Know your SMS from your MMS. Get the lowdown on all the technical terms with our glossary.



  • A2P SMS

    Application to Person SMS (A2P SMS) is a term used to describe an SMS message sent from a software application (run by an enterprise or business) to a person’s phone. Receiving a text message with your account balance from your bank, or an appointment reminder from your doctor are examples of A2P SMS messages. A2P messages are being used increasingly for businesses to communicate with their customers.

  • Account

    Account refers to your business account with Sinch. Accessing your account enables you to add and remove products and services, review current charges and credit availability, access web tools, review online reports and more.
  • ACD

    Automatic Call Distributor (ACD) is a system to handle large inbound call volumes. ACD automatically disperses calls to the specific group responsible for answering.
  • ACE

    Answered Call Event (ACE) is when a call is answered.
  • Aggregator

    An SMS aggregator is a company that makes sending a mobile message (SMS or MMS etc.) to any person, anywhere in the world, with one connection possible. SMS aggregators typically buy from multiple MNOs around the world to ensure they can achieve global reach and because of their scale, they typically qualify for bulk discounts. The ability to “send” a message is sold to enterprises and small to medium businesses who then benefit from this simplicity and affordability. The value an SMS aggregator provides is making it easier and cheaper for enterprises to deliver a message anywhere in the world, without having to integrate technically or negotiate commercially with multiple suppliers.

  • API

    An Application Programmable Interface (API) is how two machines or systems communicate and exchange information with one another. Each API comes with a specification that defines what parameters are passed between the machines through the API. There is one primary API used for SMS, and it is SMPP, but these days, REST HTTP based APIs are widely used.
  • APN

    An Access Point Name (APN) is used for mobile devices to establish a data connection from the mobile network to a different network. It describes specific characteristics of the connection.
  • ASR

    Answer Seizure Ratio (ASR) is the percentage of answered telephone calls relative to the total number of calls.


  • Binary SMS

    In order to send SMS messages containing ringtones, wallpapers, WAP push or vCards, the content needs to be sent as a binary message. In order to send a binary message to a phone, the User Data Header (UDH) construct must be used. The UDH is a short hexadecimal code which, when received by the handset indicates the type of content contained in the binary message and how to process it. In addition to the UDH, setting the correct Data Coding Scheme (DCS) value, 0x04 or 4 in the case of a binary SMS is also required.
  • Bind

    A bind, in the specific case of connecting to Sinch via SMPP, is a single connection using the SMPP protocol. There are three ways to open a connection using SMPP: Transmitter – send short messages to the SMSC and receive responses from SMSC Receiver – receive delivery receipts from the SMSC and return the corresponding responses Transceiver – send and receive messages to and from the SMSC over a single SMPP session.
  • BLE

    Bluetooth Low Energy (BLE) is a low power variant of classic Bluetooth with a comparable communication range.
  • Bulk SMS

    Bulk SMS is a term used to describe the sending of a large amount of messages via an API (like SMPP), usually as part of a marketing campaign. Typically bulk SMS implies messages are promotional in nature and the company is sending the exact same message to multiple recipients.


  • CDMA

    Code Division Multiple Access (CDMA) describes a communication channel access method that uses spread-spectrum technology and a special coding scheme (where each transmitter is assigned a code).
  • CDR

    A Call Detail Record (CDR) is a data record produced by a telephone exchange, or other telecommunication equipment, that documents the details of a telephone call or other telecommunication transaction (such as a text message) that passes through that facility or device.

    Retrieving data. Wait a few seconds and try to cut or copy again.
  • Concatenated SMS

    A standard plain text SMS can contain up to 160 characters, but it is possible to send multiple SMS joined together to form one single long message. This type of message is referred to as many things - a long SMS, a multipart SMS, an extended SMS, or a concatenated SMS.
  • Country code

    A country code is part of a comprehensive numbering plan, E.164, established by the International Telecommunication Union (ITU), defined to support interoperability among the supported networks of its members. The standard defines a country calling code (aka country code) for each state or region which is prefixed to each national numbering plan’s telephone number to support a standard for international destination routing.
  • Coverage

    Coverage is a term used to describe where (what countries and regions) and which mobile operators your account or service can use for sending and or receiving messages. To understand the coverage available on your account, log in and select pricing for the service you wish to get coverage information on. Coverage can fluctuate over time depending on market changes.
  • CPaaS

    Communications Platform as a Service (CPaaS) is a cloud based platform that enables developers to add real-time communication features (such as Voice, Video and SMS) into their own applications without needing to build backend infrastructure and interfaces.

