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The RLC supports digital trunks for connections to the Remote Office units. The RLC shares the host PBX’s digital trunks (ISDN PRI) for a PSTN connection to the Remote Office unit.

QoS Transitioning Technology

The RLC supports PSTN interfaces for local calling when used in Voice over IP (VoIP) mode. In this way, it also supports QoS Transitioning Technology. For a further explanation of QoS transition functions, refer to “Adjustable quality of service using QoS Transitioning Technology” on page 15. For exact configuration procedures, refer to “Configuring Quality of Service” on page 182.

Bandwidth utilization

The voice compression algorithm that you choose when configuring DSP resources determines the bandwidth utilization of the RLC. The RLC currently supports the following compression algorithms with the Remote Office devices indicated in the table below:

Dynamic trunk bandwidth allocation

In PSTN mode, the RLC dynamically allocates available trunk bandwidth to maximize bandwidth use. That is, as the RLC initiates calls and bandwidth requirements increase, the RLC establishes additional trunk connections for Remote Office 9150 units.

The compression algorithm

uses a

compressed bit rate of

on the following Remote Office devices:

G.711 64 Kbps 9150

G.726 32 Kbps 9150

G.729A 8 Kbps 911x, 9150, Meridian Digital

Call on-demand

The RLC supports full call on-demand (COD) functionality. This includes minimum call duration and idle timers that you can configure according to your service provider’s fee structure. COD refers to the way that the RLC handles host trunk connections. In the COD mode of operation, the RLC does not establish a host connection until the user places a call to a host DN. The COD connection stays active until the minimum call duration timer expires. The RLC then closes the host connection, if idle. If another user initiates a call to the host before the timer expires, the RLC resets the timer to track the last call

established. There is a single timer for each Remote Office 9150 or 911x unit. Timers

The RLC has two timers to help manage PSTN costs. ! Minimum call duration timer

Most PSTN tariffs specify the minimum length of time that providers can charge users for opening a connection, regardless of the call duration. This length of time determines the minimum call charges listed on long-distance telephone bills.

Remote Office 9110, 9115, and 9150 units use the minimum call duration timer in PSTN mode only. This timer specifies the minimum length of time that each PSTN call to the host PBX remains open, regardless of telephone activity. You can configure the timer on the RLC to drop the connection just before the beginning of the next charge period, when the cost of the call increases. (Refer to Example 1 on page 21.)

The minimum call duration and idle timers work together to control PSTN long distance charges. The following examples describe what happens when the minimum call duration timer is set to 59 seconds and the idle timer is set to 60 seconds.

Example 1

After a 20-second call, the minimum call duration timer still has 39 seconds remaining. If no one else at the remote site places a call, the RLC drops the PSTN connection when the timer reaches 59 seconds. In this example, the minimum call duration timer expires before the RLC initiates the idle timer. ! After the minimum call timer, PSTN signaling with no digital telephone

activity keeps the primary PSTN connection up for no longer than two idle timers.

! Every PSTN connection remains active for at least the length of the minimum call timer.

! Additional trunks and circuit-only trunks active longer than the minimum call timer remain active for an additional idle timer duration. This is the case only if no additional bandwidth requests come to the host PBX. Example 2

After a 65-second call, the idle timer starts. If no one at the remote site places a call during the next 60 seconds, the RLC drops the PSTN connection. Since the PSTN call exceeds 59 seconds, the minimum call duration timer expires before activity ceased. At the conclusion of the call, the RLC initiates the idle timer to prevent unnecessary charges.

DN priority

The RLC provides multiple priority levels for Remote Office 9150 unit users: ! PSTN only

! high ! normal ! IP only

If you configure this feature, you must also configure an amount of bandwidth to save for the High priority DNs. You must also identify the privileged DNs through Configuration Manager. This information does not apply to Remote Office 911x series or Meridian Digital Telephone IP Adapters.

The RLC uses the priority reserved bandwidth for high priority DNs. When only bandwidth for high priority DNs remains on the network, users dialing out on normal priority DNs hear a fast busy signal. For details on configuring DN priority, refer to “RLC port configuration” on page 162.

Online/Offline table

You can configure the RLC to establish or terminate host connections at specified times of the day. This feature limits excessive connection charges for idle host connections. For details on configuring the Online/Offline table, refer to “Online/Offline table configuration” on page 189.