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Table Of Contents
Related Features and Technologies
Supported Standards, MIBs, and RFCs
Configuring MLP LFI on a Bundle
Configuring MCMP on a Member Link
Configuring MCMP on a Dialer Example
MCMP and MLP Interleaving and Queueing for Real-Time Traffic Examples
Multiclass Multilink PPP
Feature History
This document describes the Multiclass Multilink PPP feature in Cisco IOS Release 12.2(13)T. It includes the following sections:
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Supported Standards, MIBs, and RFCs
Feature Overview
Previous implementations of Cisco IOS Multilink PPP (MLP) include support for Link Fragmentation Interleaving (LFI). This feature allows the delivery of delay-sensitive packets, such as the packets of a Voice call, to be expedited by omitting the PPP Multilink Protocol header and sending the packets as raw PPP packets in between the fragments of larger data packets. This feature works well on bundles consisting of a single link. However, when the bundle contains multiple links there is no way to keep the interleaved packets in sequence with respect to each other.
The Multiclass Multilink PPP (MCMP) feature in Cisco IOS Release 12.2(13)T addresses the limitations of MLP LFI on bundles containing multiple links by introducing multiple data classes. Normal data traffic and delay-sensitive data traffic are divided into Class 0 and Class 1, respectively. Class 0 data traffic is subject to fragmentation just as regular multilink packets are. Class 1 data traffic can be interleaved but never fragmented. The next transmit sequence number, expected sequence number, unassigned fragment list, working packet, lost fragment timer, fast-switching mode, and all statistics are managed per class, rather than for the bundle as a whole.
Benefits
The Multiclass Multilink PPP feature in Cisco IOS Release 12.2(13)T allows rapid delivery of real-time data over a bundle containing multiple links without loss of sequencing.
Restrictions
The ppp multilink multiclass command must be configured on each link that will be joining the bundle. Failure to configure this command could result in the peer refusing to allow mismatched links to join the bundle. The first link to join the bundle will determine whether MCMP is in effect for the bundle. Each subsequent link must negotiate the same MCMP parameters in order to join the bundle.
Because real-time traffic is encapsulated with multilink headers, the receiver will be required to buffer the packets when they arrive out of sequence. Therefore, the differential delay between the links must be small relative to the tolerable delay for such traffic. Otherwise, packets may be subject to additional delay while the receiver awaits the arrival of earlier sequence numbers sent over other links in the bundle.
The maximum number of links supported for an MCMP bundle is 64.
The Prefix Elision option specified in RFC 2686 is not supported.
Related Features and Technologies
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Related Documents
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Supported Platforms
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Determining Platform Support Through Cisco Feature Navigator
Cisco IOS software is packaged in feature sets that are supported on 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 quickly 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 found at this URL:
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:
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
None
MIBs
None
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
http://tools.cisco.com/ITDIT/MIBS/servlet/index
If Cisco MIB Locator does not support the MIB information that you need, you can also obtain a list of supported MIBs and download MIBs from the Cisco MIBs page at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
To access Cisco MIB Locator, 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 found at this URL:
RFCs
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Prerequisites
The dialer interface, BRI interface, PRI interface, multilink interface, or virtual template must be configured, and PPP encapsulation must be enabled. For information on completing these tasks, refer to the Cisco IOS Dial Technologies Configuration Guide, Release 12.2.
MLP LFI must be configured on the bundle. See the section "Configuring MLP LFI on a Bundle" in this document.
Configuration Tasks
See the following sections for configuration tasks for the Multiclass Multilink PPP feature. Each task in the list is identified as either required or optional.
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Configuring MLP LFI on a Bundle
To configure MLP LFI on a dialer, multilink, or virtual template, use the following commands beginning in interface configuration mode:
Step 1
Router(config-if)# ppp multilink
Enables MLP.
Step 2
Router(config-if)# ppp multilink interleave
Enables interleaving of packets among the fragments of larger packets on an MLP bundle.
