== Network Service (NS) === List of Messages The following tables list the NS messages used by OsmoPCU, grouped by their level of compliance with 3GPP TS 08.16. ==== Messages Compliant With 3GPP TS 08.16 The NS protocol is implemented inside libosmocore so none of the messages below are sent by OsmoPCU explicitly. Instead corresponding functions from libosmocore are called which send and receive messages as necessary. See <> for details on establishing NS connection. .Messages compliant with 3GPP TS 08.16 [options="header",cols="10%,10%,20%,35%,5%,20%"] |=== | TS 08.16 § | type code (hex) | This document § | Message | <-/-> | Received/Sent by OsmoPCU | 9.2.10 | 0x00 | <> | NS-UNITDATA | <-/-> | Received/Sent | 9.2.5 | 0x02 | <> | NS-RESET | <-/-> | Received/Sent | 9.2.6 | 0x03 | <> | NS-RESET-ACK | <-/-> | Received/Sent | 9.2.3 | 0x04 | <> | NS-BLOCK | <-/-> | Received/Sent | 9.2.4 | 0x05 | <> | NS-BLOCK-ACK | <-/-> | Received/Sent | 9.2.8 | 0x06 | <> | NS-UNBLOCK | <-/-> | Received/Sent | 9.2.9 | 0x07 | <> | NS-UNBLOCK-ACK | <-/-> | Received/Sent | 9.2.7 | 0x08 | <> | NS-STATUS | <-/-> | Received/Sent | 9.2.1 | 0x0a | <> | NS-ALIVE | <-/-> | Received/Sent | 9.2.2 | 0x0b | <> | NS-ALIVE-ACK | <-/-> | Received/Sent |=== ==== Messages Specific to OsmoPCU There are no OsmoPCU specific NS messages. ==== Messages Not Implemented by OsmoPCU All the NS protocol messages from 3GPP TS 08.16 are implemented in OsmoPCU. === Details on Compliant NS Messages [[ns_unit_data]] ==== NS-UNITDATA This PDU transfers one NS SDU (specified in 3GPP TS 08.18) between OsmoPCU and SGSN. Upon receiving it OsmoPCU passes it to BSSGP implementation to handle. It is also sent by BSSGP as necessary - see <> for details. It contains BVCI (<>) and NS SDU (<>) IEs. [[ns_reset]] ==== NS-RESET This message is send by OsmoPCU in order to initiate reset procedure described in 3GPP TS 08.16 § 7.3. The expected reply is NS-RESET-ACK (<>) message. If no expected reply is received in 3 seconds than the sending is retried up to 3 times. When this message is received it is replied with NS-RESET-ACK (<>). It might be ignored under conditions described in 3GPP TS 08.16 § 7.3.1. The message conforms to 3GPP TS 08.16 § 9.2.5 specification. It contains Cause (<>), NSVCI (<>) and NSEI (<>) IEs. [[ns_reset_ack]] ==== NS-RESET-ACK This message is sent as a response to proper NS-RESET (<>) message initiating reset procedure. The message conforms to 3GPP TS 08.16 § 9.2.6 specification. It contains NSVCI (<>) and NSEI (<>) IEs. [[ns_block]] ==== NS-BLOCK Upon receiving this message corresponding NS-VC is marked as blocked by OsmoPCU and NS-BLOCK-ACK (<>) reply is transmitted. When this message is sent by OsmoPCU corresponding NS-BLOCK-ACK (<>) reply is expected before NS-VC is actually marked as blocked. This behavior follows the blocking procedure described in 3GPP TS 08.16 § 7.2. The message conforms to 3GPP TS 08.16 § 9.2.3 specification. It contains Cause (<>) and NSVCI (<>) IEs. [[ns_block_ack]] ==== NS-BLOCK-ACK This message is sent by OsmoPCU automatically upon reception of correct NS-BLOCK (<>) message. It is expected as a reply for NS-BLOCK (<>) message sent by OsmoPCU. The message conforms to 3GPP TS 08.16 § 9.2.4 specification. It contains NSVCI (<>) IE. [[ns_unblock]] ==== NS-UNBLOCK Upon receiving this message corresponding NS-VC is unblocked by OsmoPCU and NS-UNBLOCK-ACK (<>) reply is sent. When this message is sent by OsmoPCU corresponding NS-UNBLOCK-ACK (<>) reply is expected