Contact Graph Routing enhancements for delay tolerant space communications

Abstract

In this paper we present two enhancements to Contact Graph Routing (CGR), a Delay-/ Disruption-Tolerant Networking routing algorithm developed by NASA JPL for space environments with predetermined connectivity schedules, such as Interplanetary communications and LEO satellite systems. The first enhancement, CGR-ETO, aims to improve the accuracy of predicted bundle delivery time by considering the available information on queueing delay. The second, the Overbooking Management, aims to proactively handle contact oversubscription, which occurs when high priority bundles are forwarded for transmission on a contact that is already fully subscribed by lower priority bundles. Both enhancements have been inserted as optional features in the Interplanetary Overlay Network CGR implementation in order to comparatively evaluate their performance on a GNU/Linux testbed running the full protocol stack. The results show that the two enhancements are complementary and can significantly improve routing decisions compared to standard CGR.

A Simulation module of NS3 for DTN with Time-space model based Routing

“…Along with the progress of these two area, many variants and enhanced edition are published by with different aims and different solution [7,8,12,13]. Although these enhanced edition might surmount base edition in some custom environment in some specified target, the comparing between algorithms of different design aims would be meaningless and illogical, which is the reason leads us to choose the base edition of these two algorithm for simulation.…”

“…As noted in this paper [13], CGR has its own problem, the exhaust search and pick one scheme, of which picking one operation is presented as CGR-Forward Decision affects the routing result. That is to say, in this simulation, we use a naive forward decision with no throughput optimal, which is the factor leads to the result that CGR perform no better than TEG when overhead reach its max throughput.…”

“…If we can design an advance CGR with best throughput optimal, we can more efficiently use network throughput, which is almost the most cherished performance metric in a DTN network. If we introduce earliest transmission chance into CGR, we can get CGR with Earliest Transmission Opportunity (CGR-ETO) [13].…”

Assessing Contact Graph Routing Performance and Reliability in Distributed Satellite Constellations

“…Later, in 2014, authors studied the implementation of temporal route lists as a mean to minimize CGR executions [57]. In the same year, Bezirgiannidis et al [58] suggested to monitor transmission queues within CGR as they increase the earliest transmission opportunity (CGR-ETO). On the same paper, a complementary overbooking management innovation enables proactive reforwarding of bundles whose place in the outbound queue was taken by subsequent higher priority traffic.…”

“…is not empty then (25) procedure (the overbooking management procedure defined in [58] aims at reordering the local outbound queues when bundles with higher priorities replace less urgent bundles; since in this work we assume all bundles have the same priority, this procedure is not described) (Algorithm 1, lines (25) to (26)). However, if the CGR Forward fails to find a suitable neighbor, the bundle is stored in special memory space called limbo waiting for a higher level process to either erase it or retry a new forwarding later (e.g., after a contact plan update).…”