Table Of Contents

Frame Relay Queueing and Fragmentation at the Interface

Feature Overview

How Frame Relay Queueing and Fragmentation at the Interface Works

Benefits

Restrictions

Related Documents

Supported Platforms

Supported Standards, MIBs, and RFCs

Prerequisites

Configuration Tasks

Configuring Class Policy for the Priority Queue

Configuring Class Policy for the Bandwidth Queues

Configuring the Shaping Policy Using the Class-Default Class

Configuring Queueing and Fragmentation on the Frame Relay Interface

Verifying Frame Relay Queueing and Fragmentation at the Interface

Monitoring and Maintaining Frame Relay Queueing and Fragmentation at the Interface

Configuration Examples

Frame Relay Queueing, Shaping, and Fragmentation at the Interface Example

Frame Relay Queueing and Fragmentation at the Interface Example

Command Reference

Frame Relay Queueing and Fragmentation at the Interface

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Feature History

Release	Modification
12.2(11)S	This feature was introduced.
12.2(13)T	This feature was integrated into Cisco IOS Release 12.2(13)T
Cisco IOS XE Release 2.1	This feature was introduced on Cisco ASR 1000 series routers.

This document describes the Frame Relay Queueing and Fragmentation at the Interface feature. This document includes the following sections:

•Feature Overview

•Supported Platforms

•Supported Standards, MIBs, and RFCs

•Prerequisites

•Configuration Tasks

•Monitoring and Maintaining Frame Relay Queueing and Fragmentation at the Interface

•Configuration Examples

•Command Reference

Feature Overview

The Frame Relay Queueing and Fragmentation at the Interface feature introduces support for low-latency queueing (LLQ) and FRF.12 end-to-end fragmentation on a Frame Relay interface. This new feature simplifies the configuration of low-latency, low-jitter quality of service (QoS) by enabling the queueing policy and fragmentation configured on the main interface to apply to all permanent virtual circuits (PVCs) and subinterfaces under that interface. Before the introduction of this feature, queueing and fragmentation had to be configured on each individual PVC. Subrate shaping can also be configured on the interface.

How Frame Relay Queueing and Fragmentation at the Interface Works

When FRF.12 end-to-end fragmentation is enabled on an interface, all PVCs on the main interface and its subinterfaces will have fragmentation enabled with the same configured fragment size. To maintain low latency and low jitter for high-priority traffic, the configured fragment size must be greater than the largest high-priority frames. This configuration will prevent high-priority traffic from being fragmented and queued behind lower-priority fragmented frames. If the size of a high-priority frame is larger than the configured fragment size, the high-priority frame will be fragmented. Local Management Interface (LMI) traffic will not be fragmented and is guaranteed its required bandwidth.

When a low-latency queueing policy map is applied to the interface, traffic through the interface is identified using class maps and is directed to the appropriate queue. Time-sensitive traffic such as voice should be classified as high priority and will be queued on the priority queue. Traffic that does not fall into one of the defined classes will be queued on the class-default queue. Frames from the priority queue and class queues are subject to fragmentation and interleaving. As long as the configured fragment size is larger than the high-priority frames, the priority queue traffic will not be fragmented and will be interleaved with fragmented frames from other class queues. This approach provides the highest QoS transmission for priority queue traffic. Figure 1 illustrates the interface queueing and fragmentation process.

Figure 1 Frame Relay Queueing and Fragmentation at the Interface

Subrate shaping can also be applied to the interface, but interleaving of high-priority frames will not work when shaping is configured. If shaping is not configured, each PVC will be allowed to send bursts of traffic up to the physical line rate.

When shaping is configured and traffic exceeds the rate at which the shaper can send frames, the traffic is queued at the shaping layer using fair queueing. After a frame passes through the shaper, the frame is queued at the interface using whatever queueing method is configured. If shaping is not configured, then queueing occurs only at the interface.

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Note For interleaving to work, both fragmentation and the low-latency queueing policy must be configured with shaping disabled.

