Virtually all public clouds today are run by single providers, and this creates near-monopolies, inefficient markets, and hinders innovation at the infrastructure level. There are current proposals to change this, by creating open architectures that allow providers of computing and storage resources to compete for tenant services at multiple levels, all the way down to the bare metal. Networking, however, is not part of this, and is viewed as a commodity much like power or cooling. In this paper we borrow ideas from the Internet architecture, and propose to structure the cloud datacenter network as a marketplace where multiple service providers can offer connectivity services to tenants. Our marketplace, NetEx, divides the network into independently managed pods of resources, interconnected with multiple providers through special programmable switches that play a role analogous to that of an IXP. We demonstrate the feasibility of such an architecture by a prototype in Mininet, and argue that this can be a way to provide innovation, competition, and efficiency in future cloud datacenter networks.