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-== Radio Signalling Link (RSL)
-
-=== List of Messages
-
-The following tables list the RSL messages used by OsmoBTS A-bis/IP,
-grouped by their level of compliance with 3GPP TS 08.58.
-
-==== Messages Compliant With TS 08.58
-
-Specific additions and limitations apply, see the linked sections.
-
-.Messages compliant with TS 08.58
-[options="header",cols="10%,20%,45%,5%,20%"]
-|===
-| TS 08.58 § | This document § | Message | <-/-> | Received/Sent by OsmoBTS
-5+<| *Radio link layer management messages*
-| 8.3.1 | - | DATA REQUEST | <- | Received
-| 8.3.2 | - | DATA INDICATION | -> | Sent
-| 8.3.3 | - | ERROR INDICATION | -> | Sent
-| 8.3.4 | - | ESTABLISH REQUEST | <- | Received
-| 8.3.5 | - | ESTABLISH CONFIRM | -> | Sent
-| 8.3.6 | - | ESTABLISH INDICATION | -> | Sent
-| 8.3.7 | - | RELEASE REQUEST | <- | Received
-| 8.3.8 | - | RELEASE CONFIRM | -> | Sent
-| 8.3.9 | - | RELEASE INDICATION | -> | Sent
-| 8.3.10 | - | UNIT DATA REQUEST | <- | Received
-| 8.3.11 | - | UNIT DATA INDICATION | -> | Sent
-5+<| *DEDICATED CHANNEL MANAGEMENT MESSAGES*
-| 8.4.1 | <<CHANNEL_ACTIVATION>> | CHANNEL ACTIVATION | <- | Received
-| 8.4.2 | <<CHANNEL_ACTIVATION>> | CHANNEL ACTIVATION ACKNOWLEDGE | -> | Sent
-| 8.4.3 | <<CHANNEL_ACTIVATION>> | CHANNEL ACTIVATION NEGATIVE ACKNOWLEDGE | -> | Sent
-| 8.4.4 | - | CONNECTION FAILURE INDICATION | -> | Sent
-| 8.4.5 | - | DEACTIVATE SACCH | <- | Received
-| 8.4.6 | - | ENCRYPTION COMMAND | <- | Received
-| 8.4.7 | - | HANDOVER DETECTION | -> | Sent
-| 8.4.8 | <<MEASUREMENT_RESULT>> | MEASUREMENT RESULT | -> | Sent
-| 8.4.9 | <<MODE_MODIFY>> | MODE MODIFY | <- | Received
-| 8.4.10 | - | MODE MODIFY ACKNOWLEDGE | -> | Sent
-| 8.4.11 | - | MODE MODIFY NEGATIVE ACKNOWLEDGE | -> | Sent
-| 8.4.14 | - | RF CHANNEL RELEASE | <- | Received
-| 8.4.15 | <<MS_POWER_CONTROL>> | MS POWER CONTROL | <- | Received
-| 8.4.19 | - | RF CHANNEL RELEASE ACKNOWLEDGE | -> | Sent
-| 8.4.20 | <<SACCH_INFO_MODIFY>> | SACCH INFO MODIFY | <- | Received
-5+<| *COMMON CHANNEL MANAGEMENT MESSAGES*
-| 8.5.1 | <<BCCH_INFORMATION>> | BCCH INFORMATION | <- | Received
-| 8.5.2 | - | CCCH LOAD INDICATION | -> | Sent
-| 8.5.3 | <<CHANNEL_REQUIRED>> | CHANNEL REQUIRED | -> | Sent
-| 8.5.5 | <<PAGING_COMMAND>> | PAGING COMMAND | <- | Received
-| 8.5.6 | - | IMMEDIATE ASSIGN COMMAND | <- | Received
-| 8.5.8 | <<SMS_BROADCAST_COMMAND>> | SMS BROADCAST COMMAND | <- | Received
-5+<| *TRX MANAGEMENT MESSAGES*
-| 8.6.1 | <<RF_RESOURCE_INDICATION>> | RF RESOURCE INDICATION | -> | Sent
-| 8.6.2 | <<SACCH_FILLING>> | SACCH FILLING | <- | Received
-| 8.6.4 | - | ERROR REPORT | -> | Sent
-|===
-
-==== Messages Specific to OsmoBTS
-
-.Messages specific to OsmoBTS, not found in 3GPP TS 08.58
-[options="header",cols="15%,15%,45%,5%,20%"]
-|===
-2+| This document § | Message | <-/-> | Received/Sent by OsmoBTS
-5+<| *User Plane Transport Management* (<<user_plane_txp_mgmt>>)
