Frame Relay to ATM Interworking

Note This chapter provides technical background and configuration overview information applicable to the Frame Relay port adapters for the ATM switch router. It does not provide general Frame Relay information.

Frame Relay to ATM Interworking Overview

Frame Relay to ATM interworking allows you to retain your existing Frame Relay services and, as needs expand, migrate to the higher bandwidth capabilities provided by ATM networks. Frame Relay traffic connects across high-speed ATM trunks using two interworking functions (IWFs): network interworking and service interworking.

The difference between these two interworking functions is that network interworking provides a transport between two Frame Relay devices, while service interworking provides transparent interworking between ATM devices and Frame Relay devices without either being aware of the technology used at the other end.

The implementation of network interworking and service interworking is specified in procedures jointly agreed upon by the Frame Relay Forum and the ATM Forum (FRF.5 and FRF.8).

Network Interworking

The network interworking function (network IWF) facilitates transport of Frame Relay user traffic and Frame Relay permanent virtual circuit (PVC) signaling traffic over ATM. Tunneling, multiprotocol encapsulation, and other higher layer procedures are handled just as they would be over leased lines. A network IWF application connects Frame Relay devices over an ATM backbone, as shown in Figure 12-1.

Note In this chapter PVC is used interchangeably to mean permanent virtual circuit (in the context of Frame Relay) and permanent virtual connection (in the context of ATM).

Figure 12-1: Frame Relay to ATM Network Interworking

In the example shown in Figure 12-1, the ATM network could take the place of a leased line to connect the two Frame Relay networks. The network IWF is integrated into the channelized Frame Relay port adapter. This method of connecting Frame Relay networks can provide economic savings when compared to leased lines and offers the improved scalability of ATM at the core.

If a Frame Relay port is connected across an ATM network to an ATM device, network interworking requires that the ATM device recognize that it is connected to an interworking function, such as Frame Relay. The ATM device must then exercise the appropriate service-specific convergence sublayer (SSCS), in this case the Frame Relay SSCS (FR-SSCS).

Service Interworking

The service interworking function (service IWF) provides a transport between two dissimilar devices, such as Frame Relay and ATM. Unlike network IWF, service IWF does not transport traffic transparently. Rather, it serves as a protocol converter and allows communication between dissimilar devices, as shown in Figure 12-2.

Figure 12-2: Frame Relay to ATM Service Interworking

In the example in Figure 12-2, Frame Relay traffic is sent on a PVC through the Frame Relay network to the service IWF, which then maps Frame Relay frames to ATM cells on an ATM PVC. This process illustrates a chief advantage of service interworking: each location can use the technology best suited to its applications and needs.

The service IWF converts Frame Relay PVC address information such as the data-link connection identifier (DLCI) to the ATM VPI/VCI. Additionally, the forward explicit congestion notification (FECN) bit maps to the explicit forward congestion indication (EFCI) bit in the payload type identifier (PTI), and the discard eligible (DE) bit maps to the cell loss priority (CLP) bit of the ATM cell.

The Channelized DS3 Frame Relay Port Adapter

The channelized DS3 (CDS3) Frame Relay port adapter provides one physical port (45 Mbps). Each DS3 interface consists of 28 T1 lines multiplexed through a single T3 trunk. Each T1 line operates at 1.544 Mbps, which equates to 24 time slots (DS0 channels). A DS0 time slot provides 56 or 64 Kbps of usable bandwidth. You can combine one or more DS0 time slots into a channel group to form a serial interface. A channel group provides n x 56 or 64 Kbps of usable bandwidth, where n is the number of time slots, from 1 to 24. You can configure a maximum of 127 serial interfaces, or channel groups, per port adapter.

Figure 12-3 illustrates how a T3 trunk demultiplexes into 28 T1 lines that provide single or multiple time slots mapped across the ATM network. These time slots are then multiplexed to form an outgoing T3 bit stream.

Figure 12-3: T3/T1 Time Slot Mapping

Configuration Guidelines

To configure the CDS3 Frame Relay port adapter physical interface, you need the following information:

Digital transmission link information, for example, T3 and T1 clock source and framing type
Channel information and time slot mapping
Protocols and encapsulations you plan to use on the new interfaces

Configuration Overview

Configuring the CDS3 Frame Relay port adapter interface requires the following tasks, described in the following sections:

Step 1 Configure the physical interface.

Step 2 Configure the T1 lines.

Step 3 Configure the channel group.

