pyion: A Python Extension for the Interplanetary Overlay Network

Author:Marc Sanchez Net
Address:4800 Oak Grove Dr. Pasadena, CA 91109
Contact:marc.sanchez.net@jpl.nasa.gov
Organization:Jet Propulsion Laboratory (JPL)
Release:R2019c
Repository:https://github.com/msancheznet/pyion
Abstract:pyion is provides a set of Python C extensions that interface with the Interplanetary Overlay Network (ION), JPL’s implementation of the Delay Tolerant Networking (DTN) protocol stack.

Introduction

pyion provides a Python interface to JPL’s Interplantary Overlay Network (ION) to send/receive data through ION, as well as a limited and still experimental set of administrative functions to modify the ION configuration during runtime. Note that pyion does install ION during its setup process. Instead, installation of pyion is only possible if ION is already installed and running in the host.

To quickly demonstrate how pyion works, here is a brief example of two Python nodes exchanging data by interfacing with ION’s implementation of the Bundle Protocol (BP).

Example 1: BP Transmitter

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import pyion

# Create a proxy to node 1 and attach to ION
proxy = pyion.get_bp_proxy(1)
proxy.bp_attach()

# Open endpoint 'ipn:1.1' and send data to 'ipn:2.1'
with proxy.bp_open('ipn:1.1') as eid:
    eid.bp_send('ipn:2.1', b'hello')

Example 2: BP Receiver

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python
import pyion

# Create a proxy to node 2 and attach to it
proxy = pyion.get_bp_proxy(2)
proxy.bp_attach()

# Listen to 'ipn:2.1' for incoming data
with proxy.bp_open('ipn:2.1') as eid:
    while eid.is_open:
        try:
            # This is a blocking call.
            print('Received:', eid.bp_receive())
        except InterruptedError:
            # User has triggered interruption with Ctrl+C
            break

Pyion interfaces with ION through a collection of proxies. Each proxy is intended to be linked to a protocol in the DTN protocol stack (i.e., there is a proxy to the BP protocol, as seen in the previous example, but there are different proxies to LTP and CFDP, as well ION’s SDR and PSM), as well as a node number. To avoid having muliple proxies to the same node, proxies should not be created directly by the user but rather instantiated using pyion.get_<type>_proxy(<node_number>). Proxies are used to manage service access points to a given protocol (e.g., endpoint for the BP, entity for CFDP, etc.). This includes opening and closing them, as well as interrupting their operation if necessary. In turn, the access point itself is typically only used to send and receive data.

Installation Instructions

Pyion is currently not hosted in any Python repository (e.g., pip, conda) because installation of the package is only possible in computers where ION is already available. However, installing it is as simple as downloading the package and then, in a terminal, running

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cd /pyion
export ION_HOME=/......
python3 setup.py install

The environment variable $ION_HOME should ideally be set to the base path where ION is installed, although it this is not mandatory. In fact, if not available, pyion will still be installed but all administrative/management functionality will not be available (e.g., ability to query/modify a contact plan directly from Python).

Dependencies

The only dependency pyion uses is ION itself. All tests conducted to date have been performed using ION-3.6.2 over an Ubuntu-based operating system running in either a laptop, a Docker container, or a Raspberry Pi (arm architecture). The package might also work in other setups (e.g., ION-3.6.0), but there is no guarantee that this is the case.

Pyion is internally built as a collection of Python C Extensions wrapped in Python classes or functions. These C extensions are compiled during the package’s installation process and require access to the ION’s public and potentially private interfaces (a collection of .h and .so files in an Ubuntu-based host). Therefore, the file setup.py found in the root folder of the makes assumptions on where these are located in the host file system:

  • Public ION Interface: Required for installing pyion. It is assumed to be located at /usr/local/include and usr/local/lib unless the environment variable LD_LIBRARY_PATH is available.
  • Private ION interface: Optional for installing pyion. If not available, then pyion has all administrative functions disabled. To enable them, set the environment variable ION_HOME to ION’s root folder and then run the setup process.

Multiple ION Nodes in a Single Host

If multiple instances of ION are running on the same host, each one with its own node number, then ION_NODE_LIST_DIR environment variable needs to be defined (see the ION manual for further details). This can be done from Python by simply calling

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import pyion
pyion.ION_NODE_LIST_DIR = '/<desired path>/nodes'

Contents

Indices and tables