The paper discusses the challenges faced by the current Internet architecture in environments with very long delay paths and frequent network partitions, particularly in mobile and extreme environments. It proposes a new network architecture and application interface called the Delay-Tolerant Networking (DTN) architecture, which is designed to interconnect diverse networks, including terrestrial mobile networks, exotic media networks, military ad-hoc networks, and sensor/actuator networks. The DTN architecture operates as an overlay above the transport layers of interconnected networks, providing services such as in-network data storage and retransmission, interoperable naming, authenticated forwarding, and a coarse-grained class of service. The DTN architecture is characterized by its focus on message-based operations, with message aggregates known as "bundles" and routers called "bundle forwarders" or DTN gateways. These gateways handle message forwarding, store messages in nonvolatile storage, map identifiers between different transport layers, and perform authentication and access control checks. The architecture uses a region-based approach, where regions are defined by their ability to communicate without using DTN gateways, and DTN gateways serve as points of interconnection between different regions. Key features of the DTN architecture include: - **Name Tuples**: Identifiers for objects or groups of objects, consisting of a globally-unique region name and a locally-resolvable entity name. - **Custody Transfer**: A mechanism for delegating the responsibility for delivering messages to other nodes, reducing the burden on end nodes. - **Path Selection and Scheduling**: Routes are composed of time-dependent contacts, and the architecture includes methods for selecting the next message to be sent. - **Time Synchronization**: Coarse-level time synchronization is required for identifying message fragments and purging expired messages. - **Security**: Each message includes an immutable "postage stamp" containing sender identity, class of service, and cryptographic material for verification. - **Congestion and Flow Control**: Proactive and reactive methods are used to manage congestion and flow control, considering the unique constraints of DTN. The application interface for DTN applications is non-blocking and requires applications to handle potential delays and network partitioning. The DTN architecture is designed to be flexible and interoperable, providing a robust solution for challenging environments.The paper discusses the challenges faced by the current Internet architecture in environments with very long delay paths and frequent network partitions, particularly in mobile and extreme environments. It proposes a new network architecture and application interface called the Delay-Tolerant Networking (DTN) architecture, which is designed to interconnect diverse networks, including terrestrial mobile networks, exotic media networks, military ad-hoc networks, and sensor/actuator networks. The DTN architecture operates as an overlay above the transport layers of interconnected networks, providing services such as in-network data storage and retransmission, interoperable naming, authenticated forwarding, and a coarse-grained class of service. The DTN architecture is characterized by its focus on message-based operations, with message aggregates known as "bundles" and routers called "bundle forwarders" or DTN gateways. These gateways handle message forwarding, store messages in nonvolatile storage, map identifiers between different transport layers, and perform authentication and access control checks. The architecture uses a region-based approach, where regions are defined by their ability to communicate without using DTN gateways, and DTN gateways serve as points of interconnection between different regions. Key features of the DTN architecture include: - **Name Tuples**: Identifiers for objects or groups of objects, consisting of a globally-unique region name and a locally-resolvable entity name. - **Custody Transfer**: A mechanism for delegating the responsibility for delivering messages to other nodes, reducing the burden on end nodes. - **Path Selection and Scheduling**: Routes are composed of time-dependent contacts, and the architecture includes methods for selecting the next message to be sent. - **Time Synchronization**: Coarse-level time synchronization is required for identifying message fragments and purging expired messages. - **Security**: Each message includes an immutable "postage stamp" containing sender identity, class of service, and cryptographic material for verification. - **Congestion and Flow Control**: Proactive and reactive methods are used to manage congestion and flow control, considering the unique constraints of DTN. The application interface for DTN applications is non-blocking and requires applications to handle potential delays and network partitioning. The DTN architecture is designed to be flexible and interoperable, providing a robust solution for challenging environments.