ISDN BRI and PRI Explained | Generated by AI

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Question: According to the ITU, there are two ISDN user-network interface standards defined, which are the Primary Rate Interface (PRI) and what other interface?

Answer:

The two ISDN user-network interface standards defined by the ITU are:

The missing term in the question is 基本速率接口 (Basic Rate Interface) or BRI.

Explanation:

ISDN (Integrated Services Digital Network) defines two main types of user-network interfaces:

  1. Basic Rate Interface (BRI)
    • Also called 2B+D
    • Provides 2 × 64 kbps B-channels (for user data/voice) + 1 × 16 kbps D-channel (for signaling)
    • Total bit rate: 144 kbps (2B + D)
    • Mainly used for residential users, small offices, and single-line applications
  2. Primary Rate Interface (PRI)
    • Also called 23B+D (in North America/Japan) or 30B+D (in Europe and most other regions)
    • Provides 23 or 30 × 64 kbps B-channels + 1 × 64 kbps D-channel
    • Total bit rate: 1.544 Mbps (North America) or 2.048 Mbps (Europe/international)
    • Designed for larger organizations, PBX systems, and high-capacity access

These two interfaces (BRI and PRI) are the fundamental user-network access standards defined in the ITU-T I.400 series recommendations (especially I.430 for BRI and I.431 for PRI).

Therefore, the correct answer to fill in the blank is 基本速率接口 or BRI.

References:

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