Advancements in SCPS-TP technology and deployments Charlie Younghusband XipLink Product Manager Xiphos Technologies SIW IV June 8th, 2004

Discussion Limited introduction: SCPS-TP has been presented before Updates on commercial applicability (Relevance of Internet via Satellite work) Updates on standards evolution and acceptance Active deployments

SCPS-TP Space Communications Protocol Standard – Transport Protocol (SCPS-TP) is an open solution for overcoming well-known TCP performance problems over space links. It’s an upgrade to TCP, while retaining interoperability with TCP Adds capabilities like new TCP options and redefines TCP behavior, but retains TCP state machine Can benefit from huge TCP/IP research community (e.g. data links to cell phones)

SCPS-TP Applicable from high bandwidth LEO, to GEO, to satcom, to lunar Can meet or beat all competition including custom engineered protocols, and using a reliable protocol for reliable communications makes sense SCPS has other protocols but they are not used by us

Xiphos SCPS-TP -> XipLink Implementation of SCPS-TP became basis for XipLink – “link performance enhancement technology for stressed communication IP links” Beyond transport layer, integrates other optimizations like real time data compression and HTTP Acceleration for Internet over Satellite HTTP Acceleration (aka prefetching) is an “Application Layer Gateway” to overcome chatty protocols. Other ALGs possible in the future. We maintain interoperability and standards concepts from SCPS-TP when doing enhancements. E.g. Also operate in meshed environments.

SCPS-TP Deployment Selling our own “XipLink Gateways” installed bracketing satellite links Licensed into vendor satellite terminals Specialized projects in defense Used for end-point communication to on-board spacecraft nodes, or possibly a spacecraft SCPS-TP gateway / router

Xiphos SCPS-TP Used BSD Network stack as a basis SCPS-TP implemented differently than SCPS Reference Implementation. Does T/TCP, does not do Best Effort Transport Service (BETS). More optimized for Satcom Low level implementation in kernel on Linux and VxWorks as well Many optimizations for dynamic buffering, managing 10,000 concurrent connections+, burst connection opens, really advanced rate control algorithm, UDP and TCP QoS options

New Recognition in defence SCPS-TP recommended as part of DoD’s Transformational Communications Architecture and future MILSATCOM Visit: http://64.241.27.103/npom/npom_news.html Also recognized by Canadian Military for their next gen satellite network Other governmental/international organizations support

Related Projects I Dynamic bandwidth satellite networks have strong focus for maximizing bandwidth utilization and distribution among many nodes Side channel requests, dedicated slots, ALOHA etc. DVB-RCS (Return Channel via Satellite) is a standard growing in recognition The general ‘volume’ based capacity allocation results in ~1.5 second RTT. Design expecting 1.8 seconds. Increased load can increase this. Could be applicable to formation flying etc. Completed a project with ESA for study and solution

Related Projects II: Aircraft Doing our own project via SCPS-TP to UAV SCPS-TP used in combination with UDP telemetry data streams Various link possibilities Other projects by US defense primes for aircraft communications Choice or varying communication links, paths Commercial aircraft projects also moving Possibly more than one satcom hop also high delay, possible high BER

SCPS-TP in Space! Running onboard Xiphos’ Q5 networked control card Combination logic/software Scheduled launch June 29 LatinSat 1D (commercial) Representative of fully operating the satellite via SCPS-TP Reconfigurable

SCPS-TP to the moon… NASA’s lunar plans has lead to renewed interest in communication issues at this distance CCSDS has created CisLunar group to study and provide guidance with protocol issues SCPS-TP expected to be a core element Evaluation of necessary extensions, IPV6 etc and updates Other non-transport layer issues

IP Communications through stressed links. xiphos.ca Charlie Younghusband XipLink Product Manager cwy@xiphos.ca 514-848-9640 x221 http://www.xiplink.com/

SCPS-TP Sending congestion control Rate control: bandwidth known TCP Vegas: variable, shared links Selective Negative Acknowledgments (SNACK) more responsive and efficient TCP Header Compression: removes redundancy TCP for Transactions: skips 3 way handshake ACK frequency reduction to limit return path bandwidth

SCPS-TP Uses sender side only algorithms or negotiates capabilities (extensions to normal TCP) through TCP options at connection setup Can go end-to-end or a proxy gateway architecture Very flexible architecture. Easy to change, can be done adhoc or ‘mixed’, legacy network deployment benefits Big reason for its adoption by US Military Flexible for integrating other technologies from Internet or custom developed while maintaining architecture Ease of analysis, IP transparency, when not using rate control can be QoS engineered

SatCom Operation Paradigms SCPS-TP SCPS-TP SCPS-TP TCP Gateway SCPS-TP SCPS-TP Gateway Gateway TCP TCP

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