of IP SNDCF over different types of IP sub-network.

a)ISO/IEC 8802 LAN circuit

b)Serial IP circuit

The experiment was carried out in three configurations for IPv4 and IPv6 sub-networks.

Experiment Configuration 1 (Figure 1): Two End Routeing Domains (ERD) linked by an intermediate Transit Routeing Domain (TRD) using IP sub-network connections.

Experiment Configuration 2 (Figure 2): ‘Triangle’ of three Boundary Intermediate Systems (BIS), each with an IP sub-network connection to the other two BISs. (Simplest “fully meshed” network.)

Experiment Configuration 3: As Experiment Configuration 1, but with one ISO/IEC 8208 point-to-point sub-network connection and one IP sub-network connection. In the IPv4 case (Figure 3), the IP sub-network connection is over a 64 kbps serial connection through a pair of IP routers. In the IPv6 case (Figure 4), it is a direct Ethernet connection.

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IP SNDCF Validation Experiment by ENRI ACP WGN07 (Bangkok, 29 Jan – 2 Feb 2007)

Figure 1 Experiment Configuration 1

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IP SNDCF Validation Experiment by ENRI ACP WGN07 (Bangkok, 29 Jan – 2 Feb 2007)

Figure 2 Experiment Configuration 2

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IP SNDCF Validation Experiment by ENRI ACP WGN07 (Bangkok, 29 Jan – 2 Feb 2007)

Figure 3 Experiment Configuration 3 (IPv4)

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IP SNDCF Validation Experiment by ENRI ACP WGN07 (Bangkok, 29 Jan – 2 Feb 2007)

Figure 4 Experiment Configuration 3 (IPv6)

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IP SNDCF Validation Experiment by ENRI ACP WGN07 (Bangkok, 29 Jan – 2 Feb 2007)

2.2.Protocol Stack

Figure 5 shows the protocol stacks of the ATN routers and IP routers for Experiment Configuration 3 (IPv4).

Figure 5 Router Protocol Stacks for Experiment Configuration 3 (IPv4)

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IP SNDCF Validation Experiment by ENRI ACP WGN07 (Bangkok, 29 Jan – 2 Feb 2007)

2.3.Scope Limits

The following were beyond the scope of this test, and were not carried out.

End-to-end ATN transport connection between End Systems via ATN router.

Configurations with overlapping Routeing Domain Confederations.

IP sub-networks with multiple connection paths.

Communication between different BIS router implementations.

Sub-network encryption (IPsec).

Simultaneous use of IPv4 and IPv6 sub-networks.

2.4.Apparatus

The following apparatus were used.

ATN Router / Oki Electric Industry Ground-Ground ATN Router for Linux, version 1.20
Operating system / Red Hat Enterprise Linux 2.1 ES or WS
Hardware / Hewlett-Packard ML370 server (Intel Xeon 3.2 GHz) or
Hewlett-Packard Vectra desktop (Intel Pentium III 750 MHz)
Protocols / IDRP, ES-IS, IS-IS, CLNP
Sub-networks: ISO/IEC 8802, ISO/IEC 8208, IPv4, IPv6
(ICAO Doc. 9705 Edition 3, sub-volume V).
End System / Oki Electric Industry ATN end systems (CM, D-FIS, CPDLC, ADS)
ULCS / ULCS (ICAO Doc 9705 Edition 2) or
ULCS (ICAO Doc 9705 Edition 3 + ATN security)
ICS / CLNP, ES-IS
Sub-networks: ISO/IEC 8802, ISO/IEC 8208
Operating system / Microsoft Windows NT 4.0 SP5
Hardware / Compaq desktop (Intel Pentium 4)
IP router / “Linux PC”
Operating system / RHEL 2.1 WS
Hardware / HP Vectra desktop (Intel Pentium III 750 MHz)
Serial communication / Sangoma S5141 serial card, Sangoma wanrouter driver supporting IP over PPP.

The ATN router and End System have built-in logging capability for CLNP PDUs, IDRP RPDUs and sub-network (X.25, IP) packets, and also log routeing information base (RIB) changes.

In addition, a notebook personal computer with packet-sniffing software was connected to the Ethernet LAN networks for packet capture and analysis.

All LAN connections were using 10/100BASE-TX Ethernet through Ethernet hubs. This restricted LAN communication to 10 Mbps, but allowed the capture of all Ethernet frames passing over the LAN with a packet sniffer.

