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CHAPTER 12 ■ DEVELOPING PEER-TO-PEER APPLICATIONS WITH WCF 379ramrameshreddy.blog.comFigure 12-2. Mesh networkMesh FlavorsBroadly speaking, two types of mesh networks are available, namely, the grouping and peerchannel. Each of these options has their respective service models. Grouping is primarily usedby the Data Replication service and is available in Windows XP (with SP2). The various peers,in the mesh, exchange messages by replicating records containing the data. Peer channel, onthe other hand, is primarily a message-based service and is available in WCF. The peers in themesh share data by building synchronous services. Both meshes have built-in security; groupingis implemented via a password and grouped certificates that are managed by the mesh.Peer channel security is also implemented via a password (to join the mesh) and individualcertificates that are managed directly by the applications in the mesh. Both types of meshessupport PNRP for node discovery; however, only peer channel supports a developer-suppliedmodel such as web service. While a grouping mesh implementation is unmanaged andaccessed via the Win32 API library, the peer channel is part of WCF, which is managed code.The connection types between the peers in a mesh can also be of two topology types: fullor partial. In full topology, each peer is connected to every other peer on the mesh. In partialtopology, a peer is connected only to a handful of other peers—most likely those with which itexchanges the most data and has affinity. The example in Figure 12-2 shows a partial meshbecause every peer is not connected to every other peer on the network. It is rare to comeacross a full topology mesh because it is not practical to operate in that mode. If there areN nodes in a full topology mesh, then each node is connected to N – 1 nodes at the same time.In other words, if there are 1,000 nodes in a mesh, each of the 1,000 nodes has a connectionramrameshreddyramrameshreddy