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Table Of Contents
MPLS Traffic Engineering (TE)—Scalability Enhancements
Prerequisites for MPLS Traffic Engineering (TE)—Scalability Enhancements
Restrictions for MPLS Traffic Engineering (TE)—Scalability Enhancements
Information About MPLS Traffic Engineering (TE)—Scalability Enhancements
Signaling and Management for MPLS Traffic Engineering Tunnels
Controlling IS-IS and MPLS Traffic Engineering Topology Database Interactions
Improved Diagnostic Capabilities for MPLS Traffic Engineering and RSVP Signaling
Benefits of MPLS Traffic Engineering (TE)—Scalability Enhancements
How to Configure MPLS Traffic Engineering (TE)—Scalability Enhancements
Monitoring and Maintaining Scalability Enhancements
clear mpls traffic-eng tunnel counters
mpls traffic-eng topology holddown sigerr
show mpls traffic-eng tunnels statistics
MPLS Traffic Engineering (TE)—Scalability Enhancements
First Published: February 23, 2002Last Updated: February 28, 2006The Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) Scalability Enhancement feature improves scalability performance for large numbers of traffic engineering tunnels.
These improvements allow an increase in the number of TE tunnels a router can support when the router is configured as a tunnel headend. Additionally, when the router is configured as a tunnel midpoint, the enhancements reduce the time required to establish large numbers of TE tunnels.
This feature module describes the MPLS traffic engineering scalability enhancements.
Finding Support Information for Platforms and Cisco IOS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Contents
This document contains the following sections:
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Prerequisites for MPLS Traffic Engineering (TE)—Scalability Enhancements
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Prerequisites for MPLS Traffic Engineering (TE)—Scalability Enhancements
Your network must support the following Cisco IOS features before you enable MPLS traffic engineering:
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Restrictions for MPLS Traffic Engineering (TE)—Scalability Enhancements
The number of tunnels that a particular platform can support can vary depending on:
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Information About MPLS Traffic Engineering (TE)—Scalability Enhancements
Scalability performance is improved for large numbers of traffic engineering tunnels, and includes the following enhancements:
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The following sections describe user-observable scalability enhancements:
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Pacing for RSVP Messages
A burst of RSVP traffic engineering signaling messages can overflow the input queue of a receiving router, causing some messages to be dropped. Dropped messages cause a substantial delay in completing label-switched path (LSP) signaling.
This feature provides an enhancement mechanism that controls the transmission rate for RSVP messages and reduces the likelihood of input drops on the receiving router. The default transmission rate is 200 RSVP messages per second to a given neighbor. The rate is configurable.
Signaling and Management for MPLS Traffic Engineering Tunnels
LSP recovery responsiveness is improved when a link used by an LSP fails:
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Controlling IS-IS and MPLS Traffic Engineering Topology Database Interactions
This feature reduces the interval between when the IS-IS protocol receives an IGP update and when it delivers the update to the MPLS traffic engineering topology database.
Before this feature was introduced, when IS-IS received a new LSP that contained traffic engineering type, length, and value (TLV) objects, a delay of several seconds could occur before IS-IS passed the traffic engineering TLVs to the traffic engineering database. The purpose of the delay was to provide better scalability during periods of network instability and to give the router an opportunity to receive more fragments of the LSP before passing the information to the traffic engineering database. However, this delay increased the convergence time for the traffic engineering database.
With this feature, IS-IS extracts traffic engineering TLVs from received LSPs and passes them to the traffic engineering database immediately. The exception to this occurs when there are large numbers of LSPs to process and it is important to limit CPU consumption, such as during periods of network instability. The parameters that control IS-IS delivery of traffic engineering TLVs to the traffic engineering topology database are configurable.
