Multimedia Messaging Service (MMS) is a standard way to send messages that include multimedia content to and from a mobile phone over a cellular network. Users and providers may refer to such a message as a PXT, a picture message, or a multimedia message. The MMS standard extends the core SMS (Short Message Service) capability, allowing the exchange of text messages greater than 160 characters in length. Unlike text-only SMS, MMS can deliver a variety of media, including up to forty seconds of video, one image, a slideshow of multiple images, or audio. Media companies have utilized MMS on a commercial basis as a method of delivering news and entertainment content, and retailers have deployed it as a tool for delivering scannable coupon codes, product images, videos, and other information. On (mainly) older devices, messages that start off with text, as SMS, are converted to and sent as an MMS when an emoji is added. The commercial introduction of MMS started in March 2002, although picture messaging had already been established in Japan. It was built using the technology of SMS as a captive technology which enabled service providers to "collect a fee every time anyone snaps a photo." MMS was designed to be able to work on the then-new GPRS and 3G networks and could be implemented through either a WAP-based or IP-based gateway. The 3GPP and WAP Forum groups fostered the development of the MMS standard, which was then continued by the Open Mobile Alliance (OMA).
Technical description MMS messages are delivered in a different way from SMS. The first step is for the sending device to encode the multimedia content in a fashion similar to sending a MIME message (MIME content formats are defined in the MMS Message Encapsulation specification). The message is then forwarded to the carrier's MMS store and forward server, known as the MMSC (Multimedia Messaging Service Centre). If the receiver is on a carrier different from the sender, then the MMSC acts as a relay, and forwards the message to the MMSC of the recipient's carrier using the Internet. Once the recipient's MMSC has received a message, it first determines whether the receiver's handset is "MMS capable" or not. If it supports the standards for receiving MMS, the content is extracted and sent to a temporary storage server 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 and receive the content from the embedded URL. Several other messages are exchanged to indicate the status of the delivery attempt. Before delivering content, some MMSCs 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".
If the receiver's handset is not MMS capable, the message is usually delivered to a web-based service from where the content can be viewed from a normal web browser. The URL for the content is usually sent to the receiver's phone in a normal text message. This behavior is usually known as a "legacy experience" since content can still be received by the user. The method for determining whether a handset is MMS capable is not specified by the standards. A database is usually maintained by the operator, and in it each mobile phone number is marked as being associated with a legacy handset or not. This method is unreliable, however, because customers can independently change their handsets, and many of these databases are not updated dynamically. MMS does not utilize operator-maintained "data" plans to distribute multimedia content; they are used only if the user clicks links inside the message. E-mail and web-based gateways to the MMS system are common. On the reception side, the content servers can typically receive 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 a MIME encoded message to be sent to the receiver's phone number using a special e-mail address combining the recipient's public phone number and a special domain name, which is typically carrier-specific.
Challenges There are some challenges with MMS that do not exist with SMS:
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