In Experiment Configuration 3, 64 kbps serial links were used between IP routers.

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IP SNDCF Validation Experiment by ENRI ACP WGN07 (Bangkok, 29 Jan – 2 Feb 2007)

3.Test Items

This section details the test items carried out in each configuration. Each test is repeated for IPv4 and IPv6 sub-network connections.

3.1.Experiment Configuration 1

1 / BIS Connection
Initial condition: No IDRP connections established between BIS routers.
1-1 / Establish IDRP adjacency between BIS#1 and BIS#2. (BIS#1 sends OPEN PDU.)
Confirm that NLRI of RD#2 is registered in BIS#1, and NLRI of RD#1 is registered in BIS#2.
Confirm that KEEPALIVE PDUs are exchanged at one-minute intervals.
1-2 / Establish IDRP adjacency between BIS#3 and BIS#2. (BIS#2 sends OPEN PDU.)
Confirm that NLRI of RD#2 is registered in BIS#3, and NLRI of RD#3 is registered in BIS#2.
Confirm that NLRI for RD#1 is communicated to BIS#3 by UPDATE PDU from BIS#2 to BIS#3, and that NLRI for RD#3 is communicated to BIS#1 by UPDATE PDU from BIS#2 to BIS#1.
Confirm that KEEPALIVE PDUs are exchanged at one-minute intervals.
2 / BIS Disconnection
Initial condition: IDRP connections established between BIS#1 and BIS#2, and between BIS#2 and BIS#3.
2-1 / Terminate adjacency between BIS#1 and BIS#2. (BIS#1 sends CEASE PDU.)
Confirm that NLRI for RD#1 is deleted from BIS#2, and NLRI for RD#2 and RD#3 are deleted from BIS #1.
2-2 / Confirm that NLRI for RD#1 is removed from BIS#3.
2-3 / Terminate adjacency between BIS#3 and BIS#2. (BIS#3 sends CEASE PDU.)
Confirm that NLRI for RD#2 is deleted from BIS#3, and NLRI for RD#3 is deleted from BIS#2.
3 / Data Relay
Data Relay to Adjacent RD
Initial condition: IDRP connections established between BIS#1 and BIS#2, and between BIS#2 and BIS#3. ES-IS connections established between each BIS and its corresponding ES.
3-1 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#1 to ES#2. Confirm that a corresponding ERP-NPDU is transmitted from ES#2 to ES#1.
3-2 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#2 to ES#1. Confirm that a corresponding ERP-NPDU is transmitted from ES#1 to ES#2.
Data Relay via TRD
Initial condition: IDRP connections established between BIS#1 and BIS#2, and between BIS#2 and BIS#3. ES-IS connections established between each BIS and its corresponding ES.
3-3 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#1 to ES#3. Confirm that a corresponding ERP-NPDU is transmitted from ES#3 to ES#1.
3-4 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#3 to ES#1. Confirm that a corresponding ERP-NPDU is transmitted from ES#1 to ES#3.
4 / Routeing
Initial condition: IDRP connections established between BIS#1 and BIS#2, and between BIS#2 and BIS#3. ES-IS connections established between each BIS and its corresponding ES.
4-1 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#1 to a non-existent NSAP in RD#3. Confirm that BIS#3 sends an ER-NPDU to ES#1.
4-2 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#3 to a non-existent NSAP in RD#1. Confirm that BIS#1 sends an ER-NPDU to ES#3.
5 / Failure/Recovery
Initial condition: IDRP connections established between BIS#1 and BIS#2, and between BIS#2 and BIS#3.
5-1 / Disconnect the physical connection between BIS#1 and BIS#2.
Confirm that IDRP hold timer times out, and the adjacency between BIS#1 and BIS#2 is closed.
Confirm that NLRI for RD#1 is deleted from BIS#2.
Confirm that NLRI for RD#2 is deleted from BIS#1.
Confirm that NLRI for RD#1 is deleted from BIS#3, communicated by UPDATE PDU.
5-2 / Reconnect physical connection between BIS#1 and BIS#2.
Confirm that the adjacency is automatically re-established.
Confirm that NLRI for RD#1 is added to BIS#2.
Confirm that NLRI for RD#2 is added to BIS#1.
Confirm that NLRI for RD#1 is added to BIS#3, communicated by UPDATE PDU.

