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Questions and Answers

What is a scalability constraint of the IGP in use?

  • Reconvergence at Layer 2
  • Full mesh of VCs
  • Reconvergence at Layer 3 (correct)
  • Class of Service (CoS) differentiation

    • What is the main advantage of implementing MPLS TE?

  • Combination of ATM's TE capabilities with ATM's CoS
  • Combination of IP's TE capabilities with ATM's CoS
  • Combination of IP's TE capabilities with IP's CoS
  • Combination of ATM's TE capabilities with IP's CoS (correct)

    • What controls the path taken by traffic in MPLS TE?

  • PE2-AS1 router
  • Tailend router in the network
  • Headend router in the network (correct)
  • PE1-AS1 router

    • What is the result of implementing MPLS TE in an IP network?

    <p>Transformation into a label switched domain</p> Signup and view all the answers

    What is the primary goal of using TE in IP networks?

    <p>To enable better bandwidth management and utilization</p> Signup and view all the answers

    What is the limitation of traditional IP forwarding paradigm?

    <p>Suboptimal use of available bandwidth</p> Signup and view all the answers

    What is the role of RSVP in MPLS TE?

    <p>To provide TE functionality</p> Signup and view all the answers

    What is the result of inefficient use of available bandwidth in IP networks?

    <p>Packet drops</p> Signup and view all the answers

    What is the purpose of the PATH message in MPLS TE domain?

    <p>To request label allocation</p> Signup and view all the answers

    Where is the RSVP RESERVATION message generated?

    <p>At the tailend router</p> Signup and view all the answers

    What does the RSVP RESERVATION message perform?

    <p>Label assignment</p> Signup and view all the answers

    In which direction is label allocation and distribution performed?

    <p>Downstream-on-demand</p> Signup and view all the answers

    What happens when there is unavailability of requested resources?

    <p>The router generates RSVP error messages</p> Signup and view all the answers

    What is the function of PATH messages?

    <p>Reservation requests</p> Signup and view all the answers

    At which router is the label mapping to a TE LSP first generated?

    <p>Tailend router</p> Signup and view all the answers

    What is propagated upstream in the MPLS TE domain?

    <p>Local labels mapping to a TE tunnel</p> Signup and view all the answers

    What happens if Router P1-AS1 cannot accommodate the requested resources as defined in the PATH message?

    <p>It sends a PATH ERROR message to its upstream LSR PE1-AS1.</p> Signup and view all the answers

    What type of message does the tailend router generate if the PATH message successfully reaches it?

    <p>RESERVATION message</p> Signup and view all the answers

    What does RSVP create to clear PATH or RESERVATION states on a router?

    <p>Tear messages</p> Signup and view all the answers

    What is the purpose of tear messages in RSVP?

    <p>To enable the reuse of resources on the router for other requests</p> Signup and view all the answers

    When is a PATH tear message usually generated?

    <p>In inter-area LSP creation where the inter-area LSP is not configured to be fast reroutable</p> Signup and view all the answers

    What happens to the corresponding path option after a PATH tear message is generated?

    <p>It is marked as invalid for a certain amount of time</p> Signup and view all the answers

    What happens when a link failure occurs within an area?

    <p>The LSR to which the failed link is directly attached generates an RSVP PATH error and a RESV tear message</p> Signup and view all the answers

    What is sent by the headend after receiving an RESV tear message?

    <p>A PATH tear message</p> Signup and view all the answers

    What does P2-AS1 update and append to depict the local outgoing interface in the path of the LSP tunnel?

    <p>RECORD_ROUTE object</p> Signup and view all the answers

    What is triggered at the tailend router PE2-AS1 after receiving the RSVP PATH message?

    <p>Creation of a RESERVATION message</p> Signup and view all the answers

    What type of label is assigned to the LSP tunnel by PE2-AS1?

    <p>POP label</p> Signup and view all the answers

    What is reinitiated in the RESERVATION message?

    <p>RECORD_ROUTE object</p> Signup and view all the answers

    What happens to the RECORD_ROUTE object when the RESERVATION message reaches P2-AS1?

