Protocol Layers and Messages

Protocol Layers and Messages

Last updated: December 3, 2008

This section is only applicable to the lab applications.

This section outlines in a very general sense, the test set's support for individual protocol layers, the procedures associated with them, and their respective messages. Messages not included here may be supported. Certain parameters of messages included here may not be supported.

Observation Point 1 - LAPDm Over-the-Air Messages

The Link Access Procedure on the Dm channel (LAPDm) is the protocol for use by the data link layer on the radio interface. The frame structure and procedures for proper operation of the LAPDm are described in GSM 04.06.

Operating Considerations

This observation point is not enabled by default. If you want to capture LAPDm messages using the WPA, you should enable LAPDm in the Test Set Message Filter Settings.

Observation Point 2- RLC/MAC Over-the-Air Messages

This layer contains two functions: The Radio Link Control function provides a radio-solution-dependent reliable link. The Medium Access Control function controls the access signaling (request and grant) procedures for the radio channel, and the mapping of LLC frames onto the GSM physical channel. RLC/MAC is defined in GSM 04.60 for functions operating on the Packet Data Channel (PDCH), and in GSM 04.08 for functions operating on the CCCH (Common Control Channel).


Uplink TBF establishment messages
Message Reference Supported
Packet Access Reject 04.60/11.2.1 Yes
Packet Channel Request 04.60/11.2.5 No
EGPRS Packet Channel Request 04.60/11.2.5a No
Packet Queuing Notification 04.60/11.2.15 No
Packet Resource Request 04.60/11.2.16 Yes
Packet Uplink Assignment 04.60/11.2.29 Yes

Additional MS Radio Access Capabilities


Downlink TBF establishment messages
Message Reference Supported
Packet Downlink Assignment 04.60/11.2.7 Yes
TBF release messages
Message Reference Supported
Packet TBF Release 04.60/11.2.26 Yes
Packet Paging messages
Message Reference Supported
Packet Paging Request 04.60/11.2.10 Yes
RLC messages
Message Reference Supported
Packet Downlink Ack/Nack 04.60/11.2.6 Yes
EGPRS Packet Downlink Ack/Nack 04.60/11.2.6a Yes
Packet Uplink Ack/Nack 04.60/11.2.28 Yes
Miscellaneous messages
Message Reference Supported
Packet Control Acknowledgment 04.60/11.2.2 Yes
Packet Cell Change Failure 04.60/11.2.3 No
Packet Cell Change Order 04.60/11.2.4 Yes
Packet Downlink Dummy Control Block 04.60/11.2.8 Yes
Packet Uplink Dummy Control Block 04.60/11.2.8b Yes
Packet Measurement Report 04.60/11.2.9 Yes
Packet Measurement Order 04.60/11.2.9b No
Packet Mobile TBF Status 04.60/11.2.9c Yes
Packet Enhanced Measurement Report 04.60/11.2.9d Yes
Packet PDCH Release 04.60/11.2.11 No
Packet Polling Request 04.60/11.2.12 Yes
Packet Power Control/Timing Advance 04.60/11.2.13 Yes
Packet PRACH Parameters 04.60/11.2.14 No
Packet PSI Status 04.60/11.2.17 Yes
Packet Timeslot Reconfigure 04.60/11.2.31 Yes


Radio Control Link Procedures

Medium Access Control Procedures

Observation Point 3 - LLC Over-the-Air Messages

Logical Link Control (LLC): LLC was designed to be independent of the underlying radio interface protocols in order to allow introduction of alternative GPRS radio solutions with minimum changes to the NSS (Network Subsystem). The procedures for the LLC layer are described in GSM 04.64.

Observation Point 4 -GMM/SM Over-the-Air Messages

GPRS Mobility Management and Session Management (GMM/SM): This protocol supports mobility management functionality such as GPRS attach, GPRS detach (also applicable to the test application), security, routing area update, location update, PDP context activation, and PDP context deactivation. GMM/SM is defined in GSM 04.08

GMM Messages

Message Reference Supported
Attach Request 9.4.1 Yes
Attach Accept 9.4.2 Yes
Attach Complete 9.4.3 Yes
Attach Reject 9.4.4 Yes
Detach Request 9.4.5 Yes
Detach Accept 9.4.6 Yes
P-TMSI Reallocation Command 9.4.7 No
P-TMSI Reallocation Complete 9.4.8 No
Authentication and Ciphering Request 9.4.9 No
Authentication and Ciphering Response 9.4.10 No
Authentication and Ciphering Reject 9.4.11 No
Identity Request 9.4.12 Yes
Identity Response 9.4.13 Yes
Routing Area Update Request 9.4.14 Yes
Routing Area Update Accept 9.4.15 Yes
Routing Area Update Complete 9.4.16 Yes
Routing Area Update Reject 9.4.17 No
GMM Status 9.4.18 No
GMM Information 9.4.19 Yes

