Table Of Contents
Frame Relay Hardware Configurations
Frame Relay Configuration Task List
Enabling Frame Relay Encapsulation on an Interface
Configuring Dynamic or Static Address Mapping
Explicitly Configuring the LMI
Setting the LMI Keepalive Interval
Setting the LMI Polling and Timer Intervals
Enabling Frame Relay SVC Service
Configuring SVCs on a Physical Interface
Configuring SVCs on a Subinterface
Configuring a Map Group with E.164 or X.121 Addresses
Associating the Map Class with Static Protocol Address Maps
Configuring Frame Relay Traffic Shaping
Defining VCs for Different Types of Traffic
Enabling Frame Relay Traffic Shaping on the Interface
Frame Relay ForeSight Prerequisites
Frame Relay Congestion Notification Methods
Enabling Enhanced Local Management Interface
Specifying a Traffic Shaping Map Class for the Interface
Defining a Map Class with Queueing and Traffic Shaping Parameters
Defining Priority Queue Lists for the Map Class
Defining Custom Queue Lists for the Map Class
Customizing Frame Relay for Your Network
Configuring Frame Relay End-to-End Keepalives
Verifying Frame Relay End-to-End Keepalives
Configuring PPP over Frame Relay
Configuring Frame Relay Subinterfaces
Understanding Frame Relay Subinterfaces
Defining Subinterface Addressing
Configuring Transparent Bridging for Frame Relay
Configuring a Backup Interface for a Subinterface
Configuring Frame Relay Switching
Enabling Frame Relay Switching
Configuring a Frame Relay DTE Device, DCE Switch, or NNI Support
Disabling or Reenabling Frame Relay Inverse ARP
Creating a Broadcast Queue for an Interface
Configuring Payload Compression
Configuring Standard-Based FRF.9 Compression
Selecting FRF.9 Compression Method
Configuring FRF.9 Compression Using Map Statements
Configuring FRF.9 Compression on the Subinterface
Configuring TCP/IP Header Compression
Configuring an Individual IP Map for TCP/IP Header Compression
Configuring an Interface for TCP/IP Header Compression
Disabling TCP/IP Header Compression
Configuring Real-Time Header Compression with Frame Relay Encapsulation
Configuring Discard Eligibility
Configuring DLCI Priority Levels
Monitoring and Maintaining the Frame Relay Connections
Frame Relay Configuration Examples
IETF Encapsulation on the Interface Example
IETF Encapsulation on a per-DLCI Basis Example
Static Address Mapping Examples
Two Routers in Static Mode Example
Frame Relay Multipoint Subinterface with Dynamic Addressing Example
IPX Routes over Frame Relay Subinterfaces Example
Unnumbered IP over a Point-to-Point Subinterface Example
Transparent Bridging Using Subinterfaces Example
Frame Relay Traffic Shaping Examples
Traffic Shaping with Three Point-to-Point Subinterfaces Example
Traffic Shaping with ForeSight Example
Enhanced Local Management Interface Example
Backward Compatibility Example
Booting from a Network Server over Frame Relay Example
Frame Relay End-to-End Keepalive Examples
End-to-End Keepalive Bidirectional Mode with Default Configuration Example
End-to-End Keepalive Request Mode with Default Configuration Example
End-to-End Keepalive Request Mode with Modified Configuration Example
PPP over Frame Relay DTE Example
PPP over Frame Relay DCE Example
Frame Relay Switching Examples
PVC Switching Configuration Example
Hybrid DTE/DCE PVC Switching Example
Switching over an IP Tunnel Example
FRF.9 Compression Configuration Examples
FRF.9 Compression for Subinterfaces Using the frame-relay map Command Example
FRF.9 Compression for Subinterfaces Example
TCP/IP Header Compression Examples
IP Map with Inherited TCP/IP Header Compression Example
Using an IP Map to Override TCP/IP Header Compression Example
Disabling TCP/IP Header Compression Examples
Disabling Inherited TCP/IP Header Compression Example
Disabling Explicit TCP/IP Header Compression Example
Configuring Frame Relay
This chapter describes the tasks for configuring Frame Relay on a router or access server. For further general information about Frame Relay, see the "Wide-Area Networking Overview" chapter at the beginning of this book. The following new features are included in this chapter:
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Frame Relay end-to-end keepalives
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For a complete description of the Frame Relay commands mentioned in this chapter, refer to the "Frame Relay Commands" chapter in the Cisco IOS Wide-Area Networking Command Reference. To locate documentation of other commands that appear in this chapter, use the command reference master index or search online.
