MPLS Tunnel Switching based on performance measurements
Original Publication Date: 2005-Dec-25
Included in the Prior Art Database: 2005-Dec-25
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In computer networking and telecommunications, the Multiprotocol Label Switching (MPLS) is a data-carrying mechanism, operating at a layer below protocols such as IP (Internet Protocol). It can be used to carry many different kinds of traffic, including both voice telephone traffic and IP packets. In case of Local Protection of a network using MPLS-TE (TE, Traffic Engineering) each node or link which has to be protected implies an individual Backup tunnel. If a loss of connectivity in the Main tunnel is detected by the control plane, the traffic is redirected to the Backup tunnel as shown in Figure 1. In case the MPLS LSP (Label Switching Path) is failing to deliver data traffic, it is not always possible to detect the failure using the MPLS control plane. For instance, the control plane of the MPLS LSP can be functional while the data plane is forwarding incorrect or fragmentary data. Therefore, the link conditions can be degraded in the manner that a loss of connectivity is not detected by the control plane, but in the data plane the quality cannot be maintained. In that case the protection mechanisms are not activated and the traffic is getting lost and the quality of service (QoS) is compromised. For failures detected by the MPLS control plane there are two protection mechanisms with proposed standards in the IETF (Internet Engineering Task Force): Global Protection (IETF Rfc 3469) and Local Protection (IETF Rfc 4090). These mechanisms only consider the situation of complete link failure and all packets that are already in the tunnel are lost. A disadvantage of this mechanism is the need of complete loss of connectivity in order to switch to the Backup tunnel. Concerning failures in the data plane, there are some proposals posted as drafts in the IETF which detect this kind of failure but the detection is not used to initialize the switching to the Backup tunnel.