255-700-019
3-27
PacketStar
™
PSAX 20 Access Concentrator User Guide
, Issue 1
Release 6.3.0
Chapter 3 System Features
PSAX 20 Software Features
receiving, and intrepreting F4/F5 OAM flows. This feature requires the user
to run
AQueWin
™
and the
AQueView
™
system.
OAM Functions
The OAM functions (and their cell types) are:
•
Fault management
~
detection (continuity check): periodically verifiy connection integrity
~
reporting (alarm indication signals [AISs]) and remote defect
indications [RDIs]: periodically notify connection faults in upstream
and downstream directions
~
localization (loopback): isolate failed entities if defect information is
insufficient
•
Activation/deactivation: remote activation/deactivation of continuity
check functions
OAM Cell
Characteristics
OAM cells are bidirectional and follow the same physical and logical route as
user payload cells. There are two variants for each flow: one that checks a
particular segment, and the other, an end-to-end flow. A segment is indicated
by a virtual channel identifier (VCI) of three for F4 flows, or a payload type
(PT) of 4 for F5 flows. End-to-end flows are indicated by a VCI of 4 for F4
flows, or a PT of 5 for F5 flows.
OAM cells are ATM cells with the fields shown in Figure 3-8:
•
Header: this is the same as the ATM cell header
•
OAM Cell Type: the management type (fault, activation/deactivation)
•
OAM Function Type: the specific function (AIS, RDI, continuity check,
loopback, forward monitoring, backward reporting, and so on)
•
Function-specific field: data required for the specific function
•
Reserved: reserved for further specification
•
EDC: CRC-10 error detection code computed over the cell payload
(except the CRC-10 field) and used to check for data corruption
F4/F5 Flows
OAM has two flows of management information: F4 and F5. F4/F5 in-band
maintenance flows are defined at the ATM layer for the VPC and VCC level,
respectively. F4 is used for path level connections, where the virtual path
(VP) flows are identified by reserved values within the path. F5 is used for
Figure 3-8. OAM Cell Fields
Function
Type
Reserved
OAM
Cell
Type
EDC
Function specific field
Payload
Header
Header
4 4
6
10
360 bits (45 bytes)
Summary of Contents for PacketStar PSAX 20
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