Resolving Routes for MPLS Traffic Engineering

MPLS Traffic Engineering

Contents
Executive Summary............................................................................................................................3
Demonstration Network Overview..................................................................................................4
Routing Information Databases.........................................................................................................7
Using traffic-engineering bgp..........................................................................................................11
Using IGP Shortcuts..........................................................................................................................16
Using traffic-engineering bgp-igp...................................................................................................22
Installing Single Prefixes..................................................................................................................28
Appendix A........................................................................................................................................31
RTR1...........................................................................................................................................31
RTR2...........................................................................................................................................32
RTR3...........................................................................................................................................33
RTR4...........................................................................................................................................34
RTR5...........................................................................................................................................35
RTR6...........................................................................................................................................35
RTR7...........................................................................................................................................36
Acronyms...........................................................................................................................................37

List of Figures
Figure 1: Demonstration Network Physical and Logical Topology................................................4
Figure 2: Demonstration Network BGP Topology............................................................................5
Figure 3: Demonstration Network LSP Topology.............................................................................6
Figure 4: By Default, BGP Uses Both inet.0 and inet.3....................................................................11
Figure 5: IGP Shortcuts Allow the IGP to Install Prefixes in inet.3...............................................18
Figure 6: The traffic-engineering bgp-igp Command Causes RSVP to
                 Install Prefixes into inet.0...................................................................................................22

   
List of Tables
Table 1:  Routing Tables for MPLS Traffic Engineering Route Resolution..................................7


Copyright ? 2000, Juniper Networks, Inc.


Executive Summary
Multiprotocol Label Switching (MPLS) traffic engineering maps certain data flows to
established label switched paths (LSPs) rather than to data links calculated by the IGP to be
part of the best (shortest) path. Fundamental to this function is the determination of what
traffic is to be mapped to an LSP.  
Traffic is mapped to an LSP at the tunnel's ingress label switching router (LSR) by designating
the egress LSR as the next-hop router for certain destination prefixes. It is important to
understand that the LSP does not constitute an entire route to a destination. Rather, the LSP is
a next-hop segment of the route. Therefore, packets can only be mapped to an LSP if the
egress LSR is considered to be a feasible next-hop candidate during the route resolution

process. This paper explains the various options available with Juniper Networks JUNOS
Internet software for including LSPs in the route resolution process.
This paper assumes that you understand the basics of MPLS and the JUNOS command-line
interface.
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