MPLS-TE Local Protection Overview
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Questions and Answers

What is a NNHOP tunnel required for?

  • To guarantee bandwidth protection
  • To protect against a node fault (correct)
  • To protect against a link fault
  • To create multiple backup LSPs for each hop

    • What happens at each hop in fast-reroute mode?

  • Only one detour is used regardless of the number of LSPs
  • A single backup path is created for all primary LSPs
  • The primary LSP exchanges labels with other nodes
  • Each backup LSP is created for each fast-reroutable LSP-TE (correct)

    • What role does the Merge Point (MP) play in MPLS backup tunnels?

  • It receives the same packet via a backup tunnel (correct)
  • It maintains the original LSP-TE labels during rerouting
  • It serves as a primary traffic entry point
  • It transmits packets only through the primary path

    • What is a key advantage of using backup tunnels in MPLS networks?

    <p>They help to scale bandwidth without additional overhead</p> Signup and view all the answers

    What does PLR stand for in fast reroute operations?

    <p>Path Label Router</p> Signup and view all the answers

    How does PLR handle a fault occurring in R4?

    <p>It reroutes the traffic using its existing labels and stacks a backup label</p> Signup and view all the answers

    What does the backup path label do in MPLS?

    <p>Signals a detour for packets through an alternate interface</p> Signup and view all the answers

    Which type of protection is described as being required for a link fault?

    <p>NHOP Tunnel</p> Signup and view all the answers

    What type of LSAs are used for OSPF traffic engineering?

    <p>Type 10 Opaque LSAs</p> Signup and view all the answers

    What does CSPF stand for in the context of OSPF with TE extensions?

    <p>Constrained Shortest Path First</p> Signup and view all the answers

    What is the primary function of RSVP-TE in LSP-TE setup?

    <p>To establish the LSP once it has been calculated</p> Signup and view all the answers

    Which attribute is NOT included in the OSPF-TE LSAs extensions?

    <p>Current load on the interface</p> Signup and view all the answers

    What is the purpose of Shared Risk Link Groups (SRLG) in OSPF-TE?

    <p>To indicate links sharing a common fiber or conduit</p> Signup and view all the answers

    How can administrative groups be utilized in LSP-TE path calculations?

    <p>They can be excluded or included based on routes.</p> Signup and view all the answers

    What is the default value of TE metric for OSPF links?

    <p>Equal to the OSPF link cost</p> Signup and view all the answers

    What information does the Maximum reservable bandwidth attribute provide in OSPF-TE?

    <p>The maximum amount of bandwidth that can be reserved for traffic</p> Signup and view all the answers

    What is a primary goal of Internet Traffic Engineering?

    <p>To optimize network resource utilization and performance</p> Signup and view all the answers

    What problem does the classic fish problem illustrate in routing?

    <p>Network bandwidth may not be efficiently utilized</p> Signup and view all the answers

    How does Traffic Engineering (TE) aim to manage network congestion?

    <p>By optimizing the mapping of traffic streams onto network resources</p> Signup and view all the answers

    Which technique is used in MPLS-TE to ensure routing decisions are unaffected by intermediate nodes?

    <p>Tunneling techniques between source and destination</p> Signup and view all the answers

    What does each LSP (Label Switched Path) in MPLS-TE have associated with it?

    <p>A set of unique constraints including bandwidth and affinities</p> Signup and view all the answers

    What is the impact of inefficient bandwidth resource use in a network?

    <p>Congestion in some areas while others remain underutilized</p> Signup and view all the answers

    What is the result of traffic load balancing in Traffic Engineering?

    <p>Better resource utilization and reduced congestion</p> Signup and view all the answers

    What does the configuration of an LSP-TE in ingress LERs involve?

    <p>Configuring attributes like destination address, bandwidth, and protection</p> Signup and view all the answers

    What is the primary purpose of configuring SRLG membership in backup tunnel path selection?