SM Messages

Messages Reference Supported
Activate PDP Context Request 9.5.1 Yes
Activate PDP Context Accept 9.5.2 Yes
Activate PDP Context Reject 9.5.3 Yes
Request PDP context Activation 9.5.4 Yes
Request PDP context Activation Reject 9.5.5 No
Modify PDP context Request 9.5.6 No
Modify PDP context Accept 9.5.7 No
Deactivate PDP context Request 9.5.8 Yes
Deactivate PDP context Accept 9.5.9 Yes
Activate AA PDP context Request 9.5.10 No
Activate AA PDP context Accept 9.5.11 No
Activate AA PDP context Reject 9.5.12 No
Deactivate AA PDP context Request 9.5.13 No
Deactivate AA PDP context Accept 9.5.14 No
SM Status 9.5.15 No

Observation Point 5- SMS Over-the-Air Messages

This observation point captures the messages exchanged between the LLC layer and the SMS sub-layers. See SMS Logging Control for more information.

Observation Point 6- GSM L3 Over-the-Air Messages

GSM Layer 3 (GSM L3) is defined in GSM 04.08. GSM L3 includes messages that are transmitted over the Common Control Channels. These are:

CCCH messages are useful mainly for the purpose of verifying correct channel allocation through the logging of RACH accesses and the related assignments. Note that the System Information Messages will only be visible whenever changes are made to the base station parameters. They are no continuously logged, although they are continuously broadcast on the BCCH.

All references in this section are relative to GSM 04.08 or GSM 04.60.

Message Reference Supported
Location Updating Request 04.08/9.2.15 Yes
Location Updating Accept Yes
Channel Request 04.08/9.1.8 Yes
Immediate Assignment 04.08/9.1.18 Yes
Packet System information 1 04.60/11.2.18 Yes
Packet System information 13 04.60/11.2.25 Yes
Packet System information 2 04.60/11.2.19 Yes
Packet System information 3 04.60/11.2.20 Yes
Packet System information 3bis 04.60/11.2.21 Yes

Observation Point 7 - SNDCP Over-the-Air Messages

Subnetwork Dependent Convergence Protocol (SNDCP): This transmission functionality maps network-level characteristics onto the characteristics of the underlying network. SNDCP is specified in GSM 04.65.

Message Reference Supported
SN-DATA 7.2 Yes

Observation Point 8 - IP Messages

Unlike most of the other protocols, IP only has a single type of message: the datagram. For each datagram, the IP header fields will be displayed by name and the user data will be displayed as a hex dump.

For each datagram, the following fields will be displayed:

For a more detailed explanation of these fields, refer to the Internet Engineering Task Force (IETF) document RFC 791.

Observation Point 9 - RLP Over-the-Air Messages

The Radio Link Protocol (RLP) stack layer provides reliable transportation of data between the mobile station and the PPP layer by using a Frame Check Sequence (FCS) for error detection and providing for retransmission of corrupted or missing data. RLP is specified in GSM 04.22.

Observing the messages set and received by this layer is only useful if you are using GSM data channels in non-transparent mode. See GSM Circuit Switched Data (CSD) for more information.

Observation Point 10 - PPP Over-the-Air Messages

The Point-to-Point Protocol (PPP) is associated with data channels. It allows a mobile station to transfer IP packets to and from the IP layer. PPP is specified in the Internet Engineering Task Force (IETF) document RFC 1548.

For more information about data channel support in the test set, see Data Channel .

Observation Point 11 - PPP HDLC Over-the-Air Messages

The PPP High Level Data Link Control observation point provides access to the full PPP frame that is sent or received by the test set. Some header and footer octets are removed from the frame displayed in the PPP observation point. The additional octets viewable in the PPP HDLC layer are:

Front of the Frame

  • Flag
  • Address
  • Control

Back of the Frame

  • Frame Check Sequence (FCS)
  • Closing Flag

PPP Observation Point and PPP HDLC Observation Point Comparison

Operating Considerations

This observation point is not enabled by default. If you want to capture the PPP HDLC frames using the WPA, you should enable PPP_HDLC in the Test Set Message Filter Settings.

Observation Point 12 - RRLP Over-the-Air Messages

See RRLP Configuration for more information about the RRLP layer support in the test set.

Related Topics

Protocol Logging