Nowadays　many　P2P　applications　over　the　Internet　utilize　sophisticated　protocols　and　employ　various　techniques　to　avoid　detection　and　recognition　with　standard　measurement　tools.　The　communication　analysis　of　p2p　network　is　significant　for　recognizing　P2P　traffic　and　managing　P2P　applications　effectively.　In　this　paper,　Skype　is　studied　as　a　case　to　identify　P2P　traffic　and　measure.　an　overlay　network　of　P2P　system.　Because　Skype　protocol　is　proprietary　and　its　control　information　is　encrypted　little　is　understood　about　Skype　network.　We　analyzed　large　amounts　of　data　of　Skype　traffic　and　extracted　many　application　level　signatures.　Based　on　such　signatures,　we　can　identify　Skype　traffic,　then　an　effective　tool　named　Super　Nodes　Collecting　and　Probing　Platform　(SNCPP)　was　designed　to　measure　the　overlay　of　Skype　network.　The　SNCPP　probes　online　super　nodes　in　real-time,　and　it　displays　the　distribution　in　a　three-dimensional　world　map.　The　results　in　this　paper　should　be　useful　for　future　architects　of　P2P　overlay　networks　as　well　as　for　network　security　management.