See the following chapters in other Cisco publications for information on the topics indicated below:
Cisco Frame Relay MIB
The Cisco Frame Relay MIB adds extensions to the standard Frame Relay MIB (RFC 1315). It provides additional link-level and VC-level information and statistics that are mostly specific to Cisco Frame Relay implementation. This MIB provides SNMP network management access to most of the information covered by the show frame-relay commands, such as, show frame-relay lmi, show frame-relay pvc, show frame-relay map, and show frame-relay svc.
Frame Relay Hardware Configurations
You can create Frame Relay connections using one of the following hardware configurations:
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The CSU/DSU converts V.35 or RS-449 signals to the properly coded T1 transmission signal for successful reception by the Frame Relay network. Figure 13 illustrates the connections between the different components.
Figure 13 Typical Frame Relay Configuration
The Frame Relay interface actually consists of one physical connection between the network server and the switch that provides the service. This single physical connection provides direct connectivity to each device on a network.
Frame Relay Configuration Task List
You must follow certain required, basic steps to enable Frame Relay for your network. In addition, you can customize Frame Relay for your particular network needs and monitor Frame Relay connections. The following sections outline these tasks:
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The tasks described in the following sections are used to enhance or customize your Frame Relay:
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See the "Frame Relay Configuration Examples" section at the end of this chapter for ideas of how to configure Frame Relay on your network. See the "Frame Relay Commands" chapter in the Cisco IOS Wide-Area Networking Command Reference for information about the Frame Relay commands listed in the following tasks. Use the index or search online for documentation of other commands.
Enabling Frame Relay Encapsulation on an Interface
To enable Frame Relay encapsulation on the interface level, use the following commands beginning in global configuration mode:
Frame Relay supports encapsulation of all supported protocols in conformance with RFC 1490, allowing interoperability between multiple vendors. Use the Internet Engineering Task Force (IETF) form of Frame Relay encapsulation if your router or access server is connected to another vendor's equipment across a Frame Relay network. IETF encapsulation is supported either at the interface level or on a per-VC basis.
Shut down the interface prior to changing encapsulation types. Although shutting down the interface is not required, it ensures that the interface is reset for the new encapsulation.
For an example of enabling Frame Relay encapsulation on an interface, see the "IETF Encapsulation Examples" section later in this chapter.
Configuring Dynamic or Static Address Mapping
Dynamic address mapping uses Frame Relay Inverse ARP to request the next hop protocol address for a specific connection, given its known DLCI. Responses to Inverse ARP requests are entered in an address-to-DLCI mapping table on the router or access server; the table is then used to supply the next hop protocol address or the DLCI for outgoing traffic.
Inverse ARP is enabled by default for all protocols it supports, but can be disabled for specific protocol-DLCI pairs. As a result, you can use dynamic mapping for some protocols and static mapping for other protocols on the same DLCI. You can explicitly disable Inverse ARP for a protocol-DLCI pair if you know that the protocol is not supported on the other end of the connection. See the "Disabling or Reenabling Frame Relay Inverse ARP" section later in this chapter for more information.
See the following sections for further details on configuring dynamic or static address mapping:
Configuring Dynamic Mapping
Inverse ARP is enabled by default for all protocols enabled on the physical interface. Packets are not sent out for protocols that are not enabled on the interface.
Because Inverse ARP is enabled by default, no additional command is required to configure dynamic mapping on an interface.
