Cisco Systems Network Router How SVCs and SVPs use the SPTs, How SPVCs and SPVPs use the SPTs

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Chapter 4 Planning Intermediate Route Selection

How MGX and SES Nodes Select Routes

Each class of service SPT is simply a list of the shortest paths for a particular routing metric to all known destinations. AW SPTs list the shortest paths or routes based on the lowest cumulative AW, and CTD SPTs list the shortest routes based on the lowest cumulative CTD.

The number of shortest paths stored in a SPT for any destination depends on whether there are multiple routes with the lowest routing metric value. For example, if three routes to a destination all have the same minimum CDV value, all three routes are listed in the CDV table for the appropriate class of service.

There is also a range option that you can use to make the SPTs store routes with similar values. For example, you can configure the switch to store routes that are within 5 percent of the shortest route in the table. Up to five routes can be listed in a SPT for a destination.

The default configuration of MGX and SES nodes creates all 10 class of service tables. If you do not plan to use the routing tables for a particular routing metric, you can save processor resources by disabling the construction and maintenance of the appropriate routing metric SPTs (using the cnfpnni-routing-policycommand).

Note If you disable the creation of one or more groups of SPTs and a connection attempts to use a missing table, the switch uses on-demand routing to locate a conforming route for the connection.

How SVCs and SVPs use the SPTs

SVCs and SVPs are initiated by CPE using UNI connections to the switch. UNI versions 3.0 and 3.1 cannot request a CTD or CDV value for a connection, so all UNI 3.0 and 3.1 connections are routed using the AW SPTs.

UNI 4.0 connections can request CTD and CDV values for a connection. UNI 4.0 connections use the SPTs in one of the following ways:

•If no CTD or CDV value is requested for the connection, the connection uses a route from the AW SPT for the appropriate class of service.

•If a CTD or CDV value is requested for the connection, the connection uses a route from the appropriate CTD or CDV SPT for the appropriate class of service.

•If both a CTD and a CDV value is requested for the connection, the connection uses a route from the CTD SPT for the appropriate class of service. The route chosen is a route that conforms to the CTD and CDV values requested. If a conforming route is not available in the SPT, on demand routing is used to find a conforming route.

How SPVCs and SPVPs use the SPTs

The default configuration for each SPVC and SPVP uses the appropriate AW SPT for each class of service. However, you can configure requested values for AW, CTD, and CDV for each connection using the addcon and cnfcon commands.

If multiple routing metrics are specified for an SPVC or SPVP, the switch searches the SPTs for conforming routes according to following priorities:

1.AW

2.CTD

3.CDV

For example if all three routing metrics are specified, the switch searches for conforming routes in the AW SPTs. If CTD and CDV are specified, the switch searches the CTD SPTs.

 

 

Cisco PNNI Network Planning Guide for MGX and SES Products, Release 5

 

 

 

 

 

 

Part Number OL-3847-01 Rev. D0, April, 2004

 

 

4-5

 

 

 

 

 

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Contents Text Part Number OL-3847-01 Rev. D0 Corporate HeadquartersCopyright 2003, Cisco Systems, Inc All rights reserved Iii N T E N T SCompatible Standards Worksheets Part Number OL-3847-01 Rev. D0, April Vii G U R E SViii B L E S Part Number OL-3847-01 Rev. D0, April Objectives AudienceOrganization Xii ConventionsXiii DocumentationDocumentation Notes for the April 2004 Product Releases Related DocumentationXiv Technical Manual Order of UseTerms Technical Manual Titles and DescriptionsXvi Xvii Xviii Xix Reference Guides Xxi Xxii Document Title DescriptionXxiii Xxiv Xxv Xxvi Xxvii Obtaining DocumentationCisco.com Ordering DocumentationChanges to This Document Chapter ChangesXxviii Opening a TAC Case Obtaining Technical AssistanceDocumentation Feedback Cisco TAC WebsiteObtaining Additional Publications and Information TAC Case Priority DefinitionsXxx Xxxi Xxxii Pnni Network Database Introduction to PnniSingle Peer Group Topology Example Single Peer Group Topology Hierarchical Pnni Network TopologyPeer group Ppeer Simple Node Representation Peer Group LeadersSimple Node Representation Complex Node RepresentationPnni Internetworking with Aini Border NodesHierarchical Pnni Network Benefits Example Pnni Internetworking with Aini Topology Pnni Internetworking with IispPart Number OL-3847-01 Rev. D0, April Compatible Standards SpecificationsPXM45/B PXM45Capabilities PXM1ESES Capabilities SESDAX Spvc Connection Limit AdjustmentsConnection Type Switch Connections CWM Endpoints SVCInstall Redundant Hardware in Switches Parallel Links Between Adjacent SwitchesPhysical Network Planning Multiple Paths Between Network Nodes Planning Guidelines for Individual Peer GroupsMultiple Links Between Adjacent Peer Groups Multiple Links to an External NetworkPlanning Guidelines for Hierarchical Networks Planning Guidelines for Peer Group LeadersPlanning Guidelines for Border Nodes Part Number OL-3847-01 Rev. D0, April Address Planning Overview Address and Closed User Group PlanningPnni Addressing Example Selecting an ATM Address Format Planning Address Configuration SettingsESI SEL IDP DSP Supported Address FormatsGuidelines for Selecting an Address Format ATM Field Description Default ValuesDCC Selecting a Pnni LevelAddress Registration Authorities Category Type Authorities4shows an example topology of a Pnni MPG WAN Part Number OL-3847-01 Rev. D0, April Level Peer Group ID Portion of ATM Address Bytes LengthSelecting the Pnni Peer Group ID Default Peer Group ID20-byte Node Address Selecting the ATM AddressSelecting the Ilmi Address Prefix Selecting the Spvc Address PrefixPlanning Address Prefixes for Aini and Iisp Links Additional Guidelines for Creating an Address Plan Selecting Static Addresses for UNI PortsClosed User Group Example Closed User Group OverviewPlanning CUG Configuration Settings Selecting an Interlock CodeSelecting an Index Selecting CPE Addresses Selecting Internal CUG Access OptionsSpecifying a Preferential CUG Selecting External CUG Access OptionsWorksheets Selecting a Default CUG AddressCUG Part Number OL-3847-01 Rev. D0, April Administrative Weight How MGX and SES Nodes Select RoutesLink and Route Metrics Cell Transfer Delay Cell Delay VariationAvailable Cell Rate Shortest Path Table Routing Maximum Cell RateShortest Path Tables Traffic Metric Class of Service TablesService Class Acronym Definition Guidelines CTD CDVHow SPVCs and SPVPs use the SPTs How SVCs and SVPs use the SPTsHow MGX and SES Nodes Select Links On-Demand RoutingLoad Balancing for SPT and On-Demand Routing CLR0+12 Additional Routing Features in MGX and SES NodesService Preferred RoutingGrooming Priority RoutingNodal Point-to-Multipoint Branch Restriction Soft ReroutingPriority Bumping Blocking Pass-Through ConnectionsAXSM-XG AXSM/AAXSM/B AXSM-EFarthest Node Branching Part Number OL-3847-01 Rev. D0, April Ansi APS ABRAesa AiniIN-2 P2MPCBR CTDIN-3 CUGCWM DININ-4 IN-5 PGLPnni MGX SESIN-6 IN-7 UBRUNI TACIN-8
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