# Presentation: 317613

## Space Communication Demonstration Using Internet Technologies

***Space Communication Demonstration Using Internet Technologies***

**David Israel - NASA/GSFC**
**Keith Hogie - CSC**
**Ron Parise - CSC**
**Ed Criscuolo - CSC**

## Overview

**The CANDOS Mission**
**Space Components**
**Ground Components**
**End-to-End Data Flows**
**Protocols Used**
**Summary**

- ITC 2002

- Oct. 2002

## The CANDOS Mission

**Communication And Navigation Demonstration On Shuttle (CANDOS)**
- Hitchhiker payload on STS-107, January 16, 2003
**Low Power Transceiver (LPT) space test**
- LPT is a multi-channel, programmable transceiver
- Supports SN, GN, and GPS modes
- Built on stackable PC104 form factor boards
- Initial flight test of transmitter, receiver, and GPS capabilities
**Internet Protocol (IP) tests in space**
- Test wide range of standard Internet protocols over SN and GN
- Primary test of Mobile IP
- Secondary tests of MDP, NTP, FTP, UDP, and IP operations
**Ground station upgrades**
- Initial test of issues for upgrading stations to support HDLC framing and Internet protocols on space link

- ITC 2002

- Oct. 2002

## Space Components

**Space Components**

**LPT -  2 - transmitters, 12-receivers (SN/GN, GPS)**
**4 Antennas - hi-gain, low-gain transmit, lo-gain receive, GPS receive**
**233 Mhz x86 processor running Linux 6.1**
**Synchronous serial interface between processor and transceiver clk/data**

- ITC 2002

- Oct. 2002

## Ground Components

- Closed
- IONET

_**Ground Components**_

**Existing antennas, transmitters & receivers**
**RF equipment at ground stations connected to serial port on routers**
**Routers connected to Closed IONET IP backbone**
**Laptops and workstations in control center (Linux, MacOS, Windows)**

- ITC 2002

- Oct. 2002

## Space-Ground - IP Interface for Existing RF Equipment 

**Space-Ground - IP Interface for Existing RF Equipment **

**A device similar to a commercial satellite modem is needed to connect custom RF interfaces to commercial routers**

**Downconvert**

**Receiver**

**Demod**

**Bit sync**

**Upconvert**

**Transmitter**

**Modulator**

**Antenna**

**Existing RF **
**Equipment**

- ITC 2002

- Oct. 2002

## End-to-End Data Flows

**Standard applications use UDP and TCP APIs to communicate between LPT and end user systems**
**Operating systems and routers process IP headers**
**LPT network serial driver connects IP stack and synchronous serial interface**
**Frame Relay/HDLC frames over RS-422 clock and data lines between serial interface and LPT transceiver**
**RF signal processed at ground and Frame Relay/HDLC bitstream fed to router serial port**
**Ground IP packets delivered over Closed IONET**

- ITC 2002

- Oct. 2002

## End-to-End Data Flow

**Async**
**serial**

**Sync**
**serial**

**LPT**

**Applications**

**Frame Relay**
**HDLC**
**framing**

**RS-422**

**Coding**
**Modulation**

**RF**

**Sync**
**serial**

- RS-232

**Xmit/**
**Rcvr**

**GPS**

**Data**

**Sync**
**serial**

**Ether-**
**net**

**IP**
**Network**

**Frame Relay**
**HDLC**
**framing**

**RS-422**

**Modulation**

**RF**

**LPT Processor & Transceiver**

**Ground Station**
**Router**

**End User**

**Ether-**
**net**

**CPU**
**(Linux)**

**Network driver**

**IP**

**IP**

**IP**

**CPU**

**UDP**

**TCP**

**UDP**

**TCP**

**GRID**

**Coding**

- ITC 2002

- Oct. 2002

## Protocols Used

**Mobile IP - automated routing from control center to current antenna for uplink**
**Multicast Dissemination Protocol (MDP) - UDP based, reliable file transfer**
**Network Time Protocol (NTP) - UDP clock sync**
**UDP packets for real-time telemetry**
**UDP packets for blind commanding**
**Secure Shell (SSH) & Telnet - TCP remote login**
**Secure Copy (SCP) & FTP - TCP based file xfer**

