Resilient Access Networks using Redundant Signalling

 David Andersen

 This talk discusses the design and implementation of a Resilient 
 Access Networks (RAN), which improves the end-to-end availability 
 Internet clients to servers around the Internet.  A RAN focuses on 
 ``last-mile'' access network faults and request/response-based 
 applications, and improves availability in two ways: First, by taking 
 advantage of IP-layer multihoming to recover from faults faster than 
 current IP-layer methods, and second, by using an overlay network of 
 cooperating RAN clients to route requests and responses to hosts 
 outside the overlay.  

 A RAN implements two mechanisms to improve client-perceived 
 availability without excessively burdening servers. The first is a 
 heuristic to systematically probe the several different ways of 
 communicating with a server, and the second is a simple client-side
 modification that eliminates any extra state at servers.  We have
 implemented a Web proxy system using RAN and deployed it in our lab.