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.
Purpose
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.
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.
Definition
Function Module |
Description |
---|---|
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. |
Security |
Supports Resource Reservation Protocol (RSVP) authentication, which improves signaling security over MPLS TE networks. |
P2MP TE |
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). |
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.