-.3+.| <<rsl_crcx>> | <<rsl_crcx_msg>> | RSL Create Connection (CRCX) | <- | Received
- | <<rsl_crcx_msg_ack>> | RSL Create Connection (CRCX) ACK | -> | Sent
- | <<rsl_crcx_msg_nack>> | RSL Create Connection (CRCX) NACK | -> | Sent
-.3+.| <<rsl_mdcx>> | <<rsl_mdcx_msg>> | RSL Modify Connection (MDCX) | <- | Received
- | <<rsl_mdcx_msg_ack>> | RSL Modify Connection (MDCX) ACK | -> | Sent
- | <<rsl_mdcx_msg_nack>> | RSL Modify Connection (MDCX) NACK | -> | Sent
-.3+.| <<rsl_dlcx>> | <<rsl_dlcx_msg>> | RSL Delete Connection (DLCX) | <- | Received
- | <<rsl_dlcx_msg_ack>> | RSL Delete Connection (DLCX) ACK | -> | Sent
- | <<rsl_dlcx_msg_nack>> | RSL Delete Connection (DLCX) NACK | -> | Sent
- | <<rsl_dlcx_ind>> | <<rsl_dlcx_ind_msg>> | RSL Delete Connection (DLCX) Indication | -> | Sent
-5+<| *IPA style PDCH Management* (<<ipa_style_pdch_mgmt>>)
-.3+.| <<pdch_act>> | <<rsl_pdch_act>> | RSL PDCH Activation | <- | Received
- | <<rsl_pdch_act_ack>> | RSL PDCH Activation ACK | -> | Sent
- | <<rsl_pdch_act_nack>> | RSL PDCH Activation NACK | -> | Sent
-.3+.| <<pdch_deact>> | <<rsl_pdch_deact>> | RSL PDCH Deactivation | <- | Received
- | <<rsl_pdch_deact_ack>> | RSL PDCH Deactivation ACK | -> | Sent
- | <<rsl_pdch_deact_nack>> | RSL PDCH Deactivation NACK | -> | Sent
-|===
-
-==== Messages Not Implemented by OsmoBTS
-
-.3GPP TS 08.58 messages not implemented by OsmoBTS
-[options="header",cols="10%,90%"]
-|===
-| TS 08.58 § | Message
-2+<| *DEDICATED CHANNEL MANAGEMENT MESSAGES*
-| 8.4.12 | PHYSICAL CONTEXT REQUEST
-| 8.4.13 | PHYSICAL CONTEXT CONFIRM
-| 8.4.16 | BS POWER CONTROL
-| 8.4.17 | PREPROCESS CONFIGURE
-| 8.4.18 | PREPROCESSED MEASUREMENT RESULT
-| 8.4.21 | TALKER DETECTION
-| 8.4.22 | LISTENER DETECTION
-| 8.4.23 | REMOTE CODEC CONFIGURATION REPORT
-| 8.4.24 | ROUND TRIP DELAY REPORT
-| 8.4.25 | PRE-HANDOVER NOTIFICATION
-| 8.4.26 | MULTIRATE CODEC MODIFICATION REQUEST
-| 8.4.27 | MULTIRATE CODEC MODIFICATION ACKNOWLEDGE
-| 8.4.28 | MULTIRATE CODEC MODIFICATION NEGATIVE ACKNOWLEDGE
-| 8.4.29 | MULTIRATE CODEC MODIFICATION PERFORMED
-| 8.4.30 | TFO REPORT
-| 8.4.31 | TFO MODIFICATION REQUEST
-2+<| *COMMON CHANNEL MANAGEMENT MESSAGES*
-| 8.5.4 | DELETE INDICATION
-| 8.5.7 | SMS BROADCAST REQUEST
-| 8.5.9 | CBCH LOAD INDICATION
-| 8.5.10 | NOTIFICATION COMMAND
-2+<| *TRX MANAGEMENT MESSAGES*
-| 8.6.3 | OVERLOAD
-2+<| *LOCATION SERVICES MESSAGES*
-| 8.7.1 | LOCATION INFORMATION
-|===
-
-
-=== Message Limitation Details
-
-[[CHANNEL_ACTIVATION]]
-==== Channel Activation
-
-When used on a timeslot using the non-standard channel combination
-'NM_CHANC_OSMO_TCHFull_TCHHalf_PDCH' as configured by OML, the regular
-RSL channel activation procedures can not only be used for activation
-of circuit-switched channels, but also for activation of a PDCH.
-
-See <<OSMOCOM_DYN_TS>>.
-
-NOTE:: Do not confuse this with the IPA style _PDCH ACT_ type
-dynamic PDCH protocol employed by nanoBTS devices (<<ipa_style_pdch_mgmt>>).
