If the tMSC server receives LCLS-Negotiation (request) with "Need_Send_Forward = Yes" and "Need_Receive_Forward = Yes" then it shall either:
return LCLS-Negotiation (response) set to "LCLS-Not-Allowed" or;
return LCLS-Negotiation (response) with value "Need_Send_Forward = Yes" and "Need_Receive_Forward = Yes" and set LCLS-Configuration IE to "Send Access DL, block local DL" (as shown in Figure X.2.1). If the BSS supports this configuration then LCLS will be allowed; otherwise LCLS will not be permitted.
If the tMSC server requires sending DL data to the terminating UE and receives LCLS-Negotiation (request) with "Need_Receive_Forward = Yes" and "Need_Send_Forward = No" during a LCLS negotiation request it shall either:
return LCLS-Negotiation (response) set to "LCLS-Not-Allowed" or;
set LCLS-Configuration IE to "connected both-way in the BSS and send access DL", return LCLS-Negotiation (response) with value "Need_Send_Forward = No" and "Need_Receive_Forward = Yes" and configure its Access MGW to isolate the network side termination from the access side termination when LCLS is established in order to avoid the forwarding of data from the oMGW/iMGW in the forward direction (as shown in Figure X.2.2), or;
return LCLS-Negotiation (response) with value "Need_Send_Forward = Yes" and "Need_Receive_Forward = Yes" and set LCLS-Configuration IE to "Send Access DL, block local DL" (as shown in Figure X.2.3). If the BSS supports this configuration then LCLS will be allowed; otherwise LCLS will not be permitted.
If the tMSC server requires receiving UL data from the terminating UE and it receives LCLS-Negotiation (request) with "Need_Receive_Backward = No" (as shown in Figure X.2.4) during a LCLS negotiation request then it shall either:
set LCLS-Configuration IE to "connected both-way in the BSS and bi-cast UL" and return LCLS-Negotiation (response) with "Need_Receive Backward = Yes" or;
set LCLS-Configuration IE to "connected both-way in the BSS and bi-cast UL", return LCLS-Negotiation (response) with "Need_Receive Backward = No" and configure its MGW to isolate its access side termination from the network side termination in order to avoid the forwarding of data in the backward direction through the CN.