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The Frame Relay Queueing and Fragmentation at the Interface feature supports the following functionality:

•Voice over Frame Relay

•Weighted Random Early Detection

•Frame Relay payload compression

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Note When payload compression and Frame Relay fragmentation are used at the same time, payload compression is always performed before fragmentation.

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•IP header compression

Benefits

Simple Configuration

The Frame Relay Queueing and Fragmentation at the Interface feature allows fragmentation, low-latency queueing, and subrate shaping to be configured on a Frame Relay interface queue. The fragmentation and queueing and shaping policy will apply to all PVCs and subinterfaces under the main interface, eliminating the need to configure QoS on each PVC individually.

Flexible Bandwidth

This feature allows PVCs to preserve the logical separation of traffic from different services while reducing bandwidth partitioning between PVCs. Each PVC can send bursts of traffic up to the interface shaping rate or, if shaping is not configured, the physical interface line rate.

Restrictions

•Interface fragmentation and Frame Relay traffic shaping cannot be configured at the same time.

•Interface fragmentation and class-based fragmentation cannot be configured at the same time.

•Frame Relay switched virtual circuits (SVCs) are not supported.

•Hierarchical shaping and multiple shapers are not supported.

Related Documents

For more information about shaping and low-latency queueing for Frame Relay, refer to the following documents:

•Cisco IOS Quality of Service Solutions Configuration Guide, Release 12.2

•Cisco IOS Quality of Service Solutions Command Reference, Release 12.2

•Low Latency Queueing for Frame Relay, Cisco IOS Release 12.1(2)T feature module

For more information about Frame Relay fragmentation, refer to the following documents:

•Cisco IOS Wide-Area Networking Configuration Guide, Release 12.2

•Cisco IOS Wide-Area Networking Command Reference, Release 12.2

Supported Platforms

•Cisco 800 series

•Cisco 1400 series

•Cisco 1600 series

•Cisco 2500 series

•Cisco 2600 series

•Cisco 3600 series

•Cisco 7100 series

•Cisco 7200 series

•Cisco 7500 series

•Cisco AS5300 series

•Cisco AS5400

•Cisco AS5800

•Cisco MC3810

•Cisco ubr7200 series

Determining Platform Support Through Cisco Feature Navigator

Cisco IOS software is packaged in feature sets that support specific platforms. To get updated information regarding platform support for this feature, access Cisco Feature Navigator. Cisco Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature.

Cisco Feature Navigator is a web-based tool that enables you to determine which Cisco IOS software images support a specific set of features and which features are supported in a specific Cisco IOS image. You can search by feature or release. Under the release section, you can compare releases side by side to display both the features unique to each software release and the features in common.

To access Cisco Feature Navigator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions at http://www.cisco.com/register.

Cisco Feature Navigator is updated regularly when major Cisco IOS software releases and technology releases occur. For the most current information, go to the Cisco Feature Navigator home page at the following URL:

http://www.cisco.com/go/fn

Availability of Cisco IOS Software Images

Platform support for particular Cisco IOS software releases is dependent on the availability of the software images for those platforms. Software images for some platforms may be deferred, delayed, or changed without prior notice. For updated information about platform support and availability of software images for each Cisco IOS software release, refer to the online release notes or, if supported, Cisco Feature Navigator.

Supported Standards, MIBs, and RFCs

Standards

FRF.12, Frame Relay Fragmentation Implementation Agreement, December 1997

MIBs

No new or modified MIBs are supported by this feature.

To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL:

http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml

RFCs

No new or modified RFCs are supported by this feature.

Prerequisites

The tasks in this document assume that you know how to configure low-latency queueing and shaping service policies.

The following prerequisites are specific to the Cisco 7500 series:

•The Frame Relay Queueing and Fragmentation at the Interface feature is supported on VIP-based interfaces with VIP2-50 or higher.

