Troubleshooting guide

C-3
ATM and Layer 3 Switch Router Troubleshooting Guide
OL-1969-01
Appendix
OAM Cell Structure
OAM Cell Structure
Operation, Administration, and Maintenance (OAM) performs standard loopback (end-to-end or
segment) and fault detection and notification (alarm indication signal [AIS] and remote defect
identification [RDI]) for each connection. It also maintains a group of timers for the OAM functions.
When there is an OAM state change such as loopback failure, OAM software notifies the connection
management software. You can enable or disable OAM operation for the following switch router
components:
• The entire switch router
• A specific ATM interface
• Each ATM connection
Figure C-3 shows the format of the OAM loopback cell.
Figure C-3 OAM Cell Structure
The OAM cell structure has the following features:~
• OAM cell type is coded as 0001.
• OAM function type is coded as 0010.
• 350 bits that are specific to the OAM type are divided into the following elements:
– Loopback indicator—A bit that is set to 1 before the cell is looped back. The loopback node
then sets the bit to 0, indicating it has been looped back.
– Correlation tag—Identifies (correlates) related OAM cells within the same connection.
– Loopback location ID—An optional field that identifies the site that is to loopback the cell.
– Source ID—An optional field that identifies the site generating the cell.
GFC
VPI
VCI
VPI
VCI
PTI
VCI
HEC
OAM cell type = 0001
OAM function type = 0010
Loopback information
fields
Reserved
CRC(10)
C
Loopback indication
Correlation tag
Loopback location ID
Source ID
10295