▁from ▁one ▁end ▁( o ften ▁referred ▁as ▁A - Loc ▁or ▁A - end ) ▁of ▁the ▁circuit ▁to ▁the ▁other ▁( Z - Loc ▁or ▁Z - end ). ▁ ▁It ▁may ▁be ▁detailed ▁enough ▁to ▁include ▁location , ▁floor , ▁row , ▁ra ck , ▁panel ▁and ▁port ▁for ▁each ▁circuit ▁component ▁or ▁it ▁may ▁simply ▁refer ▁to ▁another ▁previously ▁engine ered ▁circuit . ▁ ▁A ▁D LR ▁may ▁describe ▁an ▁end - to - end ▁circuit ▁that ▁compr ises ▁physical ▁or ▁virtual ▁circ uits . ▁ ▁As ▁an ▁example , ▁a ▁physical ▁facility ▁would ▁include ▁a ▁panel , ▁ra ck ▁and ▁port , ▁while ▁a ▁virtual ▁facility ▁may ▁be ▁a ▁channel ▁on ▁a ▁channel ized ▁circuit , ▁such ▁as ▁a ▁T 1 ▁on ▁a ▁previously ▁engine ered ▁D S 3 . ▁ ▁Ex plan ation ▁There ▁are ▁two ▁parts ▁to ▁a ▁circuit : ▁ ▁Phys ical ▁design / path ▁ ▁Log ical ▁design / path ▁ ▁The ▁design ▁team ▁is ▁responsible ▁to ▁find ▁the ▁best , ▁lowest - cost ▁path ▁for ▁the ▁circuit ▁being ▁designed , ▁and ▁get ▁the ▁physical ▁line ▁provision ed . ▁When ▁their ▁role ▁is ▁complete , ▁the ▁order ▁is ▁passed ▁to ▁another ▁team ▁who ▁take ▁care ▁of ▁establish ing ▁logical ▁design ▁and ▁access ibility ▁of ▁the ▁circuit . ▁Every ▁network ▁element ▁that ▁is ▁part ▁of ▁the ▁circuit ▁needs ▁to ▁be ▁built ▁and ▁checked . ▁The ▁D LR ▁provides ▁a ▁system atic ▁way ▁to ▁identify ▁the ▁network ▁elements ▁and ▁their ▁attributes . ▁With ▁the ▁aid ▁of