PSTN vs ISDN

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Cyclops
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PSTN vs ISDN

Post by Cyclops » Tue May 04, 2010 10:50 pm

PSTN

Short for Public Switched Telephone Network, which refers to the international telephone system based on copper wires carrying analog voice data. This is in contrast to newer telephone networks base on digital technologies, such as ISDN and FDDI. Telephone service carried by the PSTN is often called plain old telephone service (POTS).


ISDN

Abbreviation of integrated services digital network, an international communications standard for sending voice, video, and data over digital telephone lines or normal telephone wires. ISDN supports data transfer rates of 64 Kbps (64,000 bits per second).

There are two types of ISDN:
> Basic Rate Interface (BRI) -- consists of two 64-Kbps B-channels and one D-channel for transmitting control information.
> Primary Rate Interface (PRI) -- consists of 23 B-channels and one D-channel (U.S.) or 30 B-channels and one D-channel (Europe).

The original version of ISDN employs baseband transmission. Another version, called B-ISDN, uses broadband transmission and is able to support transmission rates of 1.5 Mbps. B-ISDN requires fiber optic cables and is not widely available.

A set of communications standards allowing a single wire or optical fibre to carry voice, digital network services and video. ISDN is intended to eventually replace the plain old telephone system.

ISDN was first published as one of the 1984 ITU-T Red Book recommendations. The 1988 Blue Book recommendations added many new features. ISDN uses mostly existing Public Switched Telephone Network (PSTN) switches and wiring, upgraded so that the basic "call" is a 64 kilobits per second, all-digital end-to-end channel. Packet and frame modes are also provided in some places.

There are different kinds of ISDN connection of varying bandwidth (see DS level):DS0 = 1 channel PCM at 64 kbpsT1 or DS1 = 24 channels PCM at 1.54 MbpsT1C or DS1C = 48 channels PCM at 3.15 MbpsT2 or DS2 = 96 channels PCM at 6.31 MbpsT3 or DS3 = 672 channels PCM at 44.736 MbpsT4 or DS4 = 4032 channels PCM at 274.1 Mbps

Each channel here is equivalent to one voice channel. DS0 is the lowest level of the circuit. T1C, T2 and T4 are rarely used, except maybe for T2 over microwave links. For some reason 64 kbps is never called "T0".

A Basic Rate Interface (BRI) is two 64K "bearer" channels and a single "delta" channel ("2B+D"). A Primary Rate Interface (PRI) in North America and Japan consists of 24 channels, usually 23 B + 1 D channel with the same physical interface as T1. Elsewhere the PRI usually has 30 B + 1 D channel and an E1 interface.

A Terminal Adaptor (TA) can be used to connect ISDN channels to existing interfaces such as EIA-232 and V.35.

Different services may be requested by specifying different values in the "Bearer Capability" field in the call setup message. One ISDN service is "telephony" (i.e. voice), which can be provided using less than the full 64 kbps bandwidth (64 kbps would provide for 8192 eight-bit samples per second) but will require the same special processing or bit diddling as ordinary PSTN calls. Data calls have a Bearer Capability of "64 kbps unrestricted".

ISDN is offered by local telephone companies, but most readily in Australia, France, Japan and Singapore, with the UK somewhat behind and availability in the USA rather spotty. (In March 1994) ISDN deployment in Germany is quite impressive, although (or perhaps, because) they use a specifically German signalling specification, called 1.TR.6. The French Numeris also uses a non-standard protocol (called VN4; the 4th version), but the popularity of ISDN in France is probably lower than in Germany, given the ludicrous pricing. There is also a specifically-Belgian V1 experimental system. The whole of Europe is now phasing in Euro-ISDN


BASEBAND

The original band of frequencies of a signal before it is modulated for transmission at a higher frequency.
1. A type of data transmission in which digital or analog data is sent over a single unmultiplexed channel, such as an Ethernet LAN.
2. Baseband transmission use TDM to send simultaneous bits of data along the full bandwidth of the transmission channel.


BROADBAND

A type of data transmission in which a single medium (wire) can carry several channels at once. Cable TV, for example, uses broadband transmission. In contrast, baseband transmission allows only one signal at a time. Most communications between computers, including the majority of local-area networks, use baseband communications. An exception is B-ISDN networks, which employ broadband transmission.


SNMP

Short for Simple Network Management Protocol, a set of protocols for managing complex networks. The first versions of SNMP were developed in the early 80s. SNMP works by sending messages, called protocol data units (PDUs), to different parts of a network. SNMP-compliant devices, called agents, store data about themselves in Management Information Bases (MIBs) and return this data to the SNMP requesters.


VPN

Short for virtual private network, a network that is constructed by using public wires to connect nodes. For example, there are a number of systems that enable you to create networks using the Internet as the medium for transporting data. These systems use encryption and other security mechanisms to ensure that only authorized users can access the network and that the data cannot be intercepted.
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jhoncena
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Re: PSTN vs ISDN

Post by jhoncena » Sun Jun 09, 2013 4:15 pm

Very very interesting post..I like this one. gotta bookmark this one.
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