  • CSCA

    The Common Short Code Administration (CSCA) is an organization designated by the CTIA to administer short codes in the United States. Companies can lease a short code directly from the CSCA or alternatively order one from Sinch.
  • CTIA

    The Cellular Telecommunications & Internet Association, is an international non-profit membership organization representing the wireless communications industry since 1984. Members include wireless carriers and their suppliers, as well as providers and manufacturers of wireless data services and products. More information can be found on their website.


  • Data Call

    A data call is a phone call over the internet, also known as VoIP (Voice Over Internet Protocol).

  • Delivery receipt

    When sending an SMS, most mobile operators will return a notification called a delivery receipt to let the sender know whether or not the message was delivered to the handset. Some Short Message Service Centers (SMSCs) will return a delivery receipt when a message has been accepted or if the message is buffered in the SMSC, for example if the handset is switched off, although not ideal this is sometimes unavoidable due to operator's restrictions.
  • Delivery receipt error code

    If an SMS is not delivered (even after the SMSC retry cycle is complete) then a delivery receipt, with an error code indicating why the message failed will be sent. A complete list of delivery receipt error codes can be found in our Developer documentation.
  • Destination number

    A destination number is the phone number of the recipient you wish to send a message to.
  • Destination operator

    The destination operator is the operator to which the subscriber’s handset is attached. In most cases the destination operator is the home network but when a subscriber is roaming, then the destination operator will be the network on which the subscriber is roaming.

  • DiCE

    Disconnected Call Event (DiCE) is when a call is disconnected.
  • DID

    Direct Inward Dialling (DID) is a service provided by a local phone company (or local exchange carrier) that provides a block of telephone numbers for calling into a company’s private branch exchange (PBX) system. Using DID, companies can offer customers individual phone numbers for each person or workstation within the company without requiring a physical line into the PBX for each connection.
  • Direct connections

    A direct connection is a valid and authenticated connection to the SMSC of a mobile network operator. At Sinch, we work directly with mobile operators to negotiate commercial contracts and to connect directly to their network.


  • End user

    End user refers to the recipient of a message. End users can also be referred to as consumers or subscribers.
  • eUICC

    Embedded Universal Integrated Circuit Card (eUICC) is a GSMA standard for changing operators on a SIM card without replacing the SIM.


  • FTEU

    Free To End User (FTEU) enables enterprises to send messages in a way that ensures the end user does not get charged.


  • GGSN

    The Gateway GPRS Support Node (GGSN) is responsible for interworking between the GPRS network and external packet switched networks.
  • GPRS

    General Support Packet Radio Service (GPRS) is a mobile data service available to users of GSM. It’s a legacy data technology that became available when 2.5G networks were rolled out. It’s the slowest form of IP connectivity that a phone can get at max 80 kbps. That’s about 7 mins to download one song!
  • Grey route

    A grey route is a route used for sending SMS where the destination operator (on which the subscriber you are sending messages to is connected) does not get paid for the message. A grey route takes advantage of a legacy ‘sender keeps all’ policy in the GSM commercial framework, and although it is not regarded as fraudulent, it is frowned upon because it tends to be less reliable and is subject to immediate blocking by the destination operator.
  • GSM

    Global System for Mobile communication (GSM) is a digital mobile telephony system which is widely used in Europe and other parts of the world. GSM uses a variation of Time Division Multiple Access (TDMA) to digitize and compress data, then send it. GSM operates at a frequency band of 850, 900, 1800 or 1900 MHz depending on the country/region.
  • GSM encoding

