what does thos code mean of TC_LINKKEY_JOIN

Hi  all
       
       what  is  the different  between disable and enable  the  TC_LINKKEY_JOIN

       i  found  that  when  i  disable  the TC_LINKKEY_JOIN.  i could  using the long address mode to send the msg ,
      
       it  always return ZNwkInvalidRequest ( 0xc2 )
 
         


#if !defined OSALMEM_LL_BLKSZ
#if defined NONWK
#define OSALMEM_LL_BLKSZ          (OSALMEM_ROUND(6) + (1 * OSALMEM_HDRSZ))
#else
/*
 * Profiling the sample apps with default settings shows the following long-lived allocations
 * which should live at the bottom of the small-block bucket so that they are never iterated over
 * by osal_mem_alloc/free(), nor ever considered for coalescing, etc. This saves significant
 * run-time throughput (on 8051 SOC if not also MSP). This is dynamic "dead space" and is not
 * available to the small-block bucket heap.
 *
 * Adjust this size accordingly to accomodate application-specific changes including changing the
 * size of long-lived objects profiled by sample apps and long-lived objects added by application.
 */
#if defined ZCL_KEY_ESTABLISH_OLD // CBKE no longer uses long lived memory allocations.
#define OSALMEM_LL_BLKSZ          (OSALMEM_ROUND(526) + (32 * OSALMEM_HDRSZ))
#elif defined TC_LINKKEY_JOIN
#define OSALMEM_LL_BLKSZ          (OSALMEM_ROUND(454) + (21 * OSALMEM_HDRSZ))
#elif ((defined SECURE) && (SECURE != 0))
#define OSALMEM_LL_BLKSZ          (OSALMEM_ROUND(418) + (19 * OSALMEM_HDRSZ))
#else
#define OSALMEM_LL_BLKSZ          (OSALMEM_ROUND(417) + (19 * OSALMEM_HDRSZ))
#endif
#endif
#endif