    <p>It is prepended with the outgoing interface</p> Signup and view all the answers

    What is generated and mapped in the LABEL object at P2-AS1?

    <p>Local label mapping to the LSP tunnel</p> Signup and view all the answers

    What is removed by P1-AS1 from the EXPLICIT_ROUTE object?

    <p>References to its local interface</p> Signup and view all the answers

    What is assigned an arbitrary value of 3 in Figure?

    <p>LABEL value</p> Signup and view all the answers

    What is the purpose of the RESERVATION message?

    <p>To notify the originating node about the actual route/path</p> Signup and view all the answers

    What is the purpose of the SESSION_ATTRIBUTE message?

    <p>To define the characteristics of the specific LSP tunnel</p> Signup and view all the answers

    What is the purpose of the EXPLICIT_ROUTE message?

    <p>To calculate the next hops using constraint-based SPF</p> Signup and view all the answers

    What is the purpose of the PATH message?

    <p>To contain the information outlined in Table 4</p> Signup and view all the answers

    What is the PHOP set to in the EXPLICIT_ROUTE message?

    <p>The router's outgoing interface address</p> Signup and view all the answers

    What is the purpose of the SESSION message?

    <p>To define the source and destination of the LSP tunnel</p> Signup and view all the answers

    What is the Record_Route (RRO) populated with in the EXPLICIT_ROUTE message?

    <p>The same address as the PHOP</p> Signup and view all the answers

    What is the purpose of the RSVP messages during the path setup process?

    <p>To identify the significance of each message type and its contents</p> Signup and view all the answers

    What does the data plane ingress router require for building an MPLS TE tunnel?

    <p>Information about resource availability on all links</p> Signup and view all the answers

    What is used to flood information about links to all routers in the IGP domain?

    <p>IGPs like OSPF and IS-IS</p> Signup and view all the answers

    What is the backbone of TE tunnel definition?

    <p>Constraint-Based Routing</p> Signup and view all the answers

    What is calculated using a constrained SPF calculation?

    <p>Probable paths from a source to destination</p> Signup and view all the answers

    What is the primary goal of Traffic Engineering in IP networks?

    <p>To facilitate efficient use of available bandwidth</p> Signup and view all the answers

    What is the purpose of RSVP in MPLS TE?

    <p>To reserve resources for TE tunnels</p> Signup and view all the answers

    What is the function of RSVP-TE in MPLS networks?

    <p>To reserve network resources for data communication sessions</p> Signup and view all the answers

    What happens when a link does not have the requested resources?

    <p>The link is not chosen for the TE tunnel</p> Signup and view all the answers

    What is the result of efficient bandwidth utilization in IP networks?

    <p>Optimized traffic engineering</p> Signup and view all the answers

    What is the role of MPLS in traffic engineering?

    <p>To replicate and expand upon the TE capabilities of Layer 2 ATM and Frame Relay networks</p> Signup and view all the answers

    What type of TLV is used in IS-IS to transmit resource availability information?

    <p>Type 22</p> Signup and view all the answers

    What is enhanced in an IP network when implementing MPLS TE?

    <p>Least cost routing</p> Signup and view all the answers

    What is the purpose of a TE tunnel configuration?

    <p>To facilitate efficient use of available bandwidth between routers</p> Signup and view all the answers

    What is MPLS TE used for in service provider networks?

    <p>To replicate and expand upon the TE capabilities of Layer 2 ATM and Frame Relay networks</p> Signup and view all the answers

    What is the benefit of MPLS TE in IP networks?

    <p>Efficient bandwidth utilization between routers</p> Signup and view all the answers

    What is the purpose of RSVP-TE in MPLS TE?

    <p>To reserve network resources for data communication sessions</p> Signup and view all the answers

    What is the primary function of TE in an MPLS network?

    <p>To map flows between two routers efficiently</p> Signup and view all the answers

    What is the purpose of configuring TE tunnels on PE routers?

    <p>To enable efficient bandwidth utilization</p> Signup and view all the answers

    What is the characteristic of TE tunnels configured on routers?

    <p>They are uni-directional</p> Signup and view all the answers

    What is the result of implementing MPLS TE?