Configuring Static Mapping
A static map links a specified next hop protocol address to a specified DLCI. Static mapping removes the need for Inverse ARP requests; when you supply a static map, Inverse ARP is automatically disabled for the specified protocol on the specified DLCI.
You must use static mapping if the router at the other end either does not support Inverse ARP at all or does not support Inverse ARP for a specific protocol that you want to use over Frame Relay.
To establish static mapping according to your network needs, use one of the following commands in interface configuration mode:
The supported protocols and the corresponding keywords to enable them are as follows:
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You can greatly simplify the configuration for the Open Shortest Path First (OSPF) protocol by adding the optional broadcast keyword when doing this task. Refer to the frame-relay map command description in the Cisco IOS Wide-Area Networking Command Reference and the examples at the end of this chapter for more information about using the broadcast keyword.
For examples of establishing static address mapping, refer to the section "Static Address Mapping Examples" later in this chapter.
Configuring the LMI
Beginning with Cisco IOS Release 11.2, the software supports Local Management Interface (LMI) autosense, which enables the interface to determine the LMI type supported by the switch. Support for LMI autosense means that you are no longer required to configure the LMI explicitly.
See the following sections for further details on configuring the LMI:
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For information on using Enhanced Local Management Interface with traffic shaping, see the "Configuring Frame Relay Traffic Shaping" section later in this chapter.
For an example of configuring the LMI, see the "Pure Frame Relay DCE Example" section later in this chapter.
Activating LMI Autosense
LMI autosense is active in the following situations:
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See the following sections for additional information concerning activating LMI autosense:
Status Request
When LMI autosense is active, it sends out a full status request, in all three LMI flavors, to the switch. The order is ANSI, ITU, cisco but is done in rapid succession. Unlike previous software capability, we can now listen in on both DLCI 1023 (cisco LMI) and DLCI 0 (ANSI and ITU) simultaneously.
Status Messages
One or more of the status requests will elicit a reply (status message) from the switch. The router will decode the format of the reply and configure itself automatically. If more than one reply is received, the router will configure itself with the type of the last received reply. This is to accommodate intelligent switches that can handle multiple formats simultaneously.
LMI Autosense
If LMI autosense is unsuccessful, an intelligent retry scheme is built in. Every N391 interval (default is 60 seconds, which is 6 keep exchanges at 10 seconds each), LMI autosense will attempt to ascertain the LMI type. For more information about N391, see the frame-relay lmi-n391dte command in the "Frame Relay Commands" chapter of the Cisco IOS Wide-Area Networking Command Reference.
The only visible indication to the user that LMI autosense is underway is when debug frame lmi is turned on. Every N391 interval, the user will now see three rapid status enquiries coming out of the serial interface. One in ANSI, one in ITU and one in cisco LMI-type.
Configuration Options
No configuration options are provided; LMI autosense is transparent to the user. You can turn off LMI autosense by explicitly configuring an LMI type. The LMI type must be written into NVRAM so that next time the router powers up, LMI autosense will be inactive. At the end of autoinstall, a frame-relay lmi-type xxx statement is included within the interface configuration. This configuration is not automatically written to NVRAM; you must explicitly write the configuration to NVRAM by using the copy system:running-config or copy nvram:startup-config commands.
Explicitly Configuring the LMI
Frame Relay software supports the industry-accepted standards for addressing the LMI, including the Cisco specification. If you want to configure the LMI and thus deactivate LMI autosense, perform the tasks in the following sections:
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Setting the LMI Type
If the router or access server is attached to a public data network (PDN), the LMI type must match the type used on the public network. Otherwise, the LMI type can be set to suit the needs of your private Frame Relay network.
You can set one of three types of LMIs on our devices: ANSI T1.617 Annex D, Cisco, and ITU-T Q.933 Annex A. To do so, use the following commands beginning in interface configuration mode:
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frame-relay lmi-type {ansi | cisco | q933a}
Sets the LMI type.
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copy nvram:startup-config destination
Writes the LMI type to NVRAM.