-
-[[MEASUREMENT_RESULT]]
-==== Measurement Result
-
-Conforms to 3GPP TS 08.58 § 8.4.8 with this limitation:
-
-._Measurement Result_ IE limitations
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.3.37 | MS Timing Offset | never sent by OsmoBTS
-|===
-
-[[MODE_MODIFY]]
-==== Mode Modify
-
-Conforms to 3GPP TS 08.58 § 8.4.9 with these limitations:
-
-._Mode Modify_ IE limitations
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.3.45 | Main channel reference | _ignored_
-| 9.3.53 | MultiRate Control | _ignored_
-| 9.3.54 | Supported Codec Types | _ignored_
-|===
-
-[[MS_POWER_CONTROL]]
-==== MS Power Control
-
-Conforms to 3GPP TS 08.58 § 8.4.15 with these limitations:
-
-._MS Power Control_ IE limitations
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.3.31 | MS Power Parameters | _ignored_
-|===
-
-
-[[SACCH_INFO_MODIFY]]
-==== SACCH Info Modify
-
-Conforms to 3GPP TS 08.58 § 8.4.20, with these exceptions:
-
-._SACCH Info Modify_ IE limitations
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.3.30 | System Info Type | See below for available types
-| 9.3.23 | Starting Time | not supported, provokes an _Error Report_ response
-|===
-
-._System Info Type_ values that can occur on the SACCH
-[options="header",width="50%",cols="20%,80%"]
-|===
-| Value | Name
-| 0x05 | RSL_SYSTEM_INFO_5
-| 0x06 | RSL_SYSTEM_INFO_6
-| 0x0d | RSL_SYSTEM_INFO_5bis
-| 0x0e | RSL_SYSTEM_INFO_5ter
-| 0x47 | RSL_EXT_MEAS_ORDER
-| 0x48 | RSL_MEAS_INFO
-|===
-
-[[BCCH_INFORMATION]]
-==== BCCH Information
-
-Conforms to 3GPP TS 08.58 § 8.5.1, with these limitations and extensions:
-
-._BCCH Information_ IE details
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.3.30 | System Info Type | See <<SACCH_INFO_MODIFY>> for available types
-| 9.3.11 | L3 Info | This IE may be included instead of a 9.3.39 _Full BCCH Info_ IE.
- The _Full BCCH Info_ takes precedence over _L3 Info_.
- To stop SI transmission, both of these IEs must be omitted.
-|===
-
-
-[[CHANNEL_REQUIRED]]
-==== Channel Required
-
-Conforms to 3GPP TS 08.58 § 8.5.3, with these limitations:
-
-._Channel Required_ message IE details
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.3.16 | Physical Context | never sent by OsmoBTS
-|===
-
-
-[[PAGING_COMMAND]]
-==== Paging Command
-
-Conforms to 3GPP TS 08.58 § 8.5.5, with these limitations:
-
-._Paging Command_ message IE details
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.3.49 | eMLPP Priority | _ignored_
-|===
-
-NOTE: If adding the identity to the paging queue fails, the BSC is not notified
-in any way.
-
-[[SMS_BROADCAST_COMMAND]]
-=== SMS Broadcast Command
-
-Conforms to 3GPP TS 08.58 § 8.5.8, with these limitations:
-
-._Broadcast Command_ message IE details
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.3.44 | SMSCB Channel Indicator | _ignored_
-|===
-
-
-[[RF_RESOURCE_INDICATION]]
-==== RF Resource Indication
-
-This message does not conform to 3GPP TS 08.58 § 8.6.1, in that it omits the
-_Resource Information_ IE that would contain the actual payload data, which
-renders this message void.
-
-._RF Resource Indication_ message IE exceptions
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.3.21 | Resource Information | OsmoBTS omits this IE, though TS 08.58
- specifies it as mandatory.
-|===
-
-
-[[SACCH_FILLING]]
-==== SACCH Filling
-
-Conforms to 3GPP TS 08.58 § 8.6.2, with these limitations:
-
-._SACCH Filling_ message IE limitations
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.3.30 | System Info Type | See <<SACCH_INFO_MODIFY>> for available types
-| 9.3.23 | Starting Time | _ignored_
-|===
-
-
-[[user_plane_txp_mgmt]]
-=== User Plane Transport Management
-
-This chapter defines the A-bis/IP specific RSL procedures that are
-introduced in addition to the 3GPP TS 08.58 standard procedures.
-
-In classic A-bis over E1, user plane traffic is carried over 16kBps
-sub-slots of 64kBps E1 time-slots according to ETSI/3GPP TS 08.60. As
-the E1 line is a dedicated line between BTS and BSC, no further
-addressing information is required.
-
-In A-bis/IP as described by the present document, new RSL procedures
-have been introduced to deal with the different properties of
-the underlying IP based transport medium.
-
-[[rsl_crcx]]
-==== RSL Create Connection (CRCX)
-
-This procedure is used by the BSC to request the BTS to allocate + bind
-to a BTS-local UDP port for the subsequent transmission of user-plane
-data via RTP.
