Understanding Channelized Interfaces

A channelized interface is an interface that is a subdivision of a larger interface. Channelization minimizes the number of Physical Interface Modules (PIMs) that an installation requires, enabling devices to provide IP services to users with different access speeds and bandwidth requirements. Users share an interface that has been divided into discrete time slots by transmitting in only their own time slot.

You can aggregate the channels on a channelized interface into bundles called channel groups to aggregate customer traffic. A channel group is a combination of DS0 or Integrated Services Digital Network Primary Rate Interface (ISDN PRI) B-channels interfaces partitioned from a channelized interface into a single logical bundle.

Each port on a channelized T1/E1/ISDN PRI PIM is software configurable for a T1, E1, or ISDN PRI service. Each channelized T1 or E1 interface can be configured as a single clear channel or for fractional or channelized operation. The J Series device supports the software-configurable interfaces on the following PIMs:

• Dual-Port Channelized T1 PIM—A T1 interface is a physical WAN interface for transmitting digital signals in the T-carrier system used in the United States, Japan, and Canada. The T1 signal format carries 24 pulse code modulation (PCM) signals using time-division multiplexing (TDM) at an overall rate of 1.544 Mbps. A channelized T1 interface can be configured as a single clear-channel T1 interface or channelized into as many as 24 discrete DS0 interfaces (channels 1–24), or up to 23 ISDN PRI B-channels and 1 D-channel. When the interface is configured for ISDN PRI service, time slot 24 is reserved for the D-channel.
• Dual-Port Channelized E1 PIM—An E1 interface is a physical WAN interface for transmitting signals in European digital transmission (E1) format. The E1 signal format transmits information at a rate of 2.048 Mbps and can carry 32 channels of 64 Kbps each. A channelized E1 interface can be configured as a single clear-channel E1 interface or channelized into as many as 31 discrete DS0 interfaces (channels 1–31), or up to 30 ISDN PRI B-channels and 1 D-channel.
• Dual-Port Channelized ISDN PRI PIM—A PRI is an ISDN service intended for higher-bandwidth applications than ISDN BRI. ISDN PRI consists of a single D-channel for control and signaling, plus a number of 64-Kbps B-channels—either 23 B-channels on a T1 line or 30 B-channels on an E1 line—to carry network traffic. The E1 channelized interface can be partitioned into up to 23 ISDN PRI B-channels and 1 D-channel when the parent interface is channelized T1, and up to 30 ISDN PRI B-channels and 1 D channel when the parent interface is channelized E1. Time slots on the interface unused by ISDN PRI can operate normally as DS0 interfaces.

  J Series ISDN PRI interfaces support the following switch types:

  • ATT5E—AT&T 5ESS
  • ETSI—NET3 for the United Kingdom and Europe
  • NI2—National ISDN-2
  • NTDMS100—Northern Telecom DMS-100
  • NTT—NTT Group switch for Japan

On J Series channelized interfaces, time slots are numbered from 1 through 31, and time slot 1 is reserved for framing. When the interface is configured for ISDN PRI service, time slot 16 is reserved for the D-channel.

Channelized interfaces support Class of Service (CoS) configurations.

Related Topics

• Junos OS Feature Support Reference for SRX Series and J Series Devices
• ISDN
• Junos OS Class of Service Configuration Guide for Security Devices