SMS Terminology

Message Types

Person-to-Person (P2P)

P2P describes conventional two-way SMS or MMS messaging between individuals. P2P messaging is lower-volume. The expectation is for one outbound message to every inbound message, with no more than a 3-to-1 ratio. P2P messages typically use long codes, though this practice can vary by country.

Application-to-Person (A2P)

A2P generally refers to anything that isn’t considered P2P, including chatbots and automated campaigns. Sometimes A2P messaging is referred to as enterprise or business messaging. A2P messaging has higher expected volumes than P2P and is typically outbound. However, depending on the number, A2P can include two-way conversational messaging. A2P messages typically use short codes (toll-free is available for the U.S. only). Account permissions limit throughput for A2P messages and rate limits apply.

Message Use Case

The message use case is relevant when determining a solution that is right for your company.

Inbound

A message sent from a customer to your company’s number.

Inbound-Initiated

A conversation initiated by a customer.

Outbound

A message sent from your company’s number to a customer. Outbound messages can be initiated by a service rep, sent through a campaign, initiated by a chatbot, and triggered by an application.

Outbound-Initiated

A conversation initiated by a service rep.

Automated Outbound

Bulk or outbound messages triggered by an action in Salesforce or with a bot. A Salesforce admin can trigger an outbound message based on a record change in their org. Examples include messages alerting customers of changes to their case or order, messages acknowledging a request for more information from a new lead, and service alerts.

Outbound Campaign (Broadcast)

A message sent to a list, most commonly used for service-related initiatives. These messages are medium-to-high volume and typically one way, although the product allows outbound messaging to convert to a conversation when a recipient replies to the message.

Number Types

Your company can send messages using several different types of numbers. It's important to understand these terms, particularly because several of them overlap with each other conceptually. For instance, a toll-free number is a type of long code.

Long Codes

These numbers are standard phone numbers like landlines, mobile numbers, and toll-free numbers that can be different lengths based on the country. Typically, long codes are used for interactive conversations or P2P messaging.

A2P Long Code

A number used specifically for A2P communication.

Short Codes

These numbers are shorter than a long code, between 4–8 digits depending on the country of origin. Short codes are only supported in the US and Canada. These codes are used for sending high-volume A2P messages, such as automated campaigns, surveys, and announcements. They can support message volumes of 10–500 messages/second. The specific volume limit is country-specific and doesn’t translate to the platform throughput. Short codes are registered with the local carrier for use case approval.

Toll-Free Number

A type of long code that uses a toll-free number.

Mobile Number (or MSISDN)

A phone number used to identify a mobile subscriber.

Other Terms

Short Message Service (SMS)

SMS messages are sent over a cellular network and support text content. An SMS message can contain 140 bytes of content.

Multimedia Messaging Service (MMS)

MMS messages are sent over a cellular network and can be used to send pictures, video, audio, and phone contacts.

GSM-7

This type of character encoding requires 7 bits per character.

Unicode

This type of character encoding is a more flexible and powerful standard than GSM-7. UTF-8 is the most common unicode encoding type. It uses 1 byte for the first 128 characters and up to 4 bytes for other characters.

Segmentation

If an SMS message is more than 140 bytes, it is segmented into multiple messages. In this case, each segmented message can contain up to 133 bytes. The remaining 7 bytes are used for the header that describes the segment order. Up to six segmented messages can be grouped together.