Source-specific routing (not to be confused with source routing) is a routing technique where routing decisions depend on both the source and the destination address of a packet. Source-specific routing solves some difficult problems related to multihoming, notably in edge networks, and is therefore a useful addition to the multihoming toolbox. In this paper, we describe the semantics of source-specific packet forwarding, and describe the design and implementation of a source-specific extension to the Babel routing protocol as well as its implementation -to our knowledge, the first complete implementation of a sourcespecific dynamic routing protocol -, including a disambiguation algorithm that makes our implementation work over widely available networking APIs. We further discuss interoperability between ordinary next-hop and source-specific dynamic routing protocols. Our implementation has seen a moderate amount of deployment, notably as a testbed for the IETF Homenet working group.

In overlay networks, both local and long-distance links appear as a single hop to a routing protocol. Traditional routing metrics (based on hop count or packet loss) fail to take the differences between such links into account. In this paper, we study a metric based on packet delay that has been designed to improve routing in overlay networks. We show a lightweight technique for measuring delay asynchronously, and show how to use the data it provides for constructing a routing metric.Using delay naively leads to persistent routing oscillations, so our routing protocol implements a number of features to bound the frequency of oscillations. We show that our protocol causes no oscillations in real-world tests, and has oscillations with a period on the order of minutes in artificially constructed worstcase setups.

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