Glossary

The SMS industry has a vocabulary that predates most of the people using it, and a Bangladeshi provider will quote you a rate card written entirely in it. These docs avoid that vocabulary on purpose — you should be able to send a message without learning what an SMSC is.

This page is here for when you meet the words anyway: in a contract, in a competitor's pricing table, or in an error from somebody else's API.

Message and encoding

Segment

The unit an SMS is actually billed in. One SMS carries 140 bytes of user data; a message that does not fit is split into several segments, each billed separately. A "message" is what you send, a segment is what you pay for. See Bangla SMS, or count a specific body with the segment calculator.

GSM-7

The original SMS character set, defined in GSM 03.38. Seven bits per character, so 140 bytes holds 160 characters. It covers basic Latin letters, digits, common punctuation and a small set of accented and Greek characters — and nothing else.

UCS-2

The fallback encoding for any text GSM-7 cannot represent, including all Bangla. Sixteen bits per character, so 140 bytes holds 70 characters. Encoding is a property of the whole message: one non-GSM-7 character moves the entire body to UCS-2.

Septet

A seven-bit unit — one GSM-7 character. Nine characters (^ { } \ [ ~ ] | and €) cost two septets each because they live in an extension table, which is why a message can exceed 160 "characters" worth of capacity at 155 visible characters.

Concatenation

Splitting a long message across several segments so the handset can reassemble it. The reassembly instructions live in a User Data Header that occupies six of the 140 bytes in every part, which is why concatenated limits are 153 and 67 rather than 160 and 70.

Unicode SMS

Market shorthand for UCS-2, and the term most Bangladeshi rate cards use. If a price list says "Unicode" it means Bangla, and it means 70 characters per segment.

Routing and identity

A2P

Application-to-person: messages sent by software to a human. Everything Nishchit sends is A2P. Distinct from P2P, person-to-person, which is ordinary texting between handsets and is priced and regulated differently.

MT and MO

Mobile-terminated is a message travelling to a handset; mobile-originated is one from a handset. Nishchit sends MT only — MO is inbound traffic, which is not available in Bangladesh. See two-way SMS.

Sender ID

What appears in the "from" line on the handset. Either numeric or alphanumeric. In Bangladesh an alphanumeric sender ID requires operator pre-registration; see Sending SMS to Bangladesh.

Masking and non-masking

Local market terms. Masking means an alphanumeric sender ID — your brand name in the from line. Non-masking means a numeric sender. Masking costs more, requires registration, and on the Bangladesh route requires a Bengali message body.

SMSC

Short Message Service Centre: the store-and-forward node inside an operator's network that actually accepts, queues and delivers a message. You will see it in other providers' error messages. You will never see it in a Nishchit response.

Aggregator

A company holding connections to several operators and reselling them as one interface. Most Bangladeshi SMS vendors are aggregators. Nishchit sits above this layer — see Exit Gate.

MNP

Mobile number portability: the ability to keep a number when changing operator. Bangladesh has it, which means a number's prefix tells you who issued it, not who carries it now.

MNP dipping

A lookup that resolves which network currently carries a ported number, so the message can be routed correctly. Some providers bill it as a separate line item on the rate card. Nishchit does not meter it — routing is included.

Short code and long code

A short code is a brief number leased for high-volume two-way messaging; a long code is an ordinary-length number used the same way. Neither is supported on Bangladesh's major networks.

Delivery

DLR

Delivery receipt (also delivery report): a message the network sends back confirming what happened to a message. This is the term that matters most in Bangladesh, because the primary route does not produce them.

delivery_status

Nishchit's field for what the network reported, as distinct from what Nishchit did. Values are unknown, delivered, undelivered and rejected. On a route with no DLR it stays unknown permanently — which is not a failure. See Delivery status.

status

Nishchit's field for what Nishchit did: accepted, sending, sent, failed. Always known, because Nishchit is the one doing it. Kept separate from delivery_status so that neither has to pretend to be the other.

Two-way SMS

Receiving replies to the messages you send. Not available in Bangladesh, so any design that depends on inbound messages — a STOP keyword handler, a reply-to-confirm flow — needs another channel.

Throughput / TPS

Transactions per second: how fast a route will accept submissions. Distinct from delivery speed, which depends on the network. Nishchit's published limits are on rate limits.

Content and compliance

OTP

One-time passcode. Treated as its own traffic class because it is the most time-sensitive and the least tolerant of a rewritten body. See OTP.

Transactional and promotional

Transactional messages arise from something the recipient did — an order, a login, a payment. Promotional messages are marketing. They are classified differently, they are subject to different rules, and promotional traffic is confined to a time window. See content policy.

KYC

Know Your Customer: identity and business verification before a provider will let you send. Nishchit runs none. Content inspection is the abuse control instead, which is why the content rules are published rather than discovered.

Trust tier

A per-project daily ceiling that is independent of your credit balance, lifting automatically as a project establishes a record. It exists because no-KYC signup needs a volume brake that is not a credit check.

Nishchit's own terms

These are ours, not the industry's. They appear in the API, so they are defined here too.

Credit

One credit buys one SMS segment. Credits are the billing unit end to end — the calculator, the pricing preview endpoint and the invoice all count the same thing. See pricing.

Content Guard

The stage that inspects every message body before it can reach a carrier: it normalises the text, detects the language, classifies the intent and applies the published policy. Every verdict is logged with the rule-set version that produced it.

Exit Gate

The only component that chooses a gateway. It filters candidates by country, sender type, declared capability and live health, enforces the per-attempt timeout, and normalises whatever the provider returns into one shape.

Idempotency key

A key you attach to a send so a retry cannot produce a second message. Claimed before the upstream call, so a concurrent duplicate gets a conflict rather than a second SMS. See Send an SMS.

Words you will not find in a Nishchit response

Deliberately. Everything above the Exit Gate speaks Nishchit; everything below it speaks provider dialect, and the boundary is enforced rather than merely intended.

• The name of the upstream gateway or aggregator carrying your message.
• A provider's own status code, error string or reason text.
• SMSC-level or operator-level errors, in their original wording.

Every upstream failure is mapped to a Nishchit error code with its own documentation anchor, so a carrier configuration problem reaches you as a carrier configuration problem — never as "insufficient credits".