    <p>Efficient use of available bandwidth</p> Signup and view all the answers

    Where are all pertinent tunnel configurations performed in an MPLS network?

    <p>On PE routers</p> Signup and view all the answers

    What is the purpose of TE in MPLS networks?

    <p>To link edge routers across the core network</p> Signup and view all the answers

    What can be configured on TE tunnels to provide preferential treatment?

    <p>Class-based traffic management</p> Signup and view all the answers

    What is the main purpose of Traffic Engineering (TE) in IP networks?

    <p>To enable better bandwidth management and utilization</p> Signup and view all the answers

    Why are pairs of tunnels configured on both PE routers in a bidirectional TE deployment?

    <p>To implement bidirectional TE deployment</p> Signup and view all the answers

    What is the primary issue with traditional IP forwarding paradigm?

    <p>Suboptimal use of available bandwidth</p> Signup and view all the answers

    What is the role of RSVP in MPLS TE?

    <p>To request and confirm the LSP, reserve resources, and apply MPLS labels</p> Signup and view all the answers

    What is the purpose of TE in IP networks?

    <p>To enable better bandwidth management and utilization</p> Signup and view all the answers

    What is the result of implementing MPLS TE in an IP network?

    <p>Relief of temporary congestion in the core of the network</p> Signup and view all the answers

    What is the result of implementing MPLS TE in an IP network?

    <p>The IP network is transformed into a label switched domain</p> Signup and view all the answers

    What is the function of the RECORD_ROUTE object in MPLS TE?

    <p>To identify the traffic engineered LSP associated with a specific bandwidth or resource requirement</p> Signup and view all the answers

    What is the role of RSVP in MPLS TE?

    <p>To establish and maintain TE label switched paths</p> Signup and view all the answers

    What is the purpose of the RESERVATION message in MPLS TE?

    <p>To confirm the LSP and reserve resources</p> Signup and view all the answers

    How does MPLS TE manage bandwidth in an IP network?

    <p>By dynamically allocating bandwidth based on resource availability</p> Signup and view all the answers

    What is the advantage of using MPLS TE over ATM?

    <p>MPLS TE does not require a full mesh of VCs</p> Signup and view all the answers

    What is the purpose of TE label switched paths in MPLS TE?

    <p>To define paths that can be used by traffic between PE1-AS1 and PE2-AS1</p> Signup and view all the answers

    What is the benefit of using TE in IP networks?

    <p>Better bandwidth management and utilization</p> Signup and view all the answers

    What is the benefit of using MPLS TE in IP networks?

    <p>It enables better bandwidth management and utilization</p> Signup and view all the answers

    What is the role of the PATH message in MPLS TE?

    <p>To request resources for the LSP</p> Signup and view all the answers

    What is the primary component of MPLS TE that provides CoS differentiation?

    <p>TE label switched paths</p> Signup and view all the answers

    What does the PATH message check at each hop?

    <p>Resource availability</p> Signup and view all the answers

    Which router generates the RSVP RESERVATION message?

    <p>Tailend router</p> Signup and view all the answers

    What happens when a router cannot accommodate the requested resources?

    <p>RSVP error messages are sent</p> Signup and view all the answers

    What is the function of the RSVP RESERVATION message?

    <p>Label assignment and confirmation</p> Signup and view all the answers

    What is the direction of label allocation and distribution in MPLS TE?

    <p>Downstream</p> Signup and view all the answers

    What is the purpose of the PATH message in MPLS TE domain?

    <p>Resource availability check</p> Signup and view all the answers

    Where is the label mapping to a TE LSP first generated?

    <p>Tailend router</p> Signup and view all the answers

    What is propagated upstream in the MPLS TE domain?

    <p>Local labels mapping to a TE tunnel</p> Signup and view all the answers

    What is the primary purpose of adding a RESERVATION to a PATH or RESERVATION message?

    <p>To notify the originating node about the actual route/path that the LSP TE tunnel traverses</p> Signup and view all the answers

    What is usually identified by IP addresses of corresponding loopback interfaces on headend and tailend routers?

