NETE0510: Communication Media and Data Communications 1 NETE0510 ISDN Dr. Supakorn Kungpisdan [email protected].

NETE0510: Communication Media and Data Communications

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NETE0510ISDN

Dr. Supakorn [email protected]


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Outline

ISDN Overview Integrated Digital Network A Conceptual View of ISDN

ISDN Interfaces and FunctionsISDN Tutorial


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Traditional Telephone Network VS Integrated Digital Network Traditional Telephone Networks

Separately designed and administrated transmission and switching systems

Demultiplexing and demodulating are necessary at each switching center

A repeated process results in an accommodation of noise as well as cost

Integration of transmission and switching systems Achievable when both systems are digital Using PCM modulation and TDM multiplexing Switching without decoding along the way Separate multiplex/demultiplex channel banks are not required


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Analog Communications w/o ISDN


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The Integrated Digital Network

Analog telephone network

Space-division switch

Multiplex and modulate signals

Demultiplex and demodulate signals

PCM: pulse-code modulation


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Digital Communications with ISDN


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The Integrated Digital Network (cont’d)

The IDN will combine the coverage of the geographically extensive telephone network with the data carrying capacity of digital data networks in a structure called the “integrated services digital network (ISDN)” “integrated” refers to the simultaneous carrying of

digitized voice and a variety of data traffic on the same digital transmission links and by the same digital exchanges


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Outline

ISDN Overview Integrated Digital Network A Conceptual View of ISDN

ISDN Interfaces and Functions Transmission Structure User-Network Interface Configurations ISDN Protocol Architecture ISDN Connection Addressing Interworking


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Principles of ISDN

1. Support of voice and non-voice applications using a limited set of standardized facilities

Defines the purpose of ISDN and the means of achieving it

2. Support for switched and non-switched applications Both circuit-switched and packet-switched connections Support non-switched services in the form of dedicated lines

3. Reliance on 64-kbps connections Fundamental block of ISDN 64 kbps were chosen because it was the standard rate for

digitized voice


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Principles of ISDN (cont’d)

4. Intelligence in the network Sophisticated serviced beyond simple setup a circuit-switched call Sophisticated network management and maintenance capabilities Use of SS7 ( (common channel) signaling system number 7) and

intelligent switching nodes in the network SS7 is a set of telephony signaling protocols which are used to set up t

he vast majority of the world's public switched telephone network telephone calls.

5. Layered protocol architecture User access to ISDN protocol is a layered architecture that can be

mapped to OSI model Standards can be developed independently for various layers and

functions6. Variety of configurations

More than one physical configuration is possible for implementing ISDN


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The User Interface


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The User Interface (cont’d)

User has access to ISDN via a local interface to a digital “pipe”.

Pipes of various sizes are available to satisfy different needs

Pipe to the user’s promises has a fixed capacity but the traffic on the pipe may be a variable mix up to the capacity limit

ISDN requires control signals to instruct how to sort out the time-multiplexed data and provide the required services

Control signals are multiplexed onto the same digital pipe


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Recommendation from I.410: more than one size of pipe is needed A single terminal (e.g. a residential telephone) Multiple terminals (e.g. a residential telephone, PC, and alarm

system) A network of devices attached to a LAN or PBX (ISDN

gateway)


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Benefits

The principle benefits of ISDN to the customer can be expressed in terms of cost savings and flexibility

Integrated voice and data means that the user does not have to buy multiple services to meet multiple needs Access charges to a single line only Purchasing services based on actual needs Product diversity, low price, and wide availability of

equipment


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ISDN Architecture


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ISDN Architecture (cont’d)

Physical interface provides a standardized means of attaching to the network

The interface supports a basic service consisting of three time-multiplexed channels, two at 64 kbps and one at 16 kbps

In addition, there is a primary service that provide multiple 64-kbps channels

An interface is defined between the customer’s terminal equipment (TE) and a device on the customer’s premises, known as a network termination (NT)

The subscriber loop is the physical path from the subscriber’s NT to the ISDN central office Must support full-duplex digital transmission for both basic and

primary data rates


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Outline

ISDN Overview ISDN Interfaces and Functions

ISDN Standard Transmission Structure ISDN Model Reference Points and Functional Groupings Access Configurations ISDN Switch Types

ISDN Tutorial Network Diagram Type of Equipment Configuring your ISDN Line and Equipment Wiring your Location for ISDN


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ISDN Standard


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Transmission Structure

Digital pipe between central office and ISDN subscriber carry a number of communication channels, varies from user to user

The transmission structure of access links includes channels of: B channel: 64 kbps D channel: 16 or 64 kbps H channel: 384 (H0), 1536 (H11), or 1920 (H12) kbps


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B Channel

A user channel, carrying digital data, PCM-encoded digital voice, or a mixture of lower-rate traffic at a fraction of 64 kbps

The information is carried in frame format, using either high-level data link control (HDLC) or PPP as the Layer 2 protocol. PPP is more robust than HDLC because it provides a mechanism for authentication and negotiation of compatible link and protocol configuration.


