Library /sys$common/syshlp/ncphelp.hlb LOOP, NODE, COUNT number  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Specifies the number of blocks to be sent during loopback testing over
 the node. The count must be a decimal integer in the range of 1
 through 65535. If the parameter is omitted,  only one block is looped.