MPLS is an acronym for Multi-Protocol Label Switching. The basic principle of MPLS is to change layer 2 devices in the network such as ATM switches into LSRs (label-switching router). LSR can be seen as a combination of ATM switching system with traditional routers.
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On the data link, the first LSR is called the Ingress LSR; The final LSR is called the Egress LSR; remaining intermediate LSRs are called Core LSRs. In an MPLS network, each packet contains a 20-bit label in the 32-bit MPLS header. First, a label will be assigned at the Ingress LSR which will then be forwarded across the network according to the routing table information. The network control function block creates and maintains these routing tables and also exchanges routing information with other network nodes.
*: LDP (Label Delivery Protocol); OSPF (traditional routing protocol).
The separation of two independent functional blocks: forwarding and control is one of the important properties of MPLS. The control function block uses a traditional routing protocol (e.g. OSPF) to create and maintain a forwarding table. When a packet arrives at an LSR, the forwarding function uses the information recorded in the header to find a suitable forwarding table and that LSR assigns a label to the packet and forwards it along the label-switched LSP (label-switched) route. path: label-switched route). All packets with the same label will follow the same LSP route from the origin to the end point. This is different from traditional routing protocols (there can be multiple routes between two points).
Core LSRs will ignore the network layer header of the packet, the forwarding function block of these LSRs use the input port number and label to do a matching forwarding table lookup and then replace it. replace the new label and move out onto the LSP route.
Thus, MPLS Technology is a version of the traditional IPoA (IP over ATM) technology, so MPLS has both the advantages of ATM (high speed, QoS and flow control) and of IP (flexibility and Ability of extension). Solving many of the problems of existing networks and supporting many new functions, MPLS is said to be the ideal IP backbone technology.
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MPLS used in VPN: Configure an MPLS-based virtual private network that can be deployed on Layer 3 or Layer 2 as follows: VPN/MPLS Layer 3
Usually built on top of IETF RFC 2547bis standard. This layer of VPN transports traffic across the network using MPLS tunneling and the MP-BGP (Multiprotocol Border Gateway Protocol) signaling protocol as shown in Figure 2.
In which, BB is the backbone routing with MPLS implementation and VRF routing in the VPN, and BO is the routing at the branch point that does not run MPLS. These are the most popular methods today, but businesses can apply MPLS on branch points to increase efficiency. The two advantages of this type of Layer 3 VPN/MPLS are that it is based on traditional standards and is easy to provide.
VPN/MPLS Layer 2
