Packet Aggregation May Harm Batched Network Coding

TL;DR

This paper investigates the effects of packet aggregation in batched network coding over UDP-Lite, revealing that excessive aggregation can reduce throughput and that careful, hop-by-hop optimization is necessary.

Contribution

It provides a preliminary analysis showing that aggressive packet aggregation may harm performance in BNC over UDP-Lite, highlighting the need for optimized, distributed strategies.

Findings

Aggressive packet aggregation can decrease throughput in BNC over UDP-Lite.

Hop-by-hop optimization may outperform simple aggregation schemes.

Casual integration of techniques with BNC can be counterproductive.

Abstract

Batched network coding (BNC) is a solution to multi-hop transmission on networks with packet loss. To be compatible with the existing infrastructure, BNC is usually implemented over UDP. A single error bit will probably result in discarding the packet. UDP-Lite is a variant of UDP that supports partial checksums. As long as the data covered by the checksum is correct, damaged payload will be delivered. With UDP-Lite, we can cope with other techniques such as payload aggregation of BNC packets to reduce the protocol overhead, and forward error correction to combat against bit errors. Unlike traditional transmissions, BNC has a loss resilience feature and there are dependencies between BNC packets. In this paper, we conduct a preliminary investigation on BNC over UDP-Lite. We show that aggregating as much as we can is not always the best strategy, and a hop-by-hop distributed efficiency optimization approach may lead to a worse throughput compared with the scheme without aggregation in a long network. These unnatural results caution that a casual integration of techniques with BNC can be harmful, and give us hints on future research directions.