1. Cross Support Services Area Cross Support Transfer Services Working Group Strawman Forward Frame CSTS Specification Technical Note (June 2010) John Pietras London, UK October 2010

2. Cross Support Services Area Cross Support Transfer Services Working Group 2 Purpose of the Service Specification Test the ability of the CSTS Framework to support specification of a forward synchronous link CSTS Provide a starting point for the definition of an actual Forward Frame CSTS –Identified by the Interagency Operations Advisory Group (IOAG) Space Internetworking Strategy Group (SISG) has identified a need for a CSTS that transfers one of the following stream types in a given service instance: Advanced Orbiting System (AOS) transfer frames destined for a synchronous forward space link AOS Channel Access Data Units (CADUs) destined for a synchronous forward space link Telecommand (TC) transfer frames destined for an asynchronous forward space link –These three stream types are to be supported by a single CSTS type

3. Cross Support Services Area Cross Support Transfer Services Working Group 3 Approach Used in Developing the Specification Apply appropriate parts of the CSTS Guidelines to create a shortened and simplified CSTS Service Specification –No ASN.1 modules defined –Different “modes” defined for TC Frames and synchronous link PDUs (AOS frames and CADUs) Driven by current requirement that only one procedure type can be the type of the prime procedure instance Essentially a CSTS mapping of the Enhanced FCLU SLE service (Orange Book), except: –There is no transfer of TC CLTUs This capability is already provided by the standard FCLTU SLE service –Transfer of TC Frames is supported –Production of TC frames into CLTUs is included –Multiplexing of frames and CADUs from multiple instances of the F- Frame service is supported

4. Cross Support Services Area Cross Support Transfer Services Working Group 4 Production and Provision of the F-Frame Service

5. Cross Support Services Area Cross Support Transfer Services Working Group 5 Need for Two Prime Procedure Types The CSTS FW Data Processing procedure is adequate for transfer of asynchronous TC frames, but not synchronous frames and CADUs –Efficient transfer of synchronous link PDUs is hampered by sequence enforcement and locking-on-PDU-expiration behavior of the Data Processing procedure A different prime procedure type needs to be defined for synchronous PDU transfer –Alternative is to define a single procedure type that has two alternating behaviors and even alternating main operation types. Ugly The two alternate prime procedures are illustrated as different “modes” of the service –Use of such modes is not formally defined for CSTSes NOTE – Decision at London meeting to allow management selection of the prime procedure type for each service instance removes the need for these modes

6. Cross Support Services Area Cross Support Transfer Services Working Group 6 F-Frame Procedures (TC Frame Mode)

7. Cross Support Services Area Cross Support Transfer Services Working Group 7 TC Frame Processing Operations

8. Cross Support Services Area Cross Support Transfer Services Working Group 8 TC Frame Processing PROCESS-DATA Extension parameters data parameter is extended to contain multiple variable-length (for TC) frames diagnostic extension adds ‘unsupported VC’

9. Cross Support Services Area Cross Support Transfer Services Working Group 9 TC Frame Processing NOTIFY Extension parameters Notification-type extension adds ‘buffer empty’ –‘data unit processing started” deleted

10. Cross Support Services Area Cross Support Transfer Services Working Group 10 Synchronous Link Mode The Red-1 CSTSFW PROCESS-DATA operation and Data Processing procedure inhibit data flow for reasons that negate efficient forward synchronous service –Discard PDUs that don’t have the expected next sequence number –Lock the service instance if any PDU expires Strawman specification postulates a new PUSH-DATA operation that has simplified content and behavior, and a new Forward Synchronous Data Processing procedure that uses it

11. Cross Support Services Area Cross Support Transfer Services Working Group 11 PUSH-DATA Operation Operation parameters Standard Operation Header diagnostic extension data-sequence-counter has no sequence- preservation enforcement requirements data parameter defined as abstract

12. Cross Support Services Area Cross Support Transfer Services Working Group 12 TC Frame Processing Procedures (Forward Synchronous Mode)

13. Cross Support Services Area Cross Support Transfer Services Working Group 13 Forward Synchronous Data Processing Procedure Operations

14. Cross Support Services Area Cross Support Transfer Services Working Group 14 Forward Synchronous Data Processing PUSH-DATA Extension parameters data parameter is extended to contain multiple delimited frames data-sequence-counter is refined to count transferred PDUs (not PUSH-DATA invocations) diagnostic values extended –‘invalid time’ –‘late data’ –‘unable to store’

15. Cross Support Services Area Cross Support Transfer Services Working Group 15 Forward Synchronous Data Processing NOTIFY Extension parameters notification-type extension values –‘data processing successfully completed’ –‘expired’ –buffer empty’

16. Cross Support Services Area Cross Support Transfer Services Working Group 16 Summary of Suitability of Red-1 CSTSFW for the F- Frame Service Red-1 CSTSFW cannot support F-Frame service as-is A simpler forward data transfer data operation and a simpler procedure that uses that operation are needed –CSTS rules don’t allow service-original operations, but they do allow service-original procedures –A stand-alone simpler operation (such as PUSH-DATA) could be defined in the FW, or the base PROCESS-DATA operation could be simplified and the “TC”-type behavior added by the Data Processing procedure –Once the simpler forward data transfer operation is available in the FW, the procedure based on it could either be contained in the FW itself or created as a service-original procedure in the F-Frame service specification The issue regarding two prime procedure types has been solved by decision at London meeting

17. Cross Support Services Area Cross Support Transfer Services Working Group 17 Possible Solutions PUSH-DATA in FW as base operation –Simple Data Processing procedure in FW, or –service-original simple data processing procedure in the service specification Make PROCESS-DATA simpler –Make Data Processing simpler (using simpler PROCESS-DATA) in FW Create “TC” Data Processing procedure by extending Data Processing procedure Need to investigate a transfer buffer to bundle invocations Need to investigate a more-efficient reporting/notification scheme