Project Title

High Performance Reliability Protocol (HPRP)



Document Number


6.09 Delay Tolerant Networking Working Group

Document Type


Description of Document

The document specifies a protocol for reliable or unreliable delivery of blocks of data over space-to-ground, ground-to-space, and space-to-space links. Reliable delivery over less reliable links is achieved by an efficient segment-level re-transmission mechanism which makes the protocol suitable for highly asymmetrical data rates with large round-trip delays as experienced in inter-planetary communications while still being suitable for ultra-high-rate links with very small latencies. HPRP is designed for high-speed processing on typical flight hardware including FPGA and ASIC, as well as providing standard user interface semantics for all transmission modes. While HPRP protocol is an evolution of the CCSDS Licklider Transmission Protocol and shares some of the concept, it is not backward compatible. As it is also covering the same use cases, it is expected that the new protocol could replace the use of LTP in the future.

Applicable Patents

There are no patent issues for this technology that are known by the CCSDS community

Patent Comments

Survey of Similar Standards
Documents or Projects
Undertaken in Other Bodies
and elsewhere in CCSDS

The proposed protocol is an evolution of the CCSDS LTP protocol which includes the use of self-delimiting numeric values (SDNVs) in some of the protocol fields. While this allows LTP to maintain bit efficiency over a wide range of operational environments (e.g. when sending different sized LTP blocks), it results in headers where the size MAY vary from segment to segment and that require parsing multiple SDNVs. This makes it difficult to implement LTP in high-speed environment or extremely resource-constrained environments where the LTP processing is moved to field programmable gate arrays (FPGAs) or other hardware accelerators. A recent ESA study performed by GMV (with contributions from DLR) analysed a variety of space and terrestrial protocols (TCP, QUIC, SCPS-TP, SRT, NORM, LTP, CFDP, COP-1/-P, 802.11 BA, AX.25) in terms of required capabilities and suitability for hardware implementations and concluded that the definition of a new protocol based on LTP is the most suitable way forward.


Book Editor


Book Editor Resources


Prototype 1


Prototype 1 Resources


Prototype 2

Prototype 2 Resources

Prototype 3

Prototype 3 Resources



Monitor Only


Resource Comments

2 prototypic implementation (software and FPGA) are already available at DLR and have been extensively tested.


Legend for Schedule Milestones
Orange Bullet = Required for Orange Books
Green Bullet = Required for Green Books
Magenta Bullet = Required for Magenta Books
Blue Bullet = Required for Blue Books
Note - Red Books are Draft Blue/Magenta Books

Schedule Milestones
Orange BookGreen BookMagenta BookBlue Book
Original Completion Date
(Date in M/D/YYYY format.)
(Date in M/D/YYYY format.)
Project ApprovedOrange BulletGreen BulletMagenta BulletBlue Bullet11/1/2023
Project Start DateOrange BulletGreen BulletMagenta BulletBlue Bullet11/6/2023
Internal WG Review
First Draft Circulated to WGOrange BulletGreen BulletMagenta BulletBlue Bullet1/31/2024
First Draft Comments DueOrange BulletGreen BulletMagenta BulletBlue Bullet2/29/2024
Second draft circulated to WGOrange BulletGreen BulletMagenta BulletBlue Bullet4/30/2024
Second Draft Comments DueOrange BulletGreen BulletMagenta BulletBlue Bullet5/31/2024
Final WB Submitted to AD for Further ProcessingOrange BulletGreen BulletMagenta BulletBlue Bullet6/28/2024
External Milestones
Secretariat Document ProcessingOrange BulletGreen BulletMagenta BulletBlue Bullet8/30/2024
First Agency ReviewMagenta BulletBlue Bullet
RID ResolutionMagenta BulletBlue Bullet
Secretariat Document Processing 2Magenta BulletBlue Bullet
Final Agency ReviewMagenta BulletBlue Bullet
RID ResolutionMagenta BulletBlue Bullet
First Prototype DevelopmentBlue Bullet
Second Prototype DevelopmentBlue Bullet
CMC ApprovalOrange BulletGreen BulletMagenta BulletBlue Bullet10/31/2024
Total Time to Complete
(in months)
Version: 45.0
Created at 9/29/2023 11:25 AM by Robert Durst
Last modified at 12/1/2023 4:20 PM by Brian Oliver