3.2.Experiment Configuration 2

1 / BIS Connection
Initial condition: No IDRP connections established between BIS routers.
1-1 / Establish IDRP adjacency between BIS#1 and BIS#2. (BIS#1 sends OPEN PDU.)
Confirm that NLRI of RD#2 is registered in BIS#1, and NLRI of RD#1 is registered in BIS#2.
Confirm that KEEPALIVE PDUs are exchanged at one-minute intervals.
1-2 / Establish IDRP adjacency between BIS#3 and BIS#2. (BIS#2 sends OPEN PDU.)
Confirm that NLRI of RD#2 is registered in BIS#3, and NLRI of RD#3 is registered in BIS#2.
Confirm that NLRI for RD#1 is communicated to BIS#3 by UPDATE PDU from BIS#2 to BIS#3, and that NLRI for RD#3 is communicated to BIS#1 by UPDATE PDU from BIS#2 to BIS#1.
Confirm that KEEPALIVE PDUs are exchanged at one-minute intervals.
1-3 / Establish IDRP adjacency between BIS#1 and BIS#3. (BIS#1 sends OPEN PDU.)
Confirm that UPDATE PDUs correctly send NLRI information for each RD from BIS#1 to BIS#3 and from BIS#3 to BIS#1.
2 / BIS Disconnection
Initial condition: IDRP connections established from each BIS router to its two adjacent peers.
2-1 / Terminate adjacency between BIS#1 and BIS#2. (BIS#1 sends CEASE PDU.)
Confirm that the IDRP connection is terminated.
Confirm that NLRI for RD2 in BIS#1 indicates reachability via BIS#3.
Confirm that NLRI for RD1 in BIS#2 indicates reachability via BIS#3.
3 / Data Relay
Data Relay to Adjacent RD
Initial condition: IDRP connections established from each BIS router to its two adjacent peers. ES-IS connections established between each BIS and its corresponding ES.
3-1 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#1 to ES#2.
Confirm that the ERQ-NPDU is transmitted via BIS#1 and BIS#2.
Confirm that a corresponding ERP-NPDU is transmitted from ES#2 to ES#1 via BIS#2 and BIS#1.
3-2 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#2 to ES#1.
Confirm that the ERQ-NPDU is transmitted via BIS#2 and BIS#1.
Confirm that a corresponding ERP-NPDU is transmitted from ES#1 to ES#2 via BIS#1 and BIS#2.
3-3 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#1 to ES#3.
Confirm that the ERQ-NPDU is transmitted via BIS#1 and BIS#3.
Confirm that a corresponding ERP-NPDU is transmitted from ES#3 to ES#1 via BIS#3 and BIS#1.
3-4 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#3 to ES#1.
Confirm that the ERQ-NPDU is transmitted via BIS#3 and BIS#1.
Confirm that a corresponding ERP-NPDU is transmitted from ES#1 to ES#3 via BIS#1 and BIS#3.
Data Relay via TRD
Initial condition: IDRP adjacencies established between BIS#1 and BIS#3 and BIS#2 and BIS#3. No adjacency established between BIS#1 and BIS#2. ES-IS connections established between each BIS and its corresponding ES.
3-5 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#1 to ES#2.
Confirm that the ERQ-NPDU is transmitted via BIS#1, BIS#3 and BIS#2.
Confirm that a corresponding ERP-NPDU is transmitted from ES#2 to ES#1 via BIS#2, BIS#3 and BIS#1.
3-6 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#2 to ES#1.
Confirm that the ERQ-NPDU is transmitted via BIS#2, BIS#3 and BIS#1.
Confirm that a corresponding ERP-NPDU is transmitted from ES#1 to ES#2 via BIS#1, BIS#3 and BIS#2.
4 / Routeing
Initial condition: IDRP adjacencies established between BIS#1 and BIS#3 and BIS#2 and BIS#3. No adjacency established between BIS#1 and BIS#2. ES-IS connections established between each BIS and its corresponding ES.
4-1 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#1 to a non-existent NSAP in RD#2.
Confirm that BIS#2 sends an ER-NPDU to ES#1 via BIS#3.
4-2 / Using the CLNP ECHO function, send an ERQ-NPDU from ES#2 to a non-existent NSAP in RD#1.
Confirm that BIS#1 sends an ER-NPDU to ES#2 via BIS#3.
5 / Failure/Recovery
Initial condition: IDRP connections established from each BIS router to its two adjacent peers.
5-1 / Disconnect the physical connection between BIS#1 and BIS#2.
Confirm that IDRP hold timer times out, and the adjacency between BIS#1 and BIS#2 is closed.
Confirm that NLRI of each BIS is updated accordingly.
5-2 / Reconnect physical connection between BIS#1 and BIS#2.
Confirm that the adjacency is automatically re-established.
Confirm that NLRI of each BIS is updated accordingly.