•Distributed Cisco Express Forwarding (dCEF) must be enabled both globally and on the Frame Relay interface.

Configuration Tasks

See the following sections for configuration tasks for the Frame Relay Queueing and Fragmentation at the Interface feature. Each task in the list is identified as either required or optional.

•Configuring Class Policy for the Priority Queue (required)

•Configuring Class Policy for the Bandwidth Queues (optional)

•Configuring the Shaping Policy Using the Class-Default Class (optional)

•Configuring Queueing and Fragmentation on the Frame Relay Interface (required)

•Verifying Frame Relay Queueing and Fragmentation at the Interface (optional)

Configuring Class Policy for the Priority Queue

To configure a policy map for the priority class, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# policy-map policy-map	Specifies the name of the policy map to be created or modified. •Use this command to define the queueing policy for the priority queue.
Step 2	Router(config-pmap)# class class-name	Specifies the name of a class to be created and included in the service policy. •The class name that you specify in the policy map defines the characteristics for that class and its match criteria as configured using the class-map command.
Step 3	Router(config-pmap-c)# priority bandwidth-kbps	Creates a strict priority class and specifies the amount of bandwidth, in kbps, to be assigned to the class.

Configuring Class Policy for the Bandwidth Queues

To configure a policy map and create class policies that make up the service policy, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# policy-map policy-map	Specifies the name of the policy map to be created or modified. •The bandwidth queues and the priority queue use the same policy map.
Step 2	Router(config-pmap)# class class-name	Specifies the name of a class to be created and included in the service policy. •The class name that you specify in the policy map defines the characteristics for that class and its match criteria as configured using the class-map command.
Step 3	Router(config-pmap-c)# bandwidth bandwidth-kbps	Specifies the amount of bandwidth to be assigned to the class, in kbps, or as a percentage of the available bandwidth. Bandwidth must be specified in kbps or as a percentage consistently across classes. (Bandwidth of the priority queue must be specified in kbps.) •The sum of all bandwidth allocation on an interface cannot exceed 75 percent of the total available interface bandwidth. However, if you need to configure more than 75 percent of the interface bandwidth to classes, you can override the 75 percent maximum by using the max-reserved-bandwidth command.

Configuring the Shaping Policy Using the Class-Default Class

In general, the class-default class is used to classify traffic that does not fall into one of the defined classes. Even though the class-default class is predefined when you create the policy map, you still have to configure it. If a default class is not configured, traffic that does not match any of the configured classes is given best-effort treatment, which means that the network will deliver the traffic if it can, without any assurance of reliability, delay prevention, or throughput.

If you configure shaping in addition to queueing on the interface, use the class-default class to configure the shaping policy. The shaping policy will serve as the parent in a hierarchical traffic policy. The queueing policy will serve as the child policy. The class-default class is used for the shaping policy so that all traffic for the entire interface is shaped and a bandwidth-limited stream can be created.

To configure the shaping policy in the class-default class, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# policy-map policy-map	Specifies the name of the policy map to be created or modified. •Use this command to define the shaping policy.
Step 2	Router(config-pmap)# class class-default	Specifies the default class so that you can configure or modify its policy.
Step 3	Router(config-pmap-c)# shape [average | peak] mean-rate [[burst-size] [excess-burst-size]]	(Optional) Shapes traffic to the indicated bit rate according to the algorithm specified.
Step 4	Router(config-pmap-c)# service-policy policy-map-name	Specifies the name of a policy map to be used as a matching criterion (for nesting traffic policies [hierarchical traffic policies] within one another). •Use this command to attach the policy map for the priority queue (the child policy) to the shaping policy (the parent policy).

