Network bottlenecks, firewalls, restrictions on IP Multicast availability and administrative policies have long prevented the use of multicast even where the fit seems obvious. The confusion around multicast poses a problem for large-scale pub/sub-based applications that need blazing speed even across WAN networks. There are a number of multicast protocols, but none is universally available. Thus relatively few applications are able to exploit multicast technology. Here, we present Quilt, a system that automatically weaves a patchwork of multicast regions each running different protocols, creating an efficient and scalable wide-area overlay. By dynamically exploring the environment at and between end-hosts, Quilt clusters nodes into patches, selecting the best multicast protocol from a developer-provided set on a patch-by-patch basis and adapting as needed. Quilt orchestrates inter-patch forwarding to maximize reliability while minimizing duplication. This paper discusses and then ...