    <p>SESSION</p> Signup and view all the answers

    What is populated by the list of next hops that are either manually specified or calculated using constraint-based SPF?

    <p>EXPLICIT_ROUTE</p> Signup and view all the answers

    What does the Record_Route (RRO) get populated with in the EXPLICIT_ROUTE message?

    <p>The same IP address as the outgoing interface address</p> Signup and view all the answers

    What is defined in the SESSION_ATTRIBUTE message?

    <p>The characteristics of the specific LSP tunnel</p> Signup and view all the answers

    What is the purpose of the PATH message in RSVP-TE?

    <p>To send the information outlined in Table 4</p> Signup and view all the answers

    What is set to the router's outgoing interface address in the EXPLICIT_ROUTE message?

    <p>PHOP</p> Signup and view all the answers

    What is used to identify the significance of each message type and its contents during the path setup process for LSP TE tunnels?

    <p>RSVP messages containing one or more of these extensions</p> Signup and view all the answers

    What is the purpose of the LABEL_REQUEST object in RSVP signaling?

    <p>To request a label mapping to the TE tunnel or LSP</p> Signup and view all the answers

    What is carried in PATH messages to request or confirm a specific path/route for the tunnel?

    <p>EXPLICIT_ROUTE object</p> Signup and view all the answers

    What is the function of RECORD_ROUTE object in RSVP signaling?

    <p>Similar to a record option with ICMP ping</p> Signup and view all the answers

    Which router computes the ordered list of IP addresses that identifies the next hops along the path of the TE tunnel or LSP?

    <p>Headend router</p> Signup and view all the answers

    What is the result of a CSPF or CBR calculation on the headend router?

    <p>An ordered list of IP addresses that identifies the next hops along the path of the TE tunnel or LSP</p> Signup and view all the answers

    What is generated by the tailend router in the RESERVATION message?

    <p>LABEL object</p> Signup and view all the answers

    What is the function of RSVP extensions in MPLS TE?

    <p>To implement TE in an MPLS environment</p> Signup and view all the answers

    What is propagated upstream in the RSVP signaling process?

    <p>LABEL object and the RESERVATION message</p> Signup and view all the answers

    What is the function of the SENDER_TEMPLATE object in the path message?

    <p>To define the interface address that will be used as the LSP-ID for the tunnel</p> Signup and view all the answers

    What is the purpose of the EXPLICIT_ROUTE object in the path message?

    <p>To identify the next hop in the tunnel path</p> Signup and view all the answers

    What happens when the L-bit is set in the RSVP path message?

    <p>The router performs a constrained-SPF calculation to identify the next hop in the tunnel path</p> Signup and view all the answers

    What happens when the L-bit is unset in the RSVP path message?

    <p>The router knows it is directly connected to the next hop in the LSP tunnel path</p> Signup and view all the answers

    What is the function of the RECORD_ROUTE object in the path message?

    <p>To depict the local router's outgoing interface address in the path of the LSP tunnel</p> Signup and view all the answers

    What is the function of the headend router in the path message propagation?

    <p>To apply the appropriate values for the fields mentioned in the Table</p> Signup and view all the answers

    What is the primary purpose of Traffic Engineering in IP networks?

    <p>To enable efficient use of available bandwidth</p> Signup and view all the answers

    What happens when P1-AS1 receives the PATH message?

    <p>The router checks the EXPLICIT_ROUTE object to see if the next hop is a directly connected network</p> Signup and view all the answers

    What is the function of the PATH message in the MPLS TE domain?

    <p>To request resources for the LSP tunnel</p> Signup and view all the answers

    What happens when the RESERVATION message is received by PE1-AS1?

    <p>The labels mapped to the LSP are used to form the MPLS LSP</p> Signup and view all the answers

    What is the role of RSVP in MPLS TE?

    <p>To reserve resources and apply MPLS labels to form the MPLS LSP</p> Signup and view all the answers

    What is the result of implementing MPLS TE in an IP network?

    <p>Temporary congestion in the core of the network is relieved</p> Signup and view all the answers

    What is the function of the RECORD_ROUTE object in MPLS TE?