For an example of setting the LMI type, see the "Pure Frame Relay DCE Example" section later in this chapter.
Setting the 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 less than the corresponding interval on the switch. To set the keepalive interval, use the following command in interface configuration mode:
To disable keepalives on networks that do not utilize LMI, use the no keepalive interface configuration command. For an example of how to specify an LMI keepalive interval, see the "Two Routers in Static Mode Example" section later in this chapter.
Setting the LMI Polling and Timer Intervals
You can set various optional counters, intervals, and thresholds to fine-tune the operation of your LMI DTE and DCE devices. Set these attributes by using one or more of the following commands in interface configuration mode:
See the "Frame Relay Commands" chapter in the Cisco IOS Wide-Area Networking Command Reference for polling and timing interval commands.
Configuring Frame Relay SVCs
Access to Frame Relay networks is made through private leased lines at speeds ranging from 56 kbps to 45 Mbps. Frame Relay is a connection-oriented packet-transfer mechanism that establishes VCs between endpoints.
Switched virtual circuits (SVCs) allow access through a Frame Relay network by setting up a path to the destination endpoints only when the need arises and tearing down the path when it is no longer needed.
SVCs can coexist with PVCs in the same sites and routers. For example, routers at remote branch offices might set up PVCs to the central headquarters for frequent communication, but set up SVCs with each other as needed for intermittent communication. As a result, any-to-any communication can be set up without any-to-any PVCs.
On SVCs, quality of service (QoS) elements can be specified on a call-by-call basis to request network resources.
SVC support is offered in the Enterprise image on Cisco platforms that include a serial or HSSI interface.
You must have the following services before Frame Relay SVCs can operate:
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For examples of configuring Frame Relay SVCs, see the "SVC Configuration Examples" section later in this chapter.
Operating SVCs
SVC operation requires that the Data Link layer (Layer 2) be set up, running ITU-T Q.922 Link Access Procedures to Frame mode bearer services (LAPF), prior to signalling for an SVC. Layer 2 sets itself up as soon as SVC support is enabled on the interface, if both the line and the line protocol are up. When the SVCs are configured and demand for a path occurs, the Q.933 signalling sequence is initiated. Once the SVC is set up, data transfer begins.
Q.922 provides a reliable link layer for Q.933 operation. All Q.933 call control information is transmitted over DLCI 0; this DLCI is also used for the management protocols specified in ANSI T1.617 Annex D or Q.933 Annex A.
You must enable SVC operation at the interface level. Once it is enabled at the interface level, it is enabled on any subinterfaces on that interface. One signalling channel, DLCI 0, is set up for the interface, and all SVCs are controlled from the physical interface.
Enabling Frame Relay SVC Service
To enable Frame Relay SVC service and set up SVCs, perform the tasks in the following sections. The subinterface tasks are not required, but offer additional flexibility for SVC configuration and operation. The LAPF tasks are not required and not recommended unless you understand thoroughly the impacts on your network.
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For examples of configuring Frame Relay SVCs, see the "SVC Configuration Examples" section later in this chapter.
Configuring SVCs on a Physical Interface
To enable SVC operation on a Frame Relay interface, use the following commands beginning in global configuration mode:
Map-group details are specified with the map-list command.
Configuring SVCs on a Subinterface
To configure Frame Relay SVCs on a subinterface, complete all the commands in the previous section, except assigning a the map group. After the physical interface is configured, use the following commands beginning in global configuration mode:
Configuring a Map Class
Perform the following tasks to configure a map class:
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To configure a map class, use the following commands beginning in global configuration mode:
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map-class frame-relay map-class-name
Specifies Frame Relay map class name and enters map class configuration mode.
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frame-relay custom-queue-list list-number
Specifies a custom queue list to be used for the map class.
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frame-relay priority-group list-number
Assigns a priority queue to VCs associated with the map class.
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frame-relay adaptive-shaping [becn | foresight]1
Enables the type of BECN feedback to throttle the frame-transmission rate.
