Delay Tolerant Networks

Protocols and Applications

Athanasios V. Vasilakos, Yan Zhang, Thrasyvoulos Spyropoulos, Athanasios V. Vasilakos, Yan Zhang, Thrasyvoulos Spyropoulos

• Publisher: CRC Press
• Year: 2016
• eBook ISBN: 9781466513013
• Topic: Computer Science
• Subtopic: Information Technology
• Index: Computer Science

A class of Delay Tolerant Networks (DTN), which may violate one or more of the assumptions regarding the overall performance characteristics of the underlying links in order to achieve smooth operation, is rapidly growing in importance but may not be well served by the current end-to-end TCP/IP model. Delay Tolerant Networks: Protocols and Applicat

Chapter 1

Delay Tolerant Networking

Maode Ma, Chao Lu and Hui Li

• 1.1 Introduction
  • 1.1.1 History of Delay Tolerant Networking
  • 1.1.2 A Delay Tolerant Network
  • 1.1.3 Requirements on DTNs
• 1.2 The Architecture
  • 1.2.1 Overlay Architecture
  • 1.2.2 Store and Forward Message Switching
  • 1.2.3 Routing and Forwarding
  • 1.2.4 Fragmentation and Reassembly
  • 1.2.5 Custody Transfer
• 1.3 The Bundle Protocol
  • 1.3.1 Bundle Service
    • 1.3.1.1 Terms
    • 1.3.1.2 Service Offered by Bundle Protocol Agent
  • 1.3.2 Bundle Format
    • 1.3.2.1 Self-Delimiting Numeric Values
    • 1.3.2.2 Endpoint IDs in Detail
    • 1.3.2.3 Formats of Bundle Blocks
  • 1.3.3 Bundle Processing
    • 1.3.3.1 Bundle Creation at Source
    • 1.3.3.2 Transmission by Source
    • 1.3.3.3 First-Hop Processing and Forwarding
    • 1.3.3.4 Second-Hop Processing and Forwarding
    • 1.3.3.5 Bundle Reception by Destination
• 1.4 Routing Schemes in DTNs
  • 1.4.1 Routing Considerations
  • 1.4.2 Classification of Routing Schemes
  • 1.4.3 Replication-Based Routing
    • 1.4.3.1 Epidemic Routing
    • 1.4.3.2 PRoPHET Routing Protocol
    • 1.4.3.3 MaxProp Routing Protocol
    • 1.4.3.4 RAPID Routing Protocol
    • 1.4.3.5 Spray and Wait Routing Protocol
• 1.5 Open Issues in Delay-Tolerant Networking
  • 1.5.1 Routing
  • 1.5.2 Custody and Congestion
  • 1.5.3 Security

1.1 Introduction

1.1.1 History of Delay Tolerant Networking

Inspired by the popularity of computing, in the 1970s, researchers began developing routing technology for non-fixed locations of computers. The field of ad-hoc routing was inactive throughout the 1980s, but the widespread use of wireless protocols reinvigorated the field in the 1990s as mobile ad-hoc networking (MANET). Vehicular ad-hoc networking also became a researcher’s area of increasing interest.

Concurrently with but separated from the MANET activities, a proposal on Interplanetary Internet (IPN) had been funded to develop the novel technologies of IPN. The Internet pioneer Vint Cerf and others have developed the initial IPN architecture relevant to the necessity of networking technologies that can cope with the significant delays and packet corruption in deep-space communications.

In 2002, Kevin Fall started to adapt some of the ideas in the IPN to design terrestrial networks. He coined the term delay tolerant networking with DTN as the acronym. The first conference paper presented in 2003 has shown the motivation for DTNs [1]. In the following years, more and more attention has been drawn from researchers including a growing number of academic conferences on delay and disruption-tolerant networking, and growing interests in combining the work from sensor networks and MANETs with the work on DTN. The research work on the topic started from optimizations on classic ad-hoc and delay-tolerant networking algorithms and began to examine issues such as security, reliability, verifiability, and other issues that are well understood in traditional computer networking.

1.1.2 A Delay Tolerant Network

DTN is the area of networking which addresses challenges in disconnected, disrupted networks without end-to-end connection. DTN is designed to operate effectively over extreme distances such as those encountered in space communications or on an interplanetary scale. In such an environment, long latency which is measured in hours or days is inevitable. And the latency is even as long as a year such as an instance in the paper on DTLSR routing protocol [2].

