Integrated Services Digital Network (ISDN) | Digital Customer Access | Services | Network Capabilities

The actual requirements of the above ISDN section 5.23, shall be verified during the conceptual and detailed design for each individual project, prior to the final design and implementation of the project.

Integrated Services Digital Network (ISDN) | Digital Customer Access | Services | Network Capabilities

5.23.1 The ISDN capabilities will provide end-to-end digital connectivity to support a wide range of services for voice, nonvoice and future video applications. The digital exchange shall be able to provide integrated customer access for achieving circuit and packet switching simultaneously.
5.23.2 For the ISDN plan, Saudi Aramco will follow ITU-T Recommendations I-series for at least the following:
a) The concept and the principle of the ISDN.
b) The service capabilities.
c) Overall network aspects and functions.
d) User/network interface.

e) Internetwork interface.

5.23.3 Digital Customer Access

The digital exchange shall be capable of providing integrated digital customer access to provide simultaneous voice and non-voice services from the end subscriber through the digital switching network. The integrated digital access shall provide the customer with circuit switching capabilities and packet switching capabilities simultaneously.
A variety of digital access shall be arranged to support a wide range of data rates and services. The structure of the digital access shall be in accordance with ITU-T I.412.
a) Channel Structure
The channel structure shall be the basic interface structure 2B+D, where the channel capacity is 64 kb/s for B and 16 kb/s for D in accordance with ITU-T I.412. The B channels may be used independently (i.e., two different simultaneous connections). This shall be valid for both the T and U interfaces.
All new and future offered switching exchanges shall be capable of and comply with the primary interface structure 30B+D, where the D channel in this case is 64 kb/s. (The primary data rate is 2.048 Mb/s).
b) Transmission
The bit rate as well as other physical characteristics of the T interface shall be in accordance with ITU-T I.430. The transmission rate on the Digital Subscriber Line (DSL) over the U interface shall be 192 kb/s.
c) D channel access protocol
The D channel access protocol shall be structured in three layers as follow:

1. Physical layer (layer 1)

This layer shall provide the electrical, mechanical, functional control of data circuits, characteristics and procedures to activate and deactivate the physical link and shall be in accordance with ITU-T I.430 for the basic rate and ITU-T I.431 for the primary rate.

2. Link layer (layer 2)

This layer shall establish, maintain, and release data links, error and flow control. This layer provides information transportation between the digital subscriber set and the exchange. The link layer procedures shall be in accordance with ITU-T I.440 for the basic rate and ITU-T I.441 for the primary rate. (ITU-T I.440 & ITU-T I.441 are published under alias number ITU-T Q.920 & Q.921 respectively). Besides ITU-T I.440 and ITU-T I.441, the following recommendations and standards are referenced: ITU-T X.200; X.210 Open System Interconnection (OSI) and X.25 Link Access Protocol (LAP.B/D). Also International Standard Organization ISO 3309 and ISO 4335 (High Level Data Link Control (HDLC) standards for frame structure and elements and procedures).

3. Network layer (3)

This layer provides the means to establish, maintain, and terminate network connections across an ISDN between communicating application entities. As a minimum, this layer shall provide the necessary signaling functions to support the ISDN services indicated in the next paragraph. The network layer shall be based on ITU-T I.450 and ITU-T I.451, which are published under alias numbers ITU-T Q.930 and Q.931 respectively.

5.23.4 ISDN Services

The digital exchange shall be capable of providing, as a minimum, the following types of services for the ISDN:
a) Supplementary telephone services using digital telephone terminals including display functions and alpha-number key sets.
b) Possible to interwork with the existing packet and circuit switched data networks by means of an adapter for connecting x and v type terminals.
c) Packet switched services according to ITU-T X.25 protocol.
d) Leased line at 64 kb/s by using semi-permanent connection through the digital switching network.
e) Alarm services by using the digital access to provide information transfer to an alarm/network operation center.

f) Telemetry services by using the digital access to fetch the readings in the subscriber end.
g) ISDN fast facsimile services, telex/teletex, video (slow scan) for teleconferencing, etc., via the H-channel’s capability for higher user data rates. [H0: 384 kb/s; H1: 1536 kb/s (H11) and 1920 kb/s (H12)].
h) Broadband ISDN (B-ISDN) services at n x 64 kb/s in future.
i) Full support of the latest Digital Subscriber Line (DSL) technology.

5.23.5 Network Capabilities

For telephone service, the numbering plan and charging method provided by ISDN shall remain unchanged. It must be possible to enhance the network capabilities when new services are introduced in the ISDN. Network signaling shall be in accordance with ITU-T Recommendation SS No. 7 (Signaling System No. 7) with possibilities to introduce the new ISDN user part (ISUP).


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