path: root/doc/rfc/rfc6921.txt

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.




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Table of Contents

   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

   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.

   There is a lot of discussion in the physics community about faster-
   than-light travel and communication.  In fact, it even has a well
   known acronym "FTL".  This acronym will be used in the remainder of
   this document.

   FTL issues have been discussed in the scientific literature for a
   long time.  For example, it was discussed in 1917 in the section
   "Velocities Greater than that of Light" on page 54 of "The Theory of
   the Relativity of Motion" [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



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      both the electromagnetic emission from pulsars (rapidly spinning,
      magnetized neutron stars) and the acoustic emission by supersonic
      rotors and propellers.

   This may be a viable approach for transmitting data FTL.

2.  Protocol Design Considerations for FTL Communication

   Most, if not all, Internet protocols were designed with the basic
   assumption that the sender would transmit the packet before the
   receiver received it.  For example, in the Transmission Control
   Protocol (TCP) [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



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   handshake mechanism.  If the processing time is smaller than the
   backward time shift, then it gets much harder, as many packets will
   be received before they are sent.  The faster the communication is
   above the speed of light, the more severe the problem becomes.

   Assuming the first case where the processing time is equivalent or
   larger than the backward time shift (i.e., after an exchange of
   packets the backward time offset is canceled out), the TCP 3-way
   handshake in an FTL environment would look like:

       TCP A                                                TCP B

   1.  CLOSED                                               LISTEN

   2.                  <SEQ=100><CTL=SYN>               --> SYN-RECEIVED

   3.  SYN-SENT    --> <SEQ=100><CTL=SYN>

   4.  ESTABLISHED <-- <SEQ=300><ACK=101><CTL=SYN,ACK>      SYN-RECEIVED

   5.  ESTABLISHED     <SEQ=300><ACK=101><CTL=SYN,ACK>  <-- SYN-RECEIVED

   6.  ESTABLISHED     <SEQ=101><ACK=301><CTL=ACK>      --> ESTABLISHED

   7.  ESTABLISHED --> <SEQ=101><ACK=301><CTL=ACK>          ESTABLISHED

   It shows remarkable forethought by the inventors of the TCP protocol
   that the 3-way handshake works in an FTL communication environment.
   This is due to the symmetrical nature of the 3-way handshake and its
   ability to deal with dropped packets.  It should be possible to use
   dropped packets as a way to mimic an FTL communication environment.
   In fact, this may provide a good vehicle to analyze and test
   protocols to see how they will work in an FTL communication
   environment.

2.1.  Related Issues

   Additional work is needed to think about protocol design
   considerations when the backward time shift is much greater than the
   processing time.  This would create challenges where it would be
   necessary to have received all of the data before the connection
   could be established.  This is left to future researchers.  In
   practical terms, this scenario isn't likely to happen for a long
   time.  That said, FTL communication might lead to FTL travel, where
   we can travel into the past.  It may be necessary to start working on
   this yesterday.





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   There is a large amount of work that has been done in a related area,
   Delay-Tolerant Networks.  For example, [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

   FTL communication has great potential for the networking research
   community.  It is clearly an exciting area for new research and
   considerable time could be spent working on it.  It is very important
   that we fully understand all of its aspects before we know how to
   achieve FTL communication.  Funding agencies should take this into
   account when allocating money and make sure that all new research
   projects look at FTL communication environments.

4.  IETF Recommendations

   The Internet Engineering Steering Group (IESG), which is the part of
   Internet Engineering Task Force (IETF) that manages the standards
   process, has area reviews as part of its review process.  For
   example, the Security area reviews proposed protocols for security
   issues.  The IETF Chair also has a General area that does overall
   reviews.

   The author recommends that the IETF create a new review group to
   evaluate all new Internet protocols to verify that FTL communication
   has been taken into consideration in the design of the protocol.
   This would be similar to what is done to make sure that new Internet
   protocols are secure or are designed to run over IPv4 and IPv6.  As
   we look forward to FTL communication, it is critical that all
   Internet protocols are designed to work in this environment.






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   Further, the author recommends that the IESG start a review process
   to do a detailed analysis of all existing Internet protocols to make
   sure they have been designed to work in FTL communication
   environments.  For protocols that do not work in this environment,
   the IESG should add work items to exiting working group charters or
   charter new working groups to update these protocols so that they
   will work in FTL communication environments.

5.  Security Considerations

   It is early to fully understand security issues relating to FTL
   communication.  The main issue is likely to be related to the
   characteristic of FTL communication that the receiver will receive a
   packet before it is sent.  Many exploits are likely to be written to
   take advantage of this property.  Also, given the number of exploits
   that are being discovered that don't have any protections available,
   it may be that the malware community is already taking advantage of
   the properties of FTL communication.

6.  Acknowledgements

   Valuable comments and support were provided by Brian Carpenter and
   Rodney Van Meter.

7.  References

7.1.  Normative References

   [RFC0793]   Postel, J., "Transmission Control Protocol", STD 7, RFC
               793, September 1981.

7.2.  Informative References

   [Ardavan]   Ardavan, A., Singleton, J., Ardavan, H., Fopma, J.,
               Hallida, D., and W. Hayes, "Experimental demonstration of
               a new radiation mechanism: emission by an oscillating,
               accelerated, superluminal polarization current", eprint
               arXiv:physics/0405062, May 2004.

   [Goldberg]  Goldberg, D., "Do faster than light neutrinos let you
               change the past?", October 2011, <http://io9.com/5846519/
               do-faster-than-light-neutrinos-let-you-change-the-past>.

   [RFC2679]   Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
               Delay Metric for IPPM", RFC 2679, September 1999.






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   [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






























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