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D Channel

Carry common-channel signaling (CCS) information to control circuit-switched calls

Traffic over the D channel employs the Link Access Procedure on the D Channel (LAPD) protocol. LAPD is a data link layer protocol based on HDLC.

May be used for packet switching or low speed (e.g. 100 bps) telemetry (data transfer over media) when no signaling information is waiting


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ISDN Channel Functions


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H Channel

Provides user information transmission at higher data rates

Use the channel as a high-speed trunk or subdivide it based on TDM

Examples: fast fax, video, high-speed data, high quality audio


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Basic and Primary Channel Structures


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ISDN Model


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ISDN Protocols at the user-network interface


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ISDN Physical Layer

Each ISDN BRI frame contains two sub-frames each containing the following: 8 bits from the B1 channel, 8 bits from the B2 channel, 2 bits from the D

channel, and 6 bits of overhead So, each BRI frame contains 48 bits


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ISDN Physical Layer (cont’d)

The overhead bits of an ISDN sub-frame are used as follows: Framing bit — Provides synchronization Load balancing bit- Adjusts the average bit value Echo of previous D channel bits — Used for contention res

olution when several terminals on a passive bus contend for a channel

Activation bit — Activates devices Spare bit — Unassigned


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ISDN Physical Layer (cont’d)

4,000 frames are transmitted per second. Each B channel, B1and B2, has a capacity of 8 * 4000 *

2 = 64 kbps, while channel D has a capacity of 2 * 4000 * 2 = 16 kbps.

This accounts for 144 kbps (B1 + B2 + D) of the total ISDN BRI physical interface bit rate of 192 kbps.

The remainder of the data rate are the overhead bits that are required for transmission: 6 * 4000 * 2 = 48 kbps.


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ISDN Data-link Layer

SAPI identifies the portal at which LAPD services are provided to Layer 3


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ISDN Data-link Layer (cont’d)

Layer 2 of the ISDN signaling channel is LAPD. LAPD is similar to HDLC. LAPD is used across the D channel to ensure that control and signaling information is received and flows properly.

The LAPD flag and control fields are identical to those of HDLC.

The LAPD address field is 2 bytes long. The first address field byte contains the service access point

identifier (SAPI), which identifies the portal at which LAPD services are provided to Layer 3. The command/response bit (C/R) indicates whether the frame contains a command or a response.

The second byte contains the terminal endpoint identifier (TEI).


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ISDN Layer 3: Q.931 Messaging Call Setup


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(Q.931 Messaging Call Setup)


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Reference Points and Functional Groupings

ITU-T approach for actual user’s physical configuration Functional grouping: certain arrangements

of physical equipment or combination of equipment

NT1, NT2, TE1, TE2, TA Reference points: conceptual points of

separation of group functionR, S, T, U


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Functional Groupings

NT1 (Network Termination 1) Includes functions similar to OSI layer 1 May be controlled by ISDN provider (a boundary to

network) Isolate the user from the transmission technology of

subscriber loop Supports multiple channels (e.g. 2B+D) using TDM Might support multiple devices in a multidrop

arrangement E.g. a residential interface might include a telephone, PC,

and alarm system, all attached to a single NT1 interface via a multidrop line


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Functional Groupings (cont’d)

NT2 (Network Termination 2) An intelligent device that may include up to OSI layer 3 Perform switching and concentration functions

Switching: the construction of a private network using semi-permanent circuit among a number of sites

Concentration: multiple devices, attached to a digital PBX, LAN, or terminal controller, may transmit data across ISDN

E.g. digital PBX, a terminal controller, LAN Digital PBX provides NT2 functions at layers 1, 2, and 3 A simple terminal controller provides layers 1 and 2 A simple Time Division MUX provides layer 1


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TE1 (Terminal Equipment type 1) Devices that support the standard ISDN interface E.g. digital telephone, integrated voice/data terminal, digital

fax

TE2 (Terminal Equipment type 2) The existing non-ISDN equipment E.g. physical interface RS-232, host computer with X.25 Requires a terminal adaptor (TA) to plug into an ISDN

interface


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TA (Terminal Adaptor) Converts standard electrical signals into the form used

by ISDN Needed for connection with TE2 devices The ISDN TA can be either a standalone device or a

board inside the TE2


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Reference Points and Functional Groupings