Improved Diagnostic Capabilities for MPLS Traffic Engineering and RSVP Signaling
With this feature, diagnostic and troubleshooting capabilities for MPLS traffic engineering and RSVP are improved:
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Benefits of MPLS Traffic Engineering (TE)—Scalability Enhancements
This feature provide the following benefits:
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How to Configure MPLS Traffic Engineering (TE)—Scalability Enhancements
This section describes the following tasks:
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Enabling RSVP Message Pacing
RSVP message pacing maintains, on an outgoing interface basis, a count of messages that were dropped because the output queue for the interface used for message pacing was full.
SUMMARY STEPS
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DETAILED STEPS
Examples
The following command enables RSVP message pacing:
Router(config)# ip rsvp msg-pacingEnter the following command to verify that RSVP message pacing is enabled:
Router# show ip rsvp neighborThe following is sample output that traffic engineering displays when RSVP message pacing is enabled:
RSVP Msg-Pacing:Period 20, Burst 4, Rate 200, MaxSize 500Interface Neighbor Encapsulation OQueue OQueue-dropsAT0.1 10.12.9.12 RSVP 0 0Hs0 10.13.9.13 RSVP 0 0If RSVP message pacing is not enabled, the OQueue or OQueue-drops column do not display.
Monitoring and Maintaining Scalability Enhancements
To monitor and maintain the scalability enhancements, use the commands shown below. For detailed command descriptions, see the "Command Reference" section.
Additional References
The following sections provide references related to the MPLS Traffic Engineering (TE)—Scalability Enhancements feature.
Related Documents
Quality of service
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MPLS
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Standards
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
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MIBs
RFCs
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.
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Technical Assistance
Command Reference
This section documents the following modified commands only:
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clear ip rsvp counters
To clear (set to zero) all IP Resource Reservation Protocol (RSVP) counters that are being maintained, use the clear ip rsvp counters command in EXEC mode.
clear ip rsvp counters [confirm]
Syntax Description
Command Modes
EXEC
Command History
Usage Guidelines
This command allows you to set all IP RSVP counters to zero so that you can see changes easily.
Examples
In the following example, all IP RSVP counters that are being maintained are cleared:
Router# clear ip rsvp countersClear rsvp counters [confirm]Related Commands
show ip rsvp counters
Displays counts of RSVP messages that were sent and received.
clear ip rsvp msg-pacing
To clear the Resource Reservation Protocol (RSVP) message pacing output from the show ip rsvp neighbor command, use the clear ip rsvp msg-pacing command in EXEC mode.
clear ip rsvp msg-pacing
Syntax Description
This command has no arguments or keywords.
Command Modes
EXEC
Command History
Examples
The following example clears the RSVP message pacing output:
Router# clear ip rsvp msg-pacingRelated Commands
clear mpls traffic-eng tunnel counters
To clear the counters for all Multiprotocol Label Switching (MPLS) traffic engineering tunnels, use the clear mpls traffic-eng tunnel counters command in EXEC mode.
clear mpls traffic-eng tunnel counters
Syntax Description
This command has no optional parameters or keywords.
Command Modes
EXEC
Command History
Usage Guidelines
This command allows you to set the MPLS traffic engineering tunnel counters to zero so that you can see changes to the counters easily.
Examples
In the following example, the counters for all MPLS traffic engineering tunnels are cleared and a request is made for confirmation that the specified action occurred:
Router# clear mpls traffic-eng tunnel countersClear traffic engineering tunnel counters [confirm]Related Commands
show mpls traffic-eng tunnels statistics
Displays event counters for one or more MPLS traffic engineering tunnels.
ip rsvp msg-pacing
To set up message pacing (that is, to control the transmission rate for Resource Reservation Protocol (RSVP) messages), use the ip rsvp msg-pacing command in global configuration mode. To disable this feature, use the no form of this command.
ip rsvp msg-pacing [period ms [burst msgs [maxsize qsize]]]
no rsvp msg-pacing
Syntax Description
Defaults
RSVP messages are not paced.
If you enter the command without the optional arguments, the transmission rate for RSVP messages is limited to 200 messages per second per outgoing interface.
