Construction, administraion and maintenance of local area network Construction, operation and maintenance of network syetem Construction, operation and maintenance of network system Planning, construction, operation and maintenance of cold chain backbone network Administration and Maintenance of Enterprise Network 并列题名：Administration and Maintenance of Enterprise Network Establishment and maintenance of data network 并列题名：Construction, operation and maintenance of network syetem Construction and maintenance of shield tunnel 并列题名：Construction, operation and maintenance of network system