    <p>To identify the traffic engineered LSP associated with a specific bandwidth</p> Signup and view all the answers

    What is the purpose of MPLS TE in IP networks?

    <p>To enable better bandwidth management and utilization</p> Signup and view all the answers

    What happens when there is unavailability of requested resources in MPLS TE?

    <p>The traffic is routed to an alternative path</p> Signup and view all the answers

    What is the benefit of using MPLS TE in IP networks?

    <p>Efficient use of available bandwidth</p> Signup and view all the answers

    What is a key aspect of implementing a scalable and efficient TE methodology in the core of the network?

    <p>Gathering information on traffic patterns to establish bandwidth guarantees</p> Signup and view all the answers

    What is the purpose of configuring TE tunnels on PE routers in an MPLS network?

    <p>To map flows between two routers for efficient use of available bandwidth</p> Signup and view all the answers

    What is required to implement bidirectional TE deployment between two routers?

    <p>Configuring a pair of TE tunnels on each router</p> Signup and view all the answers

    What can MPLS TE map to certain classes of traffic versus destinations?

    <p>To certain classes of traffic versus destinations</p> Signup and view all the answers

    What is the role of RSVP in MPLS TE?

    <p>To perform label allocation and distribution</p> Signup and view all the answers

    Where are all pertinent tunnel configurations performed in an MPLS network?

    <p>On provider edge (PE) routers</p> Signup and view all the answers

    What is the result of efficient bandwidth utilization in IP networks?

    <p>Relieved temporary congestion in the core of the network</p> Signup and view all the answers

    What is the primary purpose of TE tunnels in MPLS TE?

    <p>To link edge routers across the core of the service provider network</p> Signup and view all the answers

    What happens when CE1-A sends 45 Mbps of traffic and CE1-B sends 10 Mbps of traffic simultaneously?

    <p>Packets will be dropped at PE1-AS1</p> Signup and view all the answers

    Why is implementing TE using IP not feasible in an SP environment?

    <p>The number of routers is large</p> Signup and view all the answers

    What is the inherent problem with implementing ATM for TE?

    <p>Flooding of messages on the network</p> Signup and view all the answers

    Why is TE necessary in IP networks?

    <p>To utilize available bandwidth</p> Signup and view all the answers

    What is the limitation of traditional IP forwarding paradigm?

    <p>Inefficient use of available bandwidth</p> Signup and view all the answers

    What is the purpose of configuring PVCs between routers PE1-AS1 and PE2-AS1?

    <p>To implement TE</p> Signup and view all the answers

    What is the result of load balancing or using PATH1 and PATH2 equally in IP networks?

    <p>Efficient use of available bandwidth</p> Signup and view all the answers

    What is required to implement TE using IP in IP networks?

    <p>Implementing IGP features</p> Signup and view all the answers

    What is the primary reason for using Traffic Engineering in IP networks?

    <p>To provide better performance and avoid packet drops</p> Signup and view all the answers

    What is the result of implementing MPLS TE in an IP network?

    <p>The IP network transforms into a label switched domain</p> Signup and view all the answers

    What is the function of RSVP in MPLS TE?

    <p>To enable path setup and reservation in MPLS TE</p> Signup and view all the answers

    What is the advantage of using MPLS TE over traditional IP forwarding?

    <p>Efficient use of available bandwidth and better bandwidth management</p> Signup and view all the answers

    What is the characteristic of MPLS TE label switched paths?

    <p>They are setup and reserved using RSVP</p> Signup and view all the answers

    What is the goal of TE in IP networks?

    <p>To improve bandwidth utilization and management</p> Signup and view all the answers

    What is the requirement for implementing MPLS TE?

    <p>RSVP is required for path setup and reservation</p> Signup and view all the answers

    What is the consequence of inefficient use of available bandwidth in IP networks?

    <p>Packet drops and poor performance</p> Signup and view all the answers

    What is the primary function of RSVP in MPLS TE environment?

    <p>To reserve resources along the path of the LSP tunnel</p> Signup and view all the answers

    What is used to calculate resource availability and link status information in MPLS TE?

