Networking Software (IOS & NX-OS)

Table Of Contents

MPLS Traffic Engineering: Scalability Enhancements

Contents

Prerequisites for MPLS Traffic Engineering: Scalability Enhancements

Restrictions for MPLS Traffic Engineering: Scalability Enhancements

Information About MPLS Traffic Engineering: Scalability Enhancements

Scalability Enhancements for Traffic Engineering Tunnels

RSVP Rate Limiting

Improved Recovery Response for Signaling and Management of MPLS Traffic Engineering Tunnels

IS-IS and MPLS Traffic Engineering Topology Database Interactions

Improved Counter Capabilities for MPLS TE Tunnels Events and RSVP Signaling

Benefits of MPLS Traffic Engineering: Scalability Enhancements

How to Configure MPLS Traffic Engineering: Scalability Enhancements

Enabling RSVP Rate Limiting for MPLS Traffic Engineering Scalability Enhancements

Managing Link Failure Timeouts for MPLS Traffic Engineering Tunnels

Controlling IS-IS Communication with the MPLS Traffic Engineering Topology Database

Monitoring and Maintaining MPLS TE Scalability Enhancements

Configuration Examples for MPLS Traffic Engineering: Scalability Enhancements

Enabling RSVP Rate Limiting for MPLS Traffic Engineering Scalability Enhancements: Examples

Managing Link Failure Timeouts for MPLS Traffic Engineering Tunnels: Example

Controlling IS-IS Communication with the MPLS Traffic Engineering Topology Database: Example

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for MPLS Traffic Engineering: Scalability Enhancements

Glossary

MPLS Traffic Engineering: Scalability Enhancements

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First Published: February 23, 2002

Last Updated: July 11, 2008

The MPLS Traffic Engineering: Scalability Enhancement feature improves scalability performance for large numbers of traffic engineering tunnels.

These improvements allow an increase in the number of traffic engineering (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 contains information about and instructions on how to configure the Multiprotocol Label Switching (MPLS) traffic engineering scalability enhancements.

Finding Feature Information in This Module

Your Cisco IOS software release may not support all of the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the"Feature Information for MPLS Traffic Engineering: Scalability Enhancements" section.

Finding Support Information for Platforms and Cisco IOS and Catalyst OS Software Images

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for MPLS Traffic Engineering: Scalability Enhancements

•Restrictions for MPLS Traffic Engineering: Scalability Enhancements

•Information About MPLS Traffic Engineering: Scalability Enhancements

•How to Configure MPLS Traffic Engineering: Scalability Enhancements

•Configuration Examples for MPLS Traffic Engineering: Scalability Enhancements

•Additional References

•Feature Information for MPLS Traffic Engineering: Scalability Enhancements

•Feature Information for MPLS Traffic Engineering: Scalability Enhancements

•Glossary

Prerequisites for MPLS Traffic Engineering: Scalability Enhancements

Your network must support the following Cisco IOS features before you enable MPLS traffic engineering:

•MPLS

•Cisco Express Forwarding

•Intermediate System-to-Intermediate System (IS-IS) or Open Shortest Path First (OSPF)

Restrictions for MPLS Traffic Engineering: Scalability Enhancements

The number of tunnels that a particular platform can support can vary depending on:

•The types of interfaces that the tunnels traverse

•The manner in which the Resource Reservation Protocol (RSVP) message pacing feature is configured

•MPLS traffic engineering supports only a single IGP process/instance. Multiple IGP processes/instances are not supported and MPLS traffic engineering should not be configured in more than one IGP process/instance.

Information About MPLS Traffic Engineering: Scalability Enhancements

•Scalability Enhancements for Traffic Engineering Tunnels

•RSVP Rate Limiting

•Improved Recovery Response for Signaling and Management of MPLS Traffic Engineering Tunnels

•IS-IS and MPLS Traffic Engineering Topology Database Interactions

•Improved Counter Capabilities for MPLS TE Tunnels Events and RSVP Signaling

•Benefits of MPLS Traffic Engineering: Scalability Enhancements

Scalability Enhancements for Traffic Engineering Tunnels

Scalability performance is improved for large numbers of traffic engineering tunnels, and includes the following enhancements:

•Increase the number of traffic engineering tunnels a router can support when configured as a tunnel headend and when configured as a tunnel midpoint

•Reduce the time required to establish large numbers of traffic engineering tunnels

RSVP Rate Limiting

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 MPLS Traffic Engineering—Scalability Enhancements 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.

