The clock source priority in descending order in the format of a,b,c,d,e,f in which a through f should be replaced with 1 through 6 which has the same meaning as the options of mcmTimingPort and are repeated as follows: 0 - unknown 1 - internal 2 - link 3 - t1Port1 4 - t1Port2 5 - t1Port3 6 - t1Port4 For example, '2,5,4,6,3,1' will set the priority of the clock source with link first, followed by t1Port3, followed by t1Port2, followed by t1Port4, followed by t1Port1, followed by internal.