Toshiba DK40I, dk14, DK424I manual Call-By-CallOverview, T1 Example, 7-10

ISDN

Call-By-Call Overview

Table 7-4 ISDN PRI LDN Type Call Programming (continued)

Program	Program Data	Description
Number
*69-1	000-344 1 00	This tells the system to send the number enter in Program *68-2, as the
		Calling Party Number Identification for all stations on outbound calls.
81 - 89		Programmed as needed for incoming CO Line Ringing Assignment.
*81, *84,		Programmed as needed for incoming CO Line Ringing Assignment.
*87

Call-By-Call Overview

The Call-by-Call feature enables a group of ISDN B-channels to be assigned to calls of multiple network services or even to different carriers on a Call-by-Call basis. Call-by-Call allocates ISDN trunk groups in a more efficient manner than regular T1 service.

In order to understand the Call-by-Call concept, it is helpful to examine T1. In a T1 environment, specific channels (trunks) must be pre-assigned and provisioned to support each desired special network service, for example, outbound and inbound WATS, DID, and Tie lines. Since dedicated facilities are usually provided for peak traffic, the company pays for the unused bandwidth during normal and light traffic periods.

T1 Example

In the example shown in Figure 7-1, a span of 24 T1 channels are organized as follows:

♦Five are assigned to trunk group 1 and assigned to 800 service

♦Ten are assigned to trunk group 2 and assigned as DIDs.

♦Nine are assigned to trunk group 3 and assigned as Tie lines.

These lines are all fixed and dedicated. This is, if the traffic is low on any given trunk group, the lines cannot be re-allocated. Therefore, the user is paying for unused bandwidth.

T1 Channel Group

1		Trunk Group 1
		5 Channels dedicated to 800 numbers
2
3
4		Trunk Group 2
		10 dedicated to DID numbers
		Trunk Group 3
24		9 dedicated to Tie numbers
	4914

Figure 7-1 T1 Trunk Groups

7-10 Strata DK Programming 5/00