Cisco Systems 8600 Series manual Configuring Connections, Functional Description

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:

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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.

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Detects alarms, frame errors, and parity errors.

Detects far end errors, including framing errors, and yellow alarm indications.

Service Interface (Line) Cards 5-13