IPN Research Group V. Cerf INTERNET-DRAFT Worldcom/Jet Propulsion Laboratory <draft-irtf-ipnrg-arch-01.txt> S. Burleigh July 2002 A. Hooke Expires January 2003 L. Torgerson NASA/Jet Propulsion Laboratory R. Durst K. Scott The MITRE Corporation K. Fall Intel Corporation E. Travis Global Science and Technology H. Weiss SPARTA, Inc. Delay-Tolerant Network Architecture: The Evolving Interplanetary Internet draft-irtf-ipnrg-arch-01.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document describes an architecture for delay-tolerant networks, and is a generalization of the architecture designed for the Interplanetary Internet: a communication system to provide Internet- like services across interplanetary distances in support of deep space exploration. This generalization addresses networks whose operational characteristics conventional networking approaches unworkable or impractical. We define a message-based overlay that exists above the transport layer of the networks on which it is hosted. The document presents an architectural overview followed by discussions of services, topology, routing, security, reliability and state management. The document concludes with a discussion of end- to-end information exchange, including an example. Cerf, et al. [Page 1] Internet Draft draft-irtf-ipnrg-arch-01.txt July 2002 Table of Contents Status of this Memo................................................ 1 Abstract........................................................... 1 Table of Contents.................................................. 2 Copyright Notice................................................... 3 Acknowledgments.................................................... 4 Foreword........................................................... 5 1 Introduction ................................................ 6 2 Why an Architecture for Delay-Tolerant Networking? .......... 6 2.1 Constraints Posed by Extreme Environments .............. 6 2.2 Problems with Internet Protocols and Applications ..... 10 2.3 DTN Principles of Design .............................. 12 3 DTN Architectural Overview ................................. 14 3.1 The DTN is Based on Message Switching ................. 15 3.2 DTN Classes of Service Mimic Postal Mail-like Operation 15 3.3 Regions and Region Identifiers ........................ 15 3.4 Tuples ................................................ 16 3.5 Late Binding .......................................... 16 3.6 The "Bundle Layer" Terminates Local Transport Protocols and Operates End-to-End ............................... 17 3.7 Routing ............................................... 17 3.8 Bundle Layer Reliability and Custodianship ............ 17 3.9 Security .............................................. 18 3.10 Time Synchronization .................................. 19 4 Service Considerations: Application Instances and Bundles . 19 4.1 Networking Style Issues ............................... 19 4.2 Bundle Lifetime ....................................... 20 4.3 Classes of Service .................................... 20 4.4 Delivery Options ...................................... 21 4.5 Naming and Addressing ................................. 22 5 Topological Considerations: Node, Regions, and Gateways ... 22 5.1 Node .................................................. 22 5.2 Regions ............................................... 22 5.3 Gateways .............................................. 23 5.4 Discussion ............................................ 23 6 Routing considerations ..................................... 24 6.1 Types of Routes ....................................... 24 6.2 Store-and-forward operation ........................... 25 6.3 Contact-oriented routing .............................. 26 6.4 Routing protocols ..................................... 26 7 Security considerations .................................... 27 7.1 User-oriented security services ....................... 27 7.2 Infrastructure security services ...................... 29 8 Reliability Considerations ................................. 34 8.1 Custodial Operation ................................... 34 8.2 End-to-end Retransmission ............................. 35 8.3 Congestion Control at the Bundle Layer ................ 36 9 State Management Considerations ............................ 36 9.1 Application Interface State ........................... 36 9.2 Bundle retransmission state ........................... 37 9.3 Bundle routing state .................................. 38 9.4 Transmission queue state .............................. 38 Cerf, et al. Expires October 2002 [Page 2] Internet Draft draft-irtf-ipnrg-arch-01.txt July 2002 9.5 Receive queue state ................................... 39 9.6 Network management state .............................. 39 10 Convergence Layer Considerations for Use of Underlying Protocols .................................................. 39 11 Bundle Header Information .................................. 39 12 An Example Bundle Transfer ................................. 41 12.1 Rules for forming tuples in the example network ....... 41 12.2 Example Network Topology at the Region Level .......... 42 12.3 DTN Gateway routing ................................... 44 12.4 Systems participating in example bundle data transfer . 45 12.5 End-to-end Transfer ................................... 47 12.6 Error Conditions at the Bundle Layer .................. 49 13 Summary .................................................... 52 14 References ................................................. 52 15 Security Considerations .................................... 52 16 Authors' Addresses ......................................... 54 Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Cerf, et al. Expires October 2002 [Page 3] Internet Draft draft-irtf-ipnrg-arch-01.txt July 2002 Acknowledgments John Wroclawski, David Mills, Greg Miller, James P. G. Sterbenz, Joe Touch, Steven Low, Lloyd Wood, Robert Braden, Deborah Estrin, and Craig Partridge all contributed useful thoughts and criticisms to this document. We are grateful for their time and participation. This work was performed under DOD Contract DAA-B07-00-CC201, DARPA AO H912; JPL Task Plan No. 80-5045, DARPA AO H870; and NASA Contract NAS7-1407. Cerf, et al. Expires October 2002 [Page 4] Internet Draft draft-irtf-ipnrg-arch-01.txt July 2002 Foreword The term 'sonata' can be applied to a large work in three movements or to the three sections of a single movement: exposition, development, recapitulation. They resonate with the three acts of a movie or play, the three elements of a primal myth or legend (life, death, rebirth), the cycle of days (daylight, night, then daylight again) and of the seasons in temperate climates (nice weather, then winter, then it gets nice again), the Star Wars trilogy, etc. Basically, in any human experience we start off brightly, full of energy and hope; then we experience reality and become thoughtful and reflective, darker and slower; then Something Happens and hope is reborn, our energy returns, and we reach that happy synthesis of Innocence and Experience that is maturity. Allegro, andante, rondo..." -- Scott Burleigh Release Notes draft-irtf-ipnrg-arch-00.txt, May 2001: Allegro. Original Issue. draft-irtf-ipnrg-arch-01.txt, April 2002: Andante. Restructured document to distinguish between architecture for delay- tolerant networking and the *application* of that architecture to a number of different environments, potentially including interplanetary internetworking, military tactical networking, and sensor internetworking. Refined DTN classes of service and delivery options. Introduced a "reply-to" address to have information directed to a third party rather than the source. Further defined the topological elements of delay tolerant networks. Elaborated routing and reliability considerations. Significant work in defining the model for securing the delay tolerant network infrastructure, based on signed admission control credentials. Added section discussing state information. Updated bundle header information and end-to-end data transfer example. Cerf, et al. Expires October 2002 [Page 5] Internet Draft draft-irtf-ipnrg-arch-01.txt July 2002 1 Introduction This document describes an architecture for delay-tolerant networks. We present this as a generalization and extension of our ongoing work on the Interplanetary Internet (http://www.ipnsig.org). We have come to the realization that there are a number of different environments that share essential characteristics for which the architecture presented herein is appropriate. The particular approach we employ is that of a message-based overlay that exists above the transport layers of the networks on which it