| With the fast development of the Internet in the 21st century, new content is added every day, flows in the network are also growing, and different types of business flows are various, These flows require a wide range of quality of service (QoS) guarantees on the basis of traditional IP network., For example, high transmission efficiency, dynamic-routing adjustment, flexible network control capability, etc. But the traditional IP network, using the shortest path algorithm to choose path, is the Best-effort delivery mode, this method overlooks the available network link capacity and the business's request. It will cause the entire network work without the utilization of the best. The traffic engineering based on Multi-Protocol Label Switching (MPLS) is adapted to these requests. It can precisely control the business flow in the network, rationally use network resources, access more business, and improve network efficiency.MPLS is one kind of new network standard, this technology obtained the widespread approval. Proposed that this kind of technology's starting point is merges into one organic whole the router and the ATM switchboard, thus raises the IP package of transfer rate, simplified network, and as L3Switching (three exchanges) technical international standard. The MPLS network by marks the edge router and the mark exchange router (LSR) is composed. In LSR, the MPLS control module take the IP function as the center, the repeater module based on the mark exchange algorithm, and (LDP) completes the mark information as well as the related signaling transmission through the mark distribution agreement in the node. The LDP signaling as well as the mark binding information only transmits in the MPLS during neighbor node. Between LSR or LSR and LER still need to move the standard route agreement, and obtains the analysis situs information from this. May be clear about the selection text as soon as through these information LSR under to jump and may to establish the specific mark exchange way finally (LSP). The MPLS use control actuation model, namely to uses in based on the analysis situs drive type establishing LSP the mark binding information assignment and the repeater carries on the initialization. LSP belongs to the unidirectional transmission way, thus the full-duplex service needs two LSP, each LSP is responsible for in a direction the service. MPLS unifies closely the IP route and the ATM exchange technology, both has realized the router intelligence, and has used the ATM switchboard's highly effective hardware exchange. ATM and the IP perfect union may be more superior than any independent technology. The MPLS technology may enhance the router repeater ability, thus enhances the entire IP network the performance, and only need carry on the software on the user existing router to promote, namely may support the MPLS technology completely, thus may guarantee the user original investment. The MPLS solution, has provided the intelligent IP application service to the ATM network, this has the difference with the ATM/FR transmission service. Compares, the IP-OVER-ATM solution, makes the IP data stream and the ATM data stream same level processing, limited has realized the end-to-end IP service ability. MPLS causes the service provider through to use IP and the ATM attribute, maintenance present ATM and the FR service turnover. At the same time, in the identical network, provides the commercial IP service, if Internet and ExtranetVPN increase the output value and the profit. MPLS was only a multi-service ATM network technology, the network operator still might provide extant FR, the pronunciation and the multi-service ATM transmission service. Through the IP+ATM platform, many kinds of network service like IP, FR and ATM may use the hypothesized exchange port (VSI) technology through a sole network support. VSI is the multi-service forum (MSF) new standard, uses in exchanging two with three controls carries on separately the mold quick design, enhances switchboard's flexibility as well as the extendibility. Hypothesized exchange port (VSI) this kind of mechanism may be clear about the control to assign for each kind of service network resource, therefore each virtual network each other is independent. VSI may simultaneously support MPLS and PNNI as well as other control platform, because it allows on the identical IP+ATM switchboard simultaneously to move the different agreement stack. Does not have MPLS, IP to need a complex agreement translation process by way of the ATM transmission, must correspond the IP address route to the ATM address and the route, puts to the ATM exchange table. In this case, the ATM network needs the PNNI route agreement, ATM Address Resolution Protocol (ATMARP) to map the IP webpage in the ATM webpage, then realizes the net by-road through NHRP by. On the contrary, MPLS has abbreviated maps the IP address and the route in the ATM exchange table the complexity, the MPLS mark exchange and the ATM switchboard exchange cell mechanism is the same. Integrate not only through MPLS, IP unicast and the multicast information and the existing ATM system, cause to serve the provider to be possible to provide the IP service to give the user, moreover for Internet which day by day expands brings the advantage: Through maps the IP first rank and in the ATM switchboard's different grade of service formation, provides end-to-end QoS for the user; Each MPLS first rank's band width assignment is may adjust willfully; Predetermined and the allocation function satisfies the user through the Opticlass band width to the band width, first rank and latency various requirement. At the same time, the TrafficEngineering function causes to serve the provider to be able to assign and the adjustment band width according to the Traffic request as well as to provide such as VPN (hypothesized special net) and so on value-added services. MPLS rich, the formidable function lets serve the provider while to establish itself large-scale, to be possible activate business service network, has had the formidable market competitiveness. MPLS has the strong extendibility. Traditional IP and the ATM union is depends upon the intermediate level the translation. This ways have brought a series of consequences, like empty electric circuit "N square" question and so on. But MPLS has solved this a series of problems effectively, enabled ATM the extendibility to have the enhancement. In summary, MPLS integrated EP and the ATM technology respective superiority, uses three route mechanisms and the LDP union way establishment routing list as well as first passes on the table, uses two ATM technologies to carry on the fast exchange, has provided the superior technology base for the new generation telecommunication network, both may complete three flexibilities, the extendibility, and may complete two fast exchanges, the current capacity management, secure as well as the QoS safeguard mechanisms. MPLS already by the proof was the large-scale network extendibility best solution.This paper first introduces the basic principle of MPLS and imports the basic concept and work model of TE. On this basis, we analyze how to apply MPLS to TE and summarize the advantage of MPLS-TE. Secondly, the existing constraint-based routing algorithm are classified and analyzed. We put minimum bandwidth multi-path constraint-based routing algorithm to break the limitations of single-path algorithm's low success rate. The algorithm finds the most suitable path of the available bandwidth to meet part of a large bandwidth constraint and keep this process until all bandwidth is allocated to more paths, to reach the purpose that increases the success rate of finding bandwidth constraint path with fewest paths.Finally, we compare the simulation results with traditional routing algorithm, verify that multi-path constraint-based routing algorithm with minimum bandwidth has higher success rate than traditional single-path constraint-based routing algorithm does in meeting large bandwidth request, and therefore prove they have great effect on balancing net work load. |
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