The fields of SM-TP messages, including their order and size, are summarized in the following table, where
M means a mandatory field,
O an optional field,
E is used for fields which are mandatory in negative responses (RP-ERR) and not present in positive responses (RP-ACK),
x is a field present elsewhere: The first octet of the TPDU contains various flags including the TP-MTI field described above: By setting the TP-More-Messages-to-Send (TP-MMS) bit to 0 (reversed logic), the SMSC signals it has more messages for the recipient (often further segments of a concatenated message). The MSC usually does not close the connection to the mobile phone and does not end the MAP dialogue with the SMSC, which allows faster delivery of subsequent messages or message segments. If by coincidence the further messages vanish from the SMSC in the meantime (when they are for example deleted), the SMSC terminates the MAP dialogue with a MAP Abort message. The TP-Loop-Prevention (TP-LP) bit is designed to prevent looping of SMS-DELIVER or SMS-STATUS-REPORT messages routed to a different address than is their destination address or generated by an application. Such message may be sent only if the original message had this flag cleared and the new message must be sent with the flag set. By setting the TP-Status-Report-Indication (TP-SRI) bit to 1, the SMSC requests a status report to be returned to the SME. By setting the TP-Status-Report-Request (TP-SRR) bit to 1 in a SMS-SUBMIT or SMS-COMMAND, the mobile phone requests a status report to be returned by the SMSC. When the TP-SRQ has value of 1 in an SMS-STATUS-REPORT message, the message is the result of an SMS-COMMAND; otherwise it is a result of an SMS-SUBMIT. When TP-UDHI has value 1, the TP-UD field starts with
User Data Header. Setting the TP-RP bits turns on a feature which allows to send a reply for a message using the same path as the original message. If the originator and the recipient home networks differ, the reply would go through another SMSC then usually. The mobile operator must take special measures to charge such messages. Both SM-RP and MAP used to transmit GSM 03.40 TPDU carry enough information to return acknowledgement—the information whether a request was successful or not. However, a GSM 03.40 TPDU may be included in the acknowledgement to carry even more information. The GSM 03.40 has undergone the following development: • Up to GSM 03.40 5.2.0 SMS-DELIVER-REPORT and SMS-SUBMIT-REPORT was sent only in the case of an error. Since 5.3.0 they are sent in case of success as well. MO-ForwardSM-Res was introduced back in GSM 09.02 5.6.0 August 1997 • Up to GSM 03.40 6.0.0 SMS-DELIVER-REPORT and SMS-SUBMIT-REPORT sent in case of an error contained only TP-MTI and TP-FCS fields and the last field in SMS-STATUS-REPORT was TP-ST. Since version 6.1.0 these TPDUs has format shown in the table above. Although these changes are ancient (version 6.1.0 occurred in July 1998), old formats of MAP are frequently seen even in today's networks.
Message Content The content of the message (its text when the message is not a binary one) is carried in the TP-UD field. Its size may be up to 160 × 7 = 140 × 8 = 1120 bits. Longer messages can be split into multiple parts and sent as a
Concatenated SMS. The length of message content is given in the TP-UDL field. When the message encoding is GSM 7-bit default alphabet (depends on TP-DCS field), the TP-UDL gives length of TP-UD in 7-bit units; otherwise TP-UDL gives length of the TP-UD in octets. When TP-UDHI is 1, the TP-UD starts with
User Data Header (UDH); in this case the first octet of the TP-UD is User Data Header Length (UDHL) octet, containing the length of the UDH in octets without UDHL itself. UDH eats room from the TP-UD field. When the message encoding is GSM 7-bit default alphabet and a UDH is present, fill bits are inserted to align start of the first character of the text after UDH with septet boundary. This behaviour was designed for older mobile phones which don't understand UDH; such mobile phones might display the UDH as a jumble of strange characters; if the first character after UDH was
Carriage Return (CR), the mobile phone would rewrite the message with the rest of the message.
Addresses A GSM 03.40 message contains at most one address: destination address (TP-DA) in SMS-SUBMIT and SMS-COMMAND, originator address (TP-OA) in SMS-DELIVER and recipient address (TP-RA) in SMS-STATUS-REPORT. Other addresses are carried by
lower layers. The format of addresses in the GSM 03.40 is described in the following table: Type of number (TON): If a subscriber enters a telephone number with `+' sign at its start, the `+' sign will be removed and the address gets TON=1 (international number), NPI=1. The number itself must always start with a country code and must be formatted exactly according to the
E.164 standard. In contrast, for numbers written without `+' sign the address gets TON=0 (unknown), NPI=1. In this case the number must adhere to the mobile operator's
dial plan, which means that international numbers must have the international prefix (00 in most countries, but 011 in the USA) before the country code and numbers for long-distance calls must start with the trunk prefix (0 in most countries, 1 in the USA) followed by a trunk code. Numbering plan identification (NPI): Telephone numbers should have NPI=1. Application servers may use alphanumeric addresses which have TON=5, NPI=0 combination. The EXT bit is always 1 meaning "no extension".