Physical Interface

The CDS3 Frame Relay port adapter is preconfigured with default values for the physical interface. You can manually change any of the default configuration values by performing the following steps:

Step 1 Enter controller configuration mode and select the CDS3 Frame Relay interface to configure.

Step 2 Specify the clock distribution mode (default is loop-timed). For more information on clocking modes, see "Network Clock Synchronization."

Step 3 Specify the DS3 framing type (the default is M23).

Step 4 Specify the cable length (the default is 224).

Step 5 Configure the Maintenance Data Link (MDL) message (the default is no message). MDL messages are only supported when the framing type is set for c-bit parity.

T1 Lines

The CDS3 Frame Relay port adapter is preconfigured with default values for all T1 lines. You can manually change any of the default configuration values by performing the following steps:

Step 1 Enter controller configuration mode and select the CDS3 Frame Relay interface to configure.

Step 2 Specify the T1 framing mode for the lines you are configuring (the default is ESF).

Step 3 Specify T1 yellow alarm detection, generation, or both for the lines you are configuring (the default is both).

Channel Group

A channel group, also referred to as a serial interface, is configured on a T1 line by associating time slots to it. The channel group can have from 1 to 24 time slots (DS0s). The transmission rate or bandwidth of the channel group is calculated by multiplying the number of time slots times 56 or 64 Kbps.

Note A time slot can be part of only one channel group. Additionally, all time slots within a channel group must be on the same T1 line.

Configuring the T1 channel group requires the following steps:

Step 1 Enter controller configuration mode and select the CDS3 Frame Relay interface to configure.

Step 2 Create the channel group by specifying a channel group number, T1 line number, and the time slots that comprise the channel.

Note You can group either contiguous or noncontiguous time slots on a T1 line.

The Channelized E1 Frame Relay Port Adapter

The channelized E1 (CE1) Frame Relay port adapter provides four physical ports. Each port supports up to 31 serial interfaces, also referred to as channel groups. The E1 line operates at
2.048 Mbps, which is equivalent to 31 time slots (DS0 channels). A time slot on an E1 provides 64 Kbps of usable bandwidth. You can combine one or more time slots into a channel group to form a serial interface. A channel group provides n x 64 Kbps of usable bandwidth, where n is the number of time slots, from 1 to 31. You can configure a maximum of 124 serial interfaces, or channel groups, per port adapter.

Figure 12-4 illustrates how an E1 trunk (with four ports) provides single or multiple time slots mapped across the ATM network. Multiple n x 64 circuits can be connected to a single port, using separate time slots.

Figure 12-4: E1 Time Slot Mapping

Configuration Guidelines

To configure the CE1 Frame Relay port adapter, you will need the following information:

Digital transmission link information, for example, E1 clock source and framing type
Channel information and time slot mapping
Protocols and encapsulations you plan to use on the new interfaces

Configuration Overview

Configuring the CE1 Frame Relay port adapter interface requires the following tasks, described in the following sections:

Step 1 Configure the physical interface.

Step 2 Configure the channel group.

The following defaults are assigned to all CE1 Frame Relay port adapter interfaces:

Framing---crc4
Clock source---loop-timed
Linecode---HDB3

Physical Interface

The CE1 Frame Relay port adapter is preconfigured with default values for the physical interface. You can manually change any of the default configuration values by performing the following steps:

Step 1 Enter controller configuration mode and select the CE1 Frame Relay interface to configure.

Step 2 Specify the clock distribution mode (the default is loop-timed). For more information on clocking modes, see "Network Clock Synchronization."

Step 3 Specify the DS3 framing type (the default is CRC4).

Channel Group

A channel group, also referred to as a serial interface, is configured on an E1 line by associating time slots to it. The channel group can have from 1 to 31 time slots (DS0s). The transmission rate or bandwidth of the channel group is calculated by multiplying the number of time slots times 64 Kbps.

Configuring the channel group requires the following steps:

Step 1 Enter controller configuration mode and select the CE1 Frame Relay interface to configure.

Step 2 Create the channel group by specifying a channel group number and the time slots that comprise the channel.

Frame Relay to ATM Interworking Configuration Overview

This section outlines the steps required to enable Frame Relay to ATM interworking on your ATM switch router. In addition, you can customize Frame Relay to ATM for your particular network needs and monitor Frame Relay to ATM connections. Configuring Frame Relay to ATM interworking functions requires the following tasks:

Enable Frame Relay encapsulation on an interface
Configure the Frame Relay serial interface type

For information on how to customize your Frame Relay to ATM connections, see the "LMI Configuration Overview" section and "Frame Relay to ATM Resource Management Configuration Overview" section.

