put ▁of ▁a ▁communication ; ▁i . e . ▁the ▁number ▁of ▁useful ▁information ▁bits ▁delivered ▁by ▁the ▁network ▁to ▁a ▁certain ▁destination ▁per ▁unit ▁of ▁time . ▁The ▁amount ▁of ▁data ▁considered ▁ex cludes ▁protocol ▁overhead ▁bits ▁as ▁well ▁as ▁re trans m itted ▁data ▁packets . ▁This ▁is ▁related ▁to ▁the ▁amount ▁of ▁time ▁from ▁the ▁first ▁bit ▁of ▁the ▁first ▁packet ▁sent ▁( or ▁delivered ) ▁until ▁the ▁last ▁bit ▁of ▁the ▁last ▁packet ▁is ▁delivered . ▁▁ ▁For ▁example , ▁if ▁a ▁file ▁is ▁transferred , ▁the ▁good put ▁that ▁the ▁user ▁experiences ▁corresponds ▁to ▁the ▁file ▁size ▁in ▁bits ▁divided ▁by ▁the ▁file ▁transfer ▁time . ▁The ▁good put ▁is ▁always ▁lower ▁than ▁the ▁through put ▁( the ▁gross ▁bit ▁rate ▁that ▁is ▁transferred ▁phys ically ), ▁which ▁generally ▁is ▁lower ▁than ▁network ▁access ▁connection ▁speed ▁( the ▁channel ▁capacity ▁or ▁band width ). ▁ ▁Ex amples ▁of ▁factors ▁that ▁cause ▁lower ▁good put ▁than ▁through put ▁are : ▁ ▁Pro tocol ▁overhead : ▁Typ ically , ▁transport ▁layer , ▁network ▁layer ▁and ▁sometimes ▁dat al ink ▁layer ▁protocol ▁overhead ▁is ▁included ▁in ▁the ▁through put , ▁but ▁is ▁ex cluded ▁from ▁the ▁good put . ▁ ▁Transport ▁layer ▁flow ▁control ▁and ▁con g estion ▁avoid ance : ▁For ▁example , ▁TCP ▁slow ▁start ▁may ▁cause ▁a ▁lower ▁good put ▁than ▁the ▁maximum ▁through put . ▁ ▁Ret r ans mission ▁of ▁lost ▁or ▁cor rupt ▁packets ▁due ▁to ▁transport ▁layer ▁automatic ▁repeat ▁request ▁( AR Q ),