Tutorial Lmu1200

Section 2 — Message Structures
Messages passed between an application and the LM Direct™ interface have the same basic
packet structure. This structure consists of a 20 byte IP header, an 8 byte UDP header, the
LM Direct™ header and the LM Direct™ message.
Note that all bytes in multi-byte fields are transmitted in Net Endian format (Big Endian)
where the most significant bits aretransmitted first. For example, for a 32-bit field, bits 31-
24 are transmitted first, 16-23 second, 8-15 third and 0-7 last
Basic Message Structure
The generic message structure of an LM Direct™ message is:

An LM Direct™ message comprises the Options Header, Message Header and Message
Contents. The Options byte at the beginning of the Options Header is bit-mapped to
indicate which Options Headerfields will follow. If the most-significant bit (bit 7) of the
first bye of a message is set, the Options Header is present in the message beginning with the Options Byte. Otherwise, the message begins with the Message Header (Service Type is
the first byte); that is to say that if the first byte of an LM Direct™ message has the most significant
bit set (bit 7), than the Options Header ispresent. Likewise, if it is cleared, the
Options Header is not included in the message.
Options Header
The Options Header fields used in LM Direct™ are defined as follows:
Options
Header Content Options:
Bit 0: Mobile ID (0 = disabled, 1= enabled)
Bit 1: Mobile ID Type (0 = disabled, 1 = enabled)
Bit 2: Authentication Word (0 = disabled, 1 = enabled)
Bit 3: Routing (0 = disabled, 1 = enabled)Bit 4: Forwarding (0 = disabled, 1 = enabled)
Bit 5: Response Redirection (0=disabled, 1=enabled)
Bit 6: Not Used – Reserved for future use
Bit 7: Always set.
Mobile ID Length
The number of bytes to follow which contain the Mobile ID data
Mobile ID
The Mobile ID of the LMU that either originated the LM Direct™ message or the LMU for which
the message is intended. The Mobile ID is made up ofnumerical digits and is encoded in this field
as packed BCD. The most significant digit is placed in the upper four bits of the first byte. In the
case where an odd number of digits are used, a 0x0F is used to pad the lower 4 bits of the last byte.
Mobile ID Type Length
The number of bytes to follow which contain the Mobile ID Type data. Note that this value will
always be 1.
Mobile ID TypeThe type of Mobile ID being used by the LMU:
0 – OFF
1 – Electronic Serial Number (ESN) of the LMU
2 – International Mobile Equipment Identifier (IMEI) or Electronic Identifier (EID) of the wireless
modem
3 – International Mobile Subscriber Identifier (IMSI) of the SIM card (GSM/GPRS devices only)
4 – User Defined Mobile ID
5 – Phone Number of the mobile (if available)
6 – The current IPAddress of the LMU
Authentication Length
The number of bytes to follow which contain the Authentication word; normally this value is 4
Authentication
The Authentication word is used with an outbound message to gain access to the LMU if
authentication is enabled.
Routing Length
The number of bytes to follow which contain the Routing field. If present, this value is user defined
and can beup to 8.
Routing
The Routing field is up to 8 bytes long and can be used by the Application to store identity
information of the originating user for requests made to the LMU from an application subsystem. It
is only used in outbound messages. If the Routing field is present in a request received by the LMU,
the LMU will include the same field, byte for byte, in the response sent back to theApplication. The
Application can then route the response back to the originating user based on information received.
See Appendix D for further definition and uses of the Routing Field.
Forwarding Length
The number of bytes to follow which contain the Forwarding field. If present, this value is normally
8.
Forwarding
The Forwarding field is 8 bytes long and is used by an LM Direct™...