-
-To do so, the BSC sends the *Create Connection (CRCX)* message. In case of
-successful outcome, the BTS responds with *Create Connection (CRCX)
-ACK*. In case of any error, the BTS responds with *Create Connection
-(CRCX) NACK*.
-
-See <<rsl_crcx_msg>>, <<rsl_crcx_msg_ack>>, <<rsl_crcx_msg_nack>>
-
-[[rsl_mdcx]]
-==== RSL Modify Connection (MDCX)
-
-This procedure is used by the BSC to request the BTS to modify an
-already-bound BTS-local UDP port for user-plane RTP. It is used in
-particular to configure the remote IP address and UDP port to which the
-BTS shall send user-plane RTP traffic. This remote address is normally
-either a Media Gateway (MGW) of some sort, but could also be the RTP
-socket of the corresponding other leg of a mobile-to-mobile call.
-
-To modify a user-plane connection, the BSC sends the *Modify Connection*
-message. In case of successful outcome, the BTS responds with
-*Modify Connection (MDCX) ACK*. In case of any error, the BTS responds
-with *Modify Connection (MDCX) NACK*.
-
-See <<rsl_mdcx_msg>>, <<rsl_mdcx_msg_ack>>, <<rsl_mdcx_msg_nack>>
-
-[[rsl_dlcx]]
-==== RSL Delete Connection (DLCX)
-
-This procedure is used by the BSC to request the BTS to delete an
-already-existing BTS-local UDP port for user-plane RTP.
-
-To delete a user-plane connection, the BSC sends the *Delete Connection
-(DLCX)* message. In case of successful outcome, the BTS responds with
-*Delete Connection (DLCX) ACK*. In case of any error, the BTS responds
-with *Delete Connection (DLCX) NACK*.
-
-See <<rsl_dlcx_msg>>, <<rsl_dlcx_msg_ack>>, <<rsl_dlcx_msg_nack>>
-
-[[rsl_dlcx_ind]]
-==== RSL Delete Connection (DLCX) Indication
-
-When a BTS-local UDP connection for user-plane RTP is automatically
-released at the time of RF CHANNEL RELEASE, the BTS sends a unilateral,
-non-acknowledged *RSL Delete Connection (DLCX) Indication* to the BSC.
-
-See <<rsl_dlcx_ind_msg>>
-
-
-[[rsl-dynamic-channels]]
-=== Dynamic Channel Combinations
-
-In the classic data model established by ETSI/3GPP for A-bis, each
-timeslot (channel) is configured using a static channel combination by
-means of A-bis OML. Particularly in presence of GPRS services, this
-is very unflexible and leads to inefficient use of air interface
-resources.
-
-As such, several methods have been implemented to overcome this
-limitation. The fundamental operation can be outlined like this:
-
-* Configuration of a particular _dynamic_ channel combination via OML
-* activation of TCH works like on a classic TCH channel combination
-* activation of PDCH requires some specific PDCH activation procedure
-
-There are two variants implemented in the OsmoBTS A-bis dialect:
-
-[[ipa_style_pdch_mgmt]]
-==== IPA Style Dynamic Channels
-
-This method is used when OML uses 'NM_CHANC_IPAC_TCHFull_PDCH' (0x80)
-as channel combination for the given time-slot.
-
-'IPA style' refers to 'ip.access' compatible PDCH activation and deactivation.
-
-When the IPA style dynamic channel combination _TCH/F or PDCH_
-is set, the non-standard 'PDCH ACTIVATE' (<<pdch_act>>) and 'PDCH
-DEACTIVATE' (<<pdch_deact>>) procedures are used for switching an idle
-channel into PDCH mode and back into idle mode.
-
-When the channel is used as TCH/F, regular circuit-switched activation
-is performed, like on any traditional TCH/F. However, the BSC must
-make sure to first disable the PDCH on the timeslot, before activating
-it as TCH/F. Likewise, any circuit-switched TCH/F on the channel must
-be deactivated using standard RSL signalling, before the specific PDCH
-related procedures are used to enable the PDCH.
-
-[[pdch_act]]
-===== PDCH Activate
-
-This procedure is used by the BSC to request the BTS to activate an
-IPA style dynamic TCH/F+PDCH channel in PDCH mode.
-
-The operation is not supported on any other physical channel type.
-
-See <<rsl_pdch_act>>, <<rsl_pdch_act_ack>>, <<rsl_pdch_act_nack>>
-
-[[pdch_deact]]
-===== PDCH Deactivate
-
-This procedure is used by the BSC to request the BTS to deactivate an
-active PDCH on any an IPA style dynamic TCH/F+PDCH channel.
-
-The operation is not supported on any other physical channel type.
