
7.0 OAM Functions
RS8234
7.1 OAM Overview
ATM ServiceSAR Plus with xBR Traffic Management
7-2
N8234DSC
PRELIMINARY
7.1.2 OAM Flows Supported
7.1.2.1 F4 OAM Flow
The F4 OAM flow is the Virtual Path level, provided by OAM cells dedicated to
ATM layer OAM functions for Virtual Path Connections (VPCs). The F4 flow is
bidirectional.
OAM cells for the F4 flow have the same VPI value as the user cells of the
VPC.
F4 flow OAM cells are identified as F4 flow cells by a pre-assigned VCI value
of three (segment flow cell) or four (end-to-end flow cell). The same pre-assigned
VCI value is used for both directions of the F4 flow.
7.1.2.2 F5 OAM Flow
The F5 OAM flow is the Virtual Channel level, provided by OAM cells dedicated
to ATM layer OAM functions for VCCs. The F5 flow is bidirectional.
OAM cells for the F5 flow have the same VPI value and VCI value as the user
cells of the VCC.
F5 flow OAM cells are identified as F5 flow cells by a pre-assigned PTI code
value of 100 (segment flow cell) or 101 (end-to-end flow cell). The same
pre-assigned PTI value is used for both directions of the F5 flow.
7.1.2.3 Performance
Monitoring (PM)
Performance Monitoring includes a set of functions that monitor and process user
information on a channel to produce maintenance information specific to that
channel. This maintenance information is added to the in-rate data flow on that
channel in the form of PM cells; added at the source of a connection or link, and
extracted at the sink of a connection or link. With this maintenance information,
the user can estimate and analyze the transport integrity of that channel.
The PM flow is bidirectional, and PM cells are of two basic function types:
forward monitoring cells (which carry the forward error detection information),
and backward reporting cells (which carry the results of the performance
monitoring checks).
The RS8234 performs PM on up to 128 user-assigned channels. The SAR
enables PM for a channel by setting the PM enable bits (PM_EN) in the
Segmentation and Reassembly VCC State Table entries for that channel.
The RS8234 performs PM processing on any channel by monitoring blocks of
user cells on that channel. The size of this block of cells is set by the user, and can
have the value (N) of 128, 256, 512, or 1024 cells. The RS8234 inserts a PM cell
after every N user cells on that channel. A block size of zero is valid when the
SAR is a destination point ONLY for PM processing. In this case, the
segmentation coprocessor will only generate Backward reporting cells in
response to reassembly performance monitoring calculations.
PM as performed by the RS8234 calculates the following:
Errored blocks (by means of a BIP-16 error detection code generated over
the payloads of the user cells in the PM block)
A count of misinserted PM forward monitoring cells
The user can activate PM on any channel either during connection
establishment, or at any time after the connection has been established.