As part of a broader organisational restructure, data networking research at Swinburne University of Technology has moved from the Centre for Advanced Internet Architecture (CAIA) to the Internet For Things (I4T) Research Lab.

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SONATA - SCTP Over NAT Adaptation

Testing

Testing the NAT implementation comes in two flavours. If is not enough to verify that the NAT algorithm/implementation be functionally correct, it is also essential that the final solution be efficient in resource usage. Efficiency concerns are important to ensure that the solution is scalable to large-scale NAT implementations and also to enable it to efficiently run on low-powered routers as might be found in a home-access situation.

The functionality of the NAT implementation needs to be considered under a number of different scenarios that includes:

• End-host failure - The NAT must continue to operate correctly during an abrupt failure of one or both of the association end-hosts
• NAT failure - The SCTP session should properly terminate in the event of the NAT box failing and coming back online
• Multiple NAT boxes -This includes an end-host being behind multiple NAT boxes and the situation where both end-hosts are hidden behind a NAT
• Multiple end-points - Need to be considered to verify NAT functionality
• Collision Scenarios - While the SCTP protocol caters for a number of collision scenarios, it is essential to ensure that this functionality is not broken by the NAT implementation

Testbed Information

A flexible testbed will be built with sperate machines being used to server as each end-host and as the NAT implementation. Multi-homing will be implemented using IP-based tunnels and VTun coupled with appropriate routing table configuration. This will allow flexibility in bringing links and networks up and down easily by terminating the tunnels as required.

Generating Traffic

The SCTP test application will be modified to generate a continuous, low-rate data stream over an association using multiple IP addresses. A continuous stream allows the NAT implementation to see a continuous stream of packets for working on while the low-rate stream ensures that the packet rate is slow enough for debugging purposes. When performance testing of the NAT implementation is required the data rate will need to be increased.

Capturing and Analysing Traffic

To ensure that all traffic is captured, we need to capture on the physical interface rather than the virtual tunnel interfaces. However this makes it more difficult to decode the SCTP packets being transmitted over each individual tunnel. We aim to develop a plug-in module for Ethereal to decode the VTun datagrams and allow the existing IP/SCTP modules to decode the payload contents

SCTP NAT Test Tools

Tools to test an SCTP NAT (both functionality and performance testing) can be downloaded here. These tools are designed to test generic SCTP NAT implementations and can be used on both the SONATA NAT implementation as well as other black-box NAT implementations.