Enable Frame Relay Encapsulation

Frame Relay supports encapsulation of all supported protocols in conformance with RFC 1490, allowing interoperability between multiple vendors. Enabling Frame Relay encapsulation on the serial interface requires the following steps:

Step 1 Enter interface configuration mode and select the serial interface to configure.

Step 2 Enable IETF encapsulation on the interface.

Serial Interface Type

You can configure a serial interface as a data communications equipment (DCE) or Network-to-Network Interface (NNI) type. Configuring the serial interface type requires the following steps:

Step 1 Enter interface configuration mode and select the serial interface to configure.

Step 2 Specify the interface type.

When you specify DCE, the ATM switch router supports only network-side PVC status management procedures. When you specify NNI, the ATM switch router supports both user-side and network-side PVC status management procedures.

LMI Configuration Overview

The Local Management Interface (LMI) provides a set of enhancements to the basic Frame Relay specification, including support for a keepalive mechanism and statistics. You can configure the following LMI-related parameters on the Frame Relay interface:

LMI type
LMI keepalive interval
LMI polling and timer intervals (optional)

LMI Type

Configuring the LMI type requires the following steps:

Step 1 Enter interface configuration mode and select the serial interface to configure.

Step 2 Specify a Frame Relay LMI type (Cisco is the default type).

Step 3 Exit configuration mode and save your running configuration to the startup configuration.

LMI Keepalive Interval

A keepalive interval must be set to configure the LMI. By default, this interval is 10 seconds and, per the LMI protocol, must be set as a positive integer that is less than the lmi-t392dce interval set on the interface of the neighboring switch.

Configuring the keepalive interval requires the following steps:

Step 1 Enter interface configuration mode and select the serial interface to configure.

Step 2 Specify a keepalive interface for the interface.

LMI Polling and Timer Intervals

You can set various optional counters, intervals, and thresholds to fine-tune the operation of your LMI on your Frame Relay devices. Configuring these attributes requires the following steps:

Step 1 Enter interface configuration mode and select the serial interface to configure.

Step 2 Perform one or more of the following substeps:

(a) Specify the number of keepalive exchanges to be completed before requesting a full status message.

(b) Specify the error threshold for DCE and NNI interfaces.

(d) Specify the monitored events count on DCE and NNI interfaces.

(e) Specify the monitored event count on DTE and NNI interfaces.

(f) Specify the polling verification timer on DCE and NNI interfaces.

Frame Relay to ATM Resource Management Configuration Overview

This section describes the connection traffic table (CTT) rows used specifically for Frame Relay to ATM interworking, and provides an overview of configuring the following features:

Frame Relay to ATM connection traffic table rows
Interface resource management

For general information on ATM connection traffic table rows, see the "Connection Traffic Table" section in the "Traffic and Resource Management" chapter.

Frame Relay to ATM Connection Traffic Table

A row in the Frame Relay to ATM Connection Traffic Table (CTT) must be created for each unique combination of Frame Relay traffic parameters. All Frame Relay to ATM interworking virtual connections then provide traffic parameters for each row in the table per flow (receive and transmit). Multiple virtual connections can refer to the same traffic table row.

The Frame Relay traffic parameters (specified in the command used to create the row) are converted into equivalent ATM traffic parameters. Both parameters are stored internally and used for interworking virtual connections.

The formulas for Frame Relay to ATM traffic conversions are specified in the Broadband Inter-Carrier Interface (B-ICI) specification, V2.0, and use a frame size (n) of 250 bytes and a header size of 2 bytes. The traffic parameters are mapped between ATM and Frame Relay as follows:

Peak cell rate (0+1) (cells per second) = peak information rate/8 * (6/260)
Sustainable cell rate (0) (cells per second) = committed information rate/8 * (6/250)
Maximum burst size (0) (cells) = (committed burst size/8 * (1/(1-committed information rate/peak information rate)) + 1) * (6/250)

Note Peak information rate and committed information rate are expressed in bits per second. Committed burst size is expressed in bits.

Connection Traffic Table Rows

For PVCs, PVC connection traffic rows, or stable rows, are used to specify traffic parameters.

Note PVC connection traffic rows cannot be deleted while in use by a connection.

For SVCs, connection traffic rows, or transient rows, are used by the signaling software to obtain traffic parameters.

