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ATM Switch Router Software Configuration Guide
OL-7396-01
Chapter11 Configuring ATM Routing and PNNI
PNNI Connection Trace
(TTL) information element (IE). When a trace connection is triggered, the trace source node originates
a trace connection message. This message contains the TTL IE. Each switch receiving this message
appends its own connection information to the TTL IE and forwards it to the next connection on the
interface; consequently, the IE increases in size as the trace progresses through the network. The data in
the IEs also determine if the trace is performed for VPI/VCI values or call-reference values or both. The
trace stops at the destination switch. The trace destination switch prepares a TCAck message containing
all trace information in its TTL IE and sends it back to the source switch. Each switch along the trace
simply forwards the TCAck message back to the source without any further processing. The trace
connection is complete when the source switch receives the TCAck message. The source switch extracts
the information from the TTL IE and stores it. For point-to-multipoint connections, a connection trace
works for only one party at a time—each party needs to be traced separately.
The trace source switch maintains the results of each trace for the duration specified by its age-timeout
parameter. The default for this parameter is 10 minutes. However, if the connection or party that was
traced gets cleared, then all trace information associated with that connection or party is deleted,
regardless of the age-timeout parameter.
For a trace connection to work perfectly, all switches in the path of the connection or party being traced
should support trace connection, or in other words, the switches sho uld understand TC and TCAck
messages. Even if some intermediate switches do not support these messages, partial trace information
can be obtained if they support pass-along of signaling messages. If inte rmediate switches do not support
pass-along, then trace connections are not successful.
A trace connection is supported for both point-to-point and point-to-multipoint co nnections, and is used
on the following types of connections:
•SVPs
•SVCs
•Soft VCs
•Soft VPs
•Frame-relay Soft VC
Note The connection trace function is not supported on for point-to-multipoint soft PVC connect ions.
Initiating a Connection Trace
To initiate a trace connection, first a switch must be selected. On this switch, the trace connection can
be initiated in the following ways:
•From an ATM interface by specifying:
–
The VPI-VCI of an SVC or a soft-VC
–
The VPI of an SVP or a soft-VP
–
The VPI-VCI and the endpoint-reference for a party of a point-to-multipoint connec tion.
–
The call-reference value of an SVC or an SVP
–
The call-reference and endpoint-reference for a party of a P2MP connection.
•From a serial (Frame Relay) interface by specifying:
–
The DLCI value, such that there is a Frame Relay soft-VC associated with this DLCI. The
associated soft-VC is traced.