A method performed by data processing apparatus, the method comprising: operating one or more virtual machines on the data processing apparatus, wherein the one or more virtual machines are hosted by a host operating system that executes on the data processing apparatus, wherein the host operating system performs operations comprising: receiving, using one or more service bridges that execute in the host operating system, a plurality of requests from the one or more virtual machines, wherein each service bridge is associated with a different virtual machine of the one or more virtual machines, and wherein each request is a request to interface with one or more external services; modifying, using a respective service bridge, each request to be processed by the one or more external services; and providing each modified request from the respective service bridge to the one or more external services, where the respective service bridge communicates with the one or more external services over a network, wherein each request in the plurality of requests is received by a paravirtualized socket at the respective virtual machine, where the paravirtualized socket adapter interfaces between the respective virtual machine and the corresponding service bridge using a shared memory ring buffer. operating one or more virtual machines on the data processing apparatus, wherein the one or more virtual machines are hosted by a host operating system that executes on the data processing apparatus, wherein the host operating system performs operations comprising: receiving, using one or more service bridges that execute in the host operating system, a plurality of requests from the one or more virtual machines, wherein each service bridge is associated with a different virtual machine of the one or more virtual machines, and wherein each request is a request to interface with one or more external services; modifying, using a respective service bridge, each request to be processed by the one or more external services; and providing each modified request from the respective service bridge to the one or more external services, where the respective service bridge communicates with the one or more external services over a network, receiving, using one or more service bridges that execute in the host operating system, a plurality of requests from the one or more virtual machines, wherein each service bridge is associated with a different virtual machine of the one or more virtual machines, and wherein each request is a request to interface with one or more external services; modifying, using a respective service bridge, each request to be processed by the one or more external services; and providing each modified request from the respective service bridge to the one or more external services, where the respective service bridge communicates with the one or more external services over a network, wherein each request in the plurality of requests is received by a paravirtualized socket at the respective virtual machine, where the paravirtualized socket adapter interfaces between the respective virtual machine and the corresponding service bridge using a shared memory ring buffer.