before NS-VC is actually marked as unblocked. This behavior follows the blocking procedure described in 3GPP TS 08.16 § 7.2. The message conforms to 3GPP TS 08.16 § 9.2.8 specification. [[ns_unblock_ack]] ==== NS-UNBLOCK-ACK Receiving this message notifies OsmoPCU that NS-VC unblocking request is confirmed and thus NS-VC is marked as unblocked. This message is also sent as a reply to NS-UNBLOCK (<>) message. The message conforms to 3GPP TS 08.16 § 9.2.9 specification. [[ns_status]] ==== NS-STATUS This message is sent to inform other party about error conditions as a response to various unexpected PDUs or PDUs with unexpected/missing data. If this message is received for unknown NS-VC it is ignored in accordance with 3GPP TS 08.16 § 7.5.1, otherwise the error cause is logged if present in NS-STATUS. The message conforms to 3GPP TS 08.16 § 9.2.7 specification. It contains Cause (<>) and might (depending on actual error) contain NSVCI (<>), NS PDU (<>) and BVCI (<>) IEs. [[ns_alive]] ==== NS-ALIVE This message is sent periodically to test connectivity according to 3GPP TS 08.16 § 4.5.3. The expected response is NS-ALIVE-ACK (<>). If no such response arrives within given amount of time (3 seconds) than another NS-ALIVE message is sent and failed test attempt is recorded. After 10 failed attempts NS connection is considered dead and OsmoPCU tries to reconnect. The message conforms to 3GPP TS 08.16 § 9.2.1 specification. [[ns_alive_ack]] ==== NS-ALIVE-ACK This message is sent automatically in reply to NS-ALIVE (<>) message. The message conforms to 3GPP TS 08.16 § 9.2.2 specification. === Information Elements Overview All of the IEs handled by OsmoPCU are listed below, with limitations and additions to 3GPP TS 08.16 specified in more detail. ==== IEs Conforming to 3GPP TS 08.16 The following Information Elements are accepted by OsmoPCU. .IEs conforming to 3GPP TS 08.16 [options="header",cols="5%,10%,40%,5%,40%"] |=== | tag (hex) | TS 08.16 § | IE name | <-/-> | Received/Sent by OsmoPCU | 0x00 | 10.3.2 | Cause | <-/-> | Received/Sent | 0x01 | 10.3.5 | NSVCI | <-/-> | Received/Sent | 0x02 | 10.3.3 | NS PDU | <-/-> | Received/Sent | 0x03 | 10.3.1 | BVCI | <-/-> | Received/Sent | 0x04 | 10.3.6 | NSEI | <-/-> | Received/Sent |=== ==== IEs Not Conforming to 3GPP TS 08.16 All IEs defined in 3GPP TS 08.16 § 10.3 are supported by OsmoPCU. ==== Additional Attributes and Parameters There are no OsmoPCU specific additional Attributes and Parameters. === Details on IEs [[ie_cause]] ==== Cause This IE contains reason for a procedure or error as described in 3GPP TS 08.16 § 10.3.2. [[ie_nsvci]] ==== NSVCI This IE represents NSVCI identity described in <> and 3GPP TS 08.16 § 10.3.5. [[ie_nspdu]] ==== NS PDU This IE contains PDU (possibly truncated) which cause error described in NS-STATUS message (<>) as described in 3GPP TS 08.16 § 10.3.3. [[ie_nssdu]] ==== NS SDU This IE contains BSSGP data - see <> for details. [[ie_bvci]] ==== BVCI This IE represents BSSGP identity described in <> and 3GPP TS 08.16 § 10.3.1. [[ie_nsei]] ==== NSEI This IE represents NSEI identity described in <> and 3GPP TS 08.16 § 10.3.6. [[ns_init]] === Gb NS Initialization / PCU bring-up OsmoPCU binds and connects an UDP socket for NS using port numbers and IP information given by OsmoBTS via the PCU socket. OsmoBTS in turn receives this information from the BSC vi A-bis OML. Following successful initialization of the UDP socket, the reset procedure is initiated as described in <>.