Cisco Systems MGX 8230 manual Cell Delay Treatment, Redundancy Support for the Eight-Port Cesm

Chapter 6 Card and Service Configuration

Eight-Port Circuit Emulation Service Modules

Cell Delay Treatment

For each connection, you can configure a tolerable variation in the cell arrival time (CDVT) according to the expected reliability of the route. The CDVT applies to the receive buffer. After an underrun, the receiver places the contents of the first cell to arrive in a receive buffer then plays it out at least one CDVT value later. For each VC, the maximum cell delay and CDVT (or jitter) are:

•For T1

–Cell delay of 48 msec

–CDVT of 24 msec in increments of 125 microseconds

•For E1

–Cell delay of 64 msec

–CDVT of 32 msec in increments of 125 microseconds

Redundancy Support for the Eight-Port CESM

The AX-CESM-8T1 and AX-CESM-8E1 can have 1:N redundancy support but with some variations between the T1 and E1 modes of operation. The type of redundancy and the type of back card are interdependent. See “Service Resource Module” for more details. In general:

•With an RJ48-8T1, an MGX-SRM-3T3 can provide 1:N redundancy through the distribution bus or the redundancy bus.

•With an RJ48-8E1, an MGX-SRM-3T3 can provide 1:N redundancy through the redundancy bus. Back card requirements for the MGX-SRM-3T3 and service modules vary, as follows:

•If you are using the MGX-SRM-3T3 for bulk distribution of T1 channels, the CESMs do not use back cards, but each MGX-SRM-3T3/C must have an MGX-BNC-3T3-M back card. (Bulk distribution is not available for E1 operation.)

•If the MGX-SRM-3T3/C supports T1 or E1 1:N redundancy through the redundancy bus (no bulk distribution), the MGX-SRM-3T3/C does not require a back card, but the N CESM primary cards must have one redundant version of the back card.

Error and Alarm Response

When it detects a loss of signal (LOS) alarm, the CESM notifies the connected CPE in the upstream direction after an integration period. The CESM continues to emit cells but sets the ATM cell payload with an appropriate data pattern as specified by the ATM Forum CES V2.0 specification. Also, an OAM cell with RDI code goes to the far end to indicate out of service. See Table 6-4.

Table 6-4 CESM Errors and Alarms

	Alarm	Down
Error	Type	stream	Up Stream	Comments
Link Failure	Blue (LOS)	AIS—OAM	none	Data cells According to ATM-Forum
(RX)		cells		CES-IS V 2.0
Receive RAI	Yellow	None	None

	Cisco MGX 8230 Edge Concentrator Installation and Configuration
6-44	Release 1.1.31, Part Number 78-11215-03 Rev. B0, May 2001