The LSK parameter (0-15) contains the key for the load distribution of all traffic on a link set among the links allocated to it.
The link table of each linkset contains 16 elements each filled with an active link of this link set. When routing a MSU the link table element is selected with the help of the SLS field (4 bit: 0000 …1111 or decimal: 0…15).
Which active link is used for routing MSU dependson the way links distributed over the link table. The LSK of the link set influences the allocation of the avaliable active links to the 16 elements of link table. Finally this means that the LSK determines the assignment of a given SLS to the active link to be chosen.
The link table is divided into to called traffic units. A traffic unit can occupy 1, 2 up to 16 elements of the link table. All elements occupied by the same traffic unit are filled with the same active link.
LSK specifies the maximum number of active links which can be used for message routing. To do this. the decimal LSK is converted into a binary value. The number of bits which is set to 1 is decisive for the number of traffic units:
Number of trafic units = 2 onto number of binary 1s in the LSK
e.g. LSK=5: binary 0101 (two 1s) number of traffic units= 2 onto 2= 4
That means that linkset will consist of this 4 of traffic units.
Number of link table elements (SLS value) per traffic unit = 4
(4 x 4 = 16)
That value is good only for 4 links in linkset…with this number of links and LSK=5 you will have equal distribution of MSU’s per links.