Address examples U.S. number +1 555 123 4567 would be encoded as 0B 91 51 55 21 43 65 F7 (the F in upper four bits of the last octet is a filler which is used when the number length is odd). Alphanumeric address is at first put to the GSM 7-bit default alphabet, then encoded the same way as any message text in TP-UD field (that means it is 7-bit packed) and then the address is supplied with the "number" length and TON and NPI. For example, a fictional alphanumeric address
Design@Home is converted to the GSM 7-bit default alphabet which yields 11 bytes 44 65 73 69 67 6E 00 48 6F 6D 65 (hex), the 7-bit packing transforms it to 77 bits stored in 10 octets as C4 F2 3C 7D 76 03 90 EF 76 19; 77 bits is 20
nibbles (14 hex) which is the value of the first octet of the address. The second octet contains TON (5) and NPI (0), which yields D0 hex. The complete address in the GSM format is 14 D0 C4 F2 3C 7D 76 03 90 EF 76 19.
Message Reference The Message Reference field (TP-MR) is used in all messages on the submission side with exception of the SMS-SUBMIT-REPORT (that is in SMS-SUBMIT, SMS-COMMAND and SMS-STATUS-REPORT). It is a single-octet value which is incremented each time a new message is submitted or a new SMS-COMMAND is sent. If the message submission fails, the mobile phone should repeat the submission with the same TP-MR value and with the TP-RD bit set to 1.
Time Format A date and time used in TP-SCTS, TP-DT and in Absolute format of TP-VP is stored in 7 octets: In all octets the values are stored in binary coded decimal format with switched digits (number 35 is stored as 53 hex). Time zone is given in quarters of an hour. If the time zone offset is negative (in Western hemisphere) bit 3 of the last octet is set to 1. 23:01:56 Mar 25th 2013 PST (GMT-7) would be encoded as 31 30 52 32 10 65 8A. In this example, the time zone, 8A is binary 1000 1010. Bit 3 is 1, therefore the time zone is negative. The remaining number (bit-wise 'and' with 1111 0111) is 1000 0010, hexadecimal 82. Treat this as any previous element in the sequence, (hex 82 represents number 28). Finally the time zone offset is given by 28 × 15 minutes = 420 minutes (7 hours).
Validity Period An SMS-SUBMIT TPDU may contain a TP-VP parameter which limits the time period for which the SMSC would attempt to deliver the message. However, the validity period is usually limited globally by the SMSC configuration parameter— often to 48 or 72 hours. The Validity Period format is defined by the Validity Period Format field:
Relative format Absolute format The absolute format is identical to the other
time formats in GSM 03.40.
Enhanced format Enhanced format of TP-VP field is seldom used. It has always 7 octets, although some of them are not used. The first octet is TP-VP Functionality Indicator. Its 3 least significant bits have the following meaning: The value of 1 in the bit 6 of the first octet means that the message is Single-shot. The value of 1 in the bit 7 of the first octet indicates that TP-VP functionality indicator extends to another octet. However, no such extensions are defined.
Protocol Identifier TP-PID (Protocol identifier) either refers to the higher layer protocol being used, indicates interworking with a certain type of telematic device (like
fax,
telex,
pager,
teletex,
e-mail), specifies replace type of the message or allows download of configuration parameters to the
SIM card. Plain MO-MT messages have PID=0. For TP-PID = 63 the SC converts the SM from the received TP
Data Coding Scheme to any data coding scheme supported by that MS (e.g. the default). Short Message Type 0 is known as a
silent SMS. Any handset must be able to receive such short message irrespective of whether there is memory available in the (U)SIM or ME or not, must acknowledge receipt of the message, but must not indicate its receipt to the user and must discard its contents, so the message will not be stored in the (U)SIM or ME.
Data Coding Scheme A special 7-bit encoding called
GSM 7 bit default alphabet was designed for Short Message System in GSM. The alphabet contains the most-often used symbols from most Western-European languages (and some Greek uppercase letters). Some
ASCII characters and the
Euro sign did not fit into the GSM 7-bit default alphabet and must be encoded using two septets. These characters form GSM 7-bit default alphabet
extension table. Support of the GSM 7-bit alphabet is mandatory for GSM handsets and network elements.
Discharge Time The TP-DT field indicates the time and date associated with a particular TP-ST outcome: • if the message has been delivered or, more generally, other transaction completed (TP-ST is 0-31), the TP-DT is the time of the completion of the transaction • if the SMSC is still trying to deliver the message (TP-ST is 32-63), the TP-DT is the time of the last delivery attempt • if the SMSC is not making any more delivery attempts (TP-ST is 64-127), the TP-DT is either the time of the last delivery attempt or the time at which the SMSC disposed the message
Parameter Indicator The TP-PI field indicates presence of further fields in the SUBMIT-REPORT, DELIVER-REPORT or SMS-STATUS-REPORT TPDU. As currently there are still four free bits in TP-PI, it can be expected that the extension bit will be zero even in the future, which helps to distinguish TP-PI field from TP-FCS field when information whether TPDU is part of positive or negative response is not available: if the most significant bit of the second octet of TPDU is 1, the second octet is TP-FCS (in a negative response), otherwise it is TP-PI (in a positive response). ==See also==