Circuit-Level Gateway

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What Does Circuit-Level Gateway Mean?

A circuit-level gateway is a firewall that provides User Datagram Protocol (UDP) and Transmission Control Protocol (TCP) connection security, and works between an Open Systems Interconnection (OSI) network model’s transport and application layers such as the session layer. Unlike application gateways, circuit-level gateways monitor TCP data packet handshaking and session fulfillment of firewall rules and policies.

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Techopedia Explains Circuit-Level Gateway

A proxy server is a security barrier between internal and external computers, while a circuit-level gateway is a virtual circuit between the proxy server and internal client.

For example, when a user Web page access request passes through the circuit gateway, basic internal user information, such as IP address, is exchanged for proper feedback. Then, the proxy server forwards the request to the Web server. Upon receiving the request, the external server sees the proxy server’s IP address but does not receive any internal user information. The Web or real server sends the proxy server a proper response, which is forwarded to the client or end user via the circuit-level gateway.

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Margaret Rouse
Senior Editor
Margaret Rouse
Senior Editor

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.