Some characteristic attributes have a value that consists of a
    set of values. Use the add command to add one or more new values
    to a set value. For example:

    ncl> add node 0 osi transport cons filters {filter_2,filter_3}

    adds two new values, filter_2 and filter_3, to the set of values
    represented by the cons filters characteristic of the OSI
    Transport entity. The values are enclosed in { }, and if more
    than one value is to be added in the same command, each value is
    separated from the previous value by a comma.

    To specify the empty set (that is, a set with no values), specify
    {} as the value.

    Similarly, use the remove command to remove one or more values
    from a set value. For example:

    ncl> remove node 0 osi transport cons filters {filter_3}

    removes the value filter_3 from the set.

    Use the add and remove commands only on characteristics with set
    values (as indicated in the description of the characteristic).

    You can also use the set command to change the values of a set-
    valued characteristic. However, the set command replaces the
    current contents of the set with the values you specified.