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

2. 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

3. 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)

4. 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

5. 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.

6. 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

7. 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

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

9. 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

10. 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

11. 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

12. 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

13. IP Communications through stressed links.
xiphos.ca
Charlie Younghusband
XipLink Product Manager
x221

14. 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

15. 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

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

17. Visit www.xiplink.com for more slides….