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frame-relay cir in bps
Specifies the inbound committed information rate (CIR).
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frame-relay cir out bps
Specifies the outbound committed information rate (CIR).
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frame-relay mincir in bps 2
Sets the minimum acceptable incoming CIR.
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frame-relay mincir out bps 2
Sets the minimum acceptable outgoing CIR.
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frame-relay bc in bits 2
Sets the incoming committed burst size (Bc).
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frame-relay bc out bits 2
Sets the outgoing committed burst size (Bc).
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frame-relay be in bits 2
Sets the incoming excess burst size (Be).
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frame-relay be out bits 2
Sets the outgoing excess burst size (Be).
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frame-relay idle-timer seconds 2
Sets the idle timeout interval.
1 This command replaces the frame-relay becn-response-enable command, which will be removed in a future Cisco IOS release. If you use the frame-relay becn-response-enable command in scripts, you should replace it with the frame-relay adaptive-shaping becn command.
2 The in and out keywords are optional. Configuring the command without the in and out keywords will apply that value to both the incoming and outgoing traffic values for the SVC setup. For example, frame-relay cir 56000 applies 56000 to both incoming and outgoing traffic values for setting up the SVC.
You can define multiple map classes. A map class is associated with a static map, not with the interface or subinterface itself. Because of the flexibility this association allows, you can define different map classes for different destinations.
Configuring a Map Group with E.164 or X.121 Addresses
After you have defined a map group for an interface, you can associate the map group with a specific source and destination address to be used. You can specify E.164 addresses or X.121 addresses for the source and destination. To specify the map group to be associated with a specific interface, use the following command in global configuration mode:
Associating the Map Class with Static Protocol Address Maps
To define the protocol addresses under a map-list command and associate each protocol address with a specified map class, use the class command. Use this command for each protocol address to be associated with a map class. To associate a map class with a protocol address, use the following command in map list configuration mode:
The ietf keyword specifies RFC 1490 encapsulation; the broadcast keyword specifies that broadcasts must be carried. The trigger keyword, which can be configured only if broadcast is also configured, enables a broadcast packet to trigger an SVC. If an SVC already exists that uses this map class, the SVC will carry the broadcast.
Configuring LAPF Parameters
Frame Relay Link Access Procedure for Frame Relay (LAPF) commands are used to tune Layer 2 system parameters to work well with the Frame Relay switch. Normally, you do not need to change the default settings. However, if the Frame Relay network indicates that it does not support the Frame Reject frame (FRMR) at the LAPF Frame Reject procedure, use the following command in interface configuration mode:
no frame-relay lapf frmr
Selects not to send FRMR frames at the LAPF Frame Reject procedure.
By default, the Frame Reject frame is sent at the LAPF Frame Reject procedure.
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If you must change Layer 2 parameters for your network environment and you understand the resulting functional change, use the following commands as needed:
Configuring Frame Relay Traffic Shaping
Traffic shaping applies to both PVCs and SVCs. For information about creating and configuring SVCs, see the "Configuring Frame Relay SVCs" section of this chapter.
To configure Frame Relay traffic shaping, perform the tasks in the following sections:
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The following Frame Relay traffic shaping capabilities were introduced with Cisco IOS Release 11.2:
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For examples of configuring Frame Relay traffic shaping, see the "Frame Relay Traffic Shaping Examples" section later in this chapter.
Defining VCs for Different Types of Traffic
By defining separate VCs for different types of traffic and specifying queueing and an outbound traffic rate for each VC, you can provide guaranteed bandwidth for each type of traffic. By specifying different traffic rates for different VCs over the same line, you can perform virtual time division multiplexing. By throttling outbound traffic from high-speed lines in central offices to lower-speed lines in remote locations, you can ease congestion and data loss in the network; enhanced queueing also prevents congestion-caused data loss.
Enabling Frame Relay Traffic Shaping on the Interface
Enabling Frame Relay traffic shaping on an interface enables both traffic shaping and per-VC queueing on all the interface's PVCs and SVCs. Traffic shaping enables the router to control the circuit's output rate and react to congestion notification information if also configured.