    According to the GSM specification, a standard SMS message can contain up to 140 bytes of data (payload). Standard Latin (ISO-8859-1) character encoding represents a single character using 1 byte, which is 8 bits. Therefore, the maximum number of Latin 1 characters that could be included in an SMS is 140. GSM encoding represents characters using 7 bits instead of 8. This therefore provides a maximum of 160 characters per SMS. (140 * 8 bits) / 7 bits = 160 This effectively halves the number of characters the GSM character set can support, compared to ISO-8859-1. In order to include common characters that are usually represented using the 8th bit, these characters as well as other symbol characters must be re-mapped to a combination of lower bits. These re-mapped characters are often referred to as special characters. This re-mapping, in combination with packing 7-bit characters into 8-bit bytes is called GSM encoding.


  • HaLow

    Variant of the WiFi standard providing extended range for low power communication at a lower data rate.

    The Health Insurance Portability and Accountability Act (HIPAA) was created to establish a national standard to govern the handling of Protected Health Information (PHI). For more information on HIPAA and PHI, as well as how you can ensure compliance, take a look at our HIPAA page.
  • HLR

    A Home Location Register (HLR) is the central database containing details of each mobile phone subscriber authorized to use the GSM core network. Each mobile network has one HLR, although there may be many HLR servers creating a single virtual HLR. A HLR stores details of every SIM card issued by the mobile phone operator. Each SIM has a unique identifier called an IMSI which is one of the primary keys to each HLR record. "A HLR stores the following data about a mobile subscriber:

    - Current servicing MSC status of the subscriber
    - Temporary handset error code if applicable
    - Status – valid/invalid
    - If the subscriber is available to receive SMS
    - If there is an error code preventing SMS delivery
    - If the number has been ported to another mobile network

  • Home network

    A home network is the network that a subscriber has a contract with for their wireless service. For example, someone with an AT&T contract would say AT&T is their home network. A home network can typically be changed through the Mobile Number Portability (MNP) process which is available in most countries and allows a subscriber to take their phone number to a new network. For example, an AT&T subscriber could port their number from AT&T to Verizon at which point Verizon would become their home network.
  • Home routing

    SMS home routing is when a change made to the original GSM specification. The home routing enables mobile networks to offer a complete range of advanced services for both inbound and outbound SMS. This change provides functionality to mobile phone users and enables mobile operators an opportunity to generate additional revenue. It uses the Home Location Register (HLR) to change the flow of inbound off-net messages (messages that are not originating on the home network), directing them to an SMS router, rather than straight to target handsets. There, advanced services such as divert, copy, archiving and anti-spam can be applied before messages are delivered.
  • Hop

    For every entity (and associated store and forward machine) a message touched in its path to delivery is regarded as a hop. The count starts when an enterprise submits a message to a network and stops when the message reaches the final terminating operator SMSC. An example of a single hop: Acme Inc. sends a message to an AT&T subscriber via the Sinch network, then Sinch sends the message to AT&T for on-net delivery. An example of a multi hop: Acme Inc. needs to send a message to an AT&T subscriber, but has to use an intermediary service, like SMSAGG Inc. SMSAGG sends the message to Sinch for delivery, which would be two hops. If Sinch uses its own SMSC for delivery then this would be a zero hop connection. In general, the less hops the better, as each hop takes time and can potentially have latency and security vulnerabilities.
  • HTTP

    Hyper Text Transfer Protocol (HTTP) is the foundation of data communication over the internet.
  • Hub

    An SMS hub usually implies P2P messaging, and is used by mobile operators to send messages to operators they do not have reach to via SS7. The advantage of using a hub is that it reduces the number of commercial agreements a mobile operator needs to maintain, but it is not the highest quality route since the hub adds another hop in the delivery chain and may not report back actual delivery notifications. Sending A2P messages via an SMS hub is usually frowned upon and not permitted by most mobile operators.