-
-See <<rsl_pdch_deact>>, <<rsl_pdch_deact_ack>>, <<rsl_pdch_deact_nack>>
-
-===== IPA Style Dynamic Switchover Example
-
-.Part 1: example for dynamic channel switchover, for IPA style dynamic timeslots
-["mscgen"]
-----
-include::dyn_ts_ipa_style1.msc[]
-----
-
-.Part 2: example for dynamic channel switchover, for IPA style dynamic timeslots
-["mscgen"]
-----
-include::dyn_ts_ipa_style2.msc[]
-----
-
-
-[[OSMOCOM_DYN_TS]]
-==== Osmocom Style Dynamic Channels
-
-This method is in use when OML uses
-'NM_CHANC_OSMO_TCHFull_TCHHalf_PDCH' (0x90) for the given time-slot.
-
-The activation of PDCH is performed by using the regular 'RSL CHANNEL ACTIVATE'
-procedure according to <<CHANNEL_ACTIVATION>>, with these modifications:
-
-* The 'C-bits' part of the 'Channel Number' IE take the non-standard binary
- value 11000 (C5 thru C1 as seen in 3GPP TS 08.58 § 9.3.1).
-* The 'A-bits' part of the 'Activation Type' IE take the non-standard binary
- value 1111, with an additional fourth bit (add A4 to A3 thru A1 as seen in
- 3GPP TS 08.58 § 9.3.3; all remaining reserved bits as well as the 'R' bit are
- coded as zero).
-* The normally mandatory 'Channel Mode' IE is omitted; none of the optional IEs
- are included.
-
-Hence the message consists of exactly these IEs:
-
-.PDCH type _Channel Activation_ message IEs
-[options="header",cols="10%,30%,60%"]
-|===
-| TS 08.58 § | IE Name | Handling
-| 9.1 | Message discriminator | Dedicated Channel Management
-| 9.2 | Message type | CHANnel ACTIVation
-| 9.3.1 | Channel number | 'C-bits' 11000, plus TS bits as usual
-| 9.3.3 | Activation type | 'A-bits' 1111
-|===
-
-===== Osmocom Style Dynamic Switchover Example
-
-.Part 1: example for dynamic channel switchover, for Osmocom style dynamic timeslots
-["mscgen"]
-----
-include::dyn_ts_osmocom_style1.msc[]
-----
-
-.Part 2: example for dynamic channel switchover, for Osmocom style dynamic timeslots
-["mscgen"]
-----
-include::dyn_ts_osmocom_style2.msc[]
-----
-
-=== Message Formats and Contents
-
-[[rsl_crcx_msg]]
-==== Create Connection (CRCX)
-
-This message is sent by the BSC to the BTS to request the
-creation of a user-plane RTP connection for the specified *Channel
-number*.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Destination IP Address | <<RSL_IE_IPAC_REMOTE_IP>> | O | TV | 5
-| Destination IP Port | <<RSL_IE_IPAC_REMOTE_PORT>> | O | TV | 3
-| IP Speech Mode | <<RSL_IE_IPAC_SPEECH_MODE>> | O | TV | 2
-| RTP Payload Type 2 | <<RSL_IE_IPAC_RTP_PAYLOAD2>> | O | TV | 2
-|===
-
-[[rsl_crcx_msg_ack]]
-==== Create Connection (CRCX) ACK
-
-This message is sent by the BTS to the BSC to acknowledge the
-successful outcome of creating a user-plane RTP connection. It is sent
-in response to the *Create Connection (CRCX)*.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Connection Id | <<RSL_IE_IPAC_CONN_ID>> | M | TV | 3
-| Source IP Address | <<RSL_IE_IPAC_LOCAL_IP>> | O | TV | 5
-| Source IP Port | <<RSL_IE_IPAC_LOCAL_PORT>> | O | TV | 3
-| RTP Payload Type 2 | <<RSL_IE_IPAC_RTP_PAYLOAD2>> | O | TV | 2
-|===
-
-[[rsl_crcx_msg_nack]]
-==== Create Connection (CRCX) NACK
-
-This message is sent by the BTS to the BSC to signal the
-unsuccessful outcome of creating a user-plane RTP connection. It is
-sent in response to the *Create Connection (CRCX)*.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Destination IP Address | <<RSL_IE_IPAC_REMOTE_IP>> | O | TV | 5
-| Destination IP Port | <<RSL_IE_IPAC_REMOTE_PORT>> | O | TV | 3
-| Cause | 08.58 9.3.26 | O | TLV | >= 3
-|===
-
-
-[[rsl_mdcx_msg]]
-==== Modify Connection (MDCX)
-
-This message is sent by the BSC to the BTS to modify the
-properties of a user-plane RTP connection.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Connection Id | <<RSL_IE_IPAC_CONN_ID>> | O | TV | 3
-| Destination IP Address | <<RSL_IE_IPAC_REMOTE_IP>> | O | TV | 5
-| Destination IP Port | <<RSL_IE_IPAC_REMOTE_PORT>> | O | TV | 3
-| IP Speech Mode | <<RSL_IE_IPAC_SPEECH_MODE>> | O | TV | 2
-| RTP Payload Type 2 | <<RSL_IE_IPAC_RTP_PAYLOAD2>> | O | TV | 2
-|===
-
-[[rsl_mdcx_msg_ack]]
-==== Modify Connection (MDCX) ACK
-
-This message is sent by the BTS to the BSC to acknowledge the
