Circuit switching in the context of Packet (information technology)

A telecommunications network is a group of nodes interconnected by telecommunications links that are used to exchange messages between the nodes. The links may use a variety of technologies based on the methodologies of circuit switching, message switching, or packet switching, to pass messages and signals.

Multiple nodes may cooperate to pass the message from an originating node to the destination node, via multiple network hops. For this routing function, each node in the network is assigned a network address for identification and locating it on the network. The collection of addresses in the network is called the address space of the network.

In telecommunications and computer networking, a network packet is a formatted unit of data carried by a packet-switched network. A packet consists of control information and user data; the latter is also known as the payload. Control information provides data for delivering the payload (e.g., source and destination network addresses, error detection codes, or sequencing information). Typically, control information is found in packet headers and trailers.

In packet switching, the bandwidth of the transmission medium is shared between multiple communication sessions, in contrast to circuit switching, in which circuits are preallocated for the duration of one session and data is typically transmitted as a continuous bit stream.

A virtual circuit (VC) is a means of transporting data over a data network, based on packet switching and in which a connection is first established across the network between two endpoints. The network, rather than having a fixed data rate reservation per connection as in circuit switching, takes advantage of the statistical multiplexing on its transmission links, an intrinsic feature of packet switching.

A 1978 standardization of virtual circuits by the CCITT imposes per-connection flow controls at all user-to-network and network-to-network interfaces. This permits participation in congestion control and reduces the likelihood of packet loss in a heavily loaded network. Some circuit protocols provide reliable communication service through the use of data retransmissions invoked by error detection and automatic repeat request (ARQ).

In telecommunications, message switching involves messages routed in their entirety, one hop at a time. It evolved from circuit switching and was the precursor of packet switching.

An example of message switching is email in which the message is sent through different intermediate servers to reach the mail server for storing. Unlike packet switching, the message is not divided into smaller units and sent independently over the network.

General Packet Radio Service (GPRS), also called 2.5G, is a mobile data standard that is part of the 2G cellular communication network Global System for Mobile Communications (GSM). Networks and mobile devices with GPRS started to roll out around the year 2001; it offered, for the first time on GSM networks, seamless data transmission using packet-switched data for an "always-on" connection, eliminating the need to dial up, providing improved Internet access for web, email, Wireless Application Protocol (WAP) services, Short Message Service (SMS), Multimedia Messaging Service (MMS) and others.

Up until the rollout of GPRS, only circuit-switched data was used in cellular networks, meaning that one or more radio channels were occupied for the entire duration of a data connection. On the other hand, on GPRS networks, data is broken into small packets and transmitted through available channels. This increased efficiency also gives it theoretical data rates of 56–114 kbit/s, significantly faster than the preceding Circuit Switched Data (CSD) technology. GPRS was succeeded by EDGE ("2.75G") which provided improved performance and speeds on the 2G GSM system.

Digital AMPS (D-AMPS), most often referred to as TDMA, is a second-generation (2G) cellular phone system that was once prevalent throughout the Americas, particularly in the United States and Canada since the first commercial network was deployed in 1993. Former large D-AMPS networks included those of AT&T and Rogers Wireless. The name TDMA is based on the abbreviation for time-division multiple access, a common multiple access technique which is used in most 2G standards, including GSM. D-AMPS competed against GSM and systems based on code-division multiple access (CDMA). It is now considered end-of-life, as existing networks have shut and been replaced by GSM/GPRS or CDMA2000 technologies. The last carrier to operate a D-AMPS network was U.S. Cellular, who terminated it on February 10, 2009.

The technical names for D-AMPS are IS-54 and its successor IS-136. IS-54 was the first mobile communication system which had provision for security, and the first to employ time-division multiple access (TDMA) technology. IS-136 added a number of features to the original IS-54 specification, including text messaging (SMS), circuit switched data (CSD), and an improved compression protocol. SMS and CSD were both available as part of the GSM protocol, and IS-136 implemented them in a nearly identical fashion.

4G refers to the fourth generation of cellular network technology, introduced in the late 2000s and early 2010s. Compared to preceding third-generation (3G) technologies, 4G has been designed to support all-IP communications and broadband services, and eliminates circuit switching in voice telephony. It also has considerably higher data bandwidth compared to 3G, enabling a variety of data-intensive applications such as high-definition media streaming and the expansion of Internet of Things (IoT) applications.

The earliest deployed technologies marketed as "4G" were Long Term Evolution (LTE), developed by the 3GPP group, and Mobile Worldwide Interoperability for Microwave Access (Mobile WiMAX), based on IEEE specifications. These provided significant enhancements over previous 3G and 2G.