  • ICE

    Incoming Call Event (ICE) is when a call is placed / made.
  • IEE 802.15.4

    IEEE 802.15.4 is a technical standard which defines the operation of Low-Rate Wireless Personal Area Networks (LR-WPANs). It is maintained by the IEEE 802.15 working group which defined the standard in 2003.
  • IMSI

    An International Mobile Subscriber Identity (IMSI) is a unique number associated with all GSM and Universal Mobile Telecommunications System (UMTS) network mobile phone users. It is stored in the Subscriber Identity Module (SIM) inside the phone and is sent by the phone to the network. It is also used to acquire other details of the mobile number in the Home Location Register (HLR) or as locally copied in the Visitor Location Register (VLR). In order to avoid the subscriber being identified and tracked by eavesdroppers on the radio interface, the IMSI is rarely sent and a randomly generated Temporary Mobile Subscriber Identity (TMSI) is sent instead. An IMSI consists of three components: - Mobile Country Code (MCC) - Mobile Network Code (MNC) - Mobile Subscriber Identity Number (MSIN)
  • IPv6

    Internet Protocol version 6 (IPv6) is the version of the internet protocol that provides an identification and location system for computers on networks and routes traffic across the internet.
  • ISO-27001

    ISO-27001 is a framework of procedures to ensure best practices and a managed approach to business information protection including risk, governance and compliance. Sinch are ISO-27001 compliant.
  • ISO-8859-1

    ISO-8859-1 is the default 8-bit encoding used in most ASCII and HTML documents, also known as Latin1. For use in SMS, it must be converted using GSM Encoding.
  • IVR

    Interactive Voice Response (IVR) allows customers to interact with a company’s host system via a telephone keypad or by speech recognition, after which services can be inquired about through the IVR dialogue.


  • Latency

    SMS Latency is loosely defined as the amount of time it takes from when a message is submitted to an aggregator until the message is delivered to the handset. We say loosely because many companies define it more narrowly in their contracts to only include the time taken from when a message is accepted from an enterprise until it is passed onto the delivering SMSC, this is due mostly to the fact it is very difficult to guarantee latency in someone else’s network.
  • Least cost routing

    When a message is submitted to an aggregator, the aggregator will determine the home network of the destination telephone number and the feature requirements. Based on this information the aggregator will determine which available routes could be used to deliver the message. The type of routing algorithm chosen based on this information will determine the overall reliability and cost of the message. Choosing the lowest cost option (regardless of quality or provenance) would be regarded as least cost routing and is not recommended for mission critical traffic.
  • LiFi

    Light Fidelity (LiFi) is a wireless communication technology similar to WiFi but using visible light communication to increase bandwidth.
  • Long codes

    Long codes, also known as long numbers or 10DLC, are full mobile telephone numbers (e.g. 1408 7654321 or 447624803588) that can be used for 2-way SMS applications. They look like normal subscriber numbers but are actually virtual and are assigned to an application to ensure correct delivery of MO messages.


    Low Power Wide Area Network (LPWAN) are wireless networks designed to allow long-range communication at a low data rate, reducing power and cost for transmission.

    Low-Rate Wireless Personal Area Network (LR-WPAN) is a computer network used for data transmission amongst devices such as computers, telephones, tablets etc.
  • LTE advanced

    LTE advanced is a high speed communication specification for mobile networks. It provides enhancements to the LTE standard with extended coverage, higher throughput and lower latency.
  • LTE-M

    Long Term Evolution – Category M1 (LTE-M) is a 3GPP standard to offer IoT specific communication over the LTE network, providing cheaper modules, longer battery life, and lower connectivity fees than traditional LTE.


  • MMA

    The Mobile Marketing Association (MMA) is a trade association and provides US consumer best practices and guidelines that apply to USA mobile campaigns.
  • MMS

    Multimedia Message Service (MMS) is an extension to Short Message Service (SMS), allowing longer text messages – 160> characters. MMS allows multimedia content, including images, video (up to 40 sec) and audio to be sent. MMS is only currently available in the United States.