-successful modification of a user-plane RTP connection. It is sent in
-response to a *Modify Connection (MDCX)*
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Connection Id | <<RSL_IE_IPAC_CONN_ID>> | O | TV | 3
-| Source IP Address | <<RSL_IE_IPAC_LOCAL_IP>> | C | TV | 5
-| Source IP Port | <<RSL_IE_IPAC_LOCAL_PORT>> | C | TV | 3
-| RTP Payload Type 2 | <<RSL_IE_IPAC_RTP_PAYLOAD2>> | O | TV | 2
-|===
-
-[[rsl_mdcx_msg_nack]]
-==== Modify Connection (MDCX) NACK
-
-This message is sent by the BTS to the BSC to signal the
-unsuccessful outcome of modifying the user-plane RTP connection for the
-specified Channel number. It is sent in response to the *Modify
-Connection (MDCX)*.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Cause | 08.58 9.3.26 | M | TLV | >= 3
-|===
-
-[[rsl_dlcx_ind_msg]]
-==== Delete Connection (DLCX) Indication
-
-This message is sent by the BTS to indicate the automatic
-deletion of a BTS-local UDP connection for user-plane RTP traffic at the
-time of RF Channel release.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Connection Id | <<RSL_IE_IPAC_CONN_ID>> | M | TV | 3
-| Connection Id | <<RSL_IE_IPAC_CONN_STAT>> | M | TV | 3
-| Cause | 08.58 9.3.26 | M | TLV | >= 3
-|===
-
-[[rsl_dlcx_msg]]
-==== Delete Connection (DLCX)
-
-This message is sent by the BSC to the BTS to request the
-disconnection of a user-plane RTP connection for the specified Channel
-number.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Connection Id | <<RSL_IE_IPAC_CONN_ID>> | O | TV | 3
-|===
-
-[[rsl_dlcx_msg_ack]]
-==== Delete Connection (DLCX) ACK
-
-This message is sent by the BTS to signal the successful
-outcome of deleting the user-plane RTP connection for the specified
-Channel number. It is sent in response to the *Delete Connection
-(DLCX)*.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Connection Id | <<RSL_IE_IPAC_CONN_ID>> | O | TV | 3
-| Connection Statistics | <<RSL_IE_IPAC_CONN_STAT>> | C | TV | 29
-|===
-
-[[rsl_dlcx_msg_nack]]
-==== Delete Connection (DLCX) NACK
-
-This message is sent by the BTS to signal the unsuccessful
-outcome of deleting the user-plane RTP connection for the specified
-Channel number. It is sent in response to the *Delete Connection
-(DLCX)*.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Connection Id | <<RSL_IE_IPAC_CONN_ID>> | O | TV | 3
-| Cause | 08.58 9.3.26 | M | TLV | >= 3
-|===
-
-[[rsl_pdch_act]]
-==== PDCH Activate
-
-This message is sent by the BSC to request the activation of a PDCH on
-a IPA style dynamic TCH/F+PDCH channel.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-|===
-
-NOTE:: This message is *not* used by Osmocom style dynamic channels
-
-[[rsl_pdch_act_ack]]
-==== PDCH Activate ACK
-
-This message is sent by the BTS to confirm the successful activation
-of a PDCH on a IPA style dynamic TCH/F+PDCH channel.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Frame Number | 08.58 9.3.8 | O | TV | 3
-|===
-
-NOTE:: This message is *not* used by Osmocom style dynamic channels
-
-[[rsl_pdch_act_nack]]
-==== PDCH Activate NACK
-
-This message is sent by the BTS to reject the successful activation
-of a PDCH on a IPA style dynamic TCH/F+PDCH channel.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Cause | 08.58 9.3.26 | M | TLV | >= 3
-|===
-
-NOTE:: This message is *not* used by Osmocom style dynamic channels
-
-[[rsl_pdch_deact]]
-==== PDCH Deactivate
-
-This message is sent by the BSC to request the deactivation of a PDCH
-on a IPA style dynamic TCH/F+PDCH channel.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-|===
-
-NOTE:: This message is *not* used by Osmocom style dynamic channels
-
-[[rsl_pdch_deact_ack]]
-==== PDCH Deactivate ACK
-
-This message is sent by the BTS to confirm the successful deactivation
-of a PDCH on a IPA style dynamic TCH/F+PDCH channel.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-|===
-
-NOTE:: This message is *not* used by Osmocom style dynamic channels
-
-[[rsl_pdch_deact_nack]]
-==== PDCH Deactivate NACK
-
-This message is sent by the BTS to reject the deactivation of a PDCH
-on a IPA style dynamic TCH/F+PDCH channel.
