No abstract

The Path Computation Element Communication Protocol (PCEP)

Abstract-With the advent of MPLS, the restoration times of communications is decreased down to 50 ms by the use of preconfigured backup LSPs. To ensure there are enough resources after a failure, the backup LSPs must reserve the resources they need beforehand. However and contrarily to the primary LSPs which really use their resources, the backup LSPs do not use them until a failure of the protected component occurs. Hence, to optimize and maximize resource availability in the network, backup LSPs may share their resource reservation. Indeed, under the hypothesis of single failures in the network, some backup paths are not active at the same time since they protect against the failure of different components.In this article, we propose an efficient Distributed Bandwidth Sharing (DBS) heuristic capable to protect the primary LSPs against all types of failure risks (link, node and SRLG risks) with the transmission of a very small amount of bandwidth information. Our technique is completely distributed; it balances the computations on the different nodes of the topology and is easy to be deployed.Simulations show that with the transmission of a small vector of bandwidth information per link, the rate of rejected backup LSPs is low and close to the ideal.

Abstract

The MPLS-TE technology, relying on the signaling protocol RSVP-TE, ensures traffic engineering (TE) features for point-to-point (P2P) and point-to-multipoint (P2MP) applications with strong bandwidth and availability needs. This paper defines the concept of multi-point to multi-point (MP2MP) TE-LSP that connects a group of nodes called leaves, acting as senders and/or receivers, with potentially distinct bandwidth needs. This helps in replacing the P2P or P2MP TE-LSPs that connect a group of nodes by one MP2MP TE-LSP which leads to reducing the number of TE-LSPs in MPLS-TE networks and hence improving its scalability. An MP2MP TE-LSP can be used also to support value added multi-point to multi-point applications such as visioconferencing. The setup of an MP2MP TE-LSP relies upon minor extensions to RSVP-TE. An MP2MP TE-LSP is initiated by a root router and the signaling messages from the root to the leaves include the bandwidth requested by each leaf. The bandwidth reserved on a link in each direction is deduced from the bandwidth requested by upstream and downstream leaves. This mechanism inherits all good properties of MPLS-TE with only a few extensions and it permits to set up P2P and P2MP TE-LSPs since such TE-LSPs are special cases of MP2MP TE-LSPs. Index Terms-Multicast, Multi-Point to Multi-Point, MPLS, Traffic Engineering.

Abstract-In Multi-Protocol Label Switching-Traffic Engineering (MPLS-TE) networks with distributed tunnel path computation on head-end routers, tunnel requests are handled one by one, in an uncoordinated manner without any knowledge of future and other requests. The order in which requests are handled has a significant impact on the network optimization and blocking probability. If it is not possible to control the arrival order, in return it is possible, in some cases, to reorder requests using the preemption function. This paper evaluates the impact of the arrival order, so as to determine efficient orders. It then proposes two preemption strategies so as to reorder arrivals and evaluate these strategies applied to the shortest constrained path computation algorithm.

Status of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

International audienceTo ensure service continuity in networks, local protection pre-configuring the backup paths is preferred to global protection. Under the practical hypothesis of single physical failures in the network, the backup paths which protect against different logical failure risks (node, link and shared risk link group (SRLG)) cannot be active at the same time. Thus, sharing bandwidth between such backup paths is crucial to increase the bandwidth availability. In this article, we focus on the optimal on-line distributed computation of the band-width-guaranteed backup paths in MPLS networks. As the requests for connection establishment and release arrive dynamically without knowledge of future arrivals, we choose to use the on-line mode to avoid LSP reconfigurations. We also selected a distributed computation to offer scalability and decrease the LSP setup time. Finally, the optimization of bandwidth utilization can be achieved thanks to the flexibility of the path choice offered by MPLS and to the bandwidth sharing. For a good bandwidth sharing, the backup path computation entities (BPCEs) require the knowledge and maintenance of a great quantity of bandwidth information (e.g. non aggregated link information or per path information) which is undesirable in distributed environments. To get around this problem, we propose here a PLR (point of local repair)-based heuristic (PLRH) which aggregates and noticeably decreases the size of the band-width information advertised in the network while offering a high bandwidth sharing. PLRH permits an efficient computation of backup paths. It is scalable, easy to be deployed and balances equitably computations on the network nodes. Simulations show that with the transmission of a small quantity of aggregated information per link, the ratio of rejected backup paths is low and close to the optimum