Service Interface (Line) Cards 5-13
ASI-155, ATM Service Interface Card
Configuring Connections
Connections are routed between CPE connected to ASI ports. Before adding connections, an ASI
line is upped with the upln command and configured with the cnfln command. Then the associated
port is configured with the cnfport command and upped with the upport command. Following this,
the ATM connections are added via the addcon command with the syntax: slot.port.vpi.vci.
The slot number is the ASI card slot on the BPX switch. The port number is one of two ports on the
ASI, the VPI is the virtual path identifier, and the VCI is the virtual circuit identifier.
The VPI and VCI fields have significance only to the local BPX switch and are translated by tables
in the BPX switch to route the connection. Connections are automatically routed by the AutoRoute
feature once the connection endpoints are specified.
Connections can be either Virtual Path Connections (VPC) or Virtual Circuit Connections (VCC).
Virtual Path Connections are identified by an * in the VCI field. Virtual Circuit Connections specify
both the VPI and VCI fields.
ATM to Frame Relay Network and Service Interworking connections to the ASI are also supported.
In the case of Network Interworking, the user CPE must be aware of the interworking function and
provide the appropriate protocol mapping.
Refer to the Cisco WAN Switching Command Reference for further information.
Functional Description
For ingress traffic, the ATM Layer Interface (ALI) provides traffic management and admission
controls (UPC) for the ASI-155 (see Figure 5-7). The ASI-155 supports CBR and VBR connections
and employs a single leaky bucket GCRA mechanism for policing cell streams seeking entrance to
the network. Each PVC (VPC.VCC) is policed separately, providing firewalling between
connections, and assuring that each connection uses only a fair share of network bandwidth. The ALI
also performs ingress OAM functions.
The single leaky bucket policing function is implemented using a GCRA (Generic Rate Algorithm)
defined by two parameters:
• Rate (where I, expected arrival interval is defined as 1/Rate)
• Deviation (L)
In the ingress direction, the ASI-155 has 2 Cell Input Engines (CIEs) that convert the incoming cell
headers to the appropriate connection ID based on input from a Network Address Table.
For egress traffic, the Supervisory Cell Filter (SCF) provides routing and direction of non-data cells,
such as test cells and OAM cells.
The Serial Interface Unit (SIU) provides the ASI with an 800 Mbps cell interface to the StrataBus.
It provides serial-to-parallel conversion of data, along with loopback and test signal generation
capabilities.
The Line Interface Unit (LIU) performs the following ingress functions:
• Provides framing detection and synchronization.
• Provides the ability to extract timing from the incoming signal, and use it as a receive clock for
incoming data, while providing transmit clock in the other direction. Alternatively, loop timing
can be used to turn the receive clock back around to be used as a transmit clock. The receive clock
may also be used to synchronize the node.
• Detects alarms, frame errors, and parity errors.
• Detects far end errors, including framing errors, and yellow alarm indications.
