The Network relies on an emerging technology called web services to foster the seamless exchange of data. While web services rely on many technical components to achieve these exchanges - including XML and schema - it also requires States and EPA to have a sophisticated connection to the Network called a "Node." A node is a web server that facilitates the interface between back-end database systems and the Network. It is an entity's "point of presence" on the Exchange Network.

States and EPA building the Network strongly recommend that participating states and others in the Network build a "node" which can both request (or "consume") data from the Network as well as "publish" data to the Network in response to requests from other Network nodes. However, some states have chosen to begin with a simpler version called a node client, or "client" before moving to a "node" later. A client can request data from other nodes but it does not actively listen and respond on its own to requests for data from other nodes or clients on the Network. It can still push data to the Network but that activity would be driven internally rather than at the request of other Network partners' nodes or clients.

States and EPA have developed several node and client configurations (see client and demonstrated node configurations below). As other states develop successful configurations, we will make an effort to publish them and make them available for download as well. The CDX and Exchange Network technical teams strongly advise all node builders to take advantage of these configurations because they are free, they are proven solutions and they will further your progress (and cost savings!) greatly whether you have chosen to develop a node or just start with a client.