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Specialized Models User Guide

6

MPLS Model User Guide

Modeler/Release 10.0

SPM-6-1

6

MPLS Model User Guide

Multi-Protocol Label Switching (MPLS) is a multi-layer switching technology that 
uses labels to determine how packets are forwarded through a network. The 
first part of this document describes key features of the MPLS specialized model 
and the second part focuses on procedures for configuring MPLS in your 
network model.

Model Features

This section contains a list of the main features available in the Multi-Protocol 
Label Switching model:

The MPLS model captures the following protocol behavior:

Table 6-1   MPLS Model Features

Feature

Description

LSP (Label Switched Path) configuration

• LSPs can be created manually or 

automatically from traffic conversation 
pairs.

• LSPs are easily reused in other scenarios 

or projects by using the LSP import and 
export features.

• Both dynamic and static LSPs are created 

using the path object.

Differential Services (DiffServ)

• DiffServ extensions, as defined in 

RFC-2475, are provided.

• The model enables you to perform QoS 

(quality of service) analyses by accounting 
for different types of service.

Traffic Engineering

Traffic engineered routes are computed 
using Constrained Shortest Path First 
(CSPF) with OSPF or IS-IS routing protocols. 

End of Table 6-1

Summary of Contents for 6 MPLS

Page 1: ...odel The MPLS model captures the following protocol behavior Table 6 1 MPLS Model Features Feature Description LSP Label Switched Path configuration LSPs can be created manually or automatically from traffic conversation pairs LSPs are easily reused in other scenarios or projects by using the LSP import and export features Both dynamic and static LSPs are created using the path object Differential...

Page 2: ...itecture LSP routing OSPF TE IS IS TE RFC 2676 QoS Routing and OSPF Extensions Label distribution LDP RFC 3036 LDP Specification CR LDP RFC 3212 Constraint based LSP Setup Using LDP RSVP TE RFC 3209 RSVP TE Extensions to RSVP for LSP Tunnels PP VPNs A framework for layer 3 PP VPNs RFC 2547 BGP MPLS VPNs BGP MPLS VPNs draft ietf ppvpn framework 05 Quality of Service QOS Architecture RFC 2475 An Arc...

Page 3: ... the MPLS configuration object Router specific MPLS attributes are grouped in the MPLS Parameters attribute on each router They are described in Router Attributes on page SPM 6 6 MPLS Configuration Object Attributes Some of the important MPLS configuration object attributes are described below FEC Specifications This attribute specifies the Forwarding Equivalence Class FEC parameters used by MPLS ...

Page 4: ... row and by taking a logical OR of each of the rows In other words for a packet to qualify for a particular FEC the IP header fields must satisfy every condition of at least one row of the defined FEC For example a FEC that consists only of email and ftp traffic would be specified as shown in Figure 6 3 Figure 6 3 FEC Details for E mail and FTP Traffic Therefore if the IP header of a packet contai...

Page 5: ...fies out of profile actions and traffic classes for traffic trunks in the network Traffic trunks capture traffic characteristics such as peak rate average rate and average burst size The default Trunk Details setting configures a trunk with a value of 32 000 bits sec for maximum and average bit rate and 32 000 bits for maximum burst size Figure 6 4 Specifying Traffic Trunk Profiles EXP Drop Preced...

Page 6: ...gs between FECs and LSPs Each row of the Traffic Mapping Configuration table specifies a distinct traffic engineering TE binding Each TE binding specifies the FEC traffic trunk and LSP that is applied to the label of the incoming packet Only previously defined values appear in the attribute pull down lists If no values appear in the attribute pull down lists verify that you have defined the FECs a...

Page 7: ... TE binding Figure 6 6 Configuring TE Bindings EXP Drop Precedence and EXP PHB These attributes specify which mappings defined in the MPLS configuration object are used by the router LDP Parameters specifies Label Distribution Protocol parameters used by the LSR LDP Parameters is a compound attribute composed of the following sub attributes Discovery Configuration specifies Hello message parameter...

Page 8: ...hat traverses the failed node or link The default value for this attribute is 45 seconds LDP Discovery End Time specifies when LDP discovery ends After this time no more LDP discovery packets are sent through the network This value should occur after the network reaches a final constant state in the simulation since no network topology or device status changes are reflected in the LDP routing tabl...

Page 9: ...e experimental bits in the shim header carry the Diff Serv information This provides eight different types of service TOS per LSP For L LSP TOS information is contained in the MPLS label and all packets traversing the link are treated equally Path Details specifies which packets use the LSP and defines how packets are forwarded through the LSP This attribute is automatically configured for dynamic...

