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Circuit-level Gateway
A circuit-level gateway is a type of firewall. Circuit-level gateways work at the session layer of the OSI model, or as a "shim-layer" between the application layer and the transport layer of the TCP/IP 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 * Application-level gateway firewall * Bastion host * Dual-homed Dual-homed or dual-ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Firewall (networking)
In computing, a firewall is a network security system that monitors and controls incoming and outgoing network traffic based on configurable security rules. A firewall typically establishes a barrier between a trusted network and an untrusted network, such as the Internet or between several VLANs. Firewalls can be categorized as network-based or host-based. History The term '' firewall'' originally referred to a wall to confine a fire within a line of adjacent buildings. Later uses refer to similar structures, such as the metal sheet separating the engine compartment of a vehicle or aircraft from the passenger compartment. The term was applied in the 1980s to network technology that emerged when the Internet was fairly new in terms of its global use and connectivity. The predecessors to firewalls for network security were routers used in the 1980s. Because they already segregated networks, routers could filter packets crossing them. Before it was used in real-life computin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. Communication sessions consist of requests and responses that occur between applications. Session-layer services are commonly used in application environments that make use of remote procedure calls (RPCs). An example of a session-layer protocol is the OSI protocol suite session-layer protocol, also known as X.225 or ISO 8327. In case of a connection loss this protocol may try to recover the connection. If a connection is not used for a long period, the session-layer protocol may close it and re-open it. It provides for either full duplex or half-duplex operation and provides synchronization points in the stream of exchanged messages. Other examples of session layer implementations include Zone Information Protocol (ZIP) – the Apple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OSI Model
The Open Systems Interconnection (OSI) model is a reference model developed by the International Organization for Standardization (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems interconnection." In the OSI reference model, the components of a communication system are distinguished in seven abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application. The model describes communications from the physical implementation of transmitting bits across a transmission medium to the highest-level representation of data of a distributed application. Each layer has well-defined functions and semantics and serves a class of functionality to the layer above it and is served by the layer below it. Established, well-known communication protocols are decomposed in software development into the model's hierarchy of function calls. The Internet protocol suite as defined in and is a model of net ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Application Layer
An application layer is an abstraction layer that specifies the shared communication protocols and interface methods used by hosts in a communications network. An ''application layer'' abstraction is specified in both the Internet Protocol Suite (TCP/IP) and the OSI model. Although both models use the same term for their respective highest-level layer, the detailed definitions and purposes are different. Internet protocol suite In the Internet protocol suite, the application layer contains the communications protocols and interface methods used in process-to-process communications across an Internet Protocol (IP) computer network. The application layer only standardizes communication and depends upon the underlying transport layer protocols to establish host-to-host data transfer channels and manage the data exchange in a client–server or peer-to-peer networking model. Though the TCP/IP application layer does not describe specific rules or data formats that applications m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 communication services for applications. It provides services such as connection-oriented communication, reliability, flow control, and multiplexing. The details of implementation and semantics of the transport layer of the Internet protocol suite, which is the foundation of the Internet, and the OSI model of general networking are different. The protocols in use today in this layer for the Internet all originated in the development of TCP/IP. In the OSI model the transport layer is often referred to as Layer 4, or L4, while numbered layers are not used in TCP/IP. The best-known transport protocol of the Internet protocol suite is the Transmission Control Protocol (TCP). It is used for connection-oriented transmissions, whereas the con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TCP/IP