  • MNP

    Mobile Number Portability (MNP) is an inter-operator process (usually imposed by country regulators) to allow mobile subscribers to retain their mobile number when switching from one mobile operator to another. For the vast majority of routes, Sinch is able to do a number lookup from a database or HLR to determine their home network and route the message through to the appropriate operator to successfully deliver the message.
  • MO message

    An SMS sent from a mobile handset to an application is referred to as an MO message. The term describes the process and flow of a handset sending a short message submission to its home network SMSC utilizing the mo-ForwardSM transaction which will store and forward to the destination mobile number or short code. In the case of a short code or A2P long number, the SMSC will pass the message to the aggregator, and the aggregator will pass it onto the enterprise who has leased that number. An acknowledgement (delivery notification) is also sent back to the originating handset once the message is delivered to the enterprise.
  • MO SMS

    Mobile Originated Short Message Service (MO SMS) is a text message that originates from a mobile device.
  • Mobile Network Operator (MNO)

    A Mobile Network Operator (MNO) is typically a company that provides people with a mobile or wireless telephony service. At Sinch we refer to these companies universally as operators, but they are also known as wireless carriers or just carriers.

  • MoCA

    Multimedia over Coax Alliance (MoCA) is a specification enabling whole-home distribution of high definition video and content over existing coaxial cabling.

    MSISDN (Mobile Subscriber Integrated Services Digital Network number) is the term used to describe a mobile number in an international format. However, the MSISDN is not a direct mapping to a mobile handset, or even to the SIM card. An MSISDN allows an SMSC to determine the country and mobile operator a subscriber number belongs to; and from there the SMSC can query the mobile operator’s HLR (Home Location Register) for information used to route the SMS to the handset.
  • MT message

    An SMS message sent from an application to a handset is referred to as a Mobile Terminating (MT) message. The term describes the process and flow of an application (software) sending a short message submission to an aggregator utilizing the SubmitSM transaction which will store and forward the message onto a terminating operator SMSC that is able to reach the destination mobile number. Once the message is delivered to the handset, a delivery notification is sent back to the aggregator and then the enterprise acknowledging delivery.
  • mVoIP

    Mobile Voice over Internet Protocol (mVoIP) is when you talk over an IP using your mobile phone i.e. making a call using a phone that runs off your mobile data connection.


  • NAT

    Network Address Translation (NAT) is a method of remapping one IP address space into another by modifying network address information in Internet Protocol (IP) datagram packet headers while they are in transit across a traffic routing device.
  • NFC

    Near Field Communication (NFC) is a communication protocol enabling two electronic devices to communicate when they are within close proximity of each other.
  • NPI

    Number Plan Identifier (NPI) is a value set for both the originator and destination number in every SMS . It is used for both SMS routing and handset display purposes.


  • On-net

    On-net is a term used to describe a message delivered by the home network to a subscriber on that network. In other words, a message is delivered via a terminating operator to its own subscriber. For example, sending a message to a Telstra Australia subscriber directly to Telstra Australia. The message was delivered on-net.
  • One-hop

    A one-hop connection is another name for an operator.
  • Originator (Sender ID)

    The originator of an SMS is the label describing who or where an SMS is sent from. The most common originator is a mobile number (MSISDN), as this is what is displayed when an SMS is sent from a mobile handset.

    An Over the Air (OTA) SMS is an SMS message that is frequently used by mobile operators to provision or modify core network settings on a handset. These messages are used to optimize configuration settings e.g. SMS Service Center, web settings, or to provision new services such as MMS.

  • OTT

    Over the Top (OTT) messages are messages that flow through the data network of a mobile operator as opposed to the core network. OTT suggests something that flows ‘over the top’ of the core network. For example, a P2P SMS message travels through the core signalling infrastructure of a mobile operator, where a WhatsApp message will flow through the data connection of a mobile operator (just like any other data). In this context a WhatsApp message is regarded as an OTT message.


  • P2A SMS

    Person to Application SMS (P2A SMS) are MO messages flowing from an end user to an application.
  • P2P SMS

    Person to Person SMS, or Peer to Peer SMS (P2P SMS) are a type of SMS that flow between two end users via their individual home networks. It is distinctly different from A2P SMS in that it can easily be replaced by OTT messaging like WhatsApp.
  • PLC

    Power Line Communication (PLC) is a communication technology using electrical wiring to carry power and data – used for networking IoT devices.
  • Prefix operator or prefix network