Step 3
Router(config-if)# ppp multilink fragment delay milliseconds
Specifies a maximum size, in units of time, for packet fragments on an MLP bundle.
Step 4
Router(config-if)# ip rtp reserve lowest-udp-port range-of-ports [maximum-bandwidth]
Reserves a special queue for real-time packet flows to specified destination User Datagram Protocol (UDP) ports, allowing real-time traffic to have higher priority than other flows.
Step 5
Router(config-if)# exit
Exits interface configuration mode.
Step 6
Router(config)# multilink virtual-template number
For virtual templates only, applies the virtual template to the multilink bundle.1
1 This step is not used for dialer interfaces.
Configuring MCMP on a Member Link
To configure MCMP on a configured and operational member link, use the following commands in interface configuration mode:
Step 7
Router(config-if)# ppp multilink
Enables MLP.
Step 8
Router(config-if)# ppp multilink multiclass
Enables MCMP on an interface.
Verifying MCMP
To verify that the Multiclass Multilink PPP feature is configured correctly, enter the show ppp multilink EXEC command. The following output includes class-specific information for the PPP Multilink bundles:
Router# show ppp multilinkVirtual-Access3, bundle name is bundle1Bundle up for 01:59:35, 1/255 load, 2 receive classes, 2 transmit classesReceive buffer limit 12192 bytes per class, frag timeout 1524 msDialer interface is Dialer1!Receive Class 0:0/0 fragments/bytes in reassembly list0 lost fragments, 0 reordered0/0 discarded fragments/bytes, 0 lost received0x0 received sequence!Receive Class 1:0/0 fragments/bytes in reassembly list0 lost fragments, 0 reordered0/0 discarded fragments/bytes, 0 lost received0x0 received sequence!Transmit Class 0:0x8 sent sequence!Transmit Class 1:0x0 sent sequence!Member links: 1 (max not set, min not set)BR2/0:1, since 01:59:35, 80 weight, 72 frag sizeConfiguration Examples
This section provides the following configuration example:
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Configuring MCMP on a Dialer Example
The following partial example configures a dialer for MCMP; it does not show the configuration of the physical interfaces:
interface Dialer0ip address 10.0.0.2 255.0.0.0encapsulation pppdialer in-banddialer idle-timeout 500dialer map ip 10.0.0.1 name remote broadcast 81012345678901dialer load-threshold 30 eitherdialer-group 1ppp authentication chapppp multilinkppp multilink multiclassMCMP and MLP Interleaving and Queueing for Real-Time Traffic Examples
The following example enables MLP interleaving and MCMP on a dialer interface that controls a rotary group of BRI interfaces. This configuration permits IP packets to trigger calls.
interface BRI 0description connected into a rotary groupencapsulation pppdialer rotary-group 1!interface BRI 1no ip addressencapsulation pppdialer rotary-group 1!interface BRI 2encapsulation pppdialer rotary-group 1!interface BRI 3no ip addressencapsulation pppdialer rotary-group 1!interface BRI 4encapsulation pppdialer rotary-group 1!interface Dialer 0description Dialer group controlling the BRIsip address 10.1.1.1 255.255.255.0encapsulation pppdialer map ip 10.1.1.2 name remote 14802616900dialer-group 1ppp authentication chap! Enables Multilink Multiclass PPP interleaving on the dialer interface and reserves! a special queue.ppp multilinkppp multilink multiclassppp multilink interleaveip rtp reserve 32768 20 1000! Keeps fragments of large packets small enough to ensure delay of 20 ms or less.ppp multilink fragment delay 20dialer-list 1 protocol ip permitThe following example defines a virtual interface template that enables MLP interleaving and a maximum real-time traffic delay of 20 milliseconds. The bundle interface will be a virtual access interface cloned from the virtual template. MCMP is then configured on a member link, Serial0.
