SMS Standards

John Bittenbender kisanth88 at
Fri Oct 17 09:54:10 UTC 2008

On Thu, Oct 16, 2008 at 9:41 PM, Bruce Pinsky <bep at> wrote:
> Hash: SHA1
> Glen Kent wrote:
>> Hi,
>> Apologies in advance since this is off-topic. However, posting in on
>> nanog since i am confident that we will have some experts who would be
>> able to guide me here.
>> I want to study the standards (RFC equivalent) for sending and
>> receiving SMSs. Any ideas on what kind of protocol runs between a
>> mobile phone and a SMS center (SMSC)?
> Wiki_Pedia is your friend
> The Short Message Service - Point to Point (SMS-PP) is defined in GSM
> recommendation 03.40.[2] GSM 03.41 defines the Short Message Service - Cell
> Broadcast (SMS-CB) which allows messages (advertising, public information,
> etc.) to be broadcast to all mobile users in a specified geographical
> area.[16] Messages are sent to a Short Message Service Centre (SMSC) which
> provides a store-and-forward mechanism. It attempts to send messages to
> their recipients. If a recipient is not reachable, the SMSC queues the
> message for later retry.[17] Some SMSCs also provide a "forward and forget"
> option where transmission is tried only once. Both Mobile Terminated (MT),
> for messages sent to a mobile handset, and Mobile Originating (MO), for
> those that are sent from the mobile handset, operations are supported.
> Message delivery is best effort, so there are no guarantees that a message
> will actually be delivered to its recipient and delay or complete loss of a
> message is not uncommon, particularly when sending between networks. Users
> may choose to request delivery reports (simply add *0# or *N# to the
> beginning of your text message), which can provide positive confirmation
> that the message has reached the intended recipient.
> Transmission of short messages between the SMSC and the handset is done
> using the Mobile Application Part (MAP) of the SS7 protocol. Messages are
> sent with the MAP mo- and mt-ForwardSM operations, whose payload length is
> limited by the constraints of the signalling protocol to precisely 140
> octets (140 octets = 140 * 8 bits = 1120 bits). Short messages can be
> encoded using a variety of alphabets: the default GSM 7-bit alphabet (shown
> below), the 8-bit data alphabet, and the 16-bit UTF-16/UCS-2 alphabet.[18]
> Depending on which alphabet the subscriber has configured in the handset,
> this leads to the maximum individual Short Message sizes of 160 7-bit
> characters, 140 8-bit characters, or 70 16-bit characters (including
> spaces). Support of the GSM 7-bit alphabet is mandatory for GSM handsets
> and network elements,[18] but characters in languages such as Arabic,
> Chinese, Korean, Japanese or Cyrillic alphabet languages (e.g. Russian)
> must be encoded using the 16-bit UCS-2 character encoding (see Unicode).
> Routing data and other metadata is additional to the payload size.
> - --
> =========
> bep
> Version: GnuPG v1.4.9 (MingW32)
> Comment: Using GnuPG with Mozilla -
> iEYEARECAAYFAkj37WcACgkQE1XcgMgrtyZiVACgjSYOrHVRE9g1vufxWpa67rC6
> o8YAn1JjliEYx73fLGXbIOyeTTZtsj/S
> =2vZP

Depending on what you are doing, see also SMPP protocol as much
inter-carrier SMS is carried over SMPP links. Also many external
content providers send SMS messages to phones via SMPP to reach the
carrier (news alerts, etc).

John B

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