An ISP can purchase wholesale bandwidth from an NSP which provides connectivity for their customers. Customers then access the network through their ISP last mile infrastructure which in turn connects to the NSP backbone. From there, the NSP routes all traffic and provides the infrastructure needed for network connectivity. The NSP builds, maintains and expands its infrastructure to meet traffic demands. The ISP is responsible for its own network, sales, marketing and customer service. ISPs can also purchase other services from an nsp such as cloud-based services or Web hosting