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

Analog Communications w/o ISDN

The Integrated Digital Network Multiplex and modulate signals Space-division switch Demultiplex and demodulate signals Analog telephone network PCM: pulse-code modulation

Digital Communications with ISDN

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

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

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 the 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 functions 6. Variety of configurations More than one physical configuration is possible for implementing ISDN

The User Interface

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

The User Interface (cont’d) 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)

The User Interface (cont’d)

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

ISDN Architecture

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

Outline ISDN Overview ISDN Tutorial 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

ISDN Standard

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

NETE0510: Communication Media and Data Communications 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. NETE0510: Communication Media and Data Communications

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

ISDN Channel Functions

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

Basic and Primary Channel Structures

ISDN Model

ISDN Protocols at the user-network interface

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

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 resolution when several terminals on a passive bus contend for a channel Activation bit — Activates devices Spare bit — Unassigned

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.

ISDN Data-link Layer SAPI identifies the portal at which LAPD services are provided to Layer 3

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).

ISDN Layer 3: Q.931 Messaging Call Setup

NETE0510: Communication Media and Data Communications (Q.931 Messaging Call Setup) NETE0510: Communication Media and Data Communications

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 function R, S, T, U

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

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

Functional Groupings (cont’d) 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

Functional Groupings (cont’d) 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

Reference Points and Functional Groupings

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

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:

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

Access Configurations (cont’d) 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

Access Configurations (cont’d) 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

Examples of implementation of NT1 and NT2 functions

Examples of implementation of NT1 and NT2 functions

NT1 equipment NT1 circuit card

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.

ISDN Switch Type (cont’d)

Network Diagram

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.

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

Physical Interfaces U-Interface S/T Interface The U-interface is the 2-wire interface your phone company delivers for connection to the NT1. Many of the newer ISDN networking devices, e.g. the 3Com Impact, 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.

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.

Configuring your ISDN Line and Equipment Switch Type ISDN Phone Number (Directory Number) SPID (Service Profile Identifier) TID (Terminal Identifier)

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.

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

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.

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 two 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.

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.

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.

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.

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.

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.

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.

Wiring your Location for ISDN: ISDN Phone Jacks (cont’d) SJA11 This is identical to the RJ45 jack, but is a non-regulated product and therefore is significantly less expensive than the RJ45. Specifically request this jack when ordering your ISDN service.