To enable Frame Relay traffic shaping on the specified interface, use the following command in interface configuration mode:
frame-relay traffic-shaping
Enables Frame Relay traffic shaping and per-VC queueing.
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—When traffic shaping is enabled (by using the frame-relay traffic-shaping command), but a map class is not assigned to the VC
—When traffic shaping is enabled (by using the frame-relay traffic-shaping command) and a map class is assigned to the VC, but traffic-shaping parameters have not been defined in the map classTo configure a map class with traffic shaping and per-VC queueing parameters, see the sections "Specifying a Traffic Shaping Map Class for the Interface" and "Defining a Map Class with Queueing and Traffic Shaping Parameters".
Frame Relay ForeSight
ForeSight is the network traffic control software used in some Cisco switches. The Cisco Frame Relay switch can extend ForeSight messages over a User-to-Network Interface (UNI), passing the backward congestion notification for VCs.
ForeSight allows Cisco Frame Relay routers to process and react to ForeSight messages and adjust VC level traffic shaping in a timely manner.
ForeSight must be configured explicitly on both the Cisco router and the Cisco switch. ForeSight is enabled on the Cisco router when Frame Relay traffic shaping is configured. However, the router's response to ForeSight is not applied to any VC until the frame-relay adaptive-shaping foresight command is added to the VCs map-class. When ForeSight is enabled on the switch, the switch will periodically send out a ForeSight message based on the time value configured. The time interval can range from 40 to 5000 milliseconds.
When a Cisco router receives a ForeSight message indicating that certain DLCIs are experiencing congestion, the Cisco router reacts by activating its traffic shaping function to slow down the output rate. The router reacts as it would if it were to detect the congestion by receiving a packet with the backward explicit congestion notification (BECN) bit set.
When ForeSight is enabled, Frame Relay traffic shaping will adapt to ForeSight messages and BECN messages.
For an example of configuring Foresight, see the "Traffic Shaping with ForeSight Example" section later in this chapter.
Frame Relay ForeSight Prerequisites
For Router ForeSight to work, the following conditions must exist on the Cisco router:
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The following additional condition must exist on the Cisco switch:
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Frame Relay Router ForeSight is enabled automatically when you use the frame-relay traffic-shaping command. However, you must issue the map-class frame-relay command and the frame-relay adaptive-shaping foresight command before the router will respond to ForeSight and apply the traffic shaping effect on a specific interface, subinterface, or VC.
Frame Relay Congestion Notification Methods
The difference between the BECN and ForeSight congestion notification methods is that BECN requires a user packet to be sent in the direction of the congested DLCI to convey the signal. The sending of user packets is not predictable and, therefore, not reliable as a notification mechanism. Rather than waiting for user packets to provide the congestion notification, timed ForeSight messages guarantee that the router receives notification before congestion becomes a problem. Traffic can be slowed down in the direction of the congested DLCI.
Enabling Enhanced Local Management Interface
When used in conjunction with traffic shaping, the router can respond to changes in the network dynamically. Enhanced Local Management Interface (ELMI) allows the router to learn QoS parameters from the Cisco switch and use them for traffic shaping, configuration, or management purposes. ELMI also simplifies the process of configuring traffic shaping on the router. ELMI reduces chances of specifying inconsistent or incorrect values when configuring the router.
To configure ELMI, use the following commands beginning in interface configuration mode:
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It is not necessary to configure traffic shaping on the interface to enable ELMI, but you may want to do so in order to know the values being used by the switch. If you want the router to respond to the QoS information received from the switch by adjusting the output rate, you must configure traffic shaping on the interface. To configure traffic shaping, use the frame-relay traffic-shaping command in interface configuration mode
For an example of configuring a Frame Relay interface with QoS autosense enabled, see the section "Enhanced Local Management Interface Example" later in this chapter.
