As part of the NCS 5500 Series, the Cisco NCS 5504, the Cisco NCS 5508 and Cisco NCS 5516 chassis have a Clos fabric design that interconnects the line cards with rear-mounted fabric modules. It supports up to six switch fabric cards; all fabric cards are directly connected to all line cards. With load balancing across fabric cards, the architecture achieves optimal bandwidth distribution within the chassis.