Page 10: ...ameters Configuration TE Parameters specifies the traffic engineering constraints used by CR LDP to find a route through the network CR LDP uses Constrained Routing to find the route that is the best fit for the specified constraints This attribute applies to dynamic LSPs only Make sure you account for network bandwidth availability when configuring static LSPs Figure 6 12 TE Parameters Configurat...

Page 11: ...ues for bandwidth delay and hop counts in the LSP Hide some or all of the LSPs from view in the Project Editor workspace Export LSP configuration details to a file Figure 6 13 Using the LSP Browser These attributes set the LSP s Path Details and Setup TE and Recovery Parameters attributes Clicking here toggles the display settings the workspace is immediately refreshed to show or hide the LSPs Cli...

Page 12: ...y utilization and the amount of traffic on the LSP These statistics can be collected on a per flow or per LSP basis where flows are individual flows of traffic within an LSP Figure 6 14 Selecting Statistics to Collect When analyzing your MPLS network you may also want to look at the routes used for the LSPs You can do this by selecting the Protocols MPLS Display LSP Routes menu item ...

Page 13: ...P Details operation creates traffic profiles and forward equivalence classes FECs for the LSPs which you can modify later as you fine tune your model The model supports both static and dynamic LSPs using the strict and loose path objects in OPNET To create LSPs use the standard procedure for creating paths as described in the Building Models chapter of the User Guide manual Guru product documentat...

Page 14: ...path When a specific link is selected for the LSP path that hop is marked as strict and the LSP is always set up through that link Use this method to indicate that certain routers or links must be used when routing packets in an LSP If a node or link on a dynamic LSP s route fails the ingress LER automatically tries to find an alternate route However if the failed link or node is marked as strict ...

Page 15: ...k failures For this reason you should always specify at least one backup route when configuring static LSPs in your network Procedure 6 3 Creating Static LSPs 1 Click on the MPLS_E LSP_STATIC object in the MPLS object palette 2 In the project workspace click on the LSP s ingress LER 3 Click on the next link or router in the LSPs route The tooltips indicate which links and routers can be added to t...

Page 16: ...C assign a name then double click in the Details column to describe the FEC End of Procedure 6 4 To work correctly the model requires that you set up at least one default traffic trunk Additional trunks can be used to handle prioritized flows Procedure 6 5 Creating a Default Traffic Trunk 1 Place an MPLS configuration object in the project workspace and open its Attributes dialog box 2 Double clic...

Page 17: ...ion 2 Add a row to the table 3 Click in the Interface In column and specify which interfaces the binding applies to in the Interface Binding Specification table To select an interface click in the Apply Binding column for that interface to toggle the value to Yes The interface s you selected appear in the Traffic Mapping Configuration dialog box Note that the interface number for higher layers cor...

Page 18: ...7 The exported file contains the attribute settings of all LSPs in the network You can use the file as is in other scenarios or you can modify the file to add remove or change LSPs Notice that the LSP configuration file closely resembles the Path Details table for each LSP Procedure 6 8 Using an LSP Configuration File in a Scenario 1 Open the MPLS Configuration object s Attributes dialog box 2 Sel...

Page 19: ... for the different classes in the MPLS configuration object To do this use Procedure 6 5 on page SPM 6 16 to create a default traffic trunk However instead of setting the Trunk Details attribute to Default double click to set the traffic profile out of profile actions and traffic class of each trunk To configure quality of service parameters edit the Priority Queuing Profiles DSCP Based attribute ...

Page 20: ...PM 6 20 Modeler Release 10 0 If you change the queuing scheme later make sure you reset the queuing profile because the order of these steps is important Figure 6 15 Configuring QoS on an LER Always set the Queuing Scheme before setting the Queuing Profile ...

Page 21: ...it LSP Information Opens the LSP browser Import LSP Information Imports LSP information from files Display LSP Routes Displays the routes chosen by CR LDP Does not display link statistic information Hide all LSP Routes Hides LSP route display Show All LSPs Displays hidden LSPs in the workspace This operation does not display LSPs which are configured only in the LSP configuration file To display t...

Page 22: ...When the IP module of an LSR receives labeled packets or packets with matching FEC descriptions it performs no IP processing on the packet Instead the packet is re directed to the mpls_mgr process for MPLS forwarding mpls_mgr uses ILM incoming label map and FTN FEC to NHLFE maps to forward packets mpls_ldp_mgr Implements the LDP control plane in the LDP module of all routers This process is the di...

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