The optional Assistant System argument specifies a MOP
    client entity, from which an assistant address can be
    obtained.   This argument is meaningful for LAN circuits
    only.  The assistant address is the LAN address of the
    node to be used as the loopback assistant.

    The involvement of the assistant depends on the Assistance
    Type parameter. For assistance of type none (the default),
    no assistant is needed, and is ignored if specified. For
    other values, an assistant is required.

    An assistant can be specified either by including an
    Assistant Address or Assistant System argument in the
    command line, but not both.  If neither is provided, then
    an assistant is located by first sending a request to the
    loopback assistant multicast address.

    Address information specifying the node to receive the
    loop is required for the loop mop circuit command.  If the
    Address argument is not specified in the command, then the
    Client argument must be specified so the address
    information can be obtained from the MOP Client database.

    loop  [node node-id] mop circuit circuit-name -
      address lan-address, -
      assistance type transmit-receive-or-full, -
      assistant system client-name [,optional arguments...]

    loop  [node node-id] mop circuit circuit-name -
      client client-name, -
      assistance type transmit-receive-or-full, -
      assistant system client-name [,optional arguments...]

    Examples:

    loop mop circuit fddi-1 -
      address 08-00-2b-00-33-44, -
      assistant system barbar, - ! Client barbar has Assistant Address
      assistance type full

    loop mop circuit csmacd-1 -
      client foofoo, -            ! Client foofoo gives loop Address
      assistant system barbar, -  ! barbar gives Assistant Address
      assistance type transmit