Introduction to Real-Time WAN Transport

52.1 Introduction to Real-Time WAN Transport

Real-Time WAN Transport is a smart transport that enables secure, scalable, and high-performance communication over wide area networks (WANs), including public networks. It extends Connext capabilities to WAN environments. Real-Time WAN Transport uses UDP as the underlying IP transport-layer protocol to better anticipate and adapt to the challenges of diverse network conditions, device mobility, and the dynamic nature of WAN system architectures.

Real-Time WAN Transport, in combination with RTI Cloud Discovery Service, provides a complete, seamless solution out of the box for WAN connectivity. This WAN connectivity solution, including Real-Time WAN Transport and Cloud Discovery Service, is available as an optional add-on.

Real-Time WAN Transport replaces the transport capabilities of the Secure WAN Transport optionally available with previous Connext releases, and provides the following capabilities:

NAT (Network Address Translator) traversal: Ability to communicate between DomainParticipants running in a Local Area Network (LAN) that is behind a NAT-enabled router, and DomainParticipants on the outside of the NAT across a WAN. This functionality is provided in combination with Cloud Discovery Service (see 52.3.1 NAT Traversal ).
IP mobility: Support for network transitions and changes in IP addresses in any of the DomainParticipants participating in the communication (see 52.3.7 IP Mobility).
Security: Secure communications between DomainParticipants using Security Plugins (see 52.9 Security ).

Real-Time WAN Transport does not require third-party components, such as STUN servers, or protocols like SIP to handle session establishment. Using a single API and security model, you can leverage the extensive capabilities of the Connext framework and ecosystem, including tools and infrastructure services, even for real-time connectivity from edge to cloud and back in highly distributed systems that communicate across wide area networks.

For Real-Time WAN Transport example code, see https://github.com/rticommunity/rticonnextdds-examples/tree/develop/examples/connext_dds/real_time_wan_transport.

52.2 Key Terms

52.2.1 Basic Terms

Wide Area Network (WAN): A wide area network (WAN) is a collection of local area networks (LANs) or other networks that communicate with one another. A WAN is essentially a network of networks, with the Internet being the world's largest WAN.

Cellular Network (or Cellular WAN): A cellular network is a wide area network for voice and data that is typically provided by the cellular carriers to transmit a wireless signal over a range of several miles to a mobile device.

External DomainParticipant: A DomainParticipant using a Real-Time WAN Transport that is publicly reachable at a public address. Being reachable at a public IP address does not mean that the DomainParticipant is not behind a NAT-enabled router. It is possible that an external DomainParticipant is behind a NAT-enabled router if the network administrator configures a static NAT mapping between the DomainParticipant private address and a public address.

52.2.2 IP Address Types

IP Transport Address (or Address): The combination of the IPv4 address and the UDP Port where an application accepts incoming traffic. Sometimes you will also see the term "address" being used to refer to an IP transport address when the context is clear.

External IP Transport Address (or External Address or Public Address): An IP transport address that is routable on a WAN. When the WAN is the Internet, the term "Internet-routable address" can be used instead.

Private IP Transport Address (or Private Address or Internal Address): The IP transport address of an application that sits behind a NAT. This address is not reachable from external applications running outside the NAT.

Service Reflexive Address: The public IP transport address that Cloud Discovery Service obtains for a UUID locator contained in the participant announcement sent by a DomainParticipant.

52.2.3 Locators

RTPS Locator (or Locator): A Connext endpoint (DataWriter or DataReader) address unit that consists of a transport class, RTPS port, and locator transport address (128-bit).

Reachable Locator: Locator associated with a DDS endpoint (DataWriter or DataReader) to which another DDS endpoint can send data.

RTPS UUID WAN Locator (or UUID Locator): A WAN locator for a Real-Time WAN Transport that is not reachable. UUID locators are transformed into UUID+PUBLIC locators by associating a public IP transport address to the UUID.

RTPS UUID+PUBLIC WAN Locator (or UUID+PUBLIC Locator): A WAN locator for a Real-Time WAN Transport that is reachable. The locator encapsulates a public IP transport address as part of the locator address.

52.2.4 WAN Ecosystem

Session Traversal Utilities for NAT (STUN): Standardized set of methods, including a network protocol, for traversal of network address translator gateways in applications of real-time voice, video, messaging, and other interactive communications.

STUN Server: A STUN server enables clients to find out their public IP transport address and NAT type.

Interactive Connectivity Establishment (ICE): ICE is a protocol used for NAT traversal. ICE uses a combination of methods including STUN and Traversal Using Relay NAT (TURN) to traverse NATs.