The existing TCP/IP-based Internet protocols operate on a principle of providing end-to-end interpose communication using a concatenation of potentially dissimilar link-layer technologies. These Internet protocols do not work well for some environments tolerating long delays and predictably interrupted communications over long distances due to the fundamental assumptions built into the Internet architecture [3] as follows:

• An end-to-end path exists between source and destination during a communication session.
• For realistic communication, retransmission based on timely and stable feedback from data receivers must be composed for repairing errors.
• The end-to-end packet drop probability is small.
• All routers and end stations support the TCP/IP protocols.
• Applications need not worry about communication performance.

In a delay tolerant network, most of the above assumptions of the Internet are flexible. And the design principles of DTN architecture can be summarized as follows:

Variable-length messages will exist as the communication abstraction to facilitate the ability of the network for scheduling or path selection decisions.

A naming syntax which supports a wide range of naming and addressing conventions is applied to enhance interoperability.

Storage within the network is taken to support store-and-forward operation over multiple paths and potentially long timescales.

Security mechanisms are provided to protect the infrastructure from unauthorized users by discarding traffic as quickly as possible.

1.1.3 Requirements on DTNs

There are some networking scenarios where current Internet protocols do not work well, such as space missions to Mars and testing lake water quality in rural areas. Both these scenarios have something in common with more and more devices incorporating computing and networking technology in less traditional networking environments. Computer networking in such environments faces new challenges and new techniques and protocols are required. And all these challenges can be characterized as follows.

• Intermittent Connectivity: If there is no end-to-end path between source and destination, the end-to-end communication using the TCP/IP protocols does not work. New protocols to support the communications without an end-to-end path are required.
• Long or Variable Delay: In addition to intermittent connectivity, long propagation delays among nodes and variable queuing delays at each node contribute to end-to-end path delays that can defeat Internet protocols and applications that rely on quick return of acknowledgements or data.
• Asymmetric Data Rates: The Internet supports moderate asymmetries of bi-directional data rate for users with cable TV or asymmetric DSL access. But if asymmetries are large, conversational protocols will not work.
• High Error Rates: Bit errors over transmission links require correction or retransmission of the entire packet, which can result in more network traffic. For a given link-error rate, fewer retransmissions are needed for hop-by-hop than for end-to-end retransmission.

1.2 The Architecture

The DTN architecture is designed to accommodate network connection disruption with a framework for dealing with heterogeneity.

A multitude of different delivery protocols is used in DTN, which include TCP/IP, raw Ethernet, serial lines, or hand-carried storage devices for delivery. As each of these protocols provides somewhat different semantics, a collection of protocol-specific convergence layer adapters (CLAs) provides the functions necessary to carry DTN protocol data units, called bundles, on each of the corresponding protocols.

1.2.1 Overlay Architecture

The architecture embraces the concepts of occasionally-connected networks that may suffer from frequent partitions and that may be comprised of more than one divergent set of protocols or protocol families.

The end-to-end message overlay is defined as a “bundle layer” that exists at a layer above the transport layers of the networks on which it is hosted and below applications. Devices implementing the bundle layer are called DTN nodes. The bundle layer forms an overlay that employs persistent storage to help combat network interruption. And it includes a hop-by-hop transfer of reliable delivery responsibility and optional end-to-end acknowledgement. A number of diagnostic and management features are also included. For inter-operability, it uses a flexible naming scheme capable of overall naming syntax. And also security nodes are designed as options aimed at protecting infrastructure from unauthorized use.

1.2.2 Store and Forward Message Switching

The messages sent in a DTN are with arbitrary length as Application Data Units (ADUs), which are subject to any implementation limitations.

ADUs are transformed by the bundle layer into one or more protocol data units called “bundles,” which are forwarded by DTN nodes. Bundles have a defined format containing two or more “blocks” of data. Each block may contain either application data or control information to deliver the bundle to its destination. Blocks serve the purpose of holding information typically found in the header or payload portion of the bundles. Bundles may be fragmented into multiple constituent bundles as fragments or bundle fragments during the t...

Table of contents

• Cover
• Title Page
• Copyright Page
• Contents
• Preface
• List of Contributors
• Chapter 1 Delay Tolerant Networking
• Chapter 2 DTN Routing: Taxonomy and Design
• Chapter 3 Energy-Aware Routing Protocol for Delay Tolerant Networks
• Chapter 4 A Routing-Compatible Credit-Based Incentive Scheme for DTNs
• Chapter 5 R-P2P: a Data-Centric Middleware for Delay Tolerant Applications
• Chapter 6 Mobile P2P: Peer-to-Peer Systems over Delay Tolerant Networks
• Chapter 7 Delay Tolerant Monitoring of Mobility-Assisted WSN
• Chapter 8 Message Dissemination in Vehicular Networks
• Chapter 9 Delay Tolerant Networking (DTN) Protocols for Space Communications
• Chapter 10 DTN and Satellite Communications
• Index