A circuit-level gateway is a type of
firewall
Firewall may refer to:
* Firewall (computing), a technological barrier designed to prevent unauthorized or unwanted communications between computer networks or hosts
* Firewall (construction), a barrier inside a building, designed to limit the spr ...
.
Circuit-level gateways work at the
session layer
In the seven-layer OSI model of computer networking, the session layer is layer 5.
The session layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e., a semi-permanent dialogue. ...
of the
OSI model
The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...
, or as a "shim-layer" between the
application layer and the
transport layer
In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet protocol suite and the OSI model. The protocols of this layer provide end-to-end ...
of the
TCP/IP
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the set of communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suit ...
stack. They monitor TCP handshaking between packets to determine whether a requested session is legitimate. Information passed to a remote computer through a circuit-level gateway appears to have originated from the gateway. Firewall traffic is cleaned based on particular session rules and may be controlled to acknowledged computers only. Circuit-level firewalls conceal the details of the protected network from the external traffic, which is helpful for interdicting access to impostors. Circuit-level gateways are relatively inexpensive and have the advantage of hiding information about the private network they protect. However, they do not filter individual packets.
See also
*
Application firewall
An application firewall is a form of firewall that controls input/output or system calls of an application or service. It operates by monitoring and blocking communications based on a configured policy, generally with predefined rule sets to c ...
*
Application-level gateway
An application-level gateway (ALG, also known as application layer gateway, application gateway, application proxy, or application-level proxy) is a security component that augments a firewall or NAT employed in a computer network. It allows cust ...
firewall
*
Bastion host
*
Dual-homed Dual-homed or dual-homing can refer to either an Ethernet device that has more than one network interface, for redundancy purposes, or in firewall technology, one of the firewall architectures for implementing preventive security.
An example of dua ...
External links
* http://netsecurity.about.com/cs/generalsecurity/g/def_circgw.htm
* http://www.softheap.com/internet/circuit-level-gateway.html
* http://www.pcstats.com/articleview.cfm?articleid=1450&page=5
Internet architecture
Network socket
Transmission Control Protocol
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