Improved Recovery Response for Signaling and Management of MPLS Traffic Engineering Tunnels

The MPLS Traffic Engineering—Scalability Enhancements feature improves the recovery response for signaling and management of MPLS TE tunnels. LSP recovery responsiveness is improved when a link used by an LSP fails:

•When the upstream end of a failed link detects the failure, the software generates an RSVP No Route path error message. This enables the LSP headend to detect the link failure and initiate recovery, even when the Interior Gateway Protocol (IGP) update announcing the link failure is delayed.

•The LSP headend marks the link in question so that subsequent constraint-based shortest path first (SPF) calculations ignore the link until either a new IGP update arrives or a configurable timeout occurs. This ensures that resignaling to restore the LSP avoids the failed link.

IS-IS and MPLS Traffic Engineering Topology Database Interactions

The MPLS Traffic Engineering—Scalability Enhancements 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 the MPLS Traffic Engineering—Scalability Enhancements feature was introduced, when IS-IS received a new LSP that contained traffic engineering type, length, 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 the MPLS Traffic Engineering—Scalability Enhancements 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.

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Note MPLS traffic engineering supports only a single IGP process/instance. Multiple IGP processes/instances are not supported and MPLS traffic engineering should not be configured in more than one IGP process/instance.

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Improved Counter Capabilities for MPLS TE Tunnels Events and RSVP Signaling

With the MPLS Traffic Engineering—Scalability Enhancements feature, diagnostic and troubleshooting capabilities for MPLS traffic engineering tunnels and RSVP are improved:

•Counters record tunnel headend error events such as no route (link down), preemption, and insufficient bandwidth on a per-tunnel basis.

•Counters record RSVP messages. The counters are per-interface and record the number of RSVP messages of each type sent and received on the interface.

Benefits of MPLS Traffic Engineering: Scalability Enhancements

The MPLS Traffic Engineering—Scalability Enhancements feature provides the following benefits:

•Increased scalability: Up to 600 MPLS traffic engineering tunnel headends are supported. Up to 10,000 traffic engineering tunnel midpoints are supported, with up to 5000 midpoints per interface.

•Faster recovery after failure conditions: Message pacing provides a mechanism to throttle RSVP control messages so that they are less likely to be dropped. This results in a faster recovery from failure conditions when many MPLS traffic engineering tunnels are being set up.

•Improved reroute time: When a traffic engineering tunnel is down, the headend router needs to be notified so that it can signal for a new LSP for the tunnel along an alternate path. The headend router does not have to wait for an IGP update to signal for a new LSP for the tunnel along an alternate path.

•Improved tunnel setup time: Fewer control messages and tunnel setup messages are dropped. This reduces the average time required to set up tunnels.

How to Configure MPLS Traffic Engineering: Scalability Enhancements

•Enabling RSVP Rate Limiting for MPLS Traffic Engineering Scalability Enhancements (required)

•Managing Link Failure Timeouts for MPLS Traffic Engineering Tunnels (required)

•Controlling IS-IS Communication with the MPLS Traffic Engineering Topology Database (required)

•Monitoring and Maintaining MPLS TE Scalability Enhancements (optional)

Enabling RSVP Rate Limiting for MPLS Traffic Engineering Scalability Enhancements

Perform the following task to enable RSVP rate limiting for MPLS traffic engineering scalability enhancements. RSVP rate limiting maintains, on an outgoing interface basis, a count of messages that were dropped because the output queue for the interface used for rate limiting was full.

SUMMARY STEPS

1. enable

2. configure terminal

3. ip rsvp signalling rate-limit [burst number] [limit number] [maxsize bytes] [period ms]

4. end

5. show ip rsvp neighbor

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	ip rsvp signalling rate-limit [burst number] [limit number] [maxsize bytes] [period ms] Example: Router(config)# ip rsvp signalling rate-limit burst 5 maxsize 3 period 2	Controls the transmission rate for RSVP messages sent to a neighboring router during a specified amount of time. •The burst number keyword and argument pair indicates the maximum number of RSVP messages sent to a neighboring router during each interval. The range is from 1 to 5000. The default is 8. •The limit number keyword and argument pair indicates the maximum number of messages to send per queue interval when the number of messages sent is less than the number of messages to be sent normally. The range is from 1 to 5000. The default is 37. •The maxsize bytes keyword and argument pair indicates the maximum size of the message queue, in bytes. The range is from 1 to 5000. The default is 2000. •The period ms keyword and argument pair indicates the length of the interval (time frame) in milliseconds (ms). The range is from 10 to 5000. The default is 20.
Step 4	end Example: Router(config)# end	Exits to privileged EXEC mode.
Step 5	show ip rsvp neighbor Example: Router# show ip rsvp neighbor	Displays current RSVP neighbors. Use this command to verify that RSVP message pacing is enabled.