Note SVC connection traffic rows cannot be deleted from the CLI or SNMP. They are automatically deleted when the connection is removed.

To make the CTT management software more efficient, the CTT row-index space is split into two ranges, allocated by the CLI/SNMP and signaling. (See Table 12-1.)

Allocated By	Row-Index Range
CLI/SNMP	1 through 1,073,741,823
Signaling	1,073,741,824 through 2,147,483,647

Table 12-1: CTT Row-Index Allocation

Allocated By Row-Index Range

CLI/SNMP

1 through 1,073,741,823

Signaling

1,073,741,824 through 2,147,483,647

Predefined Rows

Table 12-2 shows the parameters and values in the predefined CTT row.

CTT Row-Index	CIR (bps¹)	Bc (bits)	Be (bits)	PIR (bps)	Service Category	ATM Row-Index
100	64000	32768	32768	64000	vbr-nrt	100

Table 12-2: Default Frame Relay to ATM CTT Row

CTT Row-Index CIR (bps¹) Bc (bits) Be (bits) PIR (bps) Service
Category ATM Row-Index

100

64000

32768

32768

64000

vbr-nrt

100

¹Bits per second

Frame Relay to ATM Connection Traffic Table Configuration Overview

To create a Frame Relay to ATM CTT row, you specify the following information:

Index of the entry created in the Frame Relay CTT
Committed information rate (CIR) value
Committed burst size (Bc) value
Peak information rate (PIR) value
Excess burst size (Be) value
The service category (ABR, VBR-NRT, or UBR)
Index of the entry created in the ATM CTT

Interface Resource Management Configuration Overview

Resource management defaults are provided for queue thresholds, committed burst size, and service overflow on Frame Relay interfaces. You can change any of these interface parameters by performing one or more of the following steps:

Step 1 Specify discard and marking thresholds for any of the supported service categories in the inbound direction.

Step 2 Specify discard and marking thresholds for any of the supported service categories in the outbound direction.

Step 3 Specify the committed burst size for ABR/UBR soft virtual connections on the destination interface.

Step 4 Configure to accept or discard overflow traffic that exceeds the CIR for VBR circuits. This applies only to CDS3 interfaces

Step 5 Specify the percentage of CIR overbooking to allow.

Frame Relay to ATM Virtual Connections Configuration Overview

This section provides an overview of configuring virtual connections for Frame Relay to ATM interworking and Frame Relay to Frame Relay switching. Descriptions of configuring the following types of connections are included:

Frame Relay to ATM network interworking PVCs
Frame Relay to ATM service interworking PVCs
Frame Relay transit PVCs
Frame Relay soft PVC connections

Configuration Prerequisites

The following configurations must be completed in the prescribed order before setting up Frame Relay to ATM interworking connections or Frame Relay to Frame Relay connections.

Step 1 Configure the controller on the Frame Relay port adapter.

Step 2 Configure the T1 interface (or E1 interface) and channel group on the Frame Relay port adapter.

Step 3 Configure Frame Relay encapsulation and the Frame Relay LMI on the serial interface corresponding to the channel group configured in Step 2.

Step 4 Configure Frame Relay connection traffic table rows and related resource management functions.

Characteristics and Types of Virtual Connections

The characteristics of the Frame Relay to ATM interworking virtual connection, established when the virtual connection is created, include the following:

Frame Relay to ATM interworking parameters
CIR, Bc, Be, PIR (that is, access rate [AR]) for Frame Relay
Peak and average transmission rates for ATM
Service category
Cell sequencing integrity
ATM adaptation layer 5 (AAL5) for terminating interworking PVCs

These switching features can be turned off with the interface configuration commands.

Note For more information about ATM connections, see "Virtual Connections."

Table 12-3 lists the types of supported virtual connections.

Connection	Point-to-Point	Point-to-Multipoint	Transit	Terminate
Permanent virtual connection (PVC)	X	--	X	X
Soft permanent virtual connection (soft PVC)	X	--	X	--

Table 12-3: Supported Frame Relay to ATM Virtual Connection Types

Connection Point-to-Point Point-to-Multipoint Transit Terminate

Permanent virtual connection (PVC)

X

--

X

X

Soft permanent virtual connection (soft PVC)

X

--

X

--

Frame Relay to ATM Network Interworking PVCs

This section describes how to configure Frame Relay to ATM network interworking PVCs. This type of connection establishes a bidirectional facility that transfers Frame Relay traffic between two Frame Relay users through an ATM network.