-
-[options="header"]
-[cols="30%,25%,15%,15%,15%"]
-|===
-| INFORMATION ELEMENT | REFERENCE | PRESENCE | FORMAT | LENGTH
-| Message discriminator | 08.58 9.1 | M | V | 1
-| Message type | <<own_msg_types>> | M | V | 1
-| Channel number | 08.58 9.3.1 | M | TV | 2
-| Cause | 08.58 9.3.26 | M | TLV | >= 3
-|===
-
-NOTE:: This message is *not* used by Osmocom style dynamic channels
-
-=== Information Element Codings
-
-[[own_msg_types]]
-==== A-bis/IP specific RSL Message discriminators
-
-The following message discriminators are used in addition to those
-indicated in 3GPP TS 08.58 Section 9.1:
-
-.OsmoBTS specific new message discriminators
-[options="header",cols="10%,50%,40%"]
-|===
-| Message Type | Message | This document §
-| 0x70 | Create Connection (CRCX) | <<rsl_crcx_msg>>
-| 0x71 | Create Connection (CRCX) ACK | <<rsl_crcx_msg_ack>>
-| 0x72 | Create Connection (CRCX) NACK | <<rsl_crcx_msg_nack>>
-| 0x73 | Modify Connection (MDCX) | <<rsl_mdcx_msg>>
-| 0x74 | Modify Connection (MDCX) ACK | <<rsl_mdcx_msg_ack>>
-| 0x75 | Modify Connection (MDCX) NACK | <<rsl_mdcx_msg_nack>>
-| 0x76 | Delete Connection (DLCX) Indication | <<rsl_dlcx_ind_msg>>
-| 0x77 | Delete Connection (DLCX) | <<rsl_dlcx_msg>>
-| 0x78 | Delete Connection (DLCX) ACK | <<rsl_dlcx_msg_ack>>
-| 0x79 | Delete Connection (DLCX) NACK | <<rsl_dlcx_msg_nack>>
-| 0x48 | PDCH Activate | <<rsl_pdch_act>>
-| 0x49 | PDCH Activate ACK | <<rsl_pdch_act_ack>>
-| 0x4a | PDCH Activate NACK | <<rsl_pdch_act_nack>>
-| 0x4b | PDCH Deactivate | <<rsl_pdch_deact>>
-| 0x4c | PDCH Deactivate ACK | <<rsl_pdch_deact_ack>>
-| 0x4d | PDCH Deactivate NACK | <<rsl_pdch_deact_nack>>
-|===
-
-==== A-bis/IP specific RSL IEIs
-
-The following Information Element Identifiers (IEIs) are used in
-addition to those indicated in 3GPP TS 08.58 Section 9.3:
-
-.A-bis/IP specific information elements
-[options="header",cols="10%,50%,40%"]
-|===
-| IEI | Name | This document §
-| 0x01 | RSL_IE_CHAN_NR | <<RSL_IE_CHAN_NR>>
-| 0xf0 | RSL_IE_IPAC_REMOTE_IP | <<RSL_IE_IPAC_REMOTE_IP>>
-| 0xf1 | RSL_IE_IPAC_REMOTE_PORT | <<RSL_IE_IPAC_REMOTE_PORT>>
-| 0xf3 | RSL_IE_IPAC_LOCAL_PORT | <<RSL_IE_IPAC_LOCAL_PORT>>
-| 0xf4 | RSL_IE_IPAC_SPEECH_MODE | <<RSL_IE_IPAC_SPEECH_MODE>>
-| 0xf5 | RSL_IE_IPAC_LOCAL_IP | <<RSL_IE_IPAC_LOCAL_IP>>
-| 0xf6 | RSL_IE_IPAC_CONN_STAT | <<RSL_IE_IPAC_CONN_STAT>>
-| 0xf8 | RSL_IE_IPAC_CONN_ID | <<RSL_IE_IPAC_CONN_ID>>
-| 0xfc | RSL_IE_IPAC_RTP_PAYLOAD2 | <<RSL_IE_IPAC_RTP_PAYLOAD2>>
-|===
-
-[[RSL_IE_CHAN_NR]]
-==== RSL_IE_CHAN_NR
-
-This information element is coded like 3GPP TS 08.58 Section 9.3.1,
-but in addition supports the following extended coding:
-
-* C5..C1 bits 0b11000 for PDCH type channels
-
-The TN-Bits are not re-defined in this case but use the same encoding
-as specified in TS 08.58 Section 9.3.1.
