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