ZyXEL Communications VMG5313-B10A User Manual page 261

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 availability between two DSL
devices. Segment flows are terminated at the connecting point which terminates a VP or VC
segment. End-to-end flows are terminated at the end point of a VP or VC connection, where an ATM
link is terminated. Segment loopback tests allow you to verify integrity of a PVC to the nearest
neighboring ATM device. End-to-end loopback tests allow you to verify integrity of an end-to-end
PVC.
Note: The DSLAM to which the VMG is connected must also support ATM F4 and/or F5 to
use this test.
Note: This screen is available only when you configure an ATM layer-2 interface.
Figure 139 Maintenance > Diagnostic > OAM Ping
The following table describes the fields in this screen.
Table 105 Maintenance > Diagnostic > OAM Ping
LABEL
F4 segment
F4 end-end
F5 segment
F5 end-end
VMG5313-B10A/-B30A Series User's Guide
DESCRIPTION
Select a PVC on which you want to perform the loopback test.
Press this to perform an OAM F4 segment loopback test.
Press this to perform an OAM F4 end-to-end loopback test.
Press this to perform an OAM F5 segment loopback test.
Press this to perform an OAM F5 end-to-end loopback test.
Chapter 34 Diagnostic
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