-
-NOTE:: The above extension is only valid on an Osmocom-style dynamic
-channel, having configured the 'NM_CHANC_IPAC_TCHFull_PDCH' channel
-combination by OML.
-
-[[RSL_IE_IPAC_REMOTE_IP]]
-==== RSL_IE_IPAC_REMOTE_IP
-
-This information element contains the remote (MGW side) IPv4 address in
-network byte order. It is encoded as fixed-size element with one byte
-IEI followed by four bytes IPv4 address.
-
-[[RSL_IE_IPAC_REMOTE_PORT]]
-==== RSL_IE_IPAC_REMOTE_PORT
-
-This information element contains the remote (MGW side) UDP port in
-network byte order. It is encoded as fixed-size element with one byte
-IEI followed by two bytes UDP port number.
-
-[[RSL_IE_IPAC_LOCAL_PORT]]
-==== RSL_IE_IPAC_LOCAL_PORT
-
-This information element contains the local (BTS side) IPv4 address in
-network byte order. It is encoded as fixed-size element with one byte
-IEI followed by two bytes UDP port number.
-
-[[RSL_IE_IPAC_SPEECH_MODE]]
-==== RSL_IE_IPAC_SPEECH_MODE
-
-This information element encodes the speech mode. It is set according
-to the voice codec used on the connection. It is encoded as a fixed-size
-element of two bytes, with one byte IEI followed by one byte Speech mode
-indicator.
-
-.A-bis/IP Speech Mode Indicator Values
-[options="header",width="40%",cols="20%,80%"]
-|===
-| Value | Description
-| 0x00 | TCH/F with FR codec
-| 0x01 | TCH/F with EFR codec
-| 0x02 | TCH/F with AMR codec
-| 0x03 | TCH/H with HR codec
-| 0x05 | TCH/H with AMR codec
-|===
-
-[[RSL_IE_IPAC_LOCAL_IP]]
-==== RSL_IE_IPAC_LOCAL_IP
-
-This information element contains the local (BTS side) IPv4 address in
-network byte order. It is encoded as fixed-size element with one byte
-IEI followed by four bytes IPv4 address.
-
-[[RSL_IE_IPAC_CONN_STAT]]
-==== RSL_IE_IPAC_CONN_STAT
-
-This information element contains statistics about the RTP connection.
-
-It is encoded as 29 bytes, with the first byte as IEI and 28 bytes
-fixed-length payload encoded as follows:
-
-.A-bis/IP Connection Statistics
-[options="header",width="60%",cols="15%,15%,70%"]
-|===
-| Offset | Size | Description
-| 0 | 4 | Total number of RTP packets sent
-| 4 | 4 | Total number of octets sent
-| 8 | 4 | Total number of RTP packets received
-| 12 | 4 | Total number of octets received
-| 16 | 4 | Total number of lost packets in Rx direction
-| 20 | 4 | Inter-arrival Jitter
-| 24 | 4 | Average transmission delay
-|===
-
-All the above values are encoded in network byte order.
-
-A detailed definition of the individual values is given in RFC 1889.
-
-[[RSL_IE_IPAC_CONN_ID]]
-==== RSL_IE_IPAC_CONN_ID
-
-This IE is a TV with a value length of two bytes. The value is a 16 bit
-connection ID in network byte order.
-
-
-[[RSL_IE_IPAC_RTP_PAYLOAD2]]
-==== RSL_IE_IPAC_RTP_PAYLOAD2
-
-This information element contains the RTP payload identifier, which is
-used in the PT (Payload Type) field of the RTP header in subsequent
-transmissions of the RTP flow.
-
-=== A-bis RSL Initialization / BTS bring-up
-
-Upon receiving the 'IPA RSL CONNECT' OML message by the respective
-'Baseband Transceiver' MO, the BTS proceeds with establishing a separate
-TCP connection for the given TRX.
-
-[[rsl-msc-pri]]
-.A-bis RSL BTS bring-up for primary TRX
-["mscgen"]
-----
-include::rsl-startup-pri.msc[]
-----
-
-[[rsl-msc-sec]]
-.A-bis RSL BTS bring-up for secondary TRXs
-["mscgen"]
-----
-include::rsl-startup-sec.msc[]
-----
-
-The initialization of the primary and secondary TRX slightly differ, as
-illustrated by the differences of <<rsl-msc-pri>> and <<rsl-msc-sec>>.
-Since the secondary TRX has no BCCH, it does not (need to) receive any 'RSL
-BCCH INFORMATION' messages from the BSC.
-