A Practical Solution to the Client-LDNS Mismatch Problem

摘要

Internet services are often deployed in multiple (tens to hundreds) of geographically distributed data centers. They rely on Global Traffic Management (GTM) solutions to direct clients to the optimal data center based on a number of criteria like network performance, geographic location, availability, etc. The GTM solutions, however, have a fundamental design limitation in their ability to accurately map clients to data centers - they use the IP address of the local DNS resolver (LDNS) used by a client as a proxy for the true client identity, which in some cases causes suboptimal performance. This issue is known as the client-LDNS mismatch problem. We argue that recent proposals to address the problem suffer from serious limitations. We then propose a simple new solution, named "FQDN extension", which can solve the client-LDNS mismatch problem completely. We build a prototype system and demonstrate the effectiveness of the proposed solution. Using JavaScript, the solution can be deployed immediately for some online services, such as Web search, without modifying either client or local resolver.