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Reference Points

Reference point R (connect TE2-TA) Provides a non-ISDN interface between user equipment that is

non-ISDN compatible and adaptor equipment Comply with X or V series ITU-T recommendation

Reference point S (connect TE1-NT2, TA-NT2) The interface of individual ISDN terminals Separate user terminal from network communications functions

Reference point T (connect NT2-NT1) A minimal ISDN network termination at CPE Separate network’s provider equipment from the user’s one

Reference point U (connect NT1-provider) Describes full-duplex data signal on the subscriber line


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Access Configurations

Based on definitions of functional grouping and reference points, several possible configurations for ISDN user-network interface have been proposed by ITU-T The most straightforward configuration is that one or

more pieces of equipment correspond to each functional grouping:


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Access Configurations (cont’d)

In second case, the line termination function is combined with other ISDN interface functions

ISDN provider may provide the NT1 function e.g. NT1 may be integrated into a PBX


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In the third case, NT2 and TE functions are combined A host that supports users, but also acts as a packet

switch in a private packet-switching network that uses ISDN for trunking


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Final case: an ISDN subscriber device can connect directly to the subscriber loop terminator or into a PBX or LAN using the same interface specifications and thus ensuring portability


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Examples of implementation of NT1 and NT2 functions


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Examples of implementation of NT1 and NT2 functions


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NT1 equipment

NT1 circuit card


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ISDN Switch Type

Routers must be configured to identify the type of switch with which they will communicate.

Available ISDN switch types vary, depending in part on the country. As a consequence of various implementations of Q.931, the D channel signaling protocol used on ISDN switches varies from vendor to vendor.

Each switch type operates slightly differently, and has a specific set of call setup requirements.

Before the router can be connected to an ISDN service, it must be configured for the switch type used at the CO.


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ISDN Switch Type (cont’d)


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Outline

ISDN Overview ISDN Interfaces and Functions ISDN Tutorial

Network Diagram Type of Equipment Configuring your ISDN Line and Equipment Wiring your Location for ISDN


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ISDN Tutorial

Southwestern Bell

Internet Service

http://public.swbell.net/ISDN/connect.html


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Network Diagram


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Types of Equipment

Network Termination Device 1 (NT1)

The NT1 is a simple device that serves as an interface between the ISDN BRI line and your other ISDN equipment.

It converts the physical wiring interface delivered by Southwestern Bell to the wiring interface needed by your ISDN equipment, and also provides a testing point for troubleshooting.

Many ISDN terminal adapters and some ISDN routers have the NT1 function built-in. This makes for an easier installation and also reduces the total cost of your ISDN setup. However, a separate NT1 is more flexible in that it can support multiple ISDN devices.


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Types of Equipment (cont’d)

ISDN Routers Perform a function similar to that of a standard router. Using an ISDN router, multiple computers on a LAN can

share a single ISDN BRI connection. Because ISDN routers use Ethernet connections, they c

an take full advantage of ISDN's speed. Many of the most popular ISDN routers also support anal

og voice, modem, or fax applications, as well as sophisticated network management capabilities.

ISDN routers are typically more than twice as expensive as TAs, but they are often worth the money since they allow multiple computers on a small LAN to leverage your ISDN investment.


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Physical Interfaces

U-Interface The U-interface is the 2-wire interface your phone company deli

vers for connection to the NT1. Many of the newer ISDN networking devices, e.g. the 3Com Imp

act, include a built-in internal NT1 and power supply, so they can connect directly to the U-interface.

Manufacturers may describe this feature as a "built-in NT1 " or simply as a U-Interface ISDN TA.

S/T Interface The S/T-interface is the 4-wire interface between the NT1 and

the ISDN networking equipment such as an ISDN TA or router. An S/T interface is used when the NT1 is a separate device.


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Physical Interfaces (cont’d)

Other interfaces The interface between your ISDN networking equipment

and your computer is usually one of the standard industry interfaces.

For example, an External TA will use the computer's serial COM port such as RS232.

ISDN routers will use a standard Ethernet connection, either directly to a computer's NIC card or via an intermediary Ethernet hub.


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Configuring your ISDN Line and Equipment

Switch TypeISDN Phone Number (Directory Number)SPID (Service Profile Identifier)TID (Terminal Identifier)


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Switch Types

The "engines" of the ISDN phone network are the complex network switches which deliver the service. There are two dominant switches that provide ISDN: Lucent Technology's 5ESS and Northern Telecom's DMS100.

While those two switches provide the same basic features and functionality, they differ in how they interact with your ISDN equipment.

It is important that you find out which switch type and which software version will be providing you with ISDN service, so you can order your ISDN service and set your ISDN networking equipment parameters correctly.


