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ATM OAM F4 and F5 Cells on ACX Series Routers

 

Circuit Emulation PICs on ACX Series routers provide Asynchronous Transfer Mode (ATM) support for the following Operations, Administration, and Maintenance (OAM) fault management cell types:

  • F4 alarm indication signal (AIS) (end-to-end)

  • F4 remote defect indication (RDI) (end-to-end)

  • F4 loopback (end-to-end)

  • F5 loopback

  • F5 AIS

  • F5 RDI

ATM OAM is supported on ACX1000, ACX2000, and ACX2200 routers, and on Channelized E1/T1 Circuit Emulation MICs on ACX4000 routers.

The following methods of processing OAM cells that traverse through pseudowires with circuit cross-connect (CCC) encapsulation are supported:

  • Virtual path (VP) pseudowires (CCC encapsulation)—In the case of ATM VP pseudowires (all virtual circuits in a VP are transported over a single N-to-one mode pseudowire), all F4 and F5 OAM cells are forwarded through the pseudowire.

  • Port pseudowires (CCC encapsulation)—Similar to VP pseudowires, with port pseudowires, all F4 and F5 OAM cells are forwarded through the pseudowire.

  • Virtual circuit (VC) pseudowires (CCC encapsulation)—In the case of VC pseudowires, F5 OAM cells are forwarded through the pseudowire, while F4 OAM cells are terminated at the Routing Engine.

For ATM pseudowires, the F4 flow cell is used to manage the VP level. On ACX Series routers with ATM pseudowires (CCC encapsulation), you can configure OAM F4 cell flows to identify and report virtual path connection (VPC) defects and failures. Junos OS supports three types of OAM F4 cells in end-to-end F4 flows:

  • Virtual path AIS

  • Virtual path RDI

  • Virtual path loopback

For OAM F4 and F5 cells, IP termination is not supported. Also, Junos OS does not support segment F4 flows, VPC continuity check, or VP performance management functions. The maximum number of ATM VCs that you can configure on ACX Series routers is 1000.

ACX Series routers do not support the transmission and reception of OAM F5 loopback cells. Therefore, for ATM1 and ATM2 IQ interfaces with an ATM encapsulation, you cannot configure the OAM F5 loopback cell period on virtual circuits on ACX Series routers.

For OAM F4 cells, on each VP, you can configure an interval during which to transmit loopback cells by including the oam-period statement at the [edit interfaces interface-name atm-options vpi vpi-identifier] hierarchy level. To modify OAM liveness values on a VP, include the oam-liveness statement at the [edit interfaces interface-name atm-options vpi vpi-identifier] hierarchy level.

For interfaces that are configured for ATM cell-relay promiscuous virtual path identifier (VPI) mode, the show interfaces command output does not display the OAM F4 cell statistics. Also, the Input OAM cell no buffers field is not displayed to indicate the number of received OAM cells or raw cells dropped because of non-availability of buffers in the output of the show interfaces command for ATM interfaces. You cannot configure a fiber channel separately for OAM cells than the one used for other packets.

Layer 2 cell-relay encapsulation supports the concatenation (aggregation) of multiple ATM cells in a single encapsulated packet that is transmitted on a pseudowire. By default, each frame contains one cell. For ATM interfaces with Layer 2 circuit cell-relay transport mode configured, you can configure the time threshold (in microseconds) that the router uses to concatenate ATM cells and transmit the cells in a single frame on the pseudowire. To set the period for which the ATM cells must be collected to be bundled in a single frame being transmitted on the pseudowire, include the cell-bundle-timeout statement at the [edit interfaces at-fpc/pic/port atm-options] or the [edit interfaces at-fpc/pic/port unit logical-unit-number] hierarchy level.

You can also configure the maximum number of ATM cells per frame on the physical or logical interface. To set the maximum number of cells per frame, include the cell-bundle-size statement at the [edit interfaces at-fpc/pic/port atm-options] and the [edit interfaces at-fpc/pic/port unit logical-unit-number] hierarchy levels. The cell bundle size can be from 1 through 26.