    <p>Constrained SPF calculation</p> Signup and view all the answers

    What is the purpose of the type 10 LSA in OSPF?

    <p>To provide resource and link status information</p> Signup and view all the answers

    What is the inspiration behind MPLS TE?

    <p>Constraint-based routing</p> Signup and view all the answers

    What happens when a link does not have the requested resources?

    <p>The link is not chosen as part of the LSP tunnel</p> Signup and view all the answers

    What information is required by the data plane ingress router to build an MPLS TE tunnel?

    <p>Resource availability information</p> Signup and view all the answers

    What is the backbone of TE tunnel definition?

    <p>Constraint-based routing</p> Signup and view all the answers

    What is used to flood information about links to all routers in the IGP domain?

    <p>IGP</p> Signup and view all the answers

    What is the primary function of MPLS label switching in TE tunnels?

    <p>To forward traffic along the defined TE tunnel path</p> Signup and view all the answers

    What is the purpose of using OSPF or IS-IS with extensions for TE?

    <p>To carry information pertaining to the tunnel configured on a router</p> Signup and view all the answers

    What determines the path taken by traffic in an MPLS TE network?

    <p>The IGP used in the core</p> Signup and view all the answers

    What is the result of implementing MPLS TE in an IP network?

    <p>Controlled paths for traffic flow</p> Signup and view all the answers

    How are TE tunnels assigned in the network?

    <p>Through dynamic signaling using RSVP-TE</p> Signup and view all the answers

    What is the primary goal of bandwidth management in MPLS TE?

    <p>To control the amount of bandwidth allocated to tunnels</p> Signup and view all the answers

    What is the purpose of TE tunnels in an MPLS network?

    <p>To forward traffic along a specific path</p> Signup and view all the answers

    What happens to packets arriving on a PE from the CE router in an MPLS TE network?

    <p>They are applied labels and forwarded to the egress PE router</p> Signup and view all the answers

    Study Notes

    MPLS TE Overview

    • MPLS TE provides a combination of ATM's TE capabilities along with the class of service (CoS) differentiation of IP.
    • In MPLS TE, the headend router in the network controls the path taken by traffic to any particular destination in the network.
    • The requirement to implement a full mesh of VCs, as in ATM, does not exist when implementing MPLS TE.

    MPLS TE Components

    • The primary topics covered in MPLS TE implementation include the components of MPLS TE and RSVP.
    • RSVP plays a crucial role in the implementation of MPLS TE.

    Traditional IP Forwarding Paradigm

    • In traditional IP forwarding, packets are forwarded on a per-hop basis where a route lookup is performed on each router from source to destination.
    • This destination-based forwarding paradigm leads to suboptimal use of available bandwidth between a pair of routers in the service provider network.
    • To avoid packet drops due to inefficient use of available bandwidth and to provide better performance, TE is employed to steer some of the traffic destined to follow the optimal path to a suboptimal path to enable better bandwidth management and utilization between a pair of routers.

    RSVP Messages

    • PATH message:
      • Checks the availability of requested resources and stores this information.
      • Functions as a label request in MPLS TE domain.
      • Generated by the headend router (Router PE1-AS1) and forwarded downstream.
    • RESERVATION message:
      • Created by the tailend router (Router PE2-AS1) in the MPLS TE domain.
      • Used to confirm the reservation request that was sent earlier with the PATH message.
      • Performs the function of label assignment for a particular LSP mapping to the TE tunnel.
    • RSVP error messages:
      • Generated in the event of unavailability of the requested resources.
      • Sent to the router from which the request or reply was received.
    • RSVP tear messages:
      • Clear the PATH or RESERVATION states on the router instantaneously.
      • Enable the reuse of resources on the router for other requests.