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Switch Types (cont’d)

In Southwestern Bell Internet Services territory, the possible switches and software versions are: Lucent Technology (formerly a part of AT&T) 5ESS -

NI2 (National ISDN version 2) and/or AT&T custom ISDN software

Northern Telecom DMS100 - Custom ISDN software Northern Telecom DMS100 - NI1 (National ISDN

version 1) software


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ISDN Phone Number

Your ISDN phone line will be assigned a phone number just like a standard phone line.

However, depending on which kind of switch you are served from and how you are going to use the ISDN service, you may get one phone number per ISDN line or one phone number for each ISDN B-channel.

It is important for you to define how you plan to use your ISDN line so Southwestern Bell can assign the correct number of phone numbers.


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ISDN Phone Number (cont’d)

DMS100 A DMS switch always assumes a multipoint configuration. If you are served from a DMS-100 switch, you should receive tw

o phone numbers, one for each B-channel. 5ESS

If you receive your ISDN service from a 5ESS switch, you need to choose either a "point-to-point" or "multipoint" configuration.

If you only intend to connect a single device/application to your ISDN line, then you only need the point-to-point configuration.

With the point-to-point configuration you are assigned a single phone number per ISDN line (not one for each B-channel).

If you intend to connect multiple devices/applications, then you need the multipoint configuration.

With multipoint configuration you are assigned a phone number for each device connected.


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SPIDs

The ISDN carrier provides a SPID to identify the line configuration of the ISDN service.

SPIDs are a series of characters (that can look like phone numbers with extra digits) that identify you to the switch at the CO. After you're identified, the switch links the services you ordered to the connection.

However, depending on which kind of switch you are served from and how you are going to use the ISDN service, you may not need a SPID or you may need a SPID for each B-channel, or each device.

It is important for you to define how you plan to use your ISDN line so Southwestern Bell can assign the correct number of SPIDs.


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SPIDs

DMS100 You should receive two SPIDs, one for each B-channel.

5ESS Need to choose either a "point-to-point" or "multipoint"

configuration. If you only intend to connect a single device/application

to your ISDN line, then you only need the point-to-point configuration and you are not assigned any SPIDs.

If you intend to connect multiple devices/applications, then you need the multipoint configuration.

With the multipoint configuration you are assigned a SPID for each device connected.


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TID

Specific to a National ISDN-1 BRI line from a DMS100 switch, is the need for a terminal identifier (TID).

The TID is comprised of two additional digits used in conjunction with the SPID when initializing devices.

The TID is intended for use on all non-initializing terminals.

All terminals in use today are initializing terminals, and most do not require a specific TID.

To minimize confusion, it is recommended that you use "00" on each terminal device, no matter how many terminal devices there are.

For further clarification, you should check with your ISDN equipment vendor for their recommendation.


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Wiring your Location for ISDN: Inside Wiring By regulation, Southwestern Bell ISDN service ends at

what is called the demarcation point ("demarc") usually just outside your residence or in an apartment building basement.

You are responsible for the wiring from the demarcation point to your ISDN equipment including the wall jacks.

You will want your ISDN phone jacks close to your ISDN equipment for the best performance.

You can choose to have Southwestern Bell install and maintain this "inside wiring" for an additional charge, or you can use an electrical contractor.


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Wiring your Location for ISDN: Inside Wiring (cont’d)

While some homes and offices may need to be re-wired for ISDN, most will not.

The copper twisted pair wiring that currently provides standard analog phone service can be successfully used for ISDN.

However, with the increasingly popularity of multiple lines you may not have spare wiring available for your ISDN service. Therefore, additional cabling may be necessary.


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Wiring your Location for ISDN: ISDN Phone Jacks RJ11

This is the standard analog phone jack, and is used to deliver 2-wire service.

The phone company will often install this jack for ISDN unless otherwise requested.

However, some NT1s required the wider RJ45 or SJA11C jack. The 3Com Impact phone cable has an RJ11 plug on one end to

connect to a RJ 11 wall jack. RJ45

Slightly wider than the RJ11, and has 8 pins but can still be used to deliver 2-wire service such as ISDN BRI.

Again, some NT1s require this jack and their associated connecting cable with the RJ45 plug will not fit into an RJ11 jack.


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Wiring your Location for ISDN: ISDN Phone Jacks (cont’d)

SJA11 This is identical to the RJ45 jack, but is a non-regulated produ

ct and therefore is significantly less expensive than the RJ45. Specifically request this jack when ordering your ISDN servic

e.


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Questions?

Next Lecture

Frame Relay

NETE0510: Communication Media and Data Communications 1 NETE0510 ISDN Dr. Supakorn Kungpisdan [email protected].

Documents

nete0510 isdn

data communications

digital communications

communication media

purpose of isdn

network ss7

extensive telephone

outline isdn overview