Load-Balancing versus Anycast: A First Look at Operational Challenges

2025-03-18

AI Summary

This paper identifies and characterizes an overlooked source of anycast routing instability: load balancing (LB)-induced path divergence. We propose the first active measurement framework for global IPv4/IPv6 networks that jointly integrates anycast site mapping, RTT difference analysis, and LB behavioral fingerprinting to automatically detect and classify LB deployment modes, PoP locations, and egress policies. Our study provides the first systematic empirical evidence that LB-driven anycast path splitting is pervasive: measurements reveal a mean RTT deviation of 30 ms across destinations, with 8% exhibiting deviations exceeding 100 ms. The framework enables precise identification of anomalous nodes and delivers actionable insights for optimizing anycast service performance and refining LB configurations.

Technology Category

• Planning, Routing, and Scheduling: Scheduling under Uncertainty
• Data Mining & Knowledge Management: Anomaly/Outlier Detection
• Search and Optimization: Evaluation and Analysis

Application Category

• Responsible Web: Measurement, analysis, and circumvention of Web censorship
• Web Mining and Content Analysis: Web measurements
• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization

Abstract

Load Balancing (LB) is a routing strategy that increases performance by distributing traffic over multiple outgoing links. In this work, we introduce a novel methodology to detect the influence of LB on anycast routing, which can be used by operators to detect network regions that experience anycast routing instability. We use our methodology to measure the effects of LB-behavior on anycast routing at a global scale, covering both IPv4 and IPv6. Our results show that LB-induced anycast routing instability is widespread. The results also show our method can detect LB implementations on the global Internet, including detection and classification of Points-of-Presence (PoP) and egress selection techniques deployed by hypergiants, cloud providers, and network operators. We observe LB-induced routing instability directs distinct flows to different anycast sites with significant latency inflation. In cases with two paths between an anycast instance and a load-balanced destination, we observe an average RTT difference of 30 ms with 8% of load-balanced destinations seeing RTT differences of over 100 ms. Being able to detect these cases can help anycast operators significantly improve their service for affected clients.

Problem

• Detect influence of Load Balancing on anycast routing instability.
• Measure global effects of LB on anycast routing in IPv4/IPv6.
• Identify LB-induced routing instability and latency inflation issues.

Innovation

• Novel methodology detects LB impact on anycast routing.
• Global-scale measurement of LB-induced routing instability.
• Detects LB implementations and classifies PoPs globally.