@@ -64,7 +64,6 @@ All GTP-U tunnels are managed in a Linux Thread, that have partially ITTI design
3. incoming packets are sent to the tunnel creator using a C callback (the callback function is given in tunnel creation order). The callback should not block
# 3. CU F1AP messages #
## startup
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@@ -170,7 +169,17 @@ The data path by itself doesn't make any difficulty:
The SRB are sent in DU RRC tasks via itti F1AP_UL_RRC_MESSAGE (see above the processing)
2. For DL, pdcp (in CU for DRBs) calls rlc_data_req (by a decoupling queue and thread rlc_data_req_thread, so function du_rlc_data_req() or enqueue_rlc_data_req()). in DU, assuming the gtp-u tunnel exists, a reception call back (du_dl_recv()) decapsulate the gtp-u packet and calls du_rlc_data_req()
Hereafter the processing design, that doesn't require to setup a new context storage, as we can use the GTP-U internal tables: rnti+rb=>teid for outgoing gtp-u packets and teid=>rnti+rb for incoming gtp-u packets
Hereafter the processing design, that doesn't require to setup a new context storage, as we can use the GTP-U internal tables: rnti+rb=>teid for outgoing gtp-u packets and teid=>rnti+rb for incoming gtp-u packets
In CU case, the DRB tunnel to DU and the tunnel on N3 have the same key (rnti, rb id), but they run in two different GTP-U instances.
Each instance binds on diffrent sockets.
For F1-U, both DU and CU binds on the full quadruplet (IP source, port source, IP destination, port destination) from the configuration file parameters:
CU: at cell level (same level as nr_cellid parameter), they are read if tr_s_preference = "f1"; is set
DU: in block MACRLCs, if tr_n_preference = "f1"; is set in this block
## tunnels setup
In GTP-U, TS 29.281 specifies a option header (NR RAN Container This extension header may be transmitted in a G-PDU over the X2-U, Xn-U and F1-U user plane interfaces), but it is not mandatory optional header (as is the N3 one).
