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Network Layer
In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers. Functions The network layer provides the means of transferring variable-length network packets from a source to a destination host via one or more networks. Within the service layering semantics of the OSI network architecture, the network layer responds to service requests from the transport layer and issues service requests to the data link layer. Functions of the network layer include: ; Connectionless communication : For example, IP is connectionless, in that a data packet can travel from a sender to a recipient without the recipient having to send an acknowledgement. Connection-oriented protocols exist at other, higher layers of the OSI model. ; Host addressing :Every host in the network must have a unique address that determines where it is. This address is normally assigned from a hierar ...
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Subsystem Number
Signalling Connection Control Part (SCCP) subsystem numbers are used to identify applications within network entities which use SCCP signalling. GSM and UMTS SSNs In Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS), subsystem numbers may be used between Public land mobile networks (PLMNs), in which case they are taken from the globally standardized range (1 - 31) or the part of the national network range (129 - 150) reserved for GSM/UMTS use between PLMNs. For use within a PLMN, numbers are taken from the part of the national network range (32 - 128 & 151 - 254) not reserved for GSM/UMTS use between PLMNs. The following globally standardized subsystem numbers have been allocated for use by GSM/UMTS: 0 Not used/Unknown 1 SCCP MG 6 HLR (MAP) 7 VLR (MAP) 8 MSC (MAP) 9 EIR (MAP) 10 is allocated for evolution (possible Authentication Centre). The following national network subsystem numbers have been allocated ...
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Stream Control Transmission Protocol
The Stream Control Transmission Protocol (SCTP) is a computer networking communications protocol in the transport layer of the Internet protocol suite. Originally intended for Signaling System 7 (SS7) message transport in telecommunication, the protocol provides the message-oriented feature of the User Datagram Protocol (UDP), while ensuring reliable, in-sequence transport of messages with congestion control like the Transmission Control Protocol (TCP). Unlike UDP and TCP, the protocol supports multihoming and redundant paths to increase resilience and reliability. SCTP is standardized by the Internet Engineering Task Force (IETF) in . The SCTP reference implementation was released as part of FreeBSD version 7, and has since been widely ported to other platforms. Formal oversight The IETF Signaling Transport (SIGTRAN) working group defined the protocol (number 132) in October 2000, and the IETF Transport Area (TSVWG) working group maintains it. defines the protocol. provides an ...
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M3UA
M3UA is a communication protocol of the SIGTRAN family, used in telephone networks to carry signaling over Internet Protocol (IP). M3UA enables the SS7 protocol's User Parts (e.g. ISUP, SCCP and TUP) to run over virtually any network technology breaking its limitation to telephony equipment like T-carrier, E-carrier or Asynchronous Transfer Mode (ATM), which highly improves scalability of the signaling networks. M3UA stands for MTP Level 3 (MTP3) User Adaptation Layer as defined by the IETF SIGTRAN working group in (which replaces and supersedes ). Like other adaptation protocols, M3UA uses service of SCTP to transmit messages between its network elements. Implementation scheme Image:M3UA-scheme.svg, 404x404px, M3UA: Transmitting MTP-3 messages: on the left is the TDM-network for SS7. On the right is the IP-network with SIGTRAN as a transport., center rect 1 1 100 72 Point code rect 1 90 593 123 ISUP rect 1 123 593 160 SCCP rect 1 160 100 232 MTP-3 rect 1 232 100 4 ...
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Internet Protocol
The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP has the task of delivering packets from the source host to the destination host solely based on the IP addresses in the packet headers. For this purpose, IP defines packet structures that encapsulate the data to be delivered. It also defines addressing methods that are used to label the datagram with source and destination information. IP was the connectionless datagram service in the original Transmission Control Program introduced by Vint Cerf and Bob Kahn in 1974, which was complemented by a connection-oriented service that became the basis for the Transmission Control Protocol (TCP). The Internet protocol suite is therefore often referred to as ''TCP/IP''. The first major version of IP, Internet Protocol Version 4 (IPv4), is the do ...
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SIGTRAN
SIGTRAN is the name, derived from ''signaling transport'', of the former Internet Task Force (I) working group that produced specifications for a family of protocols that provide reliable datagram service and user layer adaptations for Signaling System and ISDN communications protocols. The SIGTRAN protocols are an extension of the SS7 protocol family. It supports the same application and call management paradigms as SS7 but uses an Internet Protocol (IP) transport called Stream Control Transmission Protocol (SCTP), instead of TCP or UDP. Indeed, the most significant protocol defined by the SIGTRAN group is SCTP, which is used to carry PSTN signaling over IP. The SIGTRAN group was significantly influenced by telecommunications engineers intent on using the new protocols for adapting IP networks to the PSTN with special regard to signaling applications. Recently, SCTP is finding applications beyond its original purpose wherever reliable datagram service is desired. SIGTRAN has ...
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Connectionless Protocol
Connectionless communication, often referred to as CL-mode communication,Information Processing Systems - Open Systems Interconnection, "Transport Service Definition - Addendum 1: Connectionless-mode Transmission", International Organization for Standardization, International Standard 8072/AD 6, December 1986. is a data transmission (telecommunications), transmission method used in packet switching networks in which each data unit is individually addressed and routed based on information carried in each unit, rather than in the setup information of a prearranged, fixed data channel as in connection-oriented communication. Attributes Under connectionless communication between two network end points, a message can be sent from one end point to another without prior arrangement. The device at one end of the communication transmits data addressed to the other, without first ensuring that the recipient is available and ready to receive the data. Some protocols allow for error correctio ...
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