Configuring Queueing and Fragmentation on the Frame Relay Interface

To configure low-latency queueing and FRF.12 end-to-end fragmentation on a Frame Relay interface, use the following commands beginning in global configuration mode:

	Command	Purpose
Step 1	Router(config)# interface type number	Configures an interface type and enters interface configuration mode.
Step 2	Router(config-if)# encapsulation frame-relay	Enables Frame Relay encapsulation.
Step 3	Router(config-if)# service-policy output policy-map-name	Attaches a policy map to an output interface, to be used as the service policy for that interface. •If shaping is being used, use this command to attach the shaping policy (which includes the nested queueing policy) to the interface. •Interleaving of high-priority frames will not work if shaping is configured on the interface. •If shaping is not being used, use this command to attach the queueing policy to the interface.
Step 4	Router(config-if)# frame-relay fragment fragment-size end-to-end	Enables fragmentation of Frame Relay frames. •To maintain low latency and low jitter for priority queue traffic, configure the fragment size to be greater than the largest high-priority frame that would be expected.

Verifying Frame Relay Queueing and Fragmentation at the Interface

To verify the configuration and performance of Frame Relay queueing and fragmentation at the interface, perform the following steps:

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Step 1 Enter the show running-config command to verify the configuration.

Router# show running-config

Building configuration...

.

.

.

class-map match-all voice

  match ip precedence 5

!       

!policy-map llq

  class voice

    priority 64

policy-map shaper

  class class-default

   shape peak 96000

   service-policy llq

!

!interface Serial1/1

 ip address 16.0.0.1 255.255.255.0

 encapsulation frame-relay

 service-policy output shaper

 frame-relay fragment 80 end-to-end

!

Step 2 Enter the show policy-map interface command to display low-latency queueing information, packet counters, and statistics for the policy map applied to the interface. Compare the values in the "packets" and the "pkts matched" counters; under normal circumstances, the "packets" counter is much larger than the "pkts matched" counter. If the values of the two counters are nearly equal, then the interface is receiving a large number of process-switched packets or is heavily congested.

The following sample output for the show policy-map interface command is based on the configuration in Step 1:

Router# show policy-map interface serial 1/1

 Serial1/1 

  Service-policy output:shaper

    Class-map:class-default (match-any)

      12617 packets, 1321846 bytes

      5 minute offered rate 33000 bps, drop rate 0 bps

      Match:any 

      Traffic Shaping

           Target/Average   Byte   Sustain   Excess    Interval  Increment

             Rate           Limit  bits/int  bits/int  (ms)      (bytes)  

           192000/96000     1992   7968      7968      83        1992     

        Adapt  Queue     Packets   Bytes     Packets   Bytes     Shaping

        Active Depth                         Delayed   Delayed   Active

        -      0         12586     1321540   0         0         no

      Service-policy :llq

        Class-map:voice (match-all)

          3146 packets, 283140 bytes

          5 minute offered rate 7000 bps, drop rate 0 bps

          Match:ip precedence 1 

          Weighted Fair Queueing

            Strict Priority

            Output Queue:Conversation 24 

            Bandwidth 64 (kbps) Burst 1600 (Bytes)

            (pkts matched/bytes matched) 0/0

            (total drops/bytes drops) 0/0

        Class-map:class-default (match-any)

          9471 packets, 1038706 bytes

          5 minute offered rate 26000 bps

          Match:any 

Step 3 Enter the show interfaces serial command to display information about the queueing strategy, priority queue interleaving, and type of fragmentation configured on the interface. You can determine whether the interface has reached a congestion condition and packets have been queued by looking at the "Conversations" fields. A nonzero value for "max active" counter shows whether any queues have been active. If the "active" counter is a nonzero value, you can use the show queue command to view the contents of the queues.