    <p>To ensure backup tunnels do not use links in the same SRLG as the protected interfaces</p> Signup and view all the answers

    Which event is NOT a trigger for the device to send out OSPF-TE LSAs?

    <p>Activation of a new routing protocol</p> Signup and view all the answers

    What is the TE Link State database (TE-LSDB) used for in LSRs?

    <p>To maintain the TE network topology updated by IGP flooding</p> Signup and view all the answers

    Which parameter is NOT considered when calculating a TE path for a signalled LSP?

    <p>Cost of the link</p> Signup and view all the answers

    What does an LSP's hold priority determine concerning bandwidth allocation?

    <p>The likelihood of the LSP being preempted by a higher priority LSP</p> Signup and view all the answers

    What happens when an interface is no longer enabled for MPLS?

    <p>The device stops sending OSPF-TE LSAs for that interface</p> Signup and view all the answers

    What is the default setup priority for an LSP?

    <p>7</p> Signup and view all the answers

    What condition must be met for an LSP to be preempted by another LSP?

    <p>The preempting LSP must have a lower hold priority than the preempted LSP's setup priority</p> Signup and view all the answers

    What does the ingress LER do upon receiving a Path Error message from the PLR?

    <p>It triggers the search for an alternative path.</p> Signup and view all the answers

    Which method offers a local protection mechanism with fast recovery times equivalent to SONET/SDH?

    <p>Facility backup</p> Signup and view all the answers

    What is a key advantage of using backup tunnels in MPLS TE?

    <p>They can share backup capacity, reducing redundancy.</p> Signup and view all the answers

    Which drawback is associated with the one-to-one method of backup in large networks?

    <p>Limited scalability.</p> Signup and view all the answers

    What factor does the number of backup tunnels depend on in the facility method?

    <p>The number of network elements to be protected.</p> Signup and view all the answers

    What do Fast Reroute backup tunnels primarily provide?

    <p>Link protection by avoiding failed links.</p> Signup and view all the answers

    Which parameter is NOT mentioned as influencing global path protection requirements?

    <p>Node processing speed</p> Signup and view all the answers

    What is the main purpose of path reoptimization in the MPLS framework?

