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Feature Description - MPLS 01

NE05E and NE08E V300R003C10SPC500

This is NE05E and NE08E V300R003C10SPC500 Feature Description - MPLS
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Overview of MPLS TE

Overview of MPLS TE

Multiprotocol Label Switching (MPLS) traffic engineering (TE) effectively schedules, allocates, and uses existing network resources to provide sufficient bandwidth and support for quality of service (QoS). MPLS TE helps carriers minimize expenditures without requiring hardware upgrades. TE is implemented based on MPLS techniques and is easy to deploy and maintain on live networks. MPLS TE supports a range of reliability techniques, which helps backbone networks achieve carrier and device-class reliability.


Traffic engineering techniques are common for carriers operating IP/MPLS bearer networks. These techniques are used to prevent traffic congestion and uneven resource allocation.

A node on a conventional IP network selects the shortest path as an optimal route, regardless of other factors, for example, bandwidth. The shortest path may be congested with traffic, whereas other available paths are idle.

Figure 4-1 Conventional routing

Each Link on the network shown in Figure 4-1 has a bandwidth of 100 Mbit/s and the same metric value. LSRA sends LSRJ traffic at 40 Mbit/s, and LSRG sends LSRJ traffic at 80 Mbit/s. Traffic from both routers travels through the shortest path LSRA (LSRG) → LSRB → LSRC → LSRD → LSRI → LSRJ that is calculated by an Interior Gateway Protocol (IGP) protocol. As a result, the path LSRA (LSRG) → LSRB → LSRC → LSRD → LSRI → LSRJ may be congested because of overload, while the path LSRA (LSRF) → LSRB → LSRE → LSRF → LSRH → LSRI → LSRJ is idle.

Network congestion is a major cause for backbone network performance deterioration. The network congestion is resulted from insufficient resources or locally induced by incorrect resource allocation. For the former, network device expansion can prevent the problem. For the later, TE is used to allocate some traffic to idle link so that traffic allocation is improved. TE dynamically monitors network traffic and loads on network elements and adjusts the parameters for traffic management, routing, and resource constraints in real time, which prevents network congestion induced by load imbalance.

Conventional TE solutions are as follows:

  • IP traffic engineering: TE controls network traffic by adjusting the metric of a path. This method eliminates congestion only on some links. Adjusting a metric is difficult on a complex network because a link change affects multiple routes.

  • ATM traffic engineering: The overlay model, such as IP over asynchronous transfer mode (ATM), complements IGP disadvantages. An overlay model provides a virtual topology over a physical topology for a network. This helps properly adjust traffic and implement QoS features, but has high costs and poor extensibility.

    TE directs some traffic to virtual connections (VCs) based on an overlay model. The current IGPs are topology driven and applicable to only static network connections, regardless of dynamic factors, such as bandwidth and traffic attributes.

A scalable and simple solution is required to implement TE on a large-scale network. MPLS, an overlay model, allows a virtual topology to be established over a physical topology and maps traffic to the virtual topology. MPLS can be integrated with TE. MPLS TE was introduced.


MPLS TE establishes label switched paths (LSPs) based on constraints and conducts traffic to specific LSPs so that network traffic is transmitted along the specified path. The constraints include controllable paths and sufficient link bandwidth reserved for services transmitted over the LSPs. If resources are insufficient, higher-priority LSPs preempt resources, such as bandwidth, of lower-priority LSPs so that higher-priority services' requirements can be fulfilled preferentially. In addition, if an LSP fails or a node is congested, MPLS TE protects network communication using a backup path and the fast reroute (FRR) function. Using MPLS TE allows a network administrator to deploy LSPs to properly allocate network resources, which prevents network congestion. If the number of LSPs increases, a specific offline tool can be used to analyze traffic. MPLS TE can be used on the network shown in Figure 4-1 to address congestion. MPLS TE establishes an 80 Mbit/s LSP over the path LSRG → LSRB → LSRC → LSRD → LSRI → LSRJ and a 40 Mbit/s LSP over the path LSRA → LSRB → LSRE → LSRF → LSRH → LSRI → LSRJ. MPLS TE directs traffic to the two LSPs, preventing congestion.
Figure 4-2 MPLS TE
Table 4-1 describes MPLS TE functions.
Table 4-1 MPLS TE functions

Function Module


Basic function

Includes basic MPLS TE settings and the tunnel establishment capability.

Tunnel optimization

Allows existing tunnels to be reestablished over other paths if the topology is changed, or these tunnels can be reestablished using updated bandwidth if service bandwidth values are changed.

Reliability function

Supports path protection, local protection, and node protection.


Supports Resource Reservation Protocol (RSVP) authentication, which improves signaling security over MPLS TE networks.


Point-to-multipoint (P2MP) traffic engineering (TE) is a promising solution to multicast service transmission. P2MP TE helps carriers provide high TE capabilities and increased reliability on an IP/MPLS backbone network and reduce network operational expenditure (OPEX).


MPLS TE offers the following benefits:
  • Provides sufficient bandwidth and supports QoS capabilities for services.
  • Optimizes bandwidth allocation.
  • Establishes public network tunnels to isolate virtual private network (VPN) traffic.
  • Is implemented based on existing MPLS techniques and its deployment and maintenance are simple.
  • Supports carrier- and device-level reliability functions.
Updated: 2019-01-14

Document ID: EDOC1100058933

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