The following sample output for the show interfaces serial command is based on the configuration in Step 1:

Router# show interfaces serial 1/1

Serial1/1 is up, line protocol is up 

  Hardware is M4T

  Internet address is 16.0.0.1/24

  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, 

     reliability 255/255, txload 5/255, rxload 1/255

  Encapsulation FRAME-RELAY, crc 16, loopback not set

  Keepalive set (10 sec)

  Restart-Delay is 0 secs

  LMI enq sent  40, LMI stat recvd 40, LMI upd recvd 0, DTE LMI up

  LMI enq recvd 0, LMI stat sent  0, LMI upd sent  0

  LMI DLCI 1023  LMI type is CISCO  frame relay DTE

  Fragmentation type:end-to-end, size 80, PQ interleaves 0

  Broadcast queue 0/64, broadcasts sent/dropped 0/0, interface broadcasts 0

  Last input 00:00:03, output 00:00:00, output hang never

  Last clearing of "show interface" counters 00:06:34

  Input queue:0/75/0/0 (size/max/drops/flushes); Total output drops:0

  Queueing strategy:weighted fair

  Output queue:0/1000/64/0 (size/max total/threshold/drops) 

     Conversations  0/1/256 (active/max active/max total)

     Reserved Conversations 0/0 (allocated/max allocated)

     Available Bandwidth 1158 kilobits/sec

  5 minute input rate 0 bits/sec, 0 packets/sec

  5 minute output rate 33000 bits/sec, 40 packets/sec

     40 packets input, 576 bytes, 0 no buffer

     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

     15929 packets output, 1668870 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     0 output buffer failures, 0 output buffers swapped out

     0 carrier transitions     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

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Monitoring and Maintaining Frame Relay Queueing and Fragmentation at the Interface

To monitor and maintain Frame Relay queueing and fragmentation at the interface, use the following commands in privileged EXEC mode:

Command	Purpose
Router# debug frame-relay fragment [event | interface type number dlci]	Displays information related to Frame Relay fragmentation on a PVC.
Router# show frame-relay fragment [interface type number [dlci]]	Displays information about Frame Relay fragmentation.
Router# show interfaces serial number	Displays information about a serial interface.
Router# show queue interface-type interface-number	Displays the contents of packets inside a queue for a particular interface.
Router# show policy-map interface number [input | output]	Displays the packet statistics of all classes that are configured for all service policies on the specified interface.

Configuration Examples

This section provides the following configuration examples:

•Frame Relay Queueing, Shaping, and Fragmentation at the Interface Example

•Frame Relay Queueing and Fragmentation at the Interface Example

Frame Relay Queueing, Shaping, and Fragmentation at the Interface Example

The following example shows the configuration of a hierarchical policy for low-latency queueing, FRF.12 fragmentation, and shaping on serial interface 3/2. Note that traffic from the priority queue will not be interleaved with fragments from the class-default queue because shaping is configured.

class-map voice

 match access-group 101

policy-map llq

 class voice

  priority 64

policy-map shaper

 class class-default 

  shape average 96000

  service-policy llq

interface serial 3/2

 ip address 10.0.0.1 255.0.0.0

 encapsulation frame-relay

 bandwidth 128

 clock rate 128000

 service-policy output shaper

 frame-relay fragment 80 end-to-end

 access-list 101 match ip any host 10.0.0.2

Frame Relay Queueing and Fragmentation at the Interface Example

The following example shows the configuration of low-latency queueing and FRF.12 fragmentation on serial interface 3/2. Because shaping is not being used, a hierarchical traffic policy is not needed and traffic from the priority queue will be interleaved with fragments from the other queues. Without shaping, the output rate of the interface is equal to the line rate or configured clock rate. In this example, the clock rate is 128,000 bps.

class-map voice

 match access-group 101

policy-map llq

 class voice

  priority 64

 class video

  bandwidth 32

interface serial 3/2

 ip address 10.0.0.1 255.0.0.0

 encapsulation frame-relay

 bandwidth 128

 clock rate 128000

 service-policy output llq

 frame-relay fragment 80 end-to-end

 access-list 101 match ip any host 10.0.0.2

Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS Wide-Area Networking Command Reference at http://www.cisco.com/en/US/docs/ios/wan/command/reference/wan_book.html. For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or to the Cisco IOS Master Commands List.

•frame-relay fragment end-to-end

•show interfaces serial

Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.

© 2007 Cisco Systems, Inc. All rights reserved.