Farthest Node Branching | Cisco Systems Network Router instruction

Chapter 4 Planning Intermediate Route Selection

Additional Routing Features in MGX and SES Nodes

The farthest-node branch option is a PNNI enhancement that allows PNNI to use network links more efficiently. Figure 4-2demonstrates farthest-node branching.

Figure 4-2 Farthest Node Branching

Switch 1 1 SVC

Root

4 SVCs

Switch 2		Party 1
	Leaf	Party 2
		Party 3
		Party 4

Switch 3 Leaf 1,	Party 5
Leaf 2,	Party 6
Leaf 3,	Party 7
Leaf 4,	Party 8

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In Figure 4-2, Switch 2 supports branching and Switch 3 does not. When PNNI sets up the P2MP connection to parties 1 through 4, it determines that the Switch 2 outgoing interface supports branching, so PNNI establishes 1 SVC between Switch 1 and 2.

Switch 3 in Figure 4-2does not support branching, so Switch 1, which does support branching, establishes 4 SVCs to Switch 3. The destination for each SVC must be a leaf, so four leaf end points are established on Switch 3, one for each party. The four leaf end points can be on one interface, or they can be spread out on multiple interfaces. A leaf end point is an SVC endpoint.

Farthest-node branching is a PNNI feature that takes advantage of branching when it is available. Switch 1 could have originated a separate connection for each party on Switch 2, but this would have required 4 SVCs instead of 1, and all four would be carrying the same data. Farthest node branching improves network efficiency by reducing the number of SVCs required for P2MP connections and by reducing the bandwidth requirements for P2MP connections.

Previous software releases disabled branching with the branching restricted option. This option is now set by default to enable branching. If the network includes a node that does not support branching, the farthest branching node from the root creates an SVC for every downstream party.

Note This release does not support the P2MP leaf-initiated join feature, and leaf endpoints cannot use a P2MP connection to communicate with other leaf endpoints.

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

	Part Number OL-3847-01 Rev. D0, April, 2004			4-11
	Part Number OL-3847-01 Rev. D0, April, 2004			4-11

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Cisco Systems Network Router manual Farthest Node Branching

Contents

Text Part Number OL-3847-01 Rev. D0 Corporate Headquarters Copyright 2003, Cisco Systems, Inc All rights reserved Iii N T E N T S Compatible Standards Worksheets Part Number OL-3847-01 Rev. D0, April Vii G U R E S Viii B L E S Part Number OL-3847-01 Rev. D0, April Objectives AudienceOrganization Xii Conventions Documentation Notes for the April 2004 Product Releases DocumentationRelated Documentation Xiii Xiv Technical Manual Order of Use Terms Technical Manual Titles and Descriptions Xvi Xvii Xviii Xix Reference Guides Xxi Xxii Document Title Description Xxiii Xxiv Xxv Xxvi Cisco.com Obtaining DocumentationOrdering Documentation Xxvii Changes to This Document Chapter ChangesXxviii Documentation Feedback Obtaining Technical AssistanceCisco TAC Website Opening a TAC Case Obtaining Additional Publications and Information TAC Case Priority DefinitionsXxx Xxxi Xxxii Pnni Network Database Introduction to Pnni Single Peer Group Topology Example Single Peer Group Topology Hierarchical Pnni Network Topology Peer group Ppeer Simple Node Representation Peer Group Leaders Simple Node Representation Complex Node Representation Pnni Internetworking with Aini Border NodesHierarchical Pnni Network Benefits Example Pnni Internetworking with Aini Topology Pnni Internetworking with Iisp Part Number OL-3847-01 Rev. D0, April Compatible Standards Specifications Capabilities PXM45PXM1E PXM45/B SES Capabilities SES Connection Type Switch Connections CWM Endpoints Connection Limit AdjustmentsSVC DAX Spvc Install Redundant Hardware in Switches Parallel Links Between Adjacent SwitchesPhysical Network Planning Multiple Links Between Adjacent Peer Groups Planning Guidelines for Individual Peer GroupsMultiple Links to an External Network Multiple Paths Between Network Nodes Planning 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 Planning Pnni Addressing Example Selecting an ATM Address Format Planning Address Configuration Settings ESI SEL IDP DSP Supported Address Formats Guidelines for Selecting an Address Format ATM Field Description Default Values Address Registration Authorities Selecting a Pnni LevelCategory Type Authorities DCC 4shows 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 Length Selecting the Pnni Peer Group ID Default Peer Group ID 20-byte Node Address Selecting the ATM Address Selecting 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 Ports Closed User Group Example Closed User Group Overview Planning CUG Configuration Settings Selecting an Interlock CodeSelecting an Index Selecting CPE Addresses Selecting Internal CUG Access Options Specifying a Preferential CUG Selecting External CUG Access Options Worksheets Selecting a Default CUG Address CUG 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 Service Class Acronym Definition Guidelines Class of Service TablesCTD CDV Traffic Metric How SPVCs and SPVPs use the SPTs How SVCs and SVPs use the SPTs How MGX and SES Nodes Select Links On-Demand RoutingLoad Balancing for SPT and On-Demand Routing Service Additional Routing Features in MGX and SES NodesPreferred Routing CLR0+12 Grooming Priority Routing Priority Bumping Soft ReroutingBlocking Pass-Through Connections Nodal Point-to-Multipoint Branch Restriction AXSM/B AXSM/AAXSM-E AXSM-XG Farthest Node Branching Part Number OL-3847-01 Rev. D0, April Aesa ABRAini Ansi APS CBR P2MPCTD IN-2 CWM CUGDIN IN-3 IN-4 Pnni PGLMGX SES IN-5 IN-6 UNI UBRTAC IN-7 IN-8