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A Guide to X.25 in Computer Networking

X.25 was the networking protocol suite of choice in the 1980s

By Bradley Mitchell Bradley Mitchell Writer Massachusetts Institute of Technology University of Illinois An MIT graduate who brings years of technical experience to articles on SEO, computers, and wireless networking. lifewire's editorial guidelines Updated on April 4, 2020 Tweet Share Email Tweet Share Email Home Networking The Wireless Connection Routers & Firewalls Network Hubs ISP Broadband Ethernet Installing & Upgrading Wi-Fi & Wireless X.25 was a standard suite of protocols used for packet-switched communications over a wide area network — a WAN. A protocol is an agreed-upon set of procedures and rules. Two devices that follow the same protocols can understand each other and exchange data.

History of X 25

Wikimedia Commons X.25 was developed in the 1970s to carry voice over analog telephone lines — dial-up networks — and is one of the oldest packet-switched services. Typical applications of X.25 included automatic teller machine networks and credit card verification networks. X.25 also supported a variety of mainframe terminal and server applications. The 1980s were the heydays of X.25 technology when it was used by public data networks Compuserve, Tymnet, Telenet, and others. In the early '90s, many X.25 networks were replaced by Frame Relay in the U.S. Some older public networks outside the U.S. continued to use X.25 until recently. Most networks that once required X.25 now use the less complex Internet Protocol. X-25 is still used in some ATMs and credit card verification networks.

X 25 Structure

Each X.25 packet contained up to 128 bytes of data. The X.25 network handled packet assembly at the source device, the delivery, and the reassembly at the destination. X.25 packet delivery technology included not only switching and network-layer routing but also error checking and re-transmission logic should a delivery failure occur. X.25 supported multiple simultaneous conversations by multiplexing packets and using virtual communication channels. X.25 offered three basic layers of protocols: Physical layerData link layerPacket layer X.25 pre-dates the OSI Reference Model, but the X.25 layers are analogous to the physical layer, data link layer and network layer of the standard OSI model. With the widespread acceptance of Internet Protocol (IP) as a standard for corporate networks, X.25 applications migrated to cheaper solutions using IP as the network layer protocol and replacing the lower layers of X.25 with Ethernet or with new ATM hardware. Was this page helpful? Thanks for letting us know! Get the Latest Tech News Delivered Every Day Subscribe Tell us why! Other Not enough details Hard to understand Submit More from Lifewire What Is a Switch? Computer Networking How to Use the Netstat Command on Mac What Is an Intrusion Prevention System (IPS)? What Is IPSec? What Is a Wide Area Network (WAN)? An Overview of Packet Switching on Computer Networks A Short Guide on Networking Fundamentals What Is Network Encryption? Why There Are Only 13 DNS Root Name Servers Common Questions and Answers on the OSI Network Model The OSI Model Layers from Physical to Application Frame Relay Packet-Switching Technology Explained Circuit Switching vs. Packet Switching Types of Network Connections What Is a Web Browser? What Is Computer Networking? Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up Newsletter Sign Up By clicking “Accept All Cookies”, you agree to the storing of cookies on your device to enhance site navigation, analyze site usage, and assist in our marketing efforts. Cookies Settings Accept All Cookies