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{{Refimprove|date=January 2016}}
{{Refimprove|date=January 2016}}


The '''Primary Rate Interface''' (PRI) is a [[telecommunication]]s interface standard used on an [[Integrated Services Digital Network]] (ISDN) for carrying multiple [[DS0]] voice and data transmissions between the network and a user.
The '''Primary Rate Interface''' ('''PRI''') is a [[telecommunication]]s interface standard used on an [[Integrated Services Digital Network]] (ISDN) for carrying multiple [[DS0]] voice and data transmissions between the network and a user.


PRI is the standard for providing telecommunication services to offices. It is based on the [[T-carrier]] (T1) line in the US and Canada, and the [[E-carrier]] (E1) line in Europe. The T1 line consists of 24 channels, while an E1 has 32.
PRI is the standard for providing telecommunication services to enterprises and offices. It is based on [[T-carrier]] (T1) transmission in the US, Canada, and Japan, while the [[E-carrier]] (E1) is common in Europe and Australia. The T1 line consists of 23 [[B channel|bearer (B) channels]] and one [[D channel|data (D) channel]] for control purposes,<ref>https://books.google.com/books?id=0LyDQgAACAAJ&dq=newton%27s+telecom+dictionary+16th+edition</ref> for a total bandwidth of 24x64-kbit/s or 1.544 Mbit/s. The E1 carrier provides 30B- and one D-channel for a bandwidth of 2.048 Mbit/s.<ref>https://www.itu.int/rec/T-REC-I.412-198811-I/en</ref>. The first timeslot on the E1 is used for [[Frame synchronization|synchronization]] purposes and is not considered to be a B- or D-channel. The D-channel typically uses timeslot 16 on an E1, while it is timeslot 24 for a T1. Fewer active bearer channels, sometimes called user channels, may be used in fractional T1 or E1 services.


==ISDN service types==
PRI provides a varying number of channels depending on the standards in the country of implementation. In North America and Japan it consists of 23xB ([[B channel]]s (bearer channels)) and 1xD ([[D channel]] (data<ref>https://books.google.com/books?id=0LyDQgAACAAJ&dq=newton%27s+telecom+dictionary+16th+edition</ref> channel)) (23 64-kbit/s digital channels + 1 64-kbit/s signaling/control channel) on a T1 (1.544 Mbit/s). In Europe and Australia it is 30B + D<ref>https://www.itu.int/rec/T-REC-I.412-198811-I/en</ref> on an E1 2.048 Mbit/s. One timeslot(0) on the E1 is used for [[Frame synchronization|synchronization]] purposes and is not considered to be a B or D channel. The D-channel typically uses timeslot 16 on an E1, vs timeslot 24 for a T1.

== Fractional T1 ==
Fewer active B channels (also called bearer channels) can be used for a fractional T1. Bearer channels may also be known as user channels. More channels can be used with more T1s, within certain design limits.<ref>{{cite web|title=Definition: T1|url=http://grok.lsu.edu/Article.aspx?articleId=3467|publisher=LSU Grok|accessdate=18 June 2015}}</ref>

== PRI and BRI ==
The [[Integrated Services Digital Network]] (ISDN) prescribes two levels of service:<ref>{{cite web|title=A Technical Coverage of Primary Rate Interface (PRI)|url=http://ispfast.com/a-technical-coverage-of-primary-rate-interface-pri/|publisher=ISPFast|accessdate=18 June 2015}}</ref>
The [[Integrated Services Digital Network]] (ISDN) prescribes two levels of service:<ref>{{cite web|title=A Technical Coverage of Primary Rate Interface (PRI)|url=http://ispfast.com/a-technical-coverage-of-primary-rate-interface-pri/|publisher=ISPFast|accessdate=18 June 2015}}</ref>
* BRI, the [[Basic Rate Interface]]: two 64-kbit/s [[B channel]]s and one 16-kbit/s [[D channel]], intended for homes and small enterprises
* [[Basic Rate Interface]] (BRI): two 64-kbit/s [[B channel]]s and one 16-kbit/s [[D channel]], intended for small enterprises and residential service.
* PRI, the Primary Rate Interface for large organizations, with one 64-kbit/s D channel and 23 (1.536 Mbit/s [[T-carrier|T1]], a.k.a. "23B + D") or 30, 64-kbit/s [[B channel]]s (2.048 Mbit/s [[E-carrier|E1]], a.k.a. "30B + D").
* Primary Rate Interface (PRI) for large organizations, with one 64-kbit/s D channel and 23 (1.536 Mbit/s [[T-carrier|T1]], a.k.a. "23B + D") or 30, 64-kbit/s [[B channel]]s (2.048 Mbit/s [[E-carrier|E1]], a.k.a. "30B + D").