interface virtual-template 1ip unnumbered ethernet 0ppp multilinkppp multilink interleaveppp multilink fragment delay 20ip rtp interleave 32768 20 1000!multilink virtual-template 1!interface Serial0encapsulation pppppp authentication chapppp multilinkppp multilink multiclassThe following example configures MLP interleaving and a maximum real-time traffic delay of 20 milliseconds on a multilink interface. MCMP is then configured on a member link, Serial1, and the member link is restricted to joining only the designated multilink group interface.
interface Multilink1ip address 10.2.3.4 255.255.255.0ppp multilinkppp multilink interleaveppp multilink fragment delay 20!interface Serial1encapsulation pppppp authentication chapppp multilinkppp multilink multiclassppp multilink group 1Command Reference
This section documents new and modified commands. All other commands used with this feature are documented in the Cisco IOS Release 12.2 command reference publications.
ppp multilink multiclass
To enable Multiclass Multilink PPP (MCMP) on an interface, use the ppp multilink multiclass command in interface configuration mode. To disable MCMP, use the no form of this command.
ppp multilink multiclass
no ppp multilink multiclass
Syntax Description
This command has no arguments or keywords.
Defaults
MCMP is disabled.
Command Modes
Interface configuration
Command History
Usage Guidelines
This command applies only to interfaces that use PPP encapsulation.
MCMP and PPP reliable links do not work together.
When the ppp multilink multiclass command is used, the first channel will negotiate the appropriate Network Control Protocol (NCP) layers (such as the IP Control Protocol and IPX Control Protocol), but subsequent links will negotiate only the link control protocol and MCMP. NCP layers do not get negotiated. The dialer load-threshold command enables a rotary group to bring up additional links and to add them to a multilink bundle.
The ppp multilink multiclass command must be configured on each link that will be joining the bundle. Failure to configure this command could result in the peer refusing to allow mismatched links to join the bundle. The first link to join the bundle will determine whether MCMP is in effect for the bundle. Each subsequent link must negotiate the same MCMP parameters in order to join the bundle.
Examples
The following partial example configures a dialer for MCMP; it does not show the configuration of the physical interfaces:
interface Dialer0ip address 10.0.0.2 255.0.0.0encapsulation pppdialer in-banddialer idle-timeout 500dialer map ip 10.0.0.1 name router broadcast 81012345678901dialer load-threshold 30 eitherdialer-group 1ppp authentication chapppp multilinkppp multilink multiclassThe following example enables MLP interleaving and MCMP on a dialer interface that controls a rotary group of BRI interfaces. This configuration permits IP packets to trigger calls.
interface BRI 0description connected into a rotary groupencapsulation pppdialer rotary-group 1!interface BRI 1no ip addressencapsulation pppdialer rotary-group 1!interface BRI 2encapsulation pppdialer rotary-group 1!interface BRI 3no ip addressencapsulation pppdialer rotary-group 1!interface BRI 4encapsulation pppdialer rotary-group 1!interface Dialer 0description Dialer group controlling the BRIsip address 10.1.1.1 255.255.255.0encapsulation pppdialer map ip 10.1.1.2 name router 14802616900dialer-group 1ppp authentication chap! Enables Multilink Multiclass PPP interleaving on the dialer interface and reserves! a special queue.ppp multilinkppp multilink multiclassppp multilink interleaveip rtp reserve 32768 20 1000! Keeps fragments of large packets small enough to ensure delay of 20 ms or less.ppp multilink fragment delay 20dialer-list 1 protocol ip permitThe following example defines a virtual interface template that enables MLP interleaving and a maximum real-time traffic delay of 20 milliseconds. The bundle interface will be a virtual access interface cloned from the virtual template. MCMP is then configured on a member link, Serial0.