Specifying a Traffic Shaping Map Class for the Interface
If you specify a Frame Relay map class for a main interface, all the VCs on its subinterfaces inherit all the traffic shaping parameters defined for the class.
To specify a map class for the specified interface, use the following command in beginning interface configuration mode:
frame-relay class map-class-name
Specifies a Frame Relay map class for the interface.
You can override the default for a specific DLCI on a specific subinterface by using the class VC configuration command to assign the DLCI explicitly to a different class. See the "Configuring Frame Relay Subinterfaces" section for information about setting up subinterfaces.
For an example of assigning some subinterface DLCIs to the default class and assigning others explicitly to a different class, see the "Frame Relay Traffic Shaping Examples" section later in this chapter.
Defining a Map Class with Queueing and Traffic Shaping Parameters
When defining a map class for Frame Relay, you can specify the average and peak rates (in bits per second) allowed on VCs associated with the map class. You can also specify either a custom queue list or a priority queue group to use on VCs associated with the map class.
To define a map class, use the following commands beginning in global configuration mode:
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map-class frame-relay map-class-name
Specifies a map class to define.
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frame-relay traffic-rate average [peak]
Defines the traffic rate for the map class.
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frame-relay custom-queue-list list-number
Specifies a custom queue list.
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frame-relay priority-group list-number
Specifies a priority queue list.
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frame-relay adaptive-shaping {becn | foresight}1
Selects BECN or ForeSight as congestion backward-notification mechanism to which traffic shaping adapts.
1 This command replaces the frame-relay becn-response-enable command, which will be removed in a future Cisco IOS release. If you use the frame-relay becn-response-enable command in scripts, you should replace it with the frame-relay adaptive-shaping software command.
For an example of map class backward compatibility and interoperability, see the "Backward Compatibility Example" section later in this section.
Defining Access Lists
You can specify access lists and associate them with the custom queue list defined for any map class. The list number specified in the access list and the custom queue list tie them together. See the appropriate protocol chapters for information about defining access lists for the protocols you want to transmit on the Frame Relay network.
Defining Priority Queue Lists for the Map Class
You can define a priority list for a protocol and you can also define a default priority list. The number used for a specific priority list ties the list to the Frame Relay priority group defined for a specified map class.
For example, if you enter the frame relay priority-group 2 command for the map class fast_vcs and then you enter the priority-list 2 protocol decnet high command, that priority list is used for the fast_vcs map class. The average and peak traffic rates defined for the fast_vcs map class are used for DECnet traffic.
Defining Custom Queue Lists for the Map Class
You can define a queue list for a protocol and a default queue list. You can also specify the maximum number of bytes to be transmitted in any cycle. The number used for a specific queue list ties the list to the Frame Relay custom queue list defined for a specified map class.
For example, if you enter the frame relay custom-queue-list 1 command for the map class slow_vcs and then you enter the queue-list 1 protocol ip list 100 command, that queue list is used for the slow_vcs map class; access-list 100 definition is also used for that map class and queue. The average and peak traffic rates defined for the slow_vcs map class are used for IP traffic that meets the access list 100 criteria.
Customizing Frame Relay for Your Network
Perform the tasks in the following sections to customize Frame Relay:
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Configuring Frame Relay End-to-End Keepalives
Frame Relay end-to-end keepalives enable monitoring of PVC status for network monitoring or backup applications and are configurable on a per-PVC basis with configurable timers. The Frame Relay switch within the local PVC segment deduces the status of the remote PVC segment through a Network-to-Network interface (NNI) and reports the status to the local router. If LMI support within the switch is not end-to-end, end-to-end keepalives are the only source of information about the remote router. End-to-end keepalives verify that data is getting through to a remote device via end-to-end communication.
Each PVC connecting two end devices needs two separate keepalive systems, because the upstream path may not be the same as the downstream path. One system sends out requests and handles responses to those requests—the send side—while the other system handles and replies to requests from the device at the other end of the PVC—the receive side. The send side on one device communicates with the receive side on the other device, and vice versa.
