INFORMATIONAL

Independent Submission R. Hinden Request for Comments: 6921 Check Point Software Category: Informational 1 April 2013 ISSN: 2070-1721 Design Considerations for Faster-Than-Light (FTL) Communication Abstract We are approaching the time when we will be able to communicate faster than the speed of light. It is well known that as we approach the speed of light, time slows down. Logically, it is reasonable to assume that as we go faster than the speed of light, time will reverse. The major consequence of this for Internet protocols is that packets will arrive before they are sent. This will have a major impact on the way we design Internet protocols. This paper outlines some of the issues and suggests some directions for additional analysis of these issues. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This is a contribution to the RFC Series, independently of any other RFC stream. The RFC Editor has chosen to publish this document at its discretion and makes no statement about its value for implementation or deployment. Documents approved for publication by the RFC Editor are not a candidate for any level of Internet Standard; see Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6921. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Hinden Informational [Page 1]

RFC 6921 Design Considerations for FTL Communication 1 April 2013 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Protocol Design Considerations for FTL Communication . . . . . 3 2.1. Related Issues . . . . . . . . . . . . . . . . . . . . . . 4 3. FTL Communication Research . . . . . . . . . . . . . . . . . . 5 4. IETF Recommendations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . . 6 1 . Introduction Tolman]. A good overall description of the effects of FTL communication can be found in [Goldberg]. [Ardavan] describes a "polarization synchrontron", which pushes radio waves faster than the speed of light. In the paper, the author explains: ...though no superluminal source of electromagnetic fields can be point-like, there are no physical principles preventing extended faster-than-light sources. The coordinated motion of aggregates of subluminally-moving charged particles can give rise to macroscopic polarization currents whose distribution patterns move superluminally. Further relevant progress occurred with the theoretical prediction that extended sources that move faster than their own waves could be responsible for the extreme properties of Hinden Informational [Page 2]

RFC 6921 Design Considerations for FTL Communication 1 April 2013 2 . Protocol Design Considerations for FTL Communication RFC0793], protocol activity is shown in timing diagrams such as Figure 7: TCP A TCP B 1. CLOSED LISTEN 2. SYN-SENT --> <SEQ=100><CTL=SYN> --> SYN-RECEIVED 3. ESTABLISHED <-- <SEQ=300><ACK=101><CTL=SYN,ACK> <-- SYN-RECEIVED 4. ESTABLISHED --> <SEQ=101><ACK=301><CTL=ACK> --> ESTABLISHED 5. ESTABLISHED --> <SEQ=101><ACK=301><CTL=ACK><DATA> --> ESTABLISHED Basic 3-Way Handshake for Connection Synchronization Figure 7 of RFC 793 In an FTL communication environment, this assumption is no longer true, because TCP B will receive the first SYN before TCP A transmitted it. For example, the first part of a TCP 3-way handshake in an FTL environment will look like: TCP A TCP B 1. CLOSED LISTEN 2. <SEQ=100><CTL=SYN> --> SYN-RECEIVED 3. SYN-SENT --> <SEQ=100><CTL=SYN> The exact operation will depend on the difference between the backward time (i.e., from the future to the past) and the processing time to process a packet. If the processing time is greater than the backward time shift, then even though the packets are received out of order, TCP should still work due to the TCP symmetrical 3-way Hinden Informational [Page 3]

RFC 6921 Design Considerations for FTL Communication 1 April 2013 2.1 . Related Issues Hinden Informational [Page 4]

RFC 6921 Design Considerations for FTL Communication 1 April 2013 RFC4838] defines an architecture for Delay-Tolerant Networks. An FTL communication environment is similar to Delay-Tolerant Networks with the major difference that the packets arrive at the destination with a negative delay. Documents that will need review include "A One-way Delay Metric for IPPM" [RFC2679] and "A Delay Bound alternative revision of RFC 2598" [RFC3248]. Congestion control algorithms will also need serious review -- specifically, how to handle negative round-trip time (RTT) on TCP congestion control or the corner case where the RTT comes out at exactly zero. Do any of the control equations include a divide-by- RTT or sqrt(RTT)? It should also be noted that there may be the possibility for significant advancements in congestion algorithms given the properties of FTL communication. Specifically, it maybe possible to stop network congestion before it starts. This could be an important new approach for congestion control researchers. 3 . FTL Communication Research 4 . IETF Recommendations Hinden Informational [Page 5]

RFC 6921 Design Considerations for FTL Communication 1 April 2013 RFC3248] Armitage, G., Carpenter, B., Casati, A., Crowcroft, J., Halpern, J., Kumar, B., and J. Schnizlein, "A Delay Bound alternative revision of RFC 2598", RFC 3248, March 2002. [RFC4838] Cerf, V., Burleigh, S., Hooke, A., Torgerson, L., Durst, R., Scott, K., Fall, K., and H. Weiss, "Delay-Tolerant Networking Architecture", RFC 4838, April 2007. [Tolman] Tolman, R., "The Theory of the Relativity of Motion", Berkeley: University of California Press, 1917. Author's Address Robert M. Hinden Check Point Software 959 Skyway Road Suite 300 San Carlos, CA 94070 USA EMail: bob.hinden@gmail.com Hinden Informational [Page 7]