CubeSat Space Protocol (CSP) is a small network-layer delivery protocol designed for

CubeSat A CubeSat is a class of miniaturized satellite based around a form factor consisting of cubes. CubeSats have a mass of no more than per unit, and often use commercial off-the-shelf (COTS) components for their electronics and structure. CubeSat ...

s. The idea was developed by a group of students from

Aalborg University Aalborg University (AAU) is a Danish public university with campuses in Aalborg, Esbjerg, and Copenhagen founded in 1974. The university awards bachelor's degrees, master's degrees, and PhD degrees in a wide variety of subjects within humanitie ...

in 2008, and further developed for the

AAUSAT3 AAUSat-3, (Aalborg University CubeSat-3), is the third CubeSat built and operated by students from the Aalborg University in Denmark. It was launched on 25 February 2013 from the Satish Dhawan Space Centre in India on a Polar Satellite Launch ...

CubeSat mission that was launched in 2013. The protocol is based on a 32-bit header containing both network and transport layer information. Its implementation is designed for embedded systems such as the 8-bit AVR microprocessor and the 32-bit ARM and AVR from Atmel. The implementation is written in C and is ported to run on

FreeRTOS FreeRTOS is a real-time operating system kernel for embedded devices that has been ported to 35 microcontroller platforms. It is distributed under the MIT License. History The FreeRTOS kernel was originally developed by Richard Barry around 20 ...

and

POSIX The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming inte ...

and

pthreads POSIX Threads, commonly known as pthreads, is an execution model that exists independently from a language, as well as a parallel execution model. It allows a program to control multiple different flows of work that overlap in time. Each flow of ...

-based operating systems such as

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which i ...

. The three-letter acronym CSP was adopted as an abbreviation for ''CAN Space Protocol'' because the first MAC-layer driver was written for CAN-bus. The physical layer has since been extended to include several other technologies, and the name was therefore extended to the more general CubeSat Space Protocol without changing the abbreviation. The protocol and the implementation is still actively maintained by Johan de Claville Christiansen, Space Inventor and GomSpace. The source code is available under an LGPL license and hosted on

GitHub GitHub, Inc. () is an Internet hosting service for software development and version control using Git. It provides the distributed version control of Git plus access control, bug tracking, software feature requests, task management, co ...

Description

The CubeSat Space Protocol enables distributed embedded systems to deploy a service-oriented network topology. The layering of CSP corresponds to the same layers as the

TCP/IP The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...

model. The implementation supports a connection oriented transport protocol (Layer 4), a router-core (Layer 3), and several network-interfaces (Layer 1–2). A service-oriented topology eases the design of satellite subsystems, since the communication bus itself is the ''interface'' to other subsystems. This means that each subsystem developer only needs to define a service-contract, and a set of port-numbers their system will be responding on. Furthermore, subsystem inter-dependencies are reduced, and redundancy is easily added by adding multiple similar nodes to the communication bus. Key features include: * Simple

API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...

similar to

Berkeley sockets Berkeley sockets is an application programming interface (API) for Internet sockets and Unix domain sockets, used for inter-process communication (IPC). It is commonly implemented as a library of linkable modules. It originated with the 4.2BS ...

. * Router core with static routes. Supports transparent forwarding of packets over e.g. spacelink. * Support for both connectionless operation (similar to UDP), and connection oriented operation (based on RUDP). * Service handler that implements ICMP-like requests such as ping and buffer status. * Support for loopback traffic. This can e.g. be used for Inter-process communication between subsystem tasks. * Optional support for broadcast traffic if supported by the physical interface. * Optional support for promiscuous mode if supported by the physical interface. * Optional support for encrypted packets with XTEA in

CTR CTR may refer to: Engineering, science and technology * Counter mode (CTR mode), a cryptographic mode of operation for block ciphers * X-ray crystal truncation rod, a technique to measure properties of crystal surfaces * Current transfer ratio, in ...

mode. * Optional support for

HMAC In cryptography, an HMAC (sometimes expanded as either keyed-hash message authentication code or hash-based message authentication code) is a specific type of message authentication code (MAC) involving a cryptographic hash function and a secre ...

authenticated packets with truncated

SHA-1 In cryptography, SHA-1 (Secure Hash Algorithm 1) is a cryptographically broken but still widely used hash function which takes an input and produces a 160-bit (20- byte) hash value known as a message digest – typically rendered as 40 hexadec ...

