Correlation　of　network　nodes　in　terms　of　round-trip-time　(RTT)　can　be　quantified　by　the　similarity　metric　which　is　defined　as　the　extent　to　which　two　source　nodes　have　the　same　changing　trends　in　terms　of　RTT　to　the　same　destination　node.　With　this　definition,　the　effects　of　path　length,　more　specifically,　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　such　correlation　is　analyzed.　Our　analysis　shows　that　path　length　ratios　from　1:1　to　8:1　have　obviously　more　positive　effects　on　the　upward　trend　of　similarity　when　the　common　path　load　increases　or　the　private　path　loads　decrease　and　that　similarity　will　get　better　when　path　length　ratio　gets　higher　while　path　load　combinations　remain　the　same.　©　2012　Springer-Verlag　Berlin　Heidelberg.