Lucent Technologies CBX 3500 - Configurable Control Circuits; ILMI and Signaling Example

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About ATM Logical Ports
ATM UNI Concepts
ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000 1/19/052-7
ILMI and Signaling Example
Under certain conditions, enabling ILMI and/or signaling after you provision circuits
on a logical port may cause negative bandwidth for the associated QoS classes.
For example, you create an ATM logical port with both ILMI and signaling disabled.
You then create a full-bandwidth CBR circuit (PCR = 96000 cps) on this logical port.
If you later enable ILMI and/or signaling on the logical port, the bandwidth now
appears to be negative. The circuit will no longer come back up due to insufficient
bandwidth if you modify the logical port admin status or circuit.
Configurable Control Circuits
The configurable control circuit feature enables you to configure forward and reverse
traffic descriptors (TDs) on CBX 3500, CBX 500, and GX 550 switches for the
following:
• ATM UNI ILMI and signaling control channels
• ATM Direct and OPTimum trunk signaling and node-to-node management traffic
The switch software views a control circuit as a VCL between the logical port and the
internal switch processor. When you configure a control circuit, the switch creates a
VCL between this port and the switch processor. The logical port uses the forward TD
to police traffic flowing into the switch (UNI ILMI and signaling control channels
only). It uses the backward TD to determine the service category and equivalent
bandwidth for the control circuit. The backward TD is also used to calculate the
effective bandwidth of the circuit to be used for bandwidth management on the logical
port.
For control channels between a Lucent switch and another vendor device (including
the ILMI, UNI signaling, and PNNI routing control channels), the TD values calculate
both the amount of bandwidth reserved by Call Admission Control (CAC) and the rate
at which the control channels are policed.
Control channels are not policed by default. When you enable the usage parameter
control (UPC) or network parameter control (NPC) for the particular logical port, the
control channel is policed at the TD rate. Similar to the trunk control channels, the TD
values associated with the ILMI, UNI signaling, and PNNI routing control channels
do not affect the traffic shaping rate.
For more information about TDs, see Chapter 12, “Configuring ATM Traffic
Descriptors.”