    <p>To ensure the use of optimum paths.</p> Signup and view all the answers

    Study Notes

    MPLS-TE Local Protection

    • NNHOP (Non NextHOP): A backup tunnel that ends in a neighbor of the next node to the PLR (Protection Label Router). The node is called a Merge Point.
    • Fast-Reroute - One-to-One Backup: At each hop, a backup LSP (detour) is created for each fast-reroutable LSP-TE. It protects the LSP-TE against faults in the link and the node. Each node performs the same operation, and the detour avoids resources it protects.
    • Fast-Reroute - Facility Backup:
      • Requires a NHOP tunnel for link protection.
      • Requires a NNHOP (bypass) tunnel for node protection.
      • The NNHOP protects against the link between the bypassed node and the immediate upstream node.
      • Backup tunnels can be shared for more efficient bandwidth utilization.
    • MPLS-TE Recovery Mechanisms - Objectives
      • Optimize network resource utilization and performance.
      • Efficiency routing using network resources to avoid congestion.
      • Guarantee QoS.
      • Fast recovery in case of fault.
    • Traffic Engineering (TE)
      • Optimizes network resource utilization and performance.
      • Addresses inefficiencies in network resource mapping by optimizing traffic flow.
      • Reduces operational costs by ensuring efficient bandwidth usage.
      • Prevents congestion in one part of the network while other sections have unused capacity.
    • MPLS-TE Solution
      • Tunneling techniques between source and destination, allowing intermediate nodes to avoid routing decisions.
      • Each LSP (Label Switched Path) has its own constraints: bandwidth, affinities, routing constraints, etc.
    • Components of MPLS-TE
      • LSP-TE configuration in the ingress LERs (Label Edge Routers)
        • Configure attributes (destination address, bandwidth, required protection and restoration, affinities, affinity relations, etc.).
      • Distribution of resource and topology information (e.g., OSPF with TE extensions).
      • LSP-TE Computation
        • Each router calculates the constrained shortest path (CSPF) based on the available topology and resource information.
        • Define recovery mode for the LSP in case of a fault.
      • LSP-TE Setup
        • Establish the calculated path with RSVP-TE (Resource Reservation Protocol - Traffic Engineering).
      • (Labeled) packet forwarding (intermediate routers do not make routing decisions).
    • OSPF-TE (Open Shortest Path First - Traffic Engineering)
      • Carries traffic engineering information in OSPF link state advertisements.
      • OSPF-TE LSAs are Type 10 Opaque LSAs.
      • Contain extensions that specify traffic engineering information (e.g., Link ID, IP addresses, TE metric, bandwidth, administrative groups, etc.).
    • Resource and Topology Information in OSPF-TE
      • Each interface can be assigned to one or multiple administrative groups.
      • Color names (Gold, Silver, Bronze), or user-friendly names (Voice, Management, BestEffort), are used to define the group.
      • The ingress LSR uses these administrative groups to calculate paths for LSP-TEs, including or excluding specific groups.
    • Affinity in OSPF-TE
      • Used to define values and masks, which can be used for determining tunnel cost, physical link type, physical distance, etc.
    • Shared Risk Link Groups (SRLG) in OSPF-TE
      • Shared Risk Link Groups (SRLG) is a link characteristic that identifies links sharing a common fiber or conduit.
      • Used in the deployment of backup tunnels.
      • SRLG information is flooded by the IGP.
      • Backup tunnels avoid links within the same SRLG as the links they are protecting, enhancing path selection.
    • TE Link State Database (TE-LSDB or TED)
      • LSRs use IGP extensions to maintain a TE Link State database.
      • The database contains information about the network topology and is updated when changes occur (new LSP establishment, bandwidth changes).
    • LSP Attributes and Requirements in TE
      • Used to define the TE path for a signaled LSP.
      • Attributes include:
        • Destination address of the egress LER
        • Explicit path for the LSP
        • Class of Service (CoS)
        • Bandwidth required by the LSP
        • Setup and Hold priority for the LSP:
          • Hold priority: determines the LSP's ability to retain its resources when preempted by another LSP.
          • Setup priority: determines the priority of an LSP when establishing a new path.
    • Path Reoptimization in TE
      • RSVP Path Error Message: Sent by the PLR to the ingress LER to indicate a local reroute has occurred. This triggers the search for an alternative route.
    • Fast Reroute using SRLG
      • Backup tunnels are automatically created to avoid SRLGs associated with protected interfaces.
      • Backup tunnels provide link protection by rerouting traffic to the next hop, bypassing failed links or avoiding SRLGs.
    • Local MPLS-TE Protection
      • Offers very fast recovery times, comparable to SONET/SDH.
      • Provides guaranteed bandwidth, propagation delay, and jitter in case of a fault.
      • Offers high granularity in the concept of Class of Restoration (CoR).
      • The facility method provides high scalability as the number of backup tunnels is dependent on the number of network elements to be protected, not the number of fast-reroutable LSP-TEs.
    • Local MPLS-TE Protection - Drawbacks
      • Requires configuration and establishment of a number of backup LSP-TEs, which can be significant in large networks.
      • The one-to-one method has limited scalability in large networks.
    • Comparison of Global and Local Protection
      • Evaluates the number of required backup tunnels with global path protection, Fast Reroute facility backup, and one-to-one backup using various network parameters (network diameter, degree of connectivity, number of nodes, and number of links to be protected).

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    Related Documents

    MPLS-Part II_MPLS with Traffic Engineering.pdf

    Description

    This quiz covers the key concepts of MPLS-TE local protection, including the Non NextHOP (NNHOP) backup tunnel and fast-reroute mechanisms. You'll explore one-to-one backup methods and facility backup strategies, as well as the objectives of MPLS-TE recovery mechanisms. Test your understanding of these critical network protection strategies.

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