What Is an IP Network?

An IP network is a communications infrastructure that uses the Internet Protocol to address, route, and deliver data packets between devices. The Internet Protocol defines a common format for encapsulating data into discrete units called datagrams, each carrying a source address, a destination address, and control information sufficient for independent routing across heterogeneous physical links. By operating at the network layer, IP separates the addressing and forwarding logic from the underlying transmission technologies, allowing Ethernet, fiber, wireless, and other link types to interoperate within a single logical network.

The protocol was first standardized in 1981 through IETF RFC 791, which remains the foundational specification for IPv4. IP draws on earlier work in packet switching from ARPANET and the CYCLADES project, and it was designed explicitly to support reliable communication across networks with differing topologies and failure modes.

Packet Switching and Addressing

IP networks are packet-switched: rather than establishing a dedicated circuit between sender and receiver, each datagram is treated as an independent unit and forwarded hop by hop toward its destination. Each device on an IP network is assigned at least one IP address, a numerical label that identifies both the host and the network segment it belongs to. IPv4 addresses are 32-bit values written in dotted decimal notation; the address space is divided into network and host portions using a subnet mask or prefix length. Routers examine the destination address in each arriving datagram and consult a forwarding table to select the next hop. The datagram is then passed to the next router until it reaches the destination network and the final hop delivers it to the addressed host.

Routing and Forwarding

Routing is the process of building and maintaining the forwarding tables that routers use to direct traffic. Interior gateway protocols such as OSPF and IS-IS exchange topology information within a single administrative domain, allowing routers to compute shortest paths using link-state or distance-vector algorithms. The Border Gateway Protocol (BGP), standardized in RFC 4271, is the exterior gateway protocol that interconnects the tens of thousands of autonomous systems that collectively form the global Internet. BGP selects routes based on policy attributes rather than pure path length, giving network operators control over traffic engineering and peering relationships. Forwarding itself is typically performed by specialized hardware using content-addressable memory (CAM) tables that match destination prefixes to outgoing interfaces at line rate.

Network Architecture and Scalability

An IP network can range from a two-device local area network to the global Internet. At larger scales, the network is organized hierarchically: access networks aggregate end users, regional networks carry traffic between cities, and backbone networks interconnect continents. This hierarchy relies on address aggregation, in which a single routing advertisement represents a block of addresses assigned to a region, reducing the size of global routing tables. Classless inter-domain routing (CIDR), introduced in 1993, replaced the earlier fixed class-based address allocation and enabled finer-grained aggregation. The IETF TCP/IP tutorial in RFC 1180 remains a readable introduction to how IP addressing, subnetting, and routing fit together in practice.

Applications

IP networks are the foundation for a broad range of communications and computing services, including:

• The public Internet and private enterprise intranets
• Voice over IP telephony and video conferencing
• Cloud computing and data center interconnection
• Industrial control system communications
• Mobile and broadband internet service delivery