Chapter 29 Diagnostic
P-2812HNU-51c User’s Guide
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29.5 The OAM Ping Test Screen
Click Maintenance > Diagnostic > OAM Ping Test to open the screen shown
next. Use this screen to perform an OAM (Operation, Administration and
Maintenance) F4 or F5 loopback test on a PVC. The P-2812HNU-51c sends an OAM
F4 or F5 packet to the DSLAM or ATM switch and then returns it to the P-
2812HNU-51c. The test result then displays in the text box.
ATM sets up virtual circuits over which end systems communicate. The
terminology for virtual circuits is as follows:
Figure 200 Virtual Circuit Topology
Think of a virtual path as a cable that contains a bundle of wires. The cable
connects two points and wires within the cable provide individual circuits between
the two points. In an ATM cell header, a VPI (Virtual Path Identifier) identifies a
link formed by a virtual path; a VCI (Virtual Channel Identifier) identifies a
channel within a virtual path. A series of virtual paths make up a virtual circuit.
F4 cells operate at the virtual path (VP) level, while F5 cells operate at the virtual
channel (VC) level. F4 cells use the same VPI as the user data cells on VP
connections, but use different predefined VCI values. F5 cells use the same VPI
and VCI as the user data cells on the VC connections, and are distinguished from
data cells by a predefinded Payload Type Identifier (PTI) in the cell header. Both F4
flows and F5 flows are bidirectional and have two types.
• segment F4 flows (VCI=3)
• end-to-end F4 flows (VCI=4)
• segment F5 flows (PTI=100)
• end-to-end F5 flows (PTI=101)
OAM F4 or F5 tests are used to check virtual path or virtual channel availbility
between two DSL devices. Segment flows are terminated at the connecting point
• Virtual Channel (VC) Logical connections between ATM devices
• Virtual Path (VP) A bundle of virtual channels
• Virtual Circuits A series of virtual paths between circuit end points
Virtual Path
Virtual Channel
Segment
ATM Switch
Virtual Circuit (End-to-End)
