Subtending in a Digital Off-Hook Configuration

This chapter describes how to set up subtended systems in a Digital Off-Hook configuration.

This chapter includes the following sections:

Overview and Purpose

The term subtending refers to the host chassis, and subtended refers to the downstream chassis in a subtended network. Subtending allows you to use one ATM backbone for multiple Cisco 6100 chassis. In addition, once you have provisioned the primary network interface module, that configuration replicates in all subtended systems.

Subtending is a Cisco 6100 Series feature that reduces the cost per subscriber by amortizing the expense of the network interface module and the edge-switch port connection over many subscribers. Subtending provides the following advantages to your system:

Services and aggregates the data from one or more remotely located Cisco 6100/6130s into a host Cisco 6100/6130. This configuration takes advantage of the data network interface on the host Cisco 6100/6130.
Reduces the number of ATM edge-switch ports that are required to terminate the Cisco 6100/6130s.

Figure 6-1 illustrates the connections of a subtended Cisco 6100 Series system with six subtended systems.

Figure 6-1: Subtending Connections

Figure 6-2 shows valid address ranges for each Cisco 6100 Series system.

Figure 6-2: Valid ATM Connection Space

Guidelines for Subtending a Digital Off-Hook Configuration

The following guidelines apply to subtending Cisco 6100 Series nodes:

You can subtend up to six Cisco 6100/6130s to one subtending host Cisco 6100/6130 that is connected to the ATM network backbone (see to Figure 6-1).
Switch subtended VCCs to the ATM bearer service either through VCCs or VPCs. Refer to the ATM Addressing Guidelines appendix in the ViewRunner for Windows User Guide for more information.
Use standard Cisco 6100 Series system network interface modules on the subtended Cisco 6100 Series system for interconnection to the host node.
Subtend as many as seven chassis to support up to 2800 subscribers per network connection.
The Cisco 6100 Series system can support up to 9000 VCCs. The total number depends on the amount of system-controller and network-interface RAM that the resident application code consumes.
Cisco recommends a maximum of 1500 VCCs within the valid address space. Software limits might not be built in because of the temporary nature of this ceiling.
Cisco recommends that you provision transit subscribers on the subtend ports of the host Cisco 6100 Series system for each of the subscribers that are provisioned on the subtended Cisco 6100 Series ports.
You must assign the transit subscribers on the subtending host Cisco 6100 Series system the same VPI/VCI addresses that you assigned to them on the subtended Cisco 6100 Series node.

: For example, if you assign subscriber A to VPI 5 and VCI 10 on the subtended Cisco 6100 Series system, you must assign transit subscriber A to VPI 5 and VCI 10 on the host Cisco 6100 Series system. Transit subscribers on the subtending host Cisco 6100 Series system are logical containers for traffic that passes from the subtended Cisco 6100 Series system; therefore, you can create multiple transit subscribers on one port.

Each VPI/VCI must be unique on any one network interface, subtended or not, and must be the same on both ingress and egress.
You can define four VCCs per subscriber line that enters from the subtended Cisco 6100 Series system.
You can assign subscribers from the subtended node across VCCs on the subtending Cisco 6100 Series host. That is, you can assign all subscribers from a subtended node to VCC 1, or you can distribute them across all of the 32 VCCs.
You can group subscribers as you choose. For example, if you assign all subscribers from one subtended node to one VCC on the subtending host, you can lock all those subscribers at one time if you need to bring the node down for any reason.
You can subtend as many as seven chassis to support up to 2800 subscribers per network connection.
You must conduct data path tests between your Cisco 6100 Series system and far-end equipment. See "Testing Configuration Connections for the Cisco 6100 Series System" for more information on conducting data path tests.

To subtend Cisco 6100 Series systems, you provision the local subtended subscribers in the same manner as you would provision any Cisco 6100 Series system. Figure 6-3 illustrates the Subtend Host Service Provisioning dialog box that you access from the subtend host module (Cisco 6100/6130, slot 9). Notice that the dialog box is similar to the local service provisioning dialog boxes, but the subscriber side VPI/VCI connection fields read "Transit Subscriber."

Figure 6-3: Subtend Host Service Provisioning Dialog Box

You provision the transit subscriber on this dialog box just as you did that subscriber on the subtended Cisco 6100 Series system. See the "Associating Subscribers to LIM Ports" section for more information.

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