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| Inverse Address Resolution Protocol | |
|---|---|
| Name | Inverse Address Resolution Protocol |
| Acronym | INARP |
| Developer | Internet Engineering Task Force (IETF) |
| Initial release | 1980s |
| Type | Network protocol |
| Purpose | Mapping Internet Protocol addresses to link-layer addresses |
Inverse Address Resolution Protocol
Inverse Address Resolution Protocol provides a mechanism for discovering the network layer address corresponding to a link-layer address by inverting the mapping performed by Address Resolution Protocol; it is used in environments that involve legacy Stanford University network research, Xerox PARC experiments, and early Digital Equipment Corporation internetworking. INARP interacts with link-layer technologies such as Ethernet, Token Ring, and Frame Relay and with network-layer families including Internet Protocol version 4 and IPX. The protocol has been discussed in standards forums such as the Internet Engineering Task Force and implemented in router platforms from vendors like Cisco Systems and Juniper Networks.
Inverse Address Resolution Protocol functions as a request–reply protocol enabling a device to learn a logical address from a known physical address; it complements the mapping role of Address Resolution Protocol and coexists with neighbor discovery mechanisms in Sun Microsystems and Hewlett-Packard equipment. INARP is relevant to link-layer address management in environments involving RFC 826, RFC 1122, and other Request for Comments documents that shaped early Internet Protocol operation. Deployments historically spanned campus networks at Massachusetts Institute of Technology, service provider networks operated by AT&T, and experimental networks at Bell Labs.
INARP originated from research in the 1980s when interconnection of heterogeneous networks by organizations like ARPANET and Defense Advanced Research Projects Agency motivated reverse mapping techniques. Engineers from Xerox, Digital Equipment Corporation, and Intel Corporation contributed to proposals discussed at IETF working groups and in vendor drafts circulated among Novell and Cisco Systems engineers. The protocol’s conceptual predecessors include work at Stanford University and publications in proceedings of conferences such as ACM SIGCOMM and IEEE INFOCOM.
INARP operates at the boundary between link and network layers, leveraging link-layer frame delivery provided by IEEE 802.3, IEEE 802.5, or Point-to-Point Protocol implementations. A device sends an INARP Request containing a target link-layer address and expects an INARP Reply with the corresponding network-layer address, similar in transaction flow to mechanisms in X.25 networks and address discovery in OSI routing scenarios. Timing, retransmission, and caching behaviors mirror practices from Berkeley Software Distribution stacks and are implemented in routing platforms from Cisco Systems, Juniper Networks, and integrated into kernel networking code in FreeBSD and Linux releases influenced by work at University of California, Berkeley.
INARP defines a small set of messages: Request, Reply, and optionally Error or Proxy messages; fields include sender hardware address, target hardware address, sender protocol address, and target protocol address, paralleling fields found in RFC 826 ARP packets. Message framing adapts to Ethernet II and 802.2 LLC conventions as implemented by vendors such as Intel Corporation and Broadcom. Packet processing logic follows patterns used in TCP/IP stacks and diagnostic utilities influenced by tools developed at Sun Microsystems and Microsoft.
INARP inherits security challenges similar to those faced by Address Resolution Protocol and neighbor discovery mechanisms used in IPsec-related deployments and VPNs operated by Cisco Systems and Juniper Networks. Threats include spoofing, man-in-the-middle attacks, and cache poisoning, which have been analyzed in research from Massachusetts Institute of Technology, Stanford University, and ETH Zurich. Mitigations draw on access control lists in Cisco IOS, cryptographic protections in IPsec and IEEE 802.1X, and monitoring techniques from intrusion detection systems produced by Snort developers and companies like Palo Alto Networks.
Implementations of INARP have appeared in router firmware from Cisco Systems and in research stacks at University of California, Berkeley, MIT, and Carnegie Mellon University. Use cases include reverse address resolution in legacy Frame Relay clouds run by providers such as Verizon Communications and AT&T, and in laboratory environments emulating inter-network address mapping in projects at Bell Labs and Xerox PARC. INARP-inspired mechanisms also influenced neighbor discovery extensions in protocols used by Juniper Networks and embedded systems by Intel Corporation and Broadcom.
INARP is conceptually the inverse of Address Resolution Protocol as specified in RFC 826 and complements neighbor discovery approaches standardized for Internet Protocol version 6 in RFC 4861. Unlike ARP, which resolves a protocol address from a hardware address, INARP resolves a protocol address given a hardware identifier; this distinction has parallels in address mapping features of X.25, XNS, and IPX protocols used historically by Novell. Operational considerations compare to routing protocol interactions found in Open Shortest Path First and Border Gateway Protocol implementations where address discovery and reachability information are coordinated.
Category:Network protocols