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SIS-DTN LTP Protocol Specification

SIS-DTN LTP Protocol Specification. Agenda. Goals of this activity Advance LTP towards Blue Book status Overview of LTP Goals of the protocol How LTP fits in with Internetworking / Bundle Protocol LTP Operation Comments on the specification To Do

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SIS-DTN LTP Protocol Specification

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  1. SIS-DTN LTP Protocol Specification

  2. Agenda • Goals of this activity • Advance LTP towards Blue Book status • Overview of LTP • Goals of the protocol • How LTP fits in with Internetworking / Bundle Protocol • LTP Operation • Comments on the specification • To Do • Implementations exist (Burleigh, Farrell, Ramadas) • Write and execute test plan

  3. LTP Overview • LTP sits at roughly layer 2.5 in the ISO stack, providing optionally-reliable communications across a single data link ‘hop’ • In the context of CCSDS, LTP is intended to run primarily over the CCSS Encapsulation service • For DTN / SSI, LTP serves as a ‘Convergence Layer’ for the Bundle Protocol, providing reliability for 1-hop communications BP App BP App BP App BP App BP App Optionally-reliable multi-hop space internetworking BP App BP BP Provides length field and allows LTP blocks to be efficiently packed into underlying frames. LTP User BP CLA LTP User BP CLA LTP User LTP User Optionally-Reliable 1-HOP Communications LTP LTP CCSDS Encapsulation CCSDS Encapsulation CCSDS Data Link (e.g. TC/TM, Prox-1, AOS) CCSDS Data Link (e.g. TC/TM, Prox-1, AOS) CCSDS RF, coding, and modulation CCSDS RF, coding, and modulation

  4. LTP Overview • LTP sits at roughly layer 2.5 in the ISO stack, providing optionally-reliable communications across a single data link ‘hop’ • In the context of CCSDS, LTP is intended to run primarily over the CCSS Encapsulation service • For DTN / SSI, LTP serves as a ‘Convergence Layer’ for the Bundle Protocol, providing reliability for 1-hop communications BP App BP App BP App BP App BP App Optionally-reliable multi-hop space internetworking BP App BP BP Provides length field and allows LTP blocks to be efficiently packed into underlying frames. LTP User BP CLA LTP User BP CLA LTP User LTP User Optionally-Reliable 1-HOP Communications LTP LTP CCSDS Encapsulation CCSDS Encapsulation CCSDS Data Link (e.g. TC/TM, Prox-1, AOS) CCSDS Data Link (e.g. TC/TM, Prox-1, AOS) CCSDS RF, coding, and modulation CCSDS RF, coding, and modulation

  5. LTP Operation Fix me: after CP, EORP loss, retransmit.

  6. The CCSDS LTP Red Book • CCSDS Boilerplate • Overview • Service Specification (extracted from the RFC) • RFC5326 (Licklider Transmission Protocol) • Any comments on the specification? • http://tools.ietf.org/rfc/rfc5326.txt • Some LTP parameters are SDNVs (e.g. LTP session #s, checkpoint #s, report serial #s) and may be randomly selected integers – could be really really big (might want to restrict to --- a few bytes) • Note: PICS and MIB sections will cover the normatively referenced RFC • Security Extensions (RFC5327)? [authentication, cookies] – can omit if running BP over LTP? (use BAB instead) • Informative reference to SDNV RFC (pending) • Mapping LTP onto lower-layers (Link Service Adaptors for LTP – e.g. for Encap) • Issues w/ maximum LTP segment size to deal with underlying layer .e.g. TC (TC is 10 bits of length with no segmentation unless you use the MAP) • Options for multiple checkpoints when transmitting (prohibit?) • Asynchronously generated report segments (allow or deny these?)

  7. LTP Segment Format 0 1 2 3 4 5 6 7 Version Number (0x01) Segment Type Flags Control-Byte CTRL EXC Flag1 Flag0 Session ID (Engine ID of source, session number chosen by sender) Header Header Extension Count Trailer Extension Count Header Extensions Extensions Segment Content Trailer Extensions Trailer

  8. Flags CTRL EXC Flag 1 Flag 0 Code Nature of segment ---- --- ------ ------ ---- --------------------------------------- 0 0 0 0 0 Red data, NOT {Checkpoint, EORP or EOB} 0 0 0 1 1 Red data, Checkpoint, NOT {EORP or EOB} 0 0 1 0 2 Red data, Checkpoint, EORP, NOT EOB 0 0 1 1 3 Red data, Checkpoint, EORP, EOB 0 1 0 0 4 Green data, NOT EOB 0 1 0 1 5 Green data, undefined 0 1 1 0 6 Green data, undefined 0 1 1 1 7 Green data, EOB 1 0 0 0 8 Report segment 1 0 0 1 9 Report-acknowledgment segment 1 0 1 0 10 Control segment, undefined 1 0 1 1 11 Control segment, undefined 1 1 0 0 12 Cancel segment from block sender 1 1 0 1 13 Cancel-acknowledgment segment to block sender 1 1 1 0 14 Cancel segment from block receiver 1 1 1 1 15 Cancel-acknowledgment segment to block receiver

  9. Backups

  10. Portion of block to be transmitted reliably. Portion of block to be transmitted unreliably. LTP Block Transaction.request Sending LTP User Sending LTP Entity Receiving LTP Entity Receiving LTP User SessionStart.indication CP RS CP, EORP GSArrival.indications RS InitialTransmission Complete.indication CP, EORP RS RedPartReception. indication TransmissionSession Complete. indication RS Report Segment CP Checkpoint EORP End of Red Part

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