Each B-channel carries data, voice, and other services. The D-channel carries control and signaling information. Larger connections are possible using PRI pairing. A dual T1-PRI could have 24 + 23 = 47 B-channels and 1 D-channel (often called "47B + D"), but more commonly has 46 B-channels and 2 D-channels thus providing a backup signaling channel. The concept applies to E1s as well and both can include more than 2 PRIs. When configuring multiple T1's as ISDN-PRI's, it's possible to use NFAS (non-facility associated signalling) to enable one or two D-channels to support additional B-channels on separate T1 circuits.
Each B-channel carries data, voice, and other services. The D-channel carries control and signaling information. Larger connections are possible using PRI pairing. A dual T1-PRI could have 24 + 23 = 47 B-channels and 1 D-channel (often called "47B + D"), but more commonly has 46 B-channels and 2 D-channels thus providing a backup signaling channel. The concept applies to E1s as well and both can include more than 2 PRIs. When configuring multiple T1's as ISDN-PRI's, it's possible to use NFAS (non-facility associated signalling) to enable one or two D-channels to support additional B-channels on separate T1 circuits.


==Application==
==Application==
The Primary Rate Interface channels are typically used by medium to large enterprises with digital [[Private branch exchange|PBXs]] to provide them digital access to the [[Public Switched Telephone Network]] (PSTN). The 23 (or 30) B-channels can be used flexibly and reassigned when necessary to meet special needs such as video conferences. The Primary Rate user is hooked up directly to the telephone company central office.
The Primary Rate Interface channels are typically used by medium to large enterprises with digital [[private branch exchange]] (PBX) telephone systems to provide digital access to the [[public switched telephone network]] (PSTN). The B-channels may be used flexibly and reassigned when necessary to meet special needs such as video conferences.


PRI channels and [[direct inward dialing]] are also common as a means of delivering inbound calls to [[voice over IP]] gateways from the PSTN.
PRI channels and [[direct inward dialing]] are also common as a means of delivering inbound calls to [[voice over IP]] gateways from the PSTN.
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* [[Non-Facility Associated Signalling]]
* [[Non-Facility Associated Signalling]]
* [[H channel]]
* [[H channel]]
* [[D channel]]
* [[B channel]]
* [[Caller ID spoofing]]
* [[Caller ID spoofing]]
* [[DHEC]]{{dn|date=November 2016}}
* [[DHEC]]{{dn|date=November 2016}}
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==References==
==References==
{{reflist}}
<references />
*{{FS1037C}}
*{{FS1037C}}


Revision as of 01:16, 16 February 2017

The Primary Rate Interface (PRI) is a telecommunications interface standard used on an Integrated Services Digital Network (ISDN) for carrying multiple DS0 voice and data transmissions between the network and a user.

PRI is the standard for providing telecommunication services to enterprises and offices. It is based on T-carrier (T1) transmission in the US, Canada, and Japan, while the E-carrier (E1) is common in Europe and Australia. The T1 line consists of 23 bearer (B) channels and one data (D) channel for control purposes,[1] for a total bandwidth of 24x64-kbit/s or 1.544 Mbit/s. The E1 carrier provides 30B- and one D-channel for a bandwidth of 2.048 Mbit/s.[2]. The first timeslot on the E1 is used for synchronization purposes and is not considered to be a B- or D-channel. The D-channel typically uses timeslot 16 on an E1, while it is timeslot 24 for a T1. Fewer active bearer channels, sometimes called user channels, may be used in fractional T1 or E1 services.

ISDN service types

The Integrated Services Digital Network (ISDN) prescribes two levels of service:[3]

  • Basic Rate Interface (BRI): two 64-kbit/s B channels and one 16-kbit/s D channel, intended for small enterprises and residential service.
  • Primary Rate Interface (PRI) for large organizations, with one 64-kbit/s D channel and 23 (1.536 Mbit/s T1, a.k.a. "23B + D") or 30, 64-kbit/s B channels (2.048 Mbit/s E1, a.k.a. "30B + D").

Each B-channel carries data, voice, and other services. The D-channel carries control and signaling information. Larger connections are possible using PRI pairing. A dual T1-PRI could have 24 + 23 = 47 B-channels and 1 D-channel (often called "47B + D"), but more commonly has 46 B-channels and 2 D-channels thus providing a backup signaling channel. The concept applies to E1s as well and both can include more than 2 PRIs. When configuring multiple T1's as ISDN-PRI's, it's possible to use NFAS (non-facility associated signalling) to enable one or two D-channels to support additional B-channels on separate T1 circuits.

Application

The Primary Rate Interface channels are typically used by medium to large enterprises with digital private branch exchange (PBX) telephone systems to provide digital access to the public switched telephone network (PSTN). The B-channels may be used flexibly and reassigned when necessary to meet special needs such as video conferences.

PRI channels and direct inward dialing are also common as a means of delivering inbound calls to voice over IP gateways from the PSTN.

See also

References

  1. ^ https://books.google.com/books?id=0LyDQgAACAAJ&dq=newton%27s+telecom+dictionary+16th+edition
  2. ^ https://www.itu.int/rec/T-REC-I.412-198811-I/en
  3. ^ "A Technical Coverage of Primary Rate Interface (PRI)". ISPFast. Retrieved 18 June 2015.
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