Netflow was initially developed by Cisco in its Quality of Service (QoS) program. It is a switching method that allows more efficient switching of packets according to the type of packet.
cflowd was developed to collect and analyze the information available from NetFlow flow-export. It allows the user to store the information and enables several views on the data. It produces port matrices, AS matrices, network matrices and pure flow structures. The amount of data stored depends on the configuration of cflowd and varies from a few hundred Kbytes to hundreds of Mbytes in one day per router.
A user can store flow information and view the data in different ways. cflowd can produce matrices by autonomous system and network, and tables by port number and Internet protocol. With this information, engineers can evaluate traffic flow patterns between nodes on their networks and other networks. Engineers also can analyze traffic by application (for example, Web vs. e-mail vs. streaming audio vs. FTP) as well as by protocol (TCP vs. ICMP vs. DNS, for example). Insights from these types of analyses can help ISPs manage current networks and plan future network upgrades.
Jflow and Netflow are essentially identical.
some useful links to go-through,
1) http://www.proquesys.com/corporate/resources/whitepapers/the-netflowsflowcflowjflow-flow-dilemma/
2) http://kb.juniper.net/index?page=content&id=KB12512&actp=RSS&smlogin=true
3) http://en.wikipedia.org/wiki/Netflow
thanks
raheel