    Every subscriber has a mobile telephone number, and in many countries (not all), mobile number ranges are different from fixed line (land line) number ranges. In countries where the mobile number range is separate from the range for fixed line numbers, the country’s telecommunications regulator may issue numbers to mobile operators in blocks. These blocks can be used to identify the mobile operator to which the number belongs. In countries where Mobile Number Portability (MNP) is not allowed, these prefixes can be used to determine the home operator, as the home operator equals the prefix operator. In countries where MNP is allowed, another source of porting information is required to determine the home operator, so the prefix operator is relatively meaningless and only indicates to which operator the number was originally allocated. In the world of SMS, the prefix operator can be important for routing, as some routes only support certain prefix/home operator combinations. Be careful of aggregators who only support prefix routing, as this implies they do not support MNP routing, which is required in many countries to deliver a message effectively.
  • Price elasticity

    Price elasticity of supply and demand is believed to be a factor in the SMS ecosystem. Put simply, when the volume of SMS sent increases, the price decreases. Adversely, the lower the volume, the higher the price. This factor is important to consider when mobile operators set the price for an SMS.
  • PSTN

    Public Switched Telephone Network (PSTN) is the world’s collection of interconnected public telephone networks.


  • Reach

    Reach is a term commonly used in the SMS ecosystem to describe the destinations each mobile operator can send a message to. Reach is determined by commercial agreements, technical connectivity, and hub arrangements etc. A typical tier one mobile operator will have reach to hundreds of other mobile operators. If T-Mobile can send a message to Vodafone UK, then you would say T-Mobile has reach to Vodafone UK.
  • REST

    Representational State Transfer (REST) is an architectural style for designing distributed systems. It is not a standard, more a set of constraints such as being stateless, having a client / server relationship, and a uniform interface.
  • Retry schedule

    When an SMS message is sent to a recipient, it is expected it will be delivered to the handset within seconds. However, delivering an SMS is a relatively complex process, and an SMSC takes several measures to ensure a reliable service including retrying a message should it fail to deliver. An SMS may fail to deliver to a handset on its first delivery attempt for many reasons. These reasons can either be temporary or permanent, and if the latter, no additional retries will be attempted, and the delivery notification will be sent back to the sender to confirm the message failed.
  • RFID

    Radio Frequency Identification (RFID) is a technology using electromagnetic fields to read data store in tags embedded in other items such as ID cards.
  • Roaming

    When a subscriber travels outside their home operator service area, we say they are roaming onto another network. It is important SMS messages are still delivered correctly when a subscriber is roaming, and as such the foreign network’s VLR communicates with the HLR of the home network to ensure the location of the subscriber is maintained at all times. It should be noted that even while roaming, a subscriber will always send a message via their home SMSC.
  • Routing class

    A routing class is a term used by Sinch to explain a collection of routing attributes that together define the overall quality and performance of the SMS product. For example, the direct routing class is a made up of all Sinch’s direct connections and its own SMSCs to create a very high quality set of routes used for mission critical services.
  • RTC

    Real Time Communication (RTC) is live, instant communication with minimal latency.
  • RTP

    Real Time Protocol (RTP) is a network protocol for delivering audio and video over IP networks.


  • SDK

    Software Development Kit (SDK) is a set of software development tools that allows applications to be created.
  • Short Codes

    Short Codes are network specific access codes used for sending and receiving messages (both SMS and MMS) between consumers and companies. Short codes are recognized for use around the world in specific countries and are shorter than a normal mobile phone number, usually consisting of four to six digits, depending on the country. Short codes are used because they are memorable and easy to enter into a phone. They can also spell out memorable brand names (phone words) (e.g. 1-800-468-5865 for 1-800-GOT-JUNK), so the short code could be something like 485865 (GTJUNK).
  • SIM

    Subscriber Identity Module (SIM) is a removable smart card for mobile phones. SIM cards securely store the service-subscriber key (IMSI) used to identify a GSM subscriber. The SIM card allows users to change phones by simply removing the SIM card from one mobile phone and inserting it into another mobile phone.
  • SIM applet

    An application on the SIM card that holds business logic relevant for the SIM card.

