RIM Message Transfer
from BSC or RNC to eNodeB
This chapter describes
how the SGSN transfers RIM messages to/from an MME (eNodeB) via GTPv1 protocol.
It also provides details about RIM messages transferred to/from an MME
transfer is one of the standards-based RAN Information
Management procedures supported by the SGSN.
RIM procedures provide
a generic mechanism for the exchange of arbitrary information between
RAN nodes. The RAN information is transferred via the SGSN core
network node(s). In order to make the
RAN information transparent for the core network, the RAN
information is included in a RIM container that shall not be interpreted
by the core network nodes.
The RAN information
is transferred in RIM containers from the source RAN node to the destination
RAN node by use of messages. The SGSN independently routes
and relays each message carrying the RIM container.
releases, the SGSN supported RIM messages from BSS/RNC
to another BSS/RNC belonging to a different or the same
SGSNover GTPv1 protocol. Now, the SGSN also supports
transfer of RIM messages to/from an MME (eNodeB) via
The SGSN uses existing
CLI to enable the RIM transfer functionality. Whether or
not the RIM message goes from/to BSC/RNC to/from
BSC/RNC or to/from eNodeB is determined by the
addressing. To transfer RIM messages to the MME (eNodeB),
- requires RIM functionality
be enabled for the SGSN.
- requires the DNS server
be configured to respond to a TAI-based DNS query
- requires the MME (eNodeB) address
be added to the SGSNs Call Control Profile
Other Feature or Products
For this feature to
work properly, the peer-MME for the eNodeB must
also support RIM message handling.
How It Works
All the messages used
for the exchange of RAN information contain the addresses of the
source and destination RAN nodes. An eNodeB is addressed
by tracking area identity (TAI) + eNodeB
The source RAN node
sends a message to its SGSN including the source and destination addresses. From
the destination address, the SGSN shall decide whether
or not it is connected to the destination RAN node. If
the destination address is that of an eNodeB, then the
SGSN uses the destination address to route the message, encapsulated
in a GTPv1 message, to the correct MME via the Gn interface.
The MME connected to
the destination RAN node decides which RAN node to send the message
based on the destination address or the RIM routing address.
Call Flows -
Transmitter of GTP RIM Msg
The following call
flow illustrates how the SGSN behaves as the transmitter of GTP RIM messages.
Figure 1. Transmitting
In the above
illustration, the RIM message is transferred to the peer SGSN as follows:
- Upon receiving a
RIM message from the network access BSS/RNC, the SGSN determines the RIM
routing address type. If the message indicates that the target is an eNodeB,
then SGSN searches for a locally configured MME address.
- If a locally
configured MME address is not available, then a DNS-SNAPTR query will be
initiated to determine the MME address.
- On receiving the
DNS response and upon getting a valid MME address, an appropriate GTP API would
- On invocation of
this API the GTP module will encode the RAN info relay message (as per TS
29.060) and dispatch the PDU to the peer MME.
Call Flows -
Receiver of GTP RIM Msg
The following call
flow illustrates how the SGSN behaves as the receiver of GTP RIM messages.
Figure 2. Receiving a
GTP RIM Message
In this case, the
SGSN has to decode the incoming GTP message correctly and forward the RIM
message to the destination RNC/BSS.
- SGSN would decode
the received GTP RAN info relay message and construct a RANAP or BSSGP RIM
actions would be taken to forward the RIM message to the destination RNC/BSS.
The RIM application
processes the decoded RIM PDU from the access application. The
routing area identifier (RAI) -- comprised
of the mcc, mnc, rac -- is extracted
from the destination address and is used to decide if the target
routing area (RA) is local. If the RAI
is locally available, the PDU is forwarded to either the
RANAP or BSSGP stack based on the RIM routing address discriminator
The SGSN has a global
list of local RAs. Each RA in turn has a list of RNCs and
NSEIs that control it. If the destination RA is local, the
list of NSEIs which serve the RAI is fetched. Each NSEI
is searched for a matching cell id in the cellid-list. The
PDU is then forwarded to the NSEI when signaling the BVCI.
If the RNC Id is in
the destination cell identifier, then the IuPS service
serving the local RAI is identified. The PDU is encoded
in a RIM container and forwarded to the corresponding RANAP stack
instance of that IuPS service.
