Multimedia Messaging Service, MMS for short, is a cellular telephone standard for sending messages that include multimedia objects (images, audio, video, rich text). MMS is an extension of the SMS standard, allowing longer message lengths and using WAP to display the content. Its most popular use is sending photographs from camera-equipped handsets, although it is also popular as a method of delivering ringtones as well. The standard is developed by the Open Mobile Alliance (OMA), although during development it was part of the 3GPP and WAP groups.

Description

MMS messages are delivered in a fashion almost identical to SMS, but any multimedia content is first encoded and inserted into a text message in a fashion similar to sending a MIME e-mail. MMS defines a subset of MIME content formats in the MMS Message Encapsulation specification. The message is then forwarded to the carrier's SMS store and forward server, the "MMS relay". If the receiver is on another carrier, the relay forwards the message to the recipient's carrier using the Internet.

Once it reaches the correct MMS relay for the receiver, the content is extracted and sent to a temporary storage server (often the same process as the relay) with an HTTP front-end. An SMS "control message" containing the URL of the content is then sent to the recipient's handset to trigger the receiver's WAP browser to open a receive the content from the embedded URL. Several other messages are exchanged to indicate status of the delivery attempt.

Some installations also include a conversion service that will attempt to modify the multimedia content into a format suitable for the receiver. This is known as "content adaptation", or MMSC.

E-mail and web-based gateways to the MMS (and SMS) system are common. On the reception side, the content servers can typically service requests both from WAP and normal HTTP browsers, so delivery via the web is simple. For sending from external sources to handsets, most carriers allow MIME encoded message to be sent to the receiver's phone number with a special domain – for instance, Fido Solutions allows users to send MMS messages to Fido recipients via their number@fido.ca gateway.

History

The original SMS system was developed as part of the GSM family of standards, able to deliver messages of up to 160 characters. Driven by low costs, SMS rapidly grew in popularity, and by 2000 over 15 billion messages were being delivered every year.Lars Novak and Magnus Svensson, "MMS—Building on the Successes of SMS", Ericsson, 2001

In order to add some functionality to the basis SMS system, in the late 1990s Ericsson proposed the Enhanced Messaging Service (EMS). EMS added a number of control characters to control basic text style (bold, color, etc.) as well as insert a small number of pre-defined graphics. EMS never caught on, although it was a feature of some Ericsson and Sony handsets.