[ns] Why routing is performed on layer 2 in IEEE 802.11s wireless mesh networks standard

[Ghada Al-Mashaqbeh]

  Dear all,
   
  I just want to find a reasonable justfications of why the IEEE 802.11s 
standard have specified that routing must take place at layer 2 of the protocol 
stack not layer 3? and which is better routing on layer 2 or layer 3 of the 
protocol stack?
   
  Thanks,
   
  Ghada