The send side sends out a keepalive request and waits for a reply to its request. If a reply is received before the timer expires, a send side, Frame Relay end-to-end keepalives is recorded. If no reply is received before the timer expires, an error event is recorded. A number of the most recently recorded events are examined. If enough error events are accumulated, the keepalive status of the VC is changed from up to down, or if enough consecutive successful replies are received, the keepalive status of the VC will be changed from down to up. The number of events that will be examined is called the event window.
The receive side is similar to the send side. The receive side waits for requests and sends out replies to those requests. If a request is received before the timer expires, a success event is recorded. If a request is not received, an error event is recorded. If enough error events occur in the event window, the PVC state will be changed from up to down. If enough consecutive success events occur, the state will be changed from down to up.
End-to-end keepalives can be configured in one of four modes: bidirectional, request, reply, or passive-reply.
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Because end-to-end keepalives allow traffic flow in both directions, they can be used to carry control and configuration information from end-to-end. Consistency of information between end hosts is critical in applications such as those relating to prioritized traffic and Voice Over Frame Relay. While SVCs can convey such information within end-to-end signaling messages, PVCs will benefit from a bidirectional communication mechanism.
End-to-end keepalives are derived from the Frame Relay LMI protocol and work between peer Cisco communications devices. The key difference is that rather than run over the signaling channel, as is the case with LMI, end-to-end keepalives run over individual data channels.
Encapsulation of keepalive packets is proprietary; therefore, the feature is available only on Cisco devices running a software release that supports the Frame Relay End-to-End Keepalive feature.
You must configure both ends of a VC to send keepalives. If one end is configured as bidirectional, the other end must also be configured as bidirectional. If one end is configured as request, the other end must be configured as reply or passive-reply. If one end is configured as reply or passive-reply, the other end must be configured as request
To configure Frame Relay end-to-end keepalives, use the following commands beginning in global configuration mode:
The four modes determine the type of keepalive traffic each device sends and responds to:
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For an example of configuring bidirectional or request modes with default values, see the sections "End-to-End Keepalive Bidirectional Mode with Default Configuration Example" or "End-to-End Keepalive Request Mode with Default Configuration Example," and for an example of configuring request mode with modified values, see the section "End-to-End Keepalive Request Mode with Modified Configuration Example" later in this chapter.
You can modify the end-to-end keepalives default parameter values by using any of the following map-class configuration commands:
Verifying Frame Relay End-to-End Keepalives
To monitor the status of Frame Relay end-to-end keepalives, use the following command in EXEC configuration mode:
Router# show frame-relay end-to-end keepalive interface
Shows the status of Frame Relay end-to-end keepalives.
Configuring PPP over Frame Relay
Point-to-point protocol (PPP) over Frame Relay allows a router to establish end-to-end PPP sessions over Frame Relay. This is done over a PVC, which is the only circuit currently supported. The PPP session does not occur unless the associated Frame Relay PVC is in an "active" state. The Frame Relay PVC can coexist with other circuits using different Frame Relay encapsulation methods, such as RFC 1490 and the Cisco proprietary method, over the same Frame Relay link. There can be multiple PPP over Frame Relay circuits on one Frame Relay link.
One PPP connection resides on one virtual access interface. This is internally created from a virtual template interface, which contains all necessary PPP and network protocol information and is shared by multiple virtual access interfaces. The virtual access interface is coexistent with the creation of the Frame Relay circuit when the corresponding DLCI is configured. Hardware compression and fancy queueing algorithms, such as weighted fair queueing, custom queueing, and priority queueing, are not applied to virtual access interfaces.
PPP over Frame Relay is only supported on IP. IP datagrams are transported over the PPP link using RFC 1973 compliant Frame Relay framing. The frame format is shown in Figure 14.
Figure 14 PPP over Frame Relay Frame Format
Table 6 lists the Frame Relay frame format components illustrated in Figure 14.
Figure 15 shows remote users running PPP to access their Frame Relay corporate networks.
Figure 15 PPP over Frame Relay Scenario