Figure 12-5 shows an example of a Frame Relay to ATM network interworking PVC between Frame Relay user A and ATM user D through an ATM network.

Figure 12-5: Network Interworking PVC Example

Configuring a Frame Relay to ATM network interworking PVC, such as the internal cross-connect in switch B or switch C in Figure 12-5, requires the following steps:

Step 1 Enter interface configuration mode and select the serial interface to configure. The PVC is configured from the serial interface and cross-connected to the ATM interface.

Step 2 Configure the PVC, specifying the following values:

DLCI for the Frame Relay end of the PVC
Type, which is network in this case
The interface for the ATM end of the PVC
The VPI and VCI values for the ATM end of the PVC

You can optionally specify the row index for the receive and transmit rows in the CTT, if previously configured. You can also specify mapping of resource management parameters between Frame Relay and ATM.

Frame Relay to ATM Service Interworking PVCs

A Frame Relay to ATM service interworking PVC is established as a bidirectional facility to transfer Frame Relay to ATM traffic between a Frame Relay user and an ATM user. The upper user protocol encapsulation (FRF.3, RFC 1483, RFC 1490, and RFC 1577) mapping can be enabled with the translation option when the PVC is created.

Figure 12-6 shows an example of a Frame Relay to ATM service interworking PVC between Frame Relay user A and ATM user D through an ATM network.

Figure 12-6: Service Interworking PVC Example

Note VPI and VCI values can change when traffic is relayed through the ATM network.

Configuring a Frame Relay to ATM service interworking PVC, such as the internal cross-connect on switch B or switch C in Figure 12-6, requires the following steps:

Step 1 Enter interface configuration mode and select the serial interface to configure. The PVC is configured from the serial interface and cross-connected to the ATM interface.

Step 2 Configure the PVC, specifying the following values:

DLCI for the Frame Relay end of the PVC
Type, which is service in this case
Service mode (transparent or translation)
The interface for the ATM end of the PVC
The VPI and VCI values for the ATM end of the PVC

Terminating Frame Relay to ATM Service Interworking PVCs

This section describes configuring terminating Frame Relay to ATM service interworking PVCs. This type of terminating connection provides the connection from IP over Frame Relay to the ATM switch router, and is used for IP over ATM and network management.

Figure 12-7 shows an example of transmit and terminating connections. Terminating connections connect to the CPU on the ATM switch router.

Figure 12-7: Frame Relay to ATM Transmit and Terminating Connections

The internal cross-connect on switch B in Figure 12-7 is a PVC between serial interface 0/1/0:5, DLCI = 50 and the terminating connection on ATM interface 0, VPI = 0 and an unspecified VCI. Configuring this connection requires the following steps:

Step 1 Enter interface configuration mode and select the serial interface to configure. The PVC is configured from the serial interface and cross-connected to the ATM interface.

Step 2 Configure the PVC, specifying the following:

DLCI for the Frame Relay end of the PVC
Type, which is service in this case
Translation option
The interface for the ATM end of the PVC
The VPI value
Accept any VCI
Encapsulation type, which is AAL5 SNAP in this case

Frame Relay Transit PVCs

Frame Relay transit PVCs are used to establish a bidirectional facility to transfer Frame Relay traffic between two Frame Relay users. Figure 12-8 shows a Frame Relay transit PVC between Frame Relay users A and D.

Figure 12-8: Transit PVC Example

Configuring a Frame Relay transit PVC, such as the one between the serial interfaces on switch B and switch C in Figure 12-8, requires the following steps:

Step 1 Enter interface configuration mode and select the serial interface to configure.

Step 2 Configure the PVC, specifying the following values:

DLCI for the Frame Relay for the originating end of the PVC
Identifier of the serial interface at the destination end of the PVC
DLCI for the Frame Relay for the destination end of the PVC

Each subsequent cross-connection and link must be configured until the virtual connection is terminated to create the entire VCC.

Frame Relay Soft PVC Connections

This section provides guidelines and an overview of configuring the following types of Frame Relay to ATM interworking soft PVC connections:

Frame Relay to Frame Relay soft PVC, configured as network interworking
Frame Relay to ATM soft PVC, configured as network interworking
Frame Relay to ATM soft PVC, configured as service interworking

General Procedure

The following steps outline the general procedure for configuring network and service interworking soft PVC connections.

Note Frame Relay interworking soft PVCs can only be configured from a Frame Relay interface.

