AIT SLE User Guide

This user guide for AIT’s SLE implementation assumes some familiarity with the SLE standards for RAF, RCF, and F-CLTU. An overview of these specs can be found in the AIT docs here.

Configuration

The necessary configuration parameters for all protocols can be added to the config.yaml. Optionally, many of them can also be passed in at runtime for greater flexibility. Below is an example configuration which can be used as a reference, in addition to the default configuration available in the repository.

AIT will attempt connection to all of the provided hostnames and use whichever successfully connects first.

dsn:
    sle:
        initiator_id: LSE
        password: lse_pw
        responder_id: SSE
        peer_password: sse_pw
        version: 5
        downlink_frame_type: TMTransFrame
        heartbeat: 25
        deadfactor: 5
        buffer_size: 256000
        responder_port: 'default'
        auth_level: 'none'
        rcf:
            inst_id: sagr=LSE-SSC.spack=Test.rsl-fg=1.rcf=onlc2
            hostnames:
                - example.hostname.1
                - example.hostname.2
            port: 5111
        raf:
            inst_id: None
            hostnames:
                - example.hostname.1
                - example.hostname.2
            port: None
        fcltu:
            inst_id: None
            hostnames:
                - example.hostname.1
                - example.hostname.2
            port: None

Downlink (RAF and RCF)

The ait.dsn.sle.raf module implements the SLE Return All Frames (RAF) standard, while the ait.dsn.sle.rcf module implements the SLE Return Channel Frames (RCF) standard. Both are extensions of the generic ait.dsn.sle.common.SLE class.

An example script for using AIT’s RCF API is shown below and available in the AIT-DSN repository here. AIT’s RAF API is nearly identical and can be used in the same manner. The only differences are the parameters for the start call as shown in the the documentation for ait.dsn.sle.raf.start() vs ait.dsn.sle.rcf.start().

import datetime as dt
import time

import ait.dsn.sle

rcf_mngr = ait.dsn.sle.RCF(
    hostname='atb-ocio-sspsim.jpl.nasa.gov',
    port=5100,
    inst_id='sagr=LSE-SSC.spack=Test.rsl-fg=1.rcf=onlc2',
    spacecraft_id=250,
    trans_frame_ver_num=0,
    version=4,
    auth_level="none"
)

rcf_mngr.connect()
time.sleep(2)

rcf_mngr.bind()
time.sleep(2)

start = dt.datetime(2017, 01, 01)
end = dt.datetime(2019, 01, 01)
rcf_mngr.start(start, end, 250, 0, virtual_channel=6)
time.sleep(2)

rcf_mngr.stop()
time.sleep(2)

rcf_mngr.unbind()
time.sleep(2)

rcf_mngr.disconnect()
time.sleep(2)

Online vs. Offline Connection

An online connection to RAF or RCF delivers telemetry in realtime, while an offline connection delivers telemetry between a start time and an end time. An offline connection can also be used to receive realtime data if a start time in the past and an end time in the future are used.

	Online	Offline
Use	Realtime	Historical
Start/End times	None types	datetime.datetime ‘s

Uplink (F-CLTU)

The ait.dsn.sle.cltu module implements the SLE Forward Communications Link Transmission Unit (F-CLTU) standard , and is an extension of the generic ait.dsn.sle.common.SLE class.

An example script for using AIT’s F-CLTU API is shown below and available in the AIT-DSN repository here.

import datetime as dt
import time

import ait.dsn.sle

cltu_mngr = ait.dsn.sle.CLTU(
    hostname='atb-ocio-sspsim.jpl.nasa.gov',
    port=5100,
    inst_id='sagr=LSE-SSC.spack=Test.fsl-fg=1.cltu=cltu1',
    auth_level="bind")

cltu_mngr.connect()
time.sleep(2)

cltu_mngr.bind()
time.sleep(2)

cltu_mngr.start()
time.sleep(2)

junk_data = bytearray('\x00'*79)
cltu_mngr.upload_cltu(junk_data)
time.sleep(2)

cltu_mngr.stop()
time.sleep(2)

cltu_mngr.unbind()
time.sleep(2)

cltu_mngr.disconnect()
time.sleep(2)

IMPORTANT NOTE: The F-CLTU transfer service is not the same functionality as creating a CLTU PDU, which is outlined starting at Page 3-1 of the CCSDS specification.