What’s Q Signaling?

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QSIG is a protocol used for signaling on ISDN lines to connect to PBXs. It allows equipment from different vendors to work together and supports essential network functions. Q signaling uses CCS protocol, which creates a digital link based on packet switching, allowing for more efficient traffic handling. QSIG is commonly used for IP voiceover, VPNs, and carrying data across private networks. It uses two levels of communication, BC and GF, to perform different tasks.

Q signaling (QSIG) is a protocol used to carry data over integrated services high-speed digital network (ISDN) lines. QSIG is used for signaling on these lines to connect to private branch exchanges (PBXs). Signaling is the transfer of information to points on a network. A PBX is a private telephone network within a business, school, or other large entity, such as a government office.

PBXs switch calls between lines within the company and also allow users to make external calls. QSIG is used for ISDNs that use the Q.931 standard to carry information between a single user and a PBX. QSIG allows equipment from different vendors to work together to access a PBX network via ISDN line.

Networks that include the Q.931 standard use Q signaling to process incoming calls to a network. Q signaling supports the essential network functions of the Q.931 standard. These features include notifying the network of an incoming call, establishing a connection, and disconnecting when the call ends.

QSIG is a common channel signaling (CCS) protocol. CCS creates a digital link based on packet switching. Packet switching divides the information being sent into packets.

These packets can then travel through the network over the ISDN line using different paths. Packages are reassembled at the destination point. Because packets can travel separately using the fastest routes currently available, ISDN lines can handle more traffic more efficiently.

CCS uses a subnet or separate network to support communication with the main network. The subnet connects all network communication points to a central computer and its databases. This allows CCS to control and monitor all communications throughout the network. This process is part of overall network management.
Common uses of Q signaling include telephone services that use an Internet connection instead of telephone lines, better known as IP voiceover. QSIG is also used by companies that allow staff to use a private offsite connection to the corporate network. These connections are called virtual private networks (VPNs). QSIG can also be used to carry data across a company’s private network.
Q signaling works by using two levels of communication—basic call (BC) and general function (GF)—to perform different tasks. BC enables successful signal transfer across a network between different providers. GF supports advanced features within a company’s private network, such as call forwarding, and provides support for more applications.




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