    A Subscriber Identity Module – Over The Air (SIM-OTA) is used to change parameters on the SIM card remotely.
  • SIP

    Session Initiation Protocol (SIP) is a signalling protocol used for initiating, maintaining, modifying and terminating real-time sessions that involve video, voice, messaging and other communication applications and services between two or more endpoints on IP networks.
  • SIP Trunk

    A Session Initiation Protocol (SIP) Trunk or SIP Trunking is a way of communicating using VoIP rather than a traditional telephone line.
  • SMPP

    Short Message Peer-to-Peer Protocol (SMPP) is an open message transfer protocol that enables users to interact with an SMSC. The protocol defines the information which needs to be exchanged between the user and the SMSC and the operations associated with the exchange of SMS messages. Every request made using SMPP has an associated response.
  • SMS

    Short Message Service (SMS), more commonly referred to as text messaging. An SMS message is 160 characters long. The two most common forms of SMS are Person-to-Person (P2P), where messages are exchanged between two mobile phones and Application-to-Person (A2P), where messages originate from a system or application and are sent to a mobile phone.

  • SMS-MO

    A Short Message Service – Mobile Originating (SMS-MO) is an SMS sent from the SIM card.
  • SMS-MT

    A Short Message Service – Mobile Terminating (SMS-MT) is an SMS received by the SIM card.
  • SMSC

    Short Message Service Center (SMSC) is a server connected to an SS7 Network whose role is to send and receive messages to and from recipient handsets. Often it operates in a “store and forward” configuration, but some carriers operate in a “forward only” or a “forward and store” configuration.
  • SS7 network

    Signalling System 7 (SS7) is how the majority of the world’s mobile networks communicate with each other. It is a set of telephony protocols enabling the transmission of voice, data, control/session management information, and of course SMS. The SS7 protocol has layers based on the OSI (Open Systems Interchange) model. The MAP (Mobile Application Part) layer provides the functionality required for SMS transmission. The SMSC, HLR, VLR and MSC communicate together over the SS7 network utilizing MAP commands.

    Sinch Voice Application Markup Language (SVAML) is a command language to inform legacy Sinch (Voice) SDKs, it works on the same principal as HTML but is specific to Sinch technology.


  • TDMA

    Time Division Multiple Access (TDMA) is a channel access method for GSM networks. It allows several users to share the same frequency channel by dividing the signal into different time slots.
  • Terminating operator

    The terminating operator is an expression used to explain which Mobile Operator’s SMSC delivered a message to a subscriber. For example sending a message to MTN South Africa via Vodafone UK’s SMSC, we would say Vodafone UK was the terminating operator (or termination operator).
  • Text to Voice

    Text to Voice is a product used when an SMS message cannot be delivered (or sometimes as a preference). A message will delivered by calling the number and delivering the message through a voice recording that reads out the contents of the SMS message. This is a useful feature especially for people who have a visual impairment or only have a land line.
  • Thread

    Network protocol based on the IEEE 802.15.4 standard, similar to Zigbee, providing IPv6 addressing.
  • Throttle

    Closely related to throughput, throttle is a technique a server will use to prevent your application from exceeding its allowed throughput. By way of example, if your account is allowed to send at 10 msg/sec, and you try and submit at 20 msg/sec, then the receiving server will throttle your application send rate by either delaying acknowledgement or responding with throttle errors to slow your application down back down to 10 msg/sec.
  • Throughput

    Throughput is a term used to describe how many messages can be sent per second. For example a throughput of 10 messages per second suggests an SMS account can submit (and receive an acknowledgement) for up to 10 SMS messages per second. Typically throughput is limited by account service or by bind. You can increase message throughput by ensuring the SMPP/UCP client software you use is set to allow up to 10 pending operations. This is also called the asynchronous window. You can also increase your message throughput by using two separate BINDs for transmission.

  • TLS

    Transport Layer Security (TLS) is a network security protocol.
  • Toll free numbers

    Toll free numbers are an allowed Sender ID in the USA that can be used for two way text messaging.
  • TON

    Type Of Number (TON) is a value is set for both the originator and destination number in every SMS. It is used for both SMS routing and handset display purposes.