The default output queue size, specified in the maxsize keyword, is 500.Command Modes
Global configuration
Command History
Usage Guidelines
You can use this command to prevent a burst of RSVP traffic engineering signaling messages from overflowing the input queue of a receiving router, which would cause the router to drop some messages. Dropped messages substantially delay the completion of signaling for LSPs for which messages have been dropped.
Examples
In the following example, a router can send a maximum of 150 RSVP traffic engineering signaling messages in 1 second to a neighbor, and the size of the output queue is 750:
Router(config)# ip rsvp msg-pacing period 1 burst 150 maxsize 750Related Commands
clear ip rsvp msg-pacing
Clears the RSVP message pacing output from the show ip rsvp neighbor command.
mpls traffic-eng scanner
To specify how often Intermediate System-to-Intermediate System (IS-IS) extracts traffic engineering type, length, and value (TLVs) from flagged label-switched path (LSPs) and passes them to the traffic engineering topology database, and the maximum number of LSPs that the router can process immediately, use the mpls traffic-eng scanner command router IS-IS configuration subcommand. To disable this feature, use the no form of this command.
mpls traffic-eng scanner [interval sec] [max-flash LSPs]
no mpls traffic-eng scanner
Syntax Description
Defaults
The default interval is 5 seconds.
The default max-flash value is 15 LSPs.
The first 15 LSPs are sent without a delay into the traffic engineering database. If more LSPs are received, the default delay of 5 seconds applies.
If you specify the no form of this command, there is a delay of 5 seconds before IS-IS scans its database and passes traffic engineering TLVs associated with flagged LSPs to the traffic engineering database.Command Modes
Router IS-IS configuration
Command History
Usage Guidelines
When IS-IS receives a new LSP, it inserts it into the IS-IS database. If the LSP contains traffic engineering TLVs, IS-IS flags the LSPs for transmission to the traffic engineering database. At the default or user-specified interval, traffic engineering TLVs are extracted and sent to the traffic engineering database. Users can also specify the maximum number of LSPs that the router can process immediately. Processing entails checking for traffic engineering TLVs, extracting them, and passing them to the traffic engineering database. If more than 50 LSPs need to be processed, there is a delay of 5 seconds for subsequent LSPs.
Examples
In the following example, the router is allowed to process up to 50 IS-IS LSPs without any delay.
Router(isis)# mpls traffic-eng scanner interval 5 max-flash 50Related Commands
mpls traffic-eng topology holddown sigerr
To specify the amount of time that a router ignores a link in its traffic engineering topology database in tunnel path Constrained Shortest Path First (CSPF) computations following a traffic engineering tunnel error on the link, use the mpls traffic-eng topology holddown sigerr command in global configuration mode. To disable this feature, use the no form of this command.
mpls traffic-eng topology holddown sigerr seconds
no mpls traffic-eng topology holddown sigerr
Syntax Description
seconds
Length of time (in seconds) a router should ignore a link during tunnel path calculations following a traffic engineering tunnel error on the link. The value can be from 0 to 300.
Defaults
If you do not specify this command, tunnel path calculations ignore a link on which there is a traffic engineering error until either 10 seconds have elapsed or a topology update is received from the Interior Gateway Protocol (IGP).
Command Modes
Global configuration
Command History
Usage Guidelines
A router that is at the headend for traffic engineering tunnels might receive a Resource Reservation Protocol (RSVP) No Route error message for an existing tunnel or for one being signaled due to the failure of a link the tunnel traverses before the router receives a topology update from the IGP routing protocol announcing that the link is down. In such a case, the headend router ignores the link in subsequent tunnel path calculations to avoid generating paths that include the link and are likely to fail when signaled. The link is ignored until the router receives a topology update from its IGP or a link hold-down timeout occurs. You can use the mpls traffic-eng topology holddown sigerr command to change the link hold-down time from its 10 second default value.
Examples
In the following example, the link hold-down time for signaling errors is set at 15 seconds:
Router(config)# mpls traffic-eng topology holddown sigerr 15Related Commands
show mpls traffic-eng topology
Displays the MPLS traffic engineering global topology as currently known at the node.
show ip rsvp counters
To display the counts of Resource Reservation Protocol (RSVP) messages that were sent and received, use the show ip rsvp counters command in EXEC mode.
show ip rsvp counters [interface interface-name| summary]
Syntax Description
Defaults
If you enter this command without a keyword, the command displays the number of RSVP messages that were sent and received for each interface for which RSVP is configured.
Command Modes
EXEC
Command History
Examples
In the following example, values are shown for the number of RSVP messages of each type (such as Path and Resv) that were sent and received on POS2/2:
Router# show ip rsvp counters interface pos2/2POS2/2 Recv Xmit Recv XmitPath 0 112876 Resv 74414 0PathError 0 0 ResvError 0 0PathTear 0 7 ResvTear 4 0ResvConfirm 0 0 ResvTearConfirm 0 4UnknownMsg 0 0 Errors 0 0In the following example, values are shown for the number of RSVP messages of each type that were sent and received by the router over all interfaces:
Router# show ip rsvp counters summaryAll Interfaces Recv Xmit Recv XmitPath 512 224962 Resv 148446 385PathError 0 2 ResvError 0 0PathTear 8 12 ResvTear 4 4ResvConfirm 0 0 ResvTearConfirm 4 4UnknownMsg 0 0 Errors 0 0Table 1 describes the significant fields shown in the display.
Related Commands
clear ip rsvp counters
Clears (sets to zero) all IP RSVP counters that are being maintained.
show mpls traffic-eng tunnels statistics
To display event counters for one or more Multiprotocol Label Switching (MPLS) traffic engineering tunnels, use the show mpls traffic-eng tunnels statistics command in EXEC mode.
show mpls traffic-eng tunnels [tunnel tunnel-name] statistics [summary]
Syntax Description
tunnel tunnel-name
(Optional) Displays event counters accumulated for the specified tunnel.
summary
(Optional) Displays event counters accumulated for all tunnels.
Defaults
If you enter the command without any keywords, the command displays the event counters for every MPLS traffic engineering tunnel interface configured on the router.
Command Modes
EXEC
Command History
Usage Guidelines
A label switching router (LSR) maintains counters for each MPLS traffic engineering tunnel headend that counts significant events for the tunnel, such as state transitions for the tunnel, changes to the tunnel path, and various signaling failures. You can use the show mpls traffic-eng tunnels statistics command to display these counters for a single tunnel, for every tunnel, or for all tunnels (accumulated values). Displaying the counters is often useful for troubleshooting tunnel problems.
Examples
The following are examples of output from the show mpls traffic-eng tunnels statistics command:
Router# show mpls traffic-eng tunnels tunnel tunnel1001 statisticsTunnel1001 (Destination 10.8.8.8; Name Router_t1001)Management statistics:Path: 25 no path, 1 path no longer valid, 0 missing ip exp path5 path changesState: 3 transitions, 0 admin down, 1 oper downSignalling statistics:Opens: 2 succeeded, 0 timed out, 0 bad path spec0 other abortsErrors: 0 no b/w, 0 no route, 0 admin0 bad exp route, 0 rec route loop, 0 otherRouter# show mpls traffic-eng tunnels statisticsTunnel1001 (Destination 10.8.8.8; Name Router_t1001)Management statistics:Path: 25 no path, 1 path no longer valid, 0 missing ip exp path5 path changesState: 3 transitions, 0 admin down, 1 oper downSignalling statistics:Opens: 2 succeeded, 0 timed out, 0 bad path spec0 other abortsErrors: 0 no b/w, 0 no route, 0 admin0 bad exp route, 0 rec route loop, 0 other.
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.Tunnel7050 (Destination 10.8.8.8; Name Router_t7050)Management statistics:Path: 19 no path, 1 path no longer valid, 0 missing ip exp path3 path changesState: 3 transitions, 0 admin down, 1 oper downSignalling statistics:Opens: 2 succeeded, 0 timed out, 0 bad path spec0 other abortsErrors: 0 no b/w, 0 no route, 0 admin0 bad exp route, 0 rec route loop, 0 otherRouter# show mpls traffic-eng tunnels statistics summaryManagement statistics:Path: 2304 no path, 73 path no longer valid, 0 missing ip exp path432 path changesState: 300 transitions, 0 admin down, 100 oper downSignalling statistics:Opens: 200 succeeded, 0 timed out, 0 bad path spec0 other abortsErrors: 0 no b/w, 18 no route, 0 admin0 bad exp route, 0 rec route loop, 0 otherTable 2 describes the significant fields shown in the display.
Related Commands
clear mpls traffic-eng tunnel counters
Clears the counters for all MPLS traffic engineering tunnels.
Glossary
Cisco Express Forwarding—A means for accelerating the forwarding of packets within a router, by storing route lookup information in several data structures instead of in a route cache.
enterprise network—A large and diverse network connecting most major points in a company or other organization.
headend—The endpoint of a broadband network. All stations send toward the headend; the headend then sends toward the destination stations.
IGP—Interior Gateway Protocol. An Internet protocol used to exchange routing information within an autonomous system. Examples of common Internet IGPs include IGRP, OSPF, and RIP.
interface—A network connection.
IS-IS—Intermediate System-to-Intermediate System. OSI link-state hierarchical routing protocol based on DECnet Phase V routing, where ISs (routers) exchange routing information based on a single metric, to determine the network topology.
label-switched path (LSP)—A sequence of hops (R0...Rn) in which a packet travels from R0 to Rn through label switching mechanisms. A label-switched path can be chosen dynamically, based on normal routing mechanisms, or through configuration.
MPLS—Multiprotocol Label Switching (formerly known as tag switching). A method for directing packets primarily through Layer 2 switching rather than Layer 3 routing. In MPLS, packets are assigned short fixed-length labels at the ingress to an MPLS cloud by using the concept of forwarding equivalence classes. Within the MPLS domain, the labels are used to make forwarding decisions mostly without recourse to the original packet headers.
router—A network layer device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded. Routers forward packets from one network to another based on network layer information.
RSVP—Resource Reservation Protocol. A protocol that supports the reservation of resources across an IP network.
scalability—An indicator showing how quickly some measure of resource usage increases as a network gets larger.
topology—The physical arrangement of network nodes and media within an enterprise networking structure.
traffic engineering—Techniques and processes that cause routed traffic to travel through the network on a path other than the one that would have been chosen if standard routing methods were used.
traffic engineering tunnel—A label-switched tunnel that is used for traffic engineering. Such a tunnel is set up through means other than normal Layer 3 routing; it is used to direct traffic over a path different from the one that Layer 3 routing would cause the tunnel to take.
Feature Information for Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) Scalability Enhancement
Table 3 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform. Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Note
Table 3 Feature Information for Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) Scalability Enhancement
Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) Scalability Enhancement
12.0(14)ST
12.2(14)S
12.0(22)S
12.2(28)SBThe Multiprotocol Label Switching (MPLS) Traffic Engineering (TE) Scalability Enhancement feature improves scalability performance for large numbers of traffic engineering tunnels.
These improvements allow an increase in the number of TE tunnels a router can support when the router is configured as a tunnel headend. Additionally, when the router is configured as a tunnel midpoint, the enhancements reduce the time required to establish large numbers of TE tunnels.
In 12.0(14)ST, this feature was introduced.
In 12.2(14)S, this feature was integrated into Cisco IOS Release 12.2(14)S.
In 12.0(22)S, this feature was integrated into Cisco IOS Release 12.0(22)S.
In 12.2(28)SB, this feature was integrated into Cisco IOS Release 12.2(28)SB.
The following sections provide information about this feature:
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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.
© 2006 Cisco Systems, Inc. All rights reserved.