If the eNodeB Id is
in the destination cell identifier, then the PDU will be
sent to the GTP app using the appropriate event.
address is resolved using the SGSN's local configuration or a DNS
query for the TAI present in the destination address. For
a successful DNS response, the PDU is encoded in a GTP
RIM container and forwarded to the peer-MME. The
SGTP service used will be the default SGTP service associated with
the GPRS service or the SGSN service under which the source BSS/RNC
was present. The RIM app drops a PDU if the DNS response
fails. There will no retransmission or state-maintenance
for the RIM PDU at the GTP-app.
The SGSN's RIM message
transfer from/to eNodeB functionality complies with the
- 3GPP TS 29.060
- 3GPP TS 23.003
- 3GPP TS 25.413
- 3GPP TS 48.018
- 3GPP TS 24.008
Configuring RIM Msg
Transfer to or from eNodeB
To enable successful
RIM message transfer to/from an eNodeB, the following
must be included in the SGSN's configuration:
- Configuring RIM functionality
to work on SGSN
- Associating previously
configured SGTP and IuPS services
- Configuring the peer-MME's
address, in one
or both of two ways
- Configuring the peer-MME
- Configuring the DNS
Configuring RIM Functionality
The following command
sequences are used to enable RAN information management (RIM) functionality
on the SGSN. The order in which these two configurations
are performed is not significant.
The first command sequence
enables RIM for the entire SGSN (global level).
The second command sequence
associates the RNC configuration, the part of the IuPS service
configuration governing the SGSN communication with any RNC, needs
to have the RIM functionality enabled.
rnc id rnc_id
Configured SGTP and IuPS Services
The SGTP service configuration
is a mandatory part of the SGSN's setup (refer to Configuring
an SGTP Service in the SGSN Administration Guide), so
an SGTP service configuration must already exist. The SGTP
service is needed to send and/or receive GTPv1 protocol
It is also a good idea
to associate the IuPS service for the SGSN service to use for communication
with the RAN.
The following illustrates
the minimum configuration required to associate the SGTP and IuPS
services for the RIM message transfers:
associate sgtp-service service_name context context_name
ran-protocol iups-service service_name
Configuring the peer-MME's
address - Locally
Use the Call Control
Profile to define the peer-MME address.
Use the tac keyword
to configure the tracking area code (TAC) of the
target eNodeB that maps to the peer-MME address. For
RIM message transfer, you also need to configure the Gn interface. The
following is an example of the configuration to use:
peer-mme tac tac_value prefer local address ip_address interface gn
- tac_value can
be an entry from 1 to 65535.
- ip_address is
the standard format address for either IPv4 or IPv6.
- gn is the interface
selection used for RIM message transfer.
peer-MME's address - for DNS Query
If using a DNS query
to determine the peer-MME RIM address, then the DNS server must be
pre-configured to respond to a TAI-based DNS query in the following format:
Monitoring and Troubleshooting
RIM Msg Transfer
The show command statistics
illustrated below, can be used to monitor or troubleshoot
this functionality. Note that the selected output is only
a portion of the information displayed by the command.
show gmm-sm statistics verbose
Direct Transfer Sent: 0 Direct Transfer Rcvd: 0
statistics verbose | grep RIM
show gmm-sm statistics verbose | grep RIM
RIM Message Statistics:
RIM Messages dropped:
due to RIM disabled in SGSN: 0 due to RNC not Capable: 0
due to RIM Routing Address not present: 0 due to RNC does not exist: 0
show sgtpc statistics
show sgtpc statistics verbose
RAN info Relay Msg:
Total messages received: 0 Total messages sent: 0
Total messages dropped: 0
due to DNS failure: 0
due to RIM disabled in SGSN: 0
due to Invalid Routing Addr: 0
show bssgp statistics
show bssgp statistics verbose
RAN Information messages received
RAN Information messages transmitted
RAN Information Request messages received
RAN Information Request messages transmitted
RAN Information ACK messages received
RAN Information ACK messages transmitted
RAN Information Error messages received
RAN Information Error messages transmitted
RAN Information Appln Error messages received
RAN Information Appln Error messages transmitted
RIM messages dropped
due to RIM disabled in SGSN
due to destination BSC not RIM capable
due to destination cell does not exist
due to invalid destination address