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TCP Hole Punching
TCP NAT traversal and TCP hole punching (sometimes NAT punch-through) in computer networking occurs when two hosts behind a network address translation (NAT) are trying to connect to each other with outbound TCP connections. Such a scenario is particularly important in the case of peer-to-peer communications, such as Voice-over-IP (VoIP), file sharing, teleconferencing, chat systems and similar applications. TCP hole punching is an experimentally used NAT traversal technique for establishing a TCP connection between two peers on the Internet behind NAT devices. ''NAT traversal'' is a general term for techniques that establish and maintain TCP/IP network and/or TCP connections traversing NAT gateways. Terminology In the following, the terms host, client and peer are used almost interchangeably. ; ''local endpoint'', ''internal endpoint'' : the local IP:port as seen locally by the host and the internal part of the NAT. ; ''public endpoint'', ''external endpoint'' : the externa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Network
A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies, based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies. The nodes of a computer network can include personal computers, servers, networking hardware, or other specialised or general-purpose hosts. They are identified by network addresses, and may have hostnames. Hostnames serve as memorable labels for the nodes, rarely changed after initial assignment. Network addresses serve for locating and identifying the nodes by communication protocols such as the Internet Protocol. Computer networks may be classified by many criteria, including the transmission medium used to carry signals, bandwidth, communications pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Peer-to-peer
Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the network. They are said to form a peer-to-peer network of nodes. Peers make a portion of their resources, such as processing power, disk storage or network bandwidth, directly available to other network participants, without the need for central coordination by servers or stable hosts. Peers are both suppliers and consumers of resources, in contrast to the traditional client–server model in which the consumption and supply of resources are divided. While P2P systems had previously been used in many application domains, the architecture was popularized by the file sharing system Napster, originally released in 1999. The concept has inspired new structures and philosophies in many areas of human interaction. In such social contexts, peer-to-peer as a meme refers to the egalitarian so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voice-over-IP
Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet telephony, broadband telephony, and broadband phone service specifically refer to the provisioning of communications services (voice, fax, SMS, voice-messaging) over the Internet, rather than via the public switched telephone network (PSTN), also known as plain old telephone service (POTS). Overview The steps and principles involved in originating VoIP telephone calls are similar to traditional digital telephony and involve signaling, channel setup, digitization of the analog voice signals, and encoding. Instead of being transmitted over a circuit-switched network, the digital information is packetized and transmission occurs as IP packets over a packet-switched network. They transport media streams using special media delivery protocols th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NAT Traversal
Network address translation traversal is a computer networking technique of establishing and maintaining Internet protocol connections across gateways that implement network address translation (NAT). NAT traversal techniques are required for many network applications, such as peer-to-peer file sharing and Voice over IP. Network address translation NAT devices allow the use of private IP addresses on private networks behind routers with a single public IP address facing the Internet. The internal network devices communicate with hosts on the external network by changing the source address of outgoing requests to that of the NAT device and relaying replies back to the originating device. This leaves the internal network ill-suited for hosting servers, as the NAT device has no automatic method of determining the internal host for which incoming packets are destined. This is not a problem for general web access and email. However, applications such as peer-to-peer file sharing, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internet
The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, public, academic, business, and government networks of local to global scope, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries a vast range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), electronic mail, telephony, and file sharing. The origins of the Internet date back to the development of packet switching and research commissioned by the United States Department of Defense in the 1960s to enable time-sharing of computers. The primary precursor network, the ARPANET, initially served as a backbone for interconnection of regional academic and military networks in the 1970s to enable resource shari ... [...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 set of 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). In the development of this networking model, early versions of it 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 high ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission Control Protocol
The Transmission Control Protocol (TCP) is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, the entire suite is commonly referred to as TCP/IP. TCP provides reliable, ordered, and error-checked delivery of a stream of octets (bytes) between applications running on hosts communicating via an IP network. Major internet applications such as the World Wide Web, email, remote administration, and file transfer rely on TCP, which is part of the Transport Layer of the TCP/IP suite. SSL/TLS often runs on top of TCP. TCP is connection-oriented, and a connection between client and server is established before data can be sent. The server must be listening (passive open) for connection requests from clients before a connection is established. Three-way handshake (active open), retransmission, and error detection adds to reliability but lengthens latency. Applica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Port Allocation
A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as Hamburg, Manchester and Duluth; these access the sea via rivers or canals. Because of their roles as ports of entry for immigrants as well as soldiers in wartime, many port cities have experienced dramatic multi-ethnic and multicultural changes throughout their histories. Ports are extremely important to the global economy; 70% of global merchandise trade by value passes through a port. For this reason, ports are also often densely populated settlements that provide the labor for processing and handling goods and related services for the ports. Today by far the greatest growth in port development is in Asia, the continent with some of the world's largest and busiest ports, such as Singapore and the Chinese ports of Shanghai and Ningbo-Zho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carrier-grade NAT
Carrier-grade NAT (CGN or CGNAT), also known as large-scale NAT (LSN), is a type of Network address translation (NAT) for use in IPv4 network design. With CGNAT, end sites, in particular residential networks, are configured with private network addresses that are translated to public IPv4 addresses by middlebox network address translator devices embedded in the network operator's network, permitting the sharing of small pools of public addresses among many end sites. This shifts the NAT function and configuration thereof from the customer premises to the Internet service provider network (though "conventional" NAT on the customer premises will often be used additionally). Carrier-grade NAT is often used for mitigating IPv4 address exhaustion. One use scenario of CGN has been labeled as NAT444, because some customer connections to Internet services on the public Internet would pass through three different IPv4 addressing domains: the customer's own private network, the carrier's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hole Punching (networking)
Hole punching (or sometimes punch-through) is a technique in computer networking for establishing a direct connection between two parties in which one or both are behind firewalls or behind routers that use network address translation (NAT). To punch a hole, each client connects to an unrestricted third-party server that temporarily stores external and internal address and port information for each client. The server then relays each client's information to the other, and using that information each client tries to establish direct connection; as a result of the connections using valid port numbers, restrictive firewalls or routers accept and forward the incoming packets on each side. Hole punching does not require any knowledge of the network topology to function. ICMP hole punching, UDP hole punching and TCP hole punching respectively use Internet Control Message, User Datagram and Transmission Control Protocols. Overview Networked devices with public or globally accessible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ICMP Hole Punching
ICMP hole punching is a technique employed in network address translator (NAT) applications for maintaining Internet Control Message Protocol (ICMP) packet streams that traverse the NAT. NAT traversal techniques are typically required for client-to-client networking applications on the Internet involving hosts connected in private networks, especially in peer-to-peer and Voice over Internet Protocol (VoIP) deployments. ICMP hole punching establishes connectivity between two hosts communicating across one or more network address translators in either a peer-to-peer or client–server model. Typically, third party hosts on the public transit network are used to establish UDP or TCP port states that may be used for direct communications between the communicating hosts, however ICMP hole punching requires no third party involvement to pass information between one or more NATs by exploiting a NAT's loose acceptance of inbound ICMP Time Exceeded packets. Once an ICMP Time Exceeded ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