Configuring a Frame Relay interworking soft PVC requires the following steps:

Step 1 Determine which two switches you want to define as participants in the soft PVC.

Step 2 Determine the source (active) side of the soft PVC.

Step 3 Determine an available DLCI value on the source end of the soft PVC.

Step 4 Determine the destination (passive) side of the soft PVC.

Step 5 Determine the ATM address of the destination side of the soft PVC.

Step 6 If the destination side of the soft PVC is a Frame Relay interface, choose an available DLCI value. If the destination side of the soft PVC is an ATM interface, choose an available VPI/VCI value.

Step 7 Choose the interworking function type and the relevant interworking parameters (for example, de-bit/clp-bit mapping options).

Note

Step 8 Configure the Frame Relay interworking soft PVC on the source side. See the following sections for configuration steps and examples.

Frame Relay to Frame Relay Network Interworking Soft PVCs

Figure 12-9 shows a Frame Relay to Frame Relay network interworking soft PVC between
switch A and switch B.

Figure 12-9: Frame Relay to Frame Relay Network Interworking Soft PVC Example

Configuring a Frame Relay to Frame Relay network interworking soft PVC requires the following steps:

Step 1 Determine the source and destination interfaces.

Step 2 Determine an available DLCI value for the serial interface on the source side.

Step 3 Determine the ATM address for the destination serial interface.

Step 4 Determine an available DLCI value for the destination serial interface.

Step 5 Enter interface configuration mode and select the serial interface (source) to configure.

Step 6 Configure the soft PVC, specifying the following values:

DLCI value for the serial interface on the source side
ATM address of the destination serial interface
DLCI value for the destination serial interface

You can also specify the relevant interworking parameters, such as the Frame Relay to ATM traffic parameter mappings. You do not need to specify the interworking type; soft PVCs that originate and terminate on Frame Relay interfaces are configured as network interworking by default.

Frame Relay to ATM Service Interworking Soft PVCs

Figure 12-10 shows a Frame Relay to ATM service interworking soft PVC between switch A and switch B.

Figure 12-10: Frame Relay to ATM Service Interworking Soft PVC Example

Configuring Frame Relay to ATM service interworking soft PVC requires the following steps:

Step 1 Determine the source (serial) and destination (ATM) interfaces.

Step 2 Determine an available DLCI value for the serial interface.

Step 3 Determine the ATM address on the destination interface.

Step 4 Determine available VPI and VCI values on the ATM interface.

Step 5 Enter interface configuration mode and select the serial interface to configure.

Step 6 Configure the soft PVC, specifying the following values:

DLCI value for the serial interface on the source side.
ATM address of the destination interface.
VPI and VCI values for the ATM interface.
Interworking type, which is service in this case.
Service interworking mode (transparent or translation). If the soft PVC terminates on an ATM interface, the default interworking type is service interworking in translation mode.

You can also specify the relevant interworking parameters, such as the Frame Relay to ATM traffic parameter mappings.

Soft PVC Route Optimization

The soft PVC route optimization feature is supported on Frame Relay interfaces. For a detailed explanation of the feature, see the "Route Optimization for Soft PVCs" section in the chapter "Virtual Connections."

Soft PVC route optimization must be enabled and configured to determine the point at which a better route is found and the old route is reconfigured. Enabling and configuring a Frame Relay interface with route optimization requires the following steps:

Step 1 From global configuration mode, enable route optimization and specify a threshold value.

Step 2 Enter interface configuration mode and select the serial interface to configure. You configure route optimization on the source end of a soft PVC only.

Step 3 Specify during what time of day and how often routes should be recomputed on this interface.

You can also manually trigger route optimization on a specific soft PVCC or PVPC.

Note Route optimization for soft permanent virtual connections should not be configured with constant bit rate (CBR) connections.

Existing Frame Relay to ATM Interworking Soft PVC Respecification

Existing Frame Relay to ATM interworking soft PVCs are torn down while an explicit path over the PVC is being respecified. However, you can configure a Frame Relay soft PVC to allow explicit paths to be respecified without tearing down connections. Existing connections are unaffected unless a reroute takes place, and then they use the newer explicit-path configuration.

For more information, see the "Soft PVCs with Explicit Paths" section of the chapter "Virtual Connections."

Respecifying Frame Relay to ATM interworking soft PVCs requires configuring the soft PVC with the redo-explicit feature and related parameters, such as the explicit path precedence and partial path.

Table of Contents

Frame Relay to ATM Interworking