High Speed Delay Tolerant Network

Overview

Delay Tolerant Networking (or DTN) has been identified as a key technology to facilitate the development and growth of future space networks. Existing DTN implementations have emphasized operation in constrained environments with relatively limited resources and low data speeds. As various technologies have advanced, however, both the rate and efficiency with which data can be effectively transferred have grown incredibly quickly. This has left existing craft unable to utilize more than a small fraction of available capacity. Further, to date, most known implementations of DTN have been designed to operate on the spacecraft themselves. HDTN takes advantage of modern hardware platforms to offer substantial improvement on latency and throughput with respect to DTN implementations that exist today. Specifically, our implementation maintains compatibility with existing implementations of DTN that conform to IETF RFC 5050, while simultaneously defining a new data format that is better suited to higher-rate operation in many cases. It defines and adopts a massively parallel, pipelined, and message oriented architecture, which allows the system to scale gracefully as the resources available to the system increase. HDTN's architecture additionally supports hooks for replacing various elements of the processing pipeline with specialized hardware accelerators, which can be used to offer improved Size, Weight, and Power (SWaP) characteristics at the cost of increased development complexity and cost.

Build Environment

Dependencies

HDTN build environment requires:

• CMake version 3.16.3
• Boost library version 1.71
• ZeroMQ
• Python module for ZeroMQ
• gcc version 9.3.0 (Debian 8.3.0-6)
• Target: x86_64-linux-gnu
• Tested platforms: Ubuntu 20.04.2 LTS, Debian 10, Windows and Mac

Packages installation

• Ubuntu $ sudo apt install cmake $ sudo apt-get install build-essential $ sudo apt-get install libzmq3-dev $ sudo apt-get install python3-zmq $ sudo apt install libboost-dev $ sudo apt install libboost-all-dev

Known issue

• Ubuntu distributions may install an older CMake version that is not compatible
• Mac OS may not support recvmmsg and sendmmsg functions, recvmsg and sendmsg could be used
• Some processors may not support hardware acceleration or the RDSEED instruction, both ON by default in the cmake file

Getting Started

Build HDTN

• export HDTN_SOURCE_ROOT=/home/username/hdtn
• cd $HDTN_SOURCE_ROOT
• mkdir build
• cd build
• cmake -DCMAKE_BUILD_TYPE=Release ..
• make -j8

Run HDTN

Note: Ensure your config files are correct, e.g., The outduct remotePort is the same as the induct boundPort, a consistant convergenceLayer, and the outducts remoteHostname is pointed to the correct IP adress.

You can use tcpdump to test the HDTN ingress storage and egress. The generated pcap file can be read using wireshark.

• sudo tcpdump -i lo -vv -s0 port 4558 -w hdtn-traffic.pcap

In another terminal, run:

• ./runscript.sh

Note: The contact Plan which has a list of all forthcoming contacts for each node is located under module/scheduler/src/contactPlan.json and includes source/destination nodes, start/end time and data rate. Based on the schedule in the contactPlan the scheduler sends events on link availability to Ingress and Storage. When the Ingress receives Link Available event for a given destination, it sends the bundles directly to egress and when the Link is Unavailable it sends the bundles to storage. Upon receiving Link Available event, Storage releases the bundles for the corresponding destination and when receiving Link Available event it stops releasing the budles.

There are additional test scripts located under directories test_scripts_linux and test_scripts_windows that can be used to test different scenarios for all convergence layers.

Run Unit Tests

After building HDTN (see above), the unit tests can be run with the following command within the build directory:

• ./tests/unit_tests/unit-tests

Run Integrated Tests

After building HDTN (see above), the integrated tests can be run with the following command within the build directory:

• ./tests/integrated_tests/integrated-tests

Run Contact Graph Routing

HDTN relies on PyCGR for its contact graph routing. To enable the PyCGR Client, in a separate window run:

• python3 pycgr/py_cgr_client.py