Endeavouring to be in the good books : awarding DTN network use for acknowledging the reception of bundles

This paper describes an incentive scheme for promoting the cooperation, and, therefore, avoiding selfish behaviours, in Delay Tolerant Networks (DTN) by rewarding participant nodes with cryptographic keys that will be required for sending bundles. DTN are normally sparse, and there are few opportunistic contacts, so forwarding of other's bundles can be left out. Moreover, it is difficult to determine the responsible nodes in case of bundle loss. The mechanism proposed in this paper contributes to both problems at the same time. On one hand, cryptographic receipts are generated using time-limited Identity Based Cryptography (IBC) keys to keep track of bundle transmissions. On the other hand, these receipts are used to reward altruistic behaviour by providing newer IBC keys. Finally, these nodes need these IBC keys to send their own bundles. When all nodes behave in a cooperative way, this incentive scheme works as a virtuous circle and achieves a Nash equilibrium, improving very much the network performance in terms of latency. The scheme is not difficult to implement, and it can use an already existing IBC infrastructure used for other purposes in a DTN

Softwarecast : a code-based delivery Manycast scheme in heterogeneous and Opportunistic Ad Hoc Networks

In the context of Opportunistic Ad Hoc Networking paradigms, group communication schemes (Manycast) are difficult to conduct. In this article, we propose a general delivery scheme for Manycast group communications based on mobile code. Our proposal extends network addressing by moving from the static header field paradigm to a software code-based addressing scheme. We allow messages to be delivered using built-in software codes that consider application-defined, context-aware or history-based information. Additionally, we allow messages to carry a delivery state that permits them to perform refined delivery-decision-making methods. As a consequence of this scheme, we have found that new group communication schemes, besides the traditional ones, may be beneficial to improve the network performance and to provide new functionalities to emerging scenarios like intermittently connected networks of heterogeneous physical objects. We present an application of this scheme to solve, following an analytical delivery method, the problem of sending a message to k and only k nodes of a heterogeneous and opportunistic network scenario that fit best a given criterion. We show, using simulations, that our proposal performs better than traditional approaches. Finally, to show that our proposal is feasible, we present an implementation of our proposal in a real Opportunistic Ad Hoc network, a DTN network, compatible with the de facto standard Bundle Protocol

Endeavouring to be in the good books : awarding DTN network use for acknowledging the reception of bundles

This paper describes an incentive scheme for promoting the cooperation, and, therefore, avoiding selfish behaviours, in Delay Tolerant Networks (DTN) by rewarding participant nodes with cryptographic keys that will be required for sending bundles. DTN are normally sparse, and there are few opportunistic contacts, so forwarding of other's bundles can be left out. Moreover, it is difficult to determine the responsible nodes in case of bundle loss. The mechanism proposed in this paper contributes to both problems at the same time. On one hand, cryptographic receipts are generated using time-limited Identity Based Cryptography (IBC) keys to keep track of bundle transmissions. On the other hand, these receipts are used to reward altruistic behaviour by providing newer IBC keys. Finally, these nodes need these IBC keys to send their own bundles. When all nodes behave in a cooperative way, this incentive scheme works as a virtuous circle and achieves a Nash equilibrium, improving very much the network performance in terms of latency. The scheme is not difficult to implement, and it can use an already existing IBC infrastructure used for other purposes in a DTN

Maritime expressions:a corpus based exploration of maritime metaphors

This study uses a purpose-built corpus to explore the linguistic legacy of Britain’s maritime history found in the form of hundreds of specialised ‘Maritime Expressions’ (MEs), such as TAKEN ABACK, ANCHOR and ALOOF, that permeate modern English. Selecting just those expressions commencing with ’A’, it analyses 61 MEs in detail and describes the processes by which these technical expressions, from a highly specialised occupational discourse community, have made their way into modern English. The Maritime Text Corpus (MTC) comprises 8.8 million words, encompassing a range of text types and registers, selected to provide a cross-section of ‘maritime’ writing. It is analysed using WordSmith analytical software (Scott, 2010), with the 100 million-word British National Corpus (BNC) as a reference corpus. Using the MTC, a list of keywords of specific salience within the maritime discourse has been compiled and, using frequency data, concordances and collocations, these MEs are described in detail and their use and form in the MTC and the BNC is compared. The study examines the transformation from ME to figurative use in the general discourse, in terms of form and metaphoricity. MEs are classified according to their metaphorical strength and their transference from maritime usage into new registers and domains such as those of business, politics, sports and reportage etc. A revised model of metaphoricity is developed and a new category of figurative expression, the ‘resonator’, is proposed. Additionally, developing the work of Lakov and Johnson, Kovesces and others on Conceptual Metaphor Theory (CMT), a number of Maritime Conceptual Metaphors are identified and their cultural significance is discussed