1. From Bespoke to Standard Solid State Mass Memories
Aitor Viana Sánchez
Data Handling Systems
ESTEC, 27th Oct 2009
CCSDS Fall Meeting

2. Outline Solid State Mass Memories discussion What to standardize
SOIS standard SSMM
Summary
CCSDS Fall Meeting

3. Solid State Mass Memories discussion
It should be possible to develop a SSMM as a standard building block capable of being used for multiple missions, but:
For maximum architectural flexibility, a relatively low level interface should be defined to the SMMM
Unfortunately this is often implemented with a proprietary data link layer, network file and packet access protocols, and services
This means that the required software to access the SSMM has to be defined, developed and validated for each mission
CCSDS Fall Meeting

4. SSMM Traditional Design
OBC
Apps
Bespoke File Access and Packet Store Services
Bespoke Network File Access Protocol
File Access
Services
Packet Access
Services
Network File Access Protocol
Physical Transport Services
Bespoke Transport Services (data link layer and protocol)
File Store
Physical Transport Services
Mass
Memory
Mass
Memory
Network File Access Protocol
Packet Store
System
File System
Bespoke Memory Access Protocol
Memory Access Protocol
CCSDS Fall Meeting

5. SSMM Traditional Design
The SSMM services change from design to design
The SSMM services provided from the SSMM to operate with the files, i.e. open, read, write, lock, etc. may vary a lot from unit to unit.
The SSMM services implementation change from unit to unit
Even standardizing the services it is possible to implement them with many different APIs. It might be probably helpful to establish a common API
The SSMM data link change from unit to unit
There is the need to standardize the way the information is transferred between the entities (SSMM and OBC, payloads, etc)
The SSMM memory access protocol change from unit to unit
Wherever the File System is located, local to the OBC or remote in the SSMM, there is an access protocol from the FS to the memory devices. The standardization of this protocol is also standardize (i.e. Serial-ATA) would allow to exchange also the memory technology without any problem.
To provide a SSMM building block that can be used reused for multiple missions all these interfaces need to be standardized.
CCSDS Fall Meeting

6. SSMM Standard SOIS Design
Standardization of the SSMM services
The standardization of the SSMM services is provided using the File Access Service (FAS), File Management Service (FMS), File Transfer Service (FTS) and Packet Store Services (PSS)
The Network File System Protocol specifies the way the file system or packet store system are accessed. The suite of command/response sequences used to perform the operations specified in the SOIS services. SOIS does not define any NFSP nor recommend any but shall be implemented within FAS, FMS and FTS and might differ from unit to unit
CCSDS Fall Meeting

7. SSMM Standard SOIS Design
Standardization of the SSMM services
The standardization of the SSMM services is provided using the File Access Service (FAS), File Management Service (FMS), File Transfer Service (FTS) and Packet Store Services (PSS)
The Network File System Protocol specifies the way the file system or packet store system are accessed. The suite of command/response sequences used to perform the operations specified in the SOIS services. SOIS does not define any NFSP nor recommend any but shall be implemented within FAS, FMS and FTS and might differ from unit to unit
Should the Network File System Protocol be specified or recommended within SOIS??
CCSDS Fall Meeting

8. SSMM Standard SOIS Design (cont’d)
The SSMM services standardization
OBC
Standardize File Access and Packet Store Services
Apps
FAS
FMS
FTS
Network File Access Protocol
Physical Transport Services
File Store
Physical Transport Services
Mass
Memory
Mass
Memory
Network File Access Protocol
Packet Store
System
File System
CCSDS Fall Meeting
Memory Access Protocol

9. SSMM Standard SOIS Design (cont’d)
The SSMM services standardization
OBC
The SOIS FSPS standardize the user interface towards the SSMM but still lots of changes would be necessary in the Network File System Protocol to adapt to all possible different data link implementations for different SSMM units
Apps
FAS
FMS
FTS
Network File Access Protocol
Physical Transport Services
File Store
Physical Transport Services
Mass
Memory
Mass
Memory
Network File Access Protocol
Packet Store
System
File System
CCSDS Fall Meeting
Memory Access Protocol

10. SSMM Standard SOIS Design (cont’d)
Network File System Protocol
Under the RASTA SSMM activity a custom NFSP has been developed and some useful findings came out
The developed protocol is a command-response protocol as File Operations requires confirmation (ACK) for all services
1024 bytes SDU size was selected but up to 8KB may be used under Spacewire
The physical link used may be both Eth and Spacewire
Ethernet case (Spacewire may be extrapolated)
The protocol overhead is 90%. This protocol overhead is not only due to the protocol headers but the way the operating system handles the internal resources (context switch, interrupt service routines, etc.)
To ensure the results test with netperf tool have been performed
“netperf” does not do anything with the data
CCSDS Fall Meeting

