A new approach to coding in content-based MANETs

Abstract

In content-based mobile ad hoc networks (CB-MANETs), random linear network coding (NC) can be used to reliably disseminate large files under intermittent connectivity. Conventional NC involves random unrestricted coding at intermediate nodes. This however is vulnerable to pollution attacks. To avoid attacks, a brute force approach is to restrict the mixing at the source. However, source restricted NC generally reduces the robustness of the code in the face of errors, losses and mobility induced intermittence. CB-MANETs introduce a new option. Caching is common in CB MANETs and a fully reassembled cached file can be viewed as a new source. Thus, NC packets can be mixed at all sources (including the originator and the intermediate caches) yet still providing protection from pollution. The hypothesis we wish to test in this paper is whether in CB-MANETs with sufficient caches of a file, the performance (in terms of robustness) of the restricted coding equals that of unrestricted coding.In this paper, we examine and compare unrestricted coding to full cache coding, source only coding, and no coding. As expected, we find that full cache coding remains competitive with unrestricted coding while maintaining full protection against pollution attacks.

On the Performance of the Cache Coding Protocol

“…Although this fact had been shown by simulations [16], our paper provides the first confirmation using analytical models to describe the system.…”

“…This paper presents a model and full characterization for the Cache Coding protocol presented in [16] as well as an approximated, yet accurate model for this and other protocols of interest. This analysis also considers an achievable lower bound for the number of transmissions in the network, which serves as the gold standard to measure various protocols, including the Cache coding protocol.…”

“…A pollution attack occurs when a malicious or faulty node injects invalid linear combinations of generation into the network [16]. These invalid coded packets can quickly propagate into other packets via recoding in relay nodes and can prevent destination node from decoding properly [11].…”

“…As an alternative, the authors of [16] proposed a protocol solution called Cache Coding. Cache Coding allows certified relay nodes to recode data only when they have decoded an entire generation.…”

“…Although [16] presents the protocol to cope with this vulnerability and identifies some bounds on the number of transmissions, a precise analytical model to characterize the performance of Cache Coding in multi-relay networks is missing. This performance analysis is critical to understand the security-delay trade-off imposed by the protocol.…”