1. Cross Support Transfer Services – Forward Frames Service 10 – 15 November 2014 London, United Kingdom John Pietras Global Science and Technology, Inc, Greenbelt, MD, USA

2. www.ccsds.org Background 2  Two drivers for Forward Frames service  ISS uses AOS on the forward link. There is currently no CCSDS-standard data transfer service that is designed to support transfer of AOS space link data units NASA is implementing the Enhanced F-CLTU Experimental Specification (Orange Book) to provide near-term support to ISS  The IOAG Solar System Internetwork (SSI) architecture anticipates a transition stage in which relay satellites relay BP bundles and IP datagrams to client spacecraft, but continue to use Space Packets for satellite operations A single space link may carry: o Some VCs bearing transfer frames containing relay satellite command data o Other VCs bearing BP bundles and IP datagrams destined for client spacecraft. These VCs are formed at the ground terminal of the space link  Enhanced F-CLTU Orange Book provides some but not all of the capabilities of Forward Frames  Supports ISS but not SSI  IOAG also called out an intermediate “SLE” Forward Synchronous Frame Service that is essentially satisfied by FF-CSTS

3. www.ccsds.org 3 Overview of Capabilities of FF-CSTS  Three modes of operation  Forward TC Frames  Forward AOS Frames  Forward AOS CADUs  Mode is exclusively configured for the service instance provision period  Forward TC Frames mode  Transfers frames for one TC VC  Service production includes coding of frames and multiplexing of TC frames from combinations of TC VCs sources into a single PLOP stream One or more FF-CSTS instances TC VC frame generators (bearing IP datagrams, BP bundles, CFDP-PDUs, etc.)  Forward AOS Frames mode  Transfers frames for one AOS VC  Service production includes coding of frames, frame sync marker attachment, multiplexing of AOS frames from combinations of AOS VCs sources, and idle frame generation into a single physical channel  Forward AOS CADU mode  Transfers all “AOS CADUs” for one physical channel  Service production includes idle CADU generation and insertion when necessary  Provides least-common-denominator fixed-length synchronous transmission capability

4. www.ccsds.org 4 Functional Group View of FF-CSTS

5. www.ccsds.org 5 FF-CSTS and Space Internetworking

6. www.ccsds.org Functional Resources View of FF-CSTS and Associated Production 6 Only for TC Frame mode, when transmission is gated by CLCW link status

7. www.ccsds.org Readiness to Produce a CSTS Specification 7  Earlier attempt (circa 2011) was stopped due to inability of CSTS SFW procedures to provide needed capabilities  CSTS SFW forward operations and procedures were subsequently updated with support for FF service specifically in mind  Magnitude of effort TBD  Much of the complexity of the FF service is in the specification of the service production  SLE Enhanced F-CLTU Orange Book is a source of much production process specification EF-CLTU production specification already covers: o AOS frame coding, sync, and idle frame generation and insertion o AOS idle CADU generation and insertion o Gating of TC transmission based on CLCWs EF-CLTU production specification does not cover: o Coding of TC frames and multiplexing of TC frames from combinations of TC VCs sources into a single PLOP stream o Multiplexing of AOS frames from multiple sources