Chapter 35 Diagnostic
VMG1312-B Series User’s Guide
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35.5 OAM Ping Test
Click Ma int e na nce > Dia gnost ic > OAM Ping Te st t o open t he screen shown next . Use this
screen to perform an OAM (Operat ion, Adm inist ration and Maintenance) F4 or F5 loopback test on a
PVC. The Device sends an OAM F4 or F5 packet t o t he DSLAM or ATM switch and t hen ret urns it to
the Device. The test result then displays in the t ext box.
ATM set s up virtual circuit s over which end system s com m unicat e. The t erm inology for virt ual
circuit s is as follows:
Figure 147 Virt ual Circuit Topology
Think of a virt ual path as a cable t hat contains a bundle of wires. The cable connects t wo points and
wires wit hin t he cable provide individual circuit s bet ween the t wo points. I n an ATM cell header, a
VPI ( Virtual Pat h I dent ifier ) identifies a link form ed by a virt ual path; a VCI (Virtual Channel
I dent ifier) identifies a channel wit hin a virtual path. A series of virt ual paths m ake up a virt ual
circuit .
F4 cells operat e at t he virt ual path ( VP) level, while F5 cells operate at the virt ual channel (VC)
level. F4 cells use t he sam e VPI as t he user dat a cells on VP connect ions, but use differ ent
predefined VCI values. F5 cells use t he sam e VPI and VCI as t he user data cells on t he VC
connect ions, and are distinguished from dat a cells by a predefinded Payload Ty pe I dentifier ( PTI ) in
the cell header. Both F4 flows and F5 flows are bidirect ional and have tw o types.
• segm ent F4 flows ( VCI = 3)
• end-t o- end F4 flow s (VCI = 4)
• segm ent F5 flows ( PTI = 100)
• end-t o- end F5 flows ( PTI = 101)
OAM F4 or F5 test s are used t o check virtual path or virtual channel availabilit y between two DSL
devices. Segm ent flows are term inated at the connecting point which term inates a VP or VC
segm ent . End-t o- end flows are t erm inated at t he end point of a VP or VC connection, wher e an ATM
link is t erm inated. Segm ent loopback t ests allow you to verify int egrit y of a PVC to the nearest
neighboring ATM device. End- t o- end loopback t ests allow you t o verify int egrit y of an end-t o- end
PVC.
Note: The DSLAM t o which the Device is connect ed m ust also support ATM F4 and/ or F5
t o use t his test .
• Virt ual Channel (VC) Logical connections between ATM devices
• Virt ual Path ( VP) A bundle of virt ual channels
• Virtual Circuit s A series of virt ual paths between circuit end points
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