    RSVP Message Objects

    • SESSION object:
      • Defines the source and the destination of the LSP tunnel.
      • Usually identified by IP addresses of corresponding loopback interfaces on headend and tailend routers.
    • SESSION_ATTRIBUTE object:
      • Defines the characteristics of the specific LSP tunnel, such as the bandwidth requirements and resources that would need to be allocated to the tunnel.
    • EXPLICIT_ROUTE object:
      • Populated by the list of next hops that are either manually specified or calculated using constraint-based SPF.
    • RECORD_ROUTE object:
      • Populated with the same address as the previous hop (PHOP) and the local outgoing interface in the path of the LSP tunnel.
    • LABEL object:
      • Generated and mapped in the RESERVATION message.

    Label Allocation and Distribution

    • The label allocation and distribution process in MPLS TE domain is performed downstream-on-demand.
    • The label mapping to a TE tunnel is first generated by the tailend router or egress Edge LSR and then propagated upstream.
    • This process is repeated at each hop upstream where local labels mapping to a TE tunnel are assigned and propagated upstream until the headend router is reached.

    MPLS TE Overview

    • MPLS TE provides a combination of ATM's TE capabilities and IP's CoS differentiation.
    • In MPLS TE, the headend router controls the path taken by traffic to a particular destination.
    • Implementing MPLS TE does not require a full mesh of VCs, unlike ATM.
    • MPLS TE transforms the IP network into a label-switched domain, defining paths for traffic using TE labels switched paths or TE tunnels.

    Benefits of MPLS TE

    • MPLS TE relieves temporary congestion in the core of the network on primary or optimal cost links.
    • MPLS TE enables better bandwidth management and utilization between a pair of routers.
    • MPLS TE maps flows between two routers to enable efficient use of available bandwidth.

    Traffic Engineering (TE) Basics

    • TE is the process of steering traffic to facilitate efficient use of available bandwidth between a pair of routers.
    • TE was previously performed using IP or ATM, depending on the protocol in use.
    • IP TE was implemented by manipulating interface costs or using static routes.

    RSVP-TE Protocol

    • RSVP-TE is a protocol used to reserve network resources for providing optimal services to data communication sessions.
    • RSVP-TE is used to request and confirm LSPs, reserve resources, and apply MPLS labels to form the MPLS LSP.
    • RSVP-TE uses extensions to support TE tunnel features.

    MPLS TE Implementation

    • MPLS TE implementation requires gathering information on traffic patterns to establish bandwidth guarantees.
    • TE tunnels are configured on provider edge (PE) routers.
    • TE tunnels are unidirectional, requiring a pair of tunnels to be configured for bidirectional TE deployment.
    • TE tunnels can be configured to map to separate paths, enabling efficient bandwidth utilization.

    Constraint-Based Routing (CBR)

    • CBR is the inspiration behind MPLS TE, taking into account multiple paths between a source/destination pair.
    • CBR enhances IP network operation, enabling least-cost routing and variable path finding.
    • CBR requires an IGP (like OSPF or IS-IS) for its operation.
    • CBR is used to define probable paths from a source to destination based on factors like bandwidth, policies, and topology.
    • IGPs (like OSPF and IS-IS) provide information on resource availability and link status.
    • In IS-IS, a new TLV (type 22) is used to transmit resource availability and link status information.
    • In OSPF, the type 10 LSA provides resource and link status information.
    • This information is flooded in IGP updates, allowing the ingress router to gather information on available resources and topology.

    RSVP-TE Message Flow

    • PATH message is generated by the headend router (Router PE1-AS1) and forwarded downstream to check resource availability at each hop (P1-AS1 and PE2-AS1)
    • PATH message functions as a label request in MPLS TE domain
    • In downstream-on-demand label allocation mode, the request to assign a label is generated at the headend router and propagated downstream

    RSVP RESERVATION Message

    • Created by the tailend router (PE2-AS1) in response to the PATH message
    • Functions as a reservation confirmation for the availability of requested resources
    • Performs label assignment for a particular LSP mapping to the TE tunnel
    • Label mapping is generated by the tailend router and propagated upstream, repeated at each hop upstream until the headend router is reached

    RSVP Error Messages

    • Generated by the router in the event of unavailability of requested resources
    • Sent to the router from which the request or reply was received

