Internet Protocol version 4

Internet Protocol version 4
Michel Bakni · CC BY-SA 4.0 · source
Name	Internet Protocol version 4
Status	In widespread use
Initial release	1981
Developer	DARPA, Vint Cerf, Bob Kahn, RFC 791
Website	RFC 791

Internet Protocol version 4 is the fourth iteration of the Internet Protocol suite used to route packets across internetworks established by ARPANET, DARPA, Stanford University, MIT, and other early research institutions. It underpins major deployments by Cisco Systems, Juniper Networks, IBM, Microsoft, and Google and remains central to infrastructure services provided by AT&T, Verizon Communications, NTT, Deutsche Telekom, and China Telecom. Designed contemporaneously with protocols such as Transmission Control Protocol, User Datagram Protocol, File Transfer Protocol, Domain Name System, and Simple Mail Transfer Protocol, it shaped the operational model used by ICANN, IANA, RIPE NCC, ARIN, and APNIC for address management.

Overview

IPv4 emerged from research projects at Stanford Research Institute, Bolt Beranek and Newman, RAND Corporation, and standards bodies including the Internet Engineering Task Force and Internet Architecture Board. RFC publications such as RFC 791, RFC 793, RFC 791 revisions, and analyses by researchers at University of California, Berkeley, Carnegie Mellon University, University of Illinois Urbana-Champaign, and Massachusetts Institute of Technology codified packet formats, semantics, and interoperability expectations used by commercial vendors like Hewlett-Packard, Sun Microsystems, and Oracle Corporation. Operational deployment involved backbone networks operated by Telenor, Sprint Corporation, BT Group, and research grids funded by NSF and national labs including Los Alamos National Laboratory.

Technical Specifications

The protocol specifies a packet header with fields that influenced implementations by Intel Corporation and ARM Holdings in network interface controllers and by operating systems such as Unix, BSD, Linux, FreeBSD, Microsoft Windows NT, and Apple macOS. Key header fields—version, IHL, Type of Service, Total Length, Identification, Flags, Fragment Offset, Time to Live, Protocol, Header Checksum, Source Address, Destination Address, and Options—are described in RFCs and implemented in stacks by NetBSD, Cisco IOS, Juniper Junos, OpenBSD, Netgear devices, and embedded platforms produced by Broadcom. The protocol interoperates with link-layer technologies including Ethernet, Wi-Fi, FDDI, SONET, ATM, and PPP and is encapsulated within tunneling mechanisms used by MPLS, GRE, and L2TP.

Addressing and Subnetting

Addressing uses 32-bit numeric identifiers allocated by IANA and delegated by regional registries such as ARIN, RIPE NCC, APNIC, LACNIC, and AFRINIC; enterprises and service providers including Amazon Web Services, Microsoft Azure, Google Cloud Platform, Facebook, and Akamai Technologies manage large blocks via allocation policies influenced by governance from ICANN and policy discussions at IETF working groups. Classful addressing historically divided spaces into Class A, B, and C networks; later techniques such as Classless Inter-Domain Routing were introduced by Cynthia Dwork and others and standardized in RFCs adopted by IETF to mitigate exhaustion. Subnet masks, CIDR notation, Network Address Translation devices produced by Cisco Systems and Juniper Networks, private ranges documented in RFCs, and DHCP servers implemented in ISC DHCP, Microsoft DHCP Server, and cloud platforms provide operational addressing configuration. Address exhaustion drove interventions by policymakers in European Commission and coordination among registries, and spurred research in academia at Princeton University and ETH Zurich.

Routing and Protocol Operation

Routing of packets is performed by routers using control-plane protocols such as Border Gateway Protocol, Open Shortest Path First, Routing Information Protocol, and extensions including BGP4+ and route reflectors used in networks operated by Level 3 Communications and NTT Communications. Forwarding decisions rely on longest-prefix match and routing tables aggregated across autonomous systems managed by operators represented in organizations like the IETF and the Internet Society. Packet fragmentation and reassembly interact with link MTU considerations in deployments over DSL, Cable modem, Fiber to the Home, and satellite links operated by SpaceX and Intelsat. Tools and utilities such as ping, traceroute, tcpdump, Wireshark, and NetFlow are used by network engineers at Cisco and service providers for monitoring and diagnostics.

Security and Vulnerabilities

Protocol design choices have led to exploitable behaviors studied by researchers at CERT Coordination Center, SANS Institute, Krebs on Security, MITRE Corporation, and academia including Stanford University and University of California, Berkeley. Threats include IP spoofing, fragmentation attacks, denial-of-service vectors observed in incidents involving botnets like Mirai and Conficker, and amplification attacks leveraging protocols mediated by IPv4. Mitigations involve ingress and egress filtering recommended by IETF BCPs, security extensions and practices from NIST, deployment of firewalls by vendors such as Palo Alto Networks and Check Point, and adoption of IPsec standards developed by the IETF's Security Area and implemented by OpenSSL, StrongSwan, and enterprise appliances.

Transition and Coexistence with IPv6

IPv4 coexistence with successor protocols influenced transition mechanisms specified by IETF RFCs and implemented by vendors Cisco Systems, Juniper Networks, Nokia, and Huawei. Techniques include dual-stack operation used by cloud providers Amazon Web Services, Google Cloud Platform, and Microsoft Azure; tunneling methods like 6to4 and Teredo; translation systems such as NAT64 and DNS64; and carrier-grade NAT deployments by operators including Verizon Communications and China Mobile. Policy and allocation decisions by IANA and regional registries, coordinated by organizations like ICANN and Internet Society, guided depletion management and incentives for adoption of IPv6 across content providers such as Facebook, Google, Netflix, and Cloudflare.

Category:Internet protocols