HMAC.

Operating systems supported

CSP should compile on all platforms that have a recent version of the gcc compiler. CSP requires support for

C99 C99 (previously known as C9X) is an informal name for ISO/IEC 9899:1999, a past version of the C programming language standard. It extends the previous version ( C90) with new features for the language and the standard library, and helps imp ...

features such as inline functions and designated initializers. *

– Tested on

AVR8 AVR is a family of microcontrollers developed since 1996 by Atmel, acquired by Microchip Technology in 2016. These are modified Harvard architecture 8-bit RISC single-chip microcontrollers. AVR was one of the first microcontroller families t ...

AVR32 AVR32 is a 32-bit RISC microcontroller architecture produced by Atmel. The microcontroller architecture was designed by a handful of people educated at the Norwegian University of Science and Technology, including lead designer Øyvind Strøm an ...

and

ARM7 ARM7 is a group of 32-bit RISC ARM processor cores licensed by ARM Holdings for microcontroller use. The ARM7 core family consists of ARM700, ARM710, ARM7DI, ARM710a, ARM720T, ARM740T, ARM710T, ARM7TDMI, ARM7TDMI-S, ARM7EJ-S. The ARM7TDM ...

. *

– Tested on

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel based on the Intel 8086 microprocessor and its 8088 variant. The 8086 was intro ...

x86-64 x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit version of the x86 instruction set, first released in 1999. It introduced two new modes of operation, 64-bit mode and compatibility mode, along with a new 4-level paging ...

and

Blackfin The Blackfin is a family of 16-/32-bit microprocessors developed, manufactured and marketed by Analog Devices. The processors have built-in, fixed-point digital signal processor (DSP) functionality supplied by 16-bit multiply–accumulates (M ...

. *

Mac OS X macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

* Microsoft Windows

Physical layer drivers

CSP supports several physical layer technologies. The LGPL licensed source code contains an implementation of a fragmenting CAN interface and drivers for

SocketCAN SocketCAN is a set of open source CAN drivers and a networking stack contributed by Volkswagen Research to the Linux kernel. SocketCAN was formerly known as ''Low Level CAN Framework'' (LLCF). Traditional CAN drivers for Linux are based on th ...

and the Atmel AT90CAN128, AT91SAM7A1 and AT91SAM7A3 processors. From version 1.1 onwards, CSP also includes interfaces for

I2C I, or i, is the ninth letter and the third vowel letter of the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''i'' (pronounced ), plural ...

and

RS-232 In telecommunications, RS-232 or Recommended Standard 232 is a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' ('' data terminal equipment'') suc ...

. Interfaces need only to implement a function to transmit a packet, and insert received packets into the protocol stack with the csp_new_packet function. CSP has been successfully tested on top of the following layers: * CAN *

using the

KISS_(TNC) KISS (Keep It Simple, Stupid) is a protocol for communicating with a serial terminal node controller (TNC) device used for amateur radio. This allows the TNC to combine more features into a single device and standardizes communications. KISS was de ...

protocol *

CCSDS The Consultative Committee for Space Data Systems (CCSDS) was founded in 1982 for governmental and quasi-governmental space agencies to discuss and develop standards for space data and information systems. Currently composed of "eleven member agenc ...

131.0-B-1-S/131.0-B-2 space link protocol *

UDP/IP In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in packets) to other hosts on an Internet Protocol (IP) network. ...

SPI SPI may refer to: Organizations * Indian Protection Service (''Serviço de Proteção ao Índio''), Brazil * Shotmed Paper Industries, an Egyptian paper manufacturers * Simulations Publications, Inc., a former US board game publisher * Sony P ...

Protocol header

Version 1

The port range is divided into three adjustable segments. Ports 0 to 7 are used for general services such as ping and buffer status, and are implemented by the CSP service handler. The ports from 8 to 47 are used for subsystem specific services. All remaining ports, from 48 to 63, are ephemeral ports used for outgoing connections. The bits from 28 to 31 are used for marking packets with HMAC, XTEA encryption, RDP header and CRC32 checksum.

Version 2

References

{{Reflist

External links

Project Website and source code hosting

Aalborg University, Student Satellite Activities

Aalborg University, AAUSAT3
– the first AAU cubesat to use CSP">AAUSAT3">Aalborg University, AAUSAT3
– the first AAU cubesat to use CSP
GomSpace ApS
Transport layer protocols CubeSats