3.3.Experiment Configuration 3

Tests 1–4 are the same as in Experiment Configuration 1, and are omitted here.

5 / Failure/Recovery
IP subnetwork connection failure
Initial condition: IDRP connections established between BIS#1 and BIS#2 over IP subnetwork, and between BIS#2 and BIS#3 over X.25 subnetwork.
5-1 / Disconnect the physical connection between IP router#1 and IP router#2.
Confirm that IDRP hold timer times out, and the adjacency between BIS#1 and BIS#2 is closed.
Confirm that NLRI for RD#1 is deleted from BIS#2.
Confirm that NLRI for RD#2 is deleted from BIS#1.
Confirm that NLRI for RD#1 is deleted from BIS#3, communicated by UPDATE PDU.
5-2 / Reconnect physical connection between IP routert#1 and IP router#2.
Confirm that the adjacency is automatically re-established.
Confirm that NLRI for RD#1 is added to BIS#2.
Confirm that NLRI for RD#2 is added to BIS#1.
Confirm that NLRI for RD#1 is added to BIS#3, communicated by UPDATE PDU.
X.25 subnetwork connection failure
Initial condition: IDRP connections established between BIS#1 and BIS#2 over IP subnetwork, and between BIS#2 and BIS#3 over X.25 subnetwork.
5-3 / Disconnect the physical connection between BIS#2 and BIS#3.
Confirm that IDRP hold timer times out, and the adjacency between BIS#2 and BIS#3 is closed.
Confirm that NLRI for RD#3 is deleted from BIS#2.
Confirm that NLRI for RD#2 is deleted from BIS#3.
Confirm that NLRI for RD#3 is deleted from BIS#1, communicated by UPDATE PDU.
5-4 / Reconnect physical connection between BIS#2 and BIS#3.
Confirm that the adjacency is automatically re-established.
Confirm that NLRI for RD#3 is added to BIS#2.
Confirm that NLRI for RD#2 is added to BIS#3.
Confirm that NLRI for RD#3 is added to BIS#1, communicated by UPDATE PDU.

4.Results and Discussion

All tests were completed successfully. It is considered that these tests validated the IPv4 and IPv6 IPSNDCFs for communication between BIS routers, within the test scope.

It was noted that in the circuit failure cases (a failure of the IP connection between two BIS routers), while behaviour was as expected, the BIS routers took several minutes to detect the loss of connectivity, and then several minutes to recover.

In the case of a connection-orientated sub-network such as ISO8208 between ATN routers, the sub-network can send a LEAVE event to indicate a loss of connectivity, potentially allowing immediate termination of the IDRP connection without waiting for expiration of the IDRP HOLD timer, and so allow the network to more rapidly respond by adopting alternate routes.

However, in the case of a connectionless sub-network, such as IP, the sub-network cannot itself detect a loss of connectivity, and so the ATN router must wait for successive lack of KEEPALIVE PDUs from its peer, then attempt to close the IDRP connection by sending a CEASE PDU and wait for the CEASE response timeout before it can try to find an alternate route to relay packets and attempt to re-open the failed connection.

Depending on the nature of the applications running over the network, it may be necessary to reduce the KEEPALIVE hold timer in order to give faster detection of a failed link, while balancing against the slight overhead due to the additional KEEPALIVE PDUs.

5.Future Plans

During Japanese Fiscal Year 2007 (April 2007 – March 2008), ENRI plans to implement the IP SNDCF in an End System and to demonstrate ES-IS operating over an IP sub-network connection.

ENRI is currently liaising with the U.S. Federal Aviation Administration to conduct an IP SNDCF connection test during JFY07 between two dissimilar implementations, either over the public Internet or in a laboratory environment. It is hoped to be able to test both IPv4 and IPv6 sub-network connections in a more realistic network environment.

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