ZyXEL VMG1312-B10A User Guide - Page 276

to use this test.

Page 276 highlights

Chapter 40 Diagnostic ATM sets up virtual circuits over which end systems communicate. The terminology for virtual circuits is as follows: • Virtual Channel (VC) • Virtual Path (VP) • Virtual Circuits Logical connections between ATM devices A bundle of virtual channels A series of virtual paths between circuit end points Figure 167 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 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 Device 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. VMG1312-B Series User's Guide 276

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Chapter 40 Diagnostic
VMG1312-B Series User’s Guide
276
ATM sets up virtual circuits over which end systems communicate. The terminology for virtual
circuits is as follows:
Figure 167
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 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 Device 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.
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