VAN - Value Added Network - a private/public network setup to transport the information of well-defined objects in a pre-defined standard format. E.g. XML, MARC21 or RFID formats for demand-supply chains, library automation system, product tracking.
Intranet - Is the physical network of networking and computing systems spread in a building or across buildings of the same organization.
extranet provides for employee to employee communication, employee to customer and organization to organization.
Ring - The computing systems connected such that the cable runs from one system to another and thus forming a closed circuit. Thin-wire Ethernet cable is used for the ring networks. E.g. IBM/NBF token ring LAN.
Mesh - A network of computing systems where each system is connected to all other systems. The connection could be either through external physical media like cable or a switch. 10Base-T/100BaseTX Ethernet or gigabit Ethernet cables are used.