interface virtual-template 1ip unnumbered ethernet 0ppp multilinkppp multilink interleaveppp multilink fragment delay 20ip rtp interleave 32768 20 1000!multilink virtual-template 1!interface Serial0encapsulation pppppp authentication chapppp multilinkppp multilink multiclassThe following example configures MLP interleaving and a maximum real-time traffic delay of 20 milliseconds on a multilink interface. MCMP is then configured on a member link, Serial1, and the member link is restricted to joining only the designated multilink group interface.
interface Multilink1ip address 10.2.3.4 255.255.255.0ppp multilinkppp multilink interleaveppp multilink fragment delay 20!interface Serial1encapsulation pppppp authentication chapppp multilinkppp multilink multiclassppp multilink group 1Related Commands
show ppp multilink
To display bundle information for the Multilink PPP (MLP) bundles, use the show ppp multilink command in EXEC mode.
show ppp multilink [bundle-interface]
Syntax Description
bundle-interface
(Optional) The name of a bundle interface. Enter the name of a bundle interface to display information for only that bundle.
Command Modes
EXEC
Command History
Examples
The following is example output from the show ppp multilink command when no bundles are on a system:
Router# show ppp multilinkNo active bundlesThe following is example output when a single MLP bundle (named bundle1) is on a system:
Router# show ppp multilinkBundle bundle1, 3 members, first link is BRI0: B-channel 10 lost fragments, 8 reordered, 0 unassigned, sequence 0x1E/0x1E rcvd/sentThe following is example output when two active bundles are on a system. Subsequent bundles would be displayed below the previous bundle.
Router# show ppp multilinkBundle bundle1, 3 members, first link is BRI0: B-Channel 10 lost fragments, 8 reordered, 0 unassigned, sequence 0x1E/0x1E rcvd/sentBundle bundle2, 4 members, first link is BRI2: B-Channel 10 lost fragments, 28 reordered, 0 unassigned, sequence 0x12E/0x12E rcvd/sentThe following example shows output when a stack group has been created. On stack group member systema, The MLP bundle named bundle1 has bundle interface Virtual-Access4. Two child interfaces are joined to this bundle interface. The first is a local PRI channel (serial 0:4), and the second is an interface from stack group member systemb.
Router# show ppp multilinkBundle bundle1 2 members, Master link is Virtual-Access40 lost fragments, 0 reordered, 0 unassigned, 100/255 load0 discarded, 0 lost received, sequence 40/66 rcvd/sentmembers 2Serial0:4systemb:Virtual-Access6 (10.1.1.1)The following is example output when the PPP Bandwidth Allocation Control Protocol (BACP) is enabled for the multilink bundle:
Router# show ppp multilinkBundle bundle1, 1 member, Master link is Virtual-Access1Bundle under BAP controlDialer Interface is Dialer10 lost fragments, 0 reordered, 0 unassigned, sequence 0x0/0x0 rcvd/sent0 discarded, 0 lost received, 1/255 loadMember links: 1BRI0:1Discriminators Local RemoteBRI0:1 24 1Table 1 describes the significant fields shown in the display when PPP BACP is enabled.
The following example shows output when MCMP is negotiated on a virtual-access interface named Virtual-Access3:
Router# show ppp multilink Virtual-Access3Virtual-Access3, bundle name is bundle1Bundle up for 01:59:35, 1/255 load, 2 receive classes, 2 transmit classesReceive buffer limit 12192 bytes per class, frag timeout 1524 msDialer interface is Dialer1!Receive Class 0:0/0 fragments/bytes in reassembly list0 lost fragments, 0 reordered0/0 discarded fragments/bytes, 0 lost received0x0 received sequence!Receive Class 1:0/0 fragments/bytes in reassembly list0 lost fragments, 0 reordered0/0 discarded fragments/bytes, 0 lost received0x0 received sequence!Transmit Class 0:0x8 sent sequence!Transmit Class 1:0x0 sent sequence!Member links: 1 (max not set, min not set)BR2/0:1, since 01:59:35, 80 weight, 72 frag sizeTable 2 describes the significant fields shown in the display when MCMP is enabled.