- ITC 2002

- Oct. 2002

## Mobile IP

**Home**
**Agent**

**Foreign Agent**
**Ground station**

**150.15.15.x**
**subnet**

**100.10.10.x**
**subnet**

**Foreign Agent**
**Ground station**

**200.20.20.x**
**subnet**

**100.10.10.18**
**Spacecraft address**

**Mobile IP**

**Downlink data is routed normally**
**Need to automatically determine which ground station to send commands through (same problem for cars, PDAs, laptops)**
**Mobile device registration with ground agents supports automatic uplink routing configuration**
**Tests will determine if Mobile IP can establish connectivity before normal AOS  (5° elevation for GN)**

**Control**
**Center**

- ITC 2002

- Oct. 2002

## Multicast Dissemination Protocol

**Multicast Dissemination Protocol**

**UDP based, reliable file transfer protocol developed 5 years ago at Naval Research Lab**
**UDP protocol avoids TCP problems with delay and intermittent links and lets application deal with to space link delay and intermittent connectivity issues**
**Multicast protocols developed to primarily send data to thousands of receivers and minimize responses using primarily NACKs and a final ACK**
**On CANDOS MDP will also be used over TDRSS MA Return-only links to deliver data with final NACKs, retransmissions, and ACKs during two-way contact time**

- ITC 2002

- Oct. 2002

## NACK Oriented Reliable Multicast

- Reliable Multicast Transport Working Group
- The rmt working group is chartered to standardize reliable multicast transport protocols for** "one-to-many bulk data" transport**.  It is related to several other Working Groups and Research Groups in the IETF and the IRTF
- Unlike previous protocol standardization efforts, the rmt working group is taking a new approach that will see protocol specifications built using a building block approach. The aim behind this approach is to
- 1.Allow building blocks to be used within more than one protocol
- 2.Allow building blocks to be upgraded as experience is gained.
- Three Protocol Instantiations are currently being tackled within the rmt WG
- 1.NORM: Nack Oriented Reliable Multicast protocol.   Uses NACKs for reliability
- 2.TRACK: TRee ACKnowledment based protocol   Uses a tree for controlling feedback and repairs
- 3.ALC: Asynchronous Layered Coding**  Uses FEC based techniques and does not require  any feedback**

**http://rmt.motlabs.com/**

- ITC 2002

- Oct. 2002

## Other UDP Protocols

**Network Time Protocol (NTP) - UDP clock sync**
- Synchronize LPT clock with NTP timeservers on Closed IONET
- Measure timing precision achievable, possibly 1-10 ms.
- Helps ensure LPT log messages have accurate time stamps
- Same process for accurate science data time stamps
**UDP packets for real-time telemetry**
- LPT status delivered over TDRSS & GN two-way links
- LPT status delivered over TDRSS MA Return-only links
- LPT status delivered over Hitchhiker low-speed (1200 baud) link
**UDP packets for blind commanding**
- LPT receiver normally ON but transmitter OFF
- Turn transmitter on by manually setting up GRE IP routing tunnel to proper ground station and sending UDP packets with “Transmitter ON” command

- ITC 2002

- Oct. 2002

## TCP Protocols

**Secure Shell (SSH) & Telnet - TCP remote login**
- Standard remote login, SSH and Telnet, will be used to access the LPT processor for management and reconfiguration
**Secure Copy (SCP) & FTP - TCP based file xfer**
- SCP and FTP will be used to upload new configuration files and software applications
- GPS data files and other status files will be downloaded using SCP and FTP as well as MDP

- ITC 2002

- Oct. 2002

## Summary

**Demonstration of using standard IP protocols and applications for space communication**
**Detailed measurement of protocol performance and operation for later analysis**
**Demonstration of long-term, scalable concepts that can be used for command, control, and data collection for a wide range of future systems:**
- satellite science missions
- balloon and aircraft systems
- ground sensors
- collaborative/ad hoc systems with large numbers of devices

- ITC 2002

- Oct. 2002

## Jan. 16, 2003 ?

**http://ipinspace.gsfc.nasa.gov/**

- ITC 2002

- Oct. 2002