# gateway

> hardware or software components that connect between two network systems

**Wikidata**: [Q487365](https://www.wikidata.org/wiki/Q487365)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Gateway_(telecommunications))  
**Source**: https://4ort.xyz/entity/gateway

## Summary
A gateway is a hardware or software component that connects two different network systems, enabling communication and data transfer between them. It acts as an intermediary, translating protocols, managing traffic, and ensuring compatibility between disparate networks, such as linking a local network to the internet or integrating legacy systems with modern ones.

## Key Facts
- A gateway is classified as **networking hardware**, a category of devices that mediate data in computer networks.
- It can exist as both **hardware** (e.g., routers, Modbus gateways) and **software** (e.g., email gateways like MDaemon).
- The **default gateway** is a critical node in IP networks, serving as the forwarding host (router) when no other route matches a packet’s destination IP address.
- Specialized types include **XMPP transport gateways** (for legacy instant messaging), **WebRTC Gateways**, and **GSM Gateways** (for mobile networks).
- Notable examples include **DavMail** (an Exchange gateway) and **ZLAN5142** (a Modbus gateway for industrial networks).
- The term has aliases in multiple languages, including *Pasarela* (Spanish), *Passerelle* (French), and *ゲートウェー* (Japanese).
- Gateway is referenced in authoritative sources like the **Library of Congress** (ID: sh98007144) and **Encyclopedia of China** (ID: 235688).

## FAQs
### Q: What is the difference between a gateway and a router?
A: While both manage network traffic, a **gateway** connects dissimilar networks (e.g., a local network to the internet) and may perform protocol translation, whereas a **router** typically directs traffic within the same network type (e.g., between IP networks). A default gateway is often a router, but not all routers are gateways.

### Q: What are some real-world examples of gateways?
A: Examples include **DavMail** (bridging Microsoft Exchange to standard email clients), **Amazon Sidewalk bridges** (connecting IoT devices), and **SK7MQ** (a D-STAR radio gateway in Sweden). Industrial systems like **ZLAN5142** act as Modbus gateways for automation.

### Q: Can a gateway be purely software-based?
A: Yes. Software gateways like **MDaemon** (email/groupware server) or **XMPP transports** (for legacy IM systems) operate without dedicated hardware, running on standard servers or devices to facilitate cross-network communication.

### Q: What is a default gateway?
A: A default gateway is the node (usually a router) in an IP network that forwards traffic to external networks when no specific route is defined for a packet’s destination. It is essential for internet connectivity in most local networks.

### Q: Are gateways used in mobile networks?
A: Yes, **GSM Gateways** bridge mobile (cellular) networks with other systems, such as VoIP or landline networks, enabling cost-effective call routing and integration.

## Why It Matters
Gateways are fundamental to modern networking, solving the problem of **interoperability** between diverse systems. Without gateways, networks using different protocols (e.g., a corporate email server and a public internet service) would be unable to communicate. They enable critical functions like internet access (via default gateways), cross-platform messaging (XMPP transports), and industrial automation (Modbus gateways). In telecom, gateways reduce costs by routing calls between mobile and VoIP networks. Their role in bridging legacy and emerging technologies ensures continuity in infrastructure upgrades, making them indispensable in IT, IoT, and telecommunications.

## Notable For
- **Protocol translation**: Gateways convert data formats between incompatible networks (e.g., email protocols, industrial standards like Modbus).
- **Default gateway role**: The linchpin for internet connectivity in IP networks, handling traffic when no other route exists.
- **Specialized applications**: Unique implementations like **D-STAR radio gateways** (amateur radio) and **WebRTC Gateways** (real-time communication).
- **Hybrid hardware/software nature**: Can be physical devices (e.g., GSM Gateways) or software solutions (e.g., DavMail).
- **Global standardization**: Recognized in authoritative taxonomies (Library of Congress, Encyclopedia of China) and multilingual technical literature.

## Body
### Definition and Core Function
A gateway is a **network node** that interfaces between two systems with different communication protocols, architectures, or technologies. It operates at the **application layer** (Layer 7) of the OSI model but can also function at lower layers depending on the use case. Unlike bridges or switches, which connect similar networks, gateways handle **disparate environments**, such as:
- A local area network (LAN) and the internet.
- Legacy instant messaging (IM) systems and modern XMPP networks.
- Industrial control systems (e.g., Modbus) and enterprise IT networks.

### Types of Gateways
1. **Hardware Gateways**
   - **Default Gateway**: A router that forwards IP traffic to external networks when no specific route is configured. Examples include home broadband routers.
   - **GSM Gateway**: Connects cellular networks to VoIP or PSTN (Public Switched Telephone Network), often used for cost-saving call routing.
   - **Industrial Gateways**: Devices like the **ZLAN5142**, which translate Modbus protocols for factory automation.

2. **Software Gateways**
   - **Email Gateways**: **MDaemon** and **DavMail** act as intermediaries between proprietary systems (e.g., Microsoft Exchange) and standard protocols (IMAP/SMTP).
   - **XMPP Transport**: Proxies that enable legacy IM clients (e.g., ICQ, AIM) to communicate via XMPP.
   - **WebRTC Gateway**: Facilitates real-time audio/video communication between WebRTC-enabled browsers and traditional telephony systems.

3. **Specialized Gateways**
   - **D-STAR Gateway**: Used in amateur radio (e.g., **SK7MQ** in Sweden) to link digital radio networks globally.
   - **Amazon Sidewalk Bridge**: Extends low-bandwidth IoT device connectivity over long ranges using shared networks.

### Technical Components
- **Gateway Address**: A network address (e.g., IP) assigned to the gateway, used by devices to route outbound traffic.
- **Protocol Conversion**: Translates between protocols (e.g., HTTP to Modbus, SIP to PSTN).
- **Security Features**: Many gateways include firewalls, encryption (e.g., VPN gateways), or authentication (e.g., LDAP in DavMail).

### Historical and Academic Context
- The concept of gateways predates the modern internet, originating in early **packet-switched networks** (e.g., ARPANET).
- Standardized in telecommunications literature, including the **Library of Congress** (subject heading: *sh98007144*) and **Encyclopedia of China** (ID: 235688).
- Referenced in multilingual technical dictionaries (e.g., *OmegaWiki*, *Treccani Vocabulary*).

### Use Cases
- **Enterprise IT**: Connecting internal networks to cloud services or legacy systems.
- **Telecommunications**: GSM gateways reduce international call costs by routing traffic over IP.
- **Industrial IoT**: Modbus gateways integrate factory equipment with enterprise software.
- **Consumer Tech**: Home routers act as default gateways for internet access.

## Schema Markup
```json
{
  "@context": "https://schema.org",
  "@type": "Thing",
  "name": "gateway",
  "description": "Hardware or software components that connect between two network systems, enabling communication and protocol translation.",
  "url": "https://en.wikipedia.org/wiki/Gateway_(telecommunications)",
  "sameAs": [
    "https://www.wikidata.org/wiki/Q184583",
    "https://en.wikipedia.org/wiki/Gateway_(telecommunications)"
  ],
  "additionalType": "https://www.wikidata.org/wiki/Q184583"
}

## References

1. [Source](https://github.com/JohnMarkOckerbloom/ftl/blob/master/data/wikimap)
2. National Library of Israel Names and Subjects Authority File