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are the Transmission Control Protocol (TCP), the User Datagram Protocol (UDP), and the Internet Protocol (IP). Early versions of this networking model were known as the Department of Defense (DoD) model because the research and development were funded by the United States Department of Defense through DARPA. The Internet protocol suite provides end-to-end data communication specifying how data should be packetized, addressed, transmitted, routed, and received. This functionality is organized into four abstraction layers, which classify all related protocols according to each protocol's scope of networking. An implementation of the layers for a particular application forms a protocol stack. From lowest to highest, the layers are the li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 choose from. The two primary categories of application firewalls are ''network-based'' and ''host-based''. History Gene Spafford of Purdue University, Bill Cheswick at AT&T Laboratories, and Marcus Ranum described a third-generation firewall known as an application layer firewall. Marcus Ranum's work, based on the firewall created by Paul Vixie, Brian Reid, and Jeff Mogul, spearheaded the creation of the first commercial product. The product was released by DEC, named the DEC SEAL by Geoff Mulligan - Secure External Access Link. DEC's first major sale was on June 13, 1991, to Dupont. Under a broader DARPA contract at TIS, Marcus Ranum, Wei Xu, and Peter Churchyard developed the Firewall Toolkit (FWTK) and made it freely available ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 mobile network. It allows customized NAT traversal filters to be plugged into the gateway to support address and port translation for certain application layer "control/data" protocols such as FTP, BitTorrent, SIP, RTSP, file transfer in IM applications. In order for these protocols to work through NAT or a firewall, either the application has to know about an address/port number combination that allows incoming packets, or the NAT has to monitor the control traffic and open up port mappings ('' firewall pinholes'') dynamically as required. Legitimate application data can thus be passed through the security checks of the firewall or NAT that would have otherwise restricted the traffic for not meeting its limited filter criteria. Functions An ALG may offer the foll ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bastion Host
A bastion host is a special-purpose computer on a network specifically designed and configured to withstand attacks, so named by analogy to the bastion, a military fortification. The computer generally hosts a single application or process, for example, a proxy server or load balancer, and all other services are removed or limited to reduce the threat to the computer. It is hardened in this manner primarily due to its location and purpose, which is either on the outside of a firewall or inside of a demilitarized zone (DMZ) and usually involves access from untrusted networks or computers. These computers are also equipped with special networking interfaces to withstand high-bandwidth attacks through the internet. Definitions The term is generally attributed to a 1990 article discussing firewalls by Marcus J. Ranum, who defined a bastion host as "a system identified by the firewall administrator as a critical strong point in the network security. Generally, bastion hosts will h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 dual-homed devices are enthusiast computing motherboards that incorporate dual Ethernet network interface cards. Usage In Ethernet LANs, dual-homing is a network topology whereby a networked device is built with more than one network interface. Each interface or port is connected to the network, but only one connection is active at a time. The other connection is activated only if the primary connection fails. Traffic is quickly rerouted to the backup connection in the event of link failure. This feature was designed to provide telecommunications-grade reliability and redundancy to Ethernet networks. Multihoming is a more general category, referring to a device having more than one network connection. In firewalls Firewall dual-homi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internet Architecture
World Wide Web topology is distinct from Internet topology. While the former focuses on how web pages are interconnected through hyperlinks, the latter refers to the layout of network infrastructure like routers, ISPs, and backbone connections. The Jellyfish model of the World Wide Web topology represents the web as a core of highly connected nodes (web pages) surrounded by layers of less connected nodes. The Bow Tie model, on the other hand, divides the web into distinct zones: a strongly connected core, an 'IN' group leading into the core, an 'OUT' group leading out, and disconnected components. This model emphasizes the flow of hyperlinks between different parts of the web.. Models of web page topology Jellyfish Model The simplistic Jellyfish model of the World Wide Web centers around a large strongly connected core of high- degree web pages A web page (or webpage) is a World Wide Web, Web document that is accessed in a web browser. A website typically consists of many w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Socket
A network socket is a software structure within a network node of a computer network that serves as an endpoint for sending and receiving data across the network. The structure and properties of a socket are defined by an application programming interface (API) for the networking architecture. Sockets are created only during the lifetime of a process of an application running in the node. Because of the standardization of the TCP/IP protocols in the development of the Internet, the term ''network socket'' is most commonly used in the context of the Internet protocol suite, and is therefore often also referred to as Internet socket. In this context, a socket is externally identified to other hosts by its socket address, which is the triad of transport protocol, IP address, and port number. The term ''socket'' is also used for the software endpoint of node-internal inter-process communication (IPC), which often uses the same API as a network socket. Use The use of the term ''so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