11. SSMM Standard SOIS Design (cont’d)
Network File System Protocol (cont’d)
Test has been performed for:
UDP_RR: send one packet and waits for ACK for sending next one
UDP_STREAM: best effort sending (no ACKs)
TCP_STREAM: like UDP_RR but using TCP window
TCP_RR: like TCP_STREAM without sending window (like UDP_RR but using TCP)
Link speed
1000Mbps
100 Mbps
10 Mbps
UDP_RR
18.64 Mbps
24.24 Mbps
2.08 Mbps
UDP_STREAM
961 Mbps
95.80 Mbps
9.75 Mbps
TCP_RR
18.3 Mbps
24 Mbps
TCP_STREAM
940 Mbps
93.68 Mbps
9.4 Mbps
CCSDS Fall Meeting

12. SSMM Standard SOIS Design (cont’d)
Standardization of the Data Link Layer
SOIS FPSS maps down to the SOIS Packet Service (PS) and SOIS Memory Access Services (MAS), but the introduction of the SOIS Subnetwork services does not standardize the Data Link layer protocol. For that we need to agree the way the data is transferred through the physical bus. Thus, all the SOIS Subnetwork services will map down with the ECSS extension protocols
ECSS CAN (ECSS-E-ST-50-15)
ECSS MIL-STD-1553 (ECSS-E-ST-50-13C)
ECSS Spacewire (TBD)
CCSDS Fall Meeting

13. SSMM Standard SOIS Design (cont’d)
The SSMM data link standardization
OBC
Apps
SOIS FPSS
Network File Access Protocol
Standardize Transport Services (data link layer and protocol)
MAS PS
ECSS
SpW
ECSS
CAN
ECSS
1553
Physical Transport Services
Physical Transport Services
File Store
Standardize Transport Services (data link layer and protocol)
ECSS extension protocols
SOIS Subnetwork Services
Mass
Memory
Mass
Memory
Network File Access Protocol
Packet Store
System
File System
Memory Access Protocol
CCSDS Fall Meeting

14. SSMM Standard SOIS Design (cont’d)
The SSMM data link standardization
OBC
Apps
The SOIS Subnetwork MAS and PS services mapped down to the ECSS bus extension protocols fully standardize both the data link layer and data link protocol. SSMM units complying with this approach become reusable building blocks
SOIS FPSS
Network File Access Protocol
MAS PS
ECSS
SpW
ECSS
CAN
ECSS
1553
Physical Transport Services
Physical Transport Services
File Store
Standardize Transport Services (data link layer and protocol)
ECSS extension protocols
SOIS Subnetwork Services
Mass
Memory
Mass
Memory
Network File Access Protocol
Packet Store
System
File System
Memory Access Protocol
CCSDS Fall Meeting

15. SSMM Standard SOIS Design (cont’d)
Standardization of the Memory Access
Out of the SOIS scope
The file system (or packet store) interfaces to the memory devices by means of a Memory Access Protocol (MAP). This MAP has not being standardize for space usage but examples might be take from commercial world, i.e. Serial-ATA
Standardizing this protocol will de-couple the SSMM design from the memory device technology (RAM, Flash, Solid-state drives, etc.).
CCSDS Fall Meeting

16. SSMM Standard SOIS Design (cont’d)
The SSMM Memory Access standardization
OBC
Apps
SOIS FPSS
Network File Access Protocol
SOIS Subnetwork Services
ECSS
SpW
ECSS
CAN
ECSS
1553
Physical Transport Services
Physical Transport Services
File Store
ECSS extension protocols
SOIS Subnetwork Services
Mass
Memory
Mass
Memory
Standardize Memory Access Protocol
Network File Access Protocol
Packet Store
System
File System
i.e. Serial-ATA
CCSDS Fall Meeting

17. Summary
SSMM should become standard building blocks to be reused for multiple missions
SOIS assists in the standardization process by providing:
SOIS File and Packet Store Services standardize the SSMM services
Standard Network File System Protocol (TBC) ?
SOIS sub-network Packet and Memory Access Services standardize the Data link
ECSS bus extension protocols also standardize the data link transfer protocol
Outside the scope of CCSDS SOIS, the memory access protocol used by the to the file system (or packet store system) to access the memory devices could also be standardized, making the SSMM independent from the memory technology being used
CCSDS Fall Meeting