    Universal Computer Protocol – External Machine Interface (UCP-EMI) is a transfer protocol enabling users to interact with an SMSC. The protocol defines the information which needs to be exchanged between the user and the SMSC and the operations associated with the exchange of SMS messages. Every request made using UCP-EMI has an associated response, either positive or negative.
  • UCS2

    UCS2 is the unicode format required for characters in an SMS.
  • UDH

    The User Data Header (UDH) is a block of octets added to the beginning of the user data part of an SMS message. Due to the way an SMS message is limited to a maximum size of 140 bytes, the available user data length is reduced when a UDH is included. Its purpose is to inform the mobile handset of the type of data and data length of the user data part of an SMS message. Generally, the UDH is either used in combination with binary content known as smart messaging for ringtones, operator logos, WAP Push and vCards, or it is used for concatenated SMS. Binary content can also span across multiple message parts and therefore the UDH may contain both a smart message and a concatenation header.
  • UDP

    User Datagram Protocol (UDP) enables computers to send messages, or datagrams, to other hosts on an IP network.
  • UI

    A User Interface (UI) is what is used by people to interact with computers / software.
  • UMTS

    Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) cell phone technologies. To differentiate UMTS from competing network technologies, UMTS is sometimes marketed as 3GSM, emphasizing the combination of the 3G nature of the technology and the GSM standard which it was designed to succeed.
  • Username

    Username is a Sinch term used to define a distinct service that can be used to send SMS. Each username will have a different password, and can have different routing and pricing associated with it. When price updates are sent out they will be separated out by username.
  • USSD

    Unstructured Supplementary Service Data (USSD) is a GSM service that allows a phone to create a session with a software application (typically in the mobile operators network). Unlike SMS, USSD is a session based protocol which allows for real time interaction between the software and the end user. The most common use of USSD is by operators themselves to enable end users to check their balance, re-provision settings, and check settings e.g. getting your IMEI code can be done by dialling *#06#. Note that this should not be confused with ** codes, which are actual dial-able short numbers.
  • UX

    User Experience (UX) describes all elements of a customer interaction with a company, its services and its products.


  • Validity period

    Validity period is an optional value that can be set on a per message basis to control how long an SMSC should attempt to deliver an SMS message. It is usually only useful when a destination recipient handset is turned off or out of coverage, and an SMS message is time critical. The value of the validity period is the “number of minutes” from the time the SMS message is submitted, until it should expire. The value may be specified as an absolute (date and time to the second) or relative (indicated in HHMMSS). When this time is reached, an SMSC would generally return an expired delivery report. If no validity period is set, the SMSC default is used which is usually 7 days (10,080 minutes). For example - setting the validity period to 30 would result in an SMS message only being retried for delivery by an SMSC for a maximum of 30 minutes.
  • VLR

    Visitor Location Register (VLR) is a database which stores information about mobile phones that have recently joined a particular area of a mobile operator’s network. It plays a vital role in keeping track of roamed mobile phone subscribers and co-ordinates with the HLR to determine whether the mobile is a permanent subscriber or a temporary one. Whenever a Mobile Switch Center (MSC) detects a new mobile in its network, in addition to creating a new record in the VLR, it also updates the HLR of the mobile subscriber, apprising it of the new location of that mobile (the MSC address). The MSC address received during an HLR lookup for a particular mobile number is useful for identifying numbers roaming in another country. The foreign network that the number is logged onto can also be identified using this data.
  • VoIP

    Voice over Internet Protocol (VoIP) is a technology used for the delivery of voice communications (i.e. talking) over the internet.

  • VSAT

    Very Small Aperture Terminal (VSAT) is a satellite communication technology using small dish antennas for narrowband and broadband.


  • WebRTC

    Web Real Time Communications (WebRTC) is an open-source project that provides browsers and mobile applications with Real Time Communications (RTC) capabilities via simple APIs.


  • Z-Wave

    Communication protocol providing short range, low latency data transfer at rates and power consumptions lower than WiFi. Used primarily for home automation.
  • Zero-Hop

    If a message is delivered directly by the Sinch SMSC then it is a zero-hop connection.
  • Zigbee

    Communication protocol for personal area networking.