    RSVP Operation in MPLS TE

    • Headend router computes an ordered list of IP addresses that identifies the next hops along the path of the TE tunnel or LSP using CSPF or CBR calculation
    • RSVP signaling is used to request and confirm resource availability for the tunnel
    • RSVP extensions reserve appropriate resources on each LSR in the path defined by the headend router and assigns labels mapping to the TE tunnel LSP

    RSVP Extensions and Objects

    • LABEL_REQUEST: used to request a label mapping to the TE tunnel or LSP; generated by the headend router in the PATH message
    • LABEL: used to allocate labels mapping to the TE tunnel or LSP; generated by the tailend router in the RESERVATION message
    • EXPLICIT_ROUTE: carried in PATH messages and is used to request or confirm a specific path/route for the tunnel
    • RECORD_ROUTE: added to the PATH or RESERVATION messages to notify the originating node about the actual route/path that the LSP TE tunnel traverses
    • SESSION_ATTRIBUTE: used to define specific session parameters local to the TE LSP tunnel

    Path Setup Process for LSP TE Tunnels

    • RSVP messages containing one or more of these extensions are used to identify the significance of each message type and its contents
    • PATH message contains information about SESSION, SESSION_ATTRIBUTE, EXPLICIT_ROUTE, RECORD_ROUTE, and SENDER_TEMPLATE objects

    PATH and RESV Message Propagation

    • Step 1: headend router applies values to the fields mentioned in the table and sends the PATH message to the next-hop router
    • Step 2: next-hop router checks the EXPLICIT_ROUTE object to see if the next hop is a directly connected network
    • Step 7: headend router receives the RESERVATION message, and the RECORD_ROUTE identifies the traffic engineered LSP associated with a specific bandwidth or resource requirement

    TE Tunnels and MPLS TE

    • TE tunnels are data flows with properties or attributes associated with them, including bandwidth requirements and CoS for data forwarding.
    • TE tunnels are assigned specific label switched paths (LSPs) in the network from source to destination, usually PE routers.
    • MPLS LSPs have a one-to-one mapping with TE tunnels, which are not bound to a specific path through the SP network to a destination PE router.
    • TE tunnels can reroute packets via any path through the network associated with an MPLS LSP unless explicitly configured.

    TE Tunnel Configuration

    • TE tunnels are configured on PE routers and are unidirectional.
    • To implement bidirectional TE deployment between routers, a pair of tunnels must be configured on each router.
    • TE tunnels can map flows between two routers to enable efficient use of available bandwidth in the core of the network.

    MPLS TE Benefits

    • MPLS TE provides a combination of ATM's TE capabilities along with IP's CoS differentiation.
    • Implementing MPLS TE does not require a full mesh of VCs, unlike ATM.
    • MPLS TE allows for better bandwidth management and utilization between a pair of routers.

    MPLS TE Components

    • Components of MPLS TE include:
      • RSVP (Resource Reservation Protocol) for signaling
      • IGPs (OSPF and IS-IS) with extensions for TE tunnel features
      • MPLS-enabled routers for data plane forwarding

    TE and IP Forwarding

    • Traditional IP forwarding is based on a per-hop basis, leading to suboptimal use of available bandwidth.
    • TE is employed to steer some traffic to suboptimal paths to enable better bandwidth management and utilization.

    RSVP and TE

    • RSVP is used for signaling in an MPLS TE environment with extensions to support TE tunnel features.
    • The data plane ingress router requires information about resource availability on all links capable of being part of the MPLS TE tunnel.

    IGP and TE

    • IGPs (OSPF and IS-IS) provide information about resource availability and link status in the IGP domain.
    • This information is used by the ingress router to gather information on available resources in the network and define tunnels through the network.

    Constraint-Based Routing (CBR)

    • CBR is the inspiration behind MPLS TE, enhancing IP network operation to implement least cost routing and finding paths from source to destination.
    • CBR requires an IGP (OSPF or IS-IS) for its operation and is defined on the ingress routers to the MPLS domain when implementing MPLS TE.

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    Related Documents

    W4_JTO_Ph2_Datacom_IT-part-4.pdf

    Description

    Learn about MPLS TE, its features and components, including CoS differentiation and path control. Understand how it differs from ATM and its implementation requirements.

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