Similarity　of　network　nodes　based　on　RTT　is　quantified　by　a　metric　that　is　defined　as　the　extent　to　which　two　source　nodes　have　the　same　changing　trends　of　RTT　to　the　same　destination　node.　By　this　definition,　the　effects　of　path　length,　in　particular,　the　path　length　ratio　that　is　defined　as　the　ratio　of　the　length　of　the　common　path　to　that　of　the　longer　private　path,　on　the　similarity　of　the　sources　are　studied.　Our　study　shows　that　path　length　ratios　from　2:1　to　4:1　as　well　as　from　7:1　to　9:1　have　more　positive　performance　than　others　according　to　the　overall　characteristics　of　the　effects　of　load　on　similarity.　As　the　result,　we　give　the　order　of　the　load　combinations　and　the　condition　regarding　path　load　and　length　for　getting　a　stronger　similarity.　Factor　analysis　on　the　load　can　reduce　the　27　load　combinations　to　2　factors,　i.e.,　the　heavy　common　load　and　heavy　private　load,　which　dominate　the　similarity.