Managing Link Failure Timeouts for MPLS Traffic Engineering Tunnels

Perform this task to manage link failure timeouts for MPLS traffic engineering tunnels.

This allows the configuration of a timeout during which the router ignores a link in its path calculation to avoid paths that contain a failed link and are likely to fail when signaled.

SUMMARY STEPS

1. enable

2. configure terminal

3. mpls traffic-eng topology holddown sigerr seconds

4. end

5. show mpls traffic-eng topology [brief]

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	mpls traffic-eng topology holddown sigerr seconds Example: Router(config)# mpls traffic-eng topology holddown sigerr 15	Specifies 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. •The seconds argument specifies the 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. The default is 10.
Step 4	end Example: Router(config)# end	Exits to privileged EXEC mode.
Step 5	show mpls traffic-eng topology [brief] Example: Router# show mpls traffic-eng topology brief	Displays the MPLS traffic engineering global topology as currently known at this node. •The brief keyword provides a less detailed version of the topology.

Controlling IS-IS Communication with the MPLS Traffic Engineering Topology Database

Perform the following task to control IS-IS and MPLS traffic engineering topology database interactions. This reduces the interval time between when the IS-IS protocol receives an IGP update and when IS-IS delivers the update to the MPLS traffic engineering topology database, which reduces convergence time for the database.

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Note MPLS traffic engineering supports only a single IGP process/instance. Multiple IGP processes/instances are not supported and MPLS traffic engineering should not be configured in more than one IGP process/instance.

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SUMMARY STEPS

1. enable

2. configure terminal

3. router isis [area-tag]

4. mpls traffic-eng scanner [interval seconds] [max-flash LSPs]

5. end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. •Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	router isis [area-tag] Example: Router(config)# router isis	Enables the IS-IS routing protocol and specifies an IS-IS process. •The area-tag argument is a meaningful name for a routing process. If it is not specified, a null tag is assumed and the process is referenced with a null tag. This name must be unique among all IP or Connectionless Network Service (CLNS) router processes for a given router. Note This argument is Required for multiarea IS-IS configuration and optional for conventional IS-IS configuration.
Step 4	mpls traffic-eng scanner [interval seconds] [max-flash LSPs] Example: Router(config-router)# mpls traffic-eng scanner interval 5 max-flash 100	Specifies how often IS-IS extracts traffic engineering TLVs from flagged LSPs and passes them to the traffic engineering topology database, and specifies the maximum number of LSPs that the router can process immediately. •The interval seconds keyword and argument specify the frequency, in seconds, at which IS-IS sends traffic engineering TLVs into the traffic engineering database. The value can be from 1 to 60. The default value is 5. •The max-flash LSPs keyword and argument specify the maximum number of LSPs that the router can process immediately without incurring a delay. The value can be from 0 to 200. The default value is 15.
Step 5	end Example: Router(config-router)# end	Exits to privileged EXEC mode.

Monitoring and Maintaining MPLS TE Scalability Enhancements

SUMMARY STEPS

1. enable

2. show ip rsvp neighbor [detail]

3. show ip rsvp counters [summary]

4. clear ip rsvp counters

5. clear ip rsvp signalling rate-limit

6. show mpls traffic-eng tunnels statistics

7. clear mpls traffic-eng tunnels counters

8. show mpls traffic-eng topology [brief]

9. exit

DETAILED STEPS

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Step 1 enable

Use this command to enable privileged EXEC mode. Enter your password if prompted. For example:

Router> enable

Router#

Step 2 show ip rsvp neighbor [detail]

Use this command to verify that RSVP message pacing is turned on. For example:

Router# show ip rsvp neighbor detail

Neighbor:10.0.0.1

    Encapsulation:RSVP

    Rate-Limiting:

      Dropped messages:0

Refresh Reduction:

      Remote epoch:0x1BFEA5

      Out of order messages:0

      Retransmitted messages:0

      Highest rcvd message id:1059

      Last rcvd message:00:00:04

Neighbor:10.0.0.2

    Encapsulation:RSVP

    Rate-Limiting:

      Dropped messages:0

    Refresh Reduction:

      Remote epoch:0xB26B1

      Out of order messages:0

      Retransmitted messages:0

      Highest rcvd message id:945

      Last rcvd message:00:00:05

Step 3 show ip rsvp counters [summary]

Use this command to display the counts of RSVP messages that were sent and received. For example:

Router# show ip rsvp counters summary

All Interfaces          Recv      Xmit                        Recv      Xmit

    Path                  110        15    Resv                   50        28

    PathError               0         0    ResvError               0         0

    PathTear                0         0    ResvTear                0         0

    ResvConf                0         0    RTearConf               0         0

    Ack                     0         0    Srefresh                0         0

    Hello                5555      5554    IntegrityChalle         0         0

    IntegrityRespon         0         0    DSBM_WILLING            0         0

    I_AM_DSBM               0         0

    Unknown                 0         0    Errors                  0         0

Recv Msg Queues                Current       Max

    RSVP                             0         2

    Hello (per-I/F)                  0         1

    Awaiting Authentication          0         0

Step 4 clear ip rsvp counters

Use this command to clear (set to zero) all IP RSVP counters that are being maintained. For example:

Router# clear ip rsvp counters

Clear rsvp counters [confirm] 

Step 5 clear ip rsvp signalling rate-limit

Use this command to clear (set to zero) counts of the messages that message pacing was forced to drop because the output queue for the interface used for message pacing was full. For example:

Router# clear ip rsvp signalling rate-limit

Step 6 show mpls traffic-eng tunnels statistics

Use this command to display event counters for one or more MPLS traffic engineering tunnels. For example:

Router# show mpls traffic-eng tunnels statistics

Tunnel1001 (Destination 10.8.8.8; Name Router_t1001)

  Management statistics:

    Path:	25 no path, 1 path no longer valid, 0 missing ip exp path

	5 path changes

    State:	3 transitions, 0 admin down, 1 oper down

  Signalling statistics:

    Opens:	2 succeeded, 0 timed out, 0 bad path spec

	0 other aborts

    Errors:	0 no b/w, 0 no route, 0 admin

	0 bad exp route, 0 rec route loop, 0 other

.
.
.

Tunnel7050 (Destination 10.8.8.8; Name Router_t7050)

  Management statistics:

    Path: 	19 no path, 1 path no longer valid, 0 missing ip exp path

	3 path changes

    State: 	3 transitions, 0 admin down, 1 oper down

  Signalling statistics:

    Opens: 	2 succeeded, 0 timed out, 0 bad path spec

	0 other aborts

    Errors:	0 no b/w, 0 no route, 0 admin

	0 bad exp route, 0 rec route loop, 0 other

Step 7 clear mpls traffic-eng tunnels counters

Use this command to clear counters for all MPLS traffic engineering tunnels. For example:

Router# clear mpls traffic-eng tunnels counters

Clear traffic engineering tunnel counters [confirm]

Step 8 show mpls traffic-eng topology [brief]

Use this command to display the MPLS traffic engineering topology database. For example:

Router# show mpls traffic-eng topology brief

My_System_id:0000.0000.0003.00 (isis  level-2)

Signalling error holddown:10 sec Global Link Generation 9

IGP Id:0000.0000.0003.00, MPLS TE Id:10.0.3.1 Router Node  (isis

level-2)

      link[0]:Point-to-Point, Nbr IGP Id:0000.0000.0004.00,

nbr_node_id:2, gen:9

          frag_id 0, Intf Address:10.0.0.33, Nbr Intf Address:10.0.0.34

          TE metric:10, IGP metric:10, attribute_flags:0x0

          SRLGs:1 2

Step 9 exit

Use this command to exit to user EXEC mode. For example:

Router# exit

Router>

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Configuration Examples for MPLS Traffic Engineering: Scalability Enhancements

•Enabling RSVP Rate Limiting for MPLS Traffic Engineering Scalability Enhancements: Examples

•Managing Link Failure Timeouts for MPLS Traffic Engineering Tunnels: Example

•Controlling IS-IS Communication with the MPLS Traffic Engineering Topology Database: Example

Enabling RSVP Rate Limiting for MPLS Traffic Engineering Scalability Enhancements: Examples

The following examples show how to enable RSVP rate limiting for MPLS traffic engineering scalability enhancements:

configure terminal 

 ip rsvp signalling rate-limit

 end

The following is sample output that traffic engineering displays when RSVP rate limiting is enabled:

Router# show ip rsvp signalling rate-limit 

Rate Limiting: enabled

  Burst: 10

  Limit: 37

  Maxsize: 5000

  Period (msec): 100

  Max rate (msgs/sec): 100

The following example shows how to configure a router to send a maximum of 5 RSVP traffic engineering signaling messages in 1 second to a neighbor. The size of the output queue is 35.

configure terminal

 ip rsvp signalling rate-limit period 1 burst 5 maxsize 35

Managing Link Failure Timeouts for MPLS Traffic Engineering Tunnels: Example

The following example shows how to manage link failure timeouts for MPLS traffic engineering tunnels:

configure terminal

 mpls traffic-eng topology holddown sigerr 15

 end

In this example, the link hold-down time for signaling errors is set to 15 seconds.

Controlling IS-IS Communication with the MPLS Traffic Engineering Topology Database: Example

The following example shows how to control IS-IS communication with the MPLS traffic engineering topology database:

configure terminal

router isis

 mpls traffic-eng scanner interval 5 max-flash 50

 end

In this example, the router is enabled to process up to 50 IS-IS LSPs without any delay.

Additional References

The following sections provide references related to the MPLS Traffic Engineering (TE): Scalability Enhancements feature.

Related Documents

Related Topic	Document Title
Quality of service	•Cisco IOS Quality of Service Solutions Command Reference •Cisco IOS Quality of Service Solutions Configuration Guide
MPLS	•Cisco IOS Multiprotocol Label Switching Command Reference •Cisco IOS Multiprotocol Label Switching Configuration Guide

Standards

Standard	Title
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.	—

MIBs

MIB	MIBs Link
No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.	To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: http://www.cisco.com/go/mibs

RFCs

RFC	Title
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.	—

Technical Assistance

Description

Link

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http://www.cisco.com/techsupport

Feature Information for MPLS Traffic Engineering: Scalability Enhancements

Table 1 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.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

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Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

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Table 1 Feature Information for MPLS Traffic Engineering: Scalability Enhancements

Feature Name	Releases	Feature Information
MPLS Traffic Engineering: Scalability Enhancements	12.0(14)ST 12.2(14)S 12.0(22)S 12.2(28)SB 12.4(20)T	The MPLS Traffic Engineering: Scalability Enhancements feature improves scalability performance for large numbers of traffic engineering tunnels. These improvements allow an increase in the number of traffic engineering (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 contains information about and instructions on how to configure the Multiprotocol Label Switching (MPLS) traffic engineering scalability enhancements. In 12.0(14)ST, this feature was introduced. In 12.2(14)S, this feature was integrated into a Cisco IOS 12.2S release. 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 a Cisco IOS 12.2SB release. In 12.4(20)T, this feature was integrated into a Cisco IOS 12.4T release.
		The following sections provide information about this feature: •RSVP Rate Limiting •Improved Recovery Response for Signaling and Management of MPLS Traffic Engineering Tunnels •IS-IS and MPLS Traffic Engineering Topology Database Interactions •Improved Counter Capabilities for MPLS TE Tunnels Events and RSVP Signaling •Benefits of MPLS Traffic Engineering: Scalability Enhancements •Enabling RSVP Rate Limiting for MPLS Traffic Engineering Scalability Enhancements •Monitoring and Maintaining MPLS TE Scalability Enhancements The following commands were introduced or modified: clear ip rsvp counters, clear ip rsvp signalling rate-limit, clear mpls traffic-eng tunnel counters, ip rsvp signalling rate-limit, mpls traffic-eng scanner, mpls traffic-eng topology holddown sigerr, show ip rsvp counters, and show mpls traffic-eng tunnels statistics.

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.

CLNS—Connectionless Network Services. The Open System Interconnection (OSI) network layer service that does not require a circuit to be established before the data is transmitted. CLNS routes messages to their destination independently of any other messages.

CSPF—Constrained Shortest Path First. A routing protocol that calculates the shortest path based on a set of constraints, such as a minimum bandwidth requirement, maximum number of nodes, or nodes to include or exclude.

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.

LSP—label-switched path. 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.

message-pacing—The former name of the rate limiting feature.

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.

OSPF—Open Shortest Path First. A link-state, hierarchical Interior Gateway Protocol (IGP) routing protocol. derived from the Intermediate System-Intermediate System (IS-IS) protocol. OSPF features are least-cost routing, multipath routing, and load balancing.

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.

TLV—type, length, value objects. TLVs are used in data communication to provide optional information. The type field indicates the type of items in the value field. The length field indicates the length of the value field. The value field is the data portion of the packet.

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.

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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.

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