▁pass ▁through ▁the ▁sim ulator ▁and ▁be ▁affected ▁by ▁objects ▁within ▁the ▁simulation . ▁ ▁The ▁typical ▁method ology ▁is ▁that ▁real ▁packets ▁from ▁a ▁live ▁application ▁are ▁sent ▁to ▁the ▁em ulation ▁server ▁( where ▁the ▁virtual ▁network ▁is ▁sim ulated ). ▁The ▁real ▁packet ▁gets ▁' mod ulated ' ▁into ▁a ▁simulation ▁packet . ▁The ▁simulation ▁packet ▁gets ▁dem od ulated ▁into ▁a ▁real ▁packet ▁after ▁experien cing ▁effects ▁of ▁loss , ▁errors , ▁delay , ▁j itter ▁etc ., ▁thereby ▁transfer ring ▁these ▁network ▁effects ▁into ▁the ▁real ▁packet . ▁Thus ▁it ▁is ▁as - if ▁the ▁real ▁packet ▁flow ed ▁through ▁a ▁real ▁network ▁but ▁in ▁reality ▁it ▁flow ed ▁through ▁the ▁sim ulated ▁network . ▁ ▁Em ulation ▁is ▁widely ▁used ▁in ▁the ▁design ▁stage ▁for ▁valid ating ▁communication ▁networks ▁prior ▁to ▁deployment . ▁ ▁List ▁of ▁network ▁sim ul ators ▁There ▁are ▁both ▁free / open - source ▁and ▁propriet ary ▁network ▁sim ul ators ▁available . ▁Ex amples ▁of ▁notable ▁network ▁sim ul ators ▁/ ▁em ul ators ▁include : ▁▁▁▁ ▁OP NET ▁T et cos ▁Net Sim ▁ ▁NS 2 ▁/ ▁NS 3 ▁ ▁Us es ▁of ▁network ▁sim ul ators ▁ ▁Network ▁sim ul ators ▁provide ▁a ▁cost - effect ive ▁method ▁for ▁▁ ▁Network ▁design ▁validation ▁for ▁enter pr ises ▁/ ▁data ▁cent ers ▁/ ▁sensor ▁networks ▁etc . ▁ ▁Network ▁R ▁& ▁D ▁( More ▁than ▁ 7 0 % ▁of ▁all ▁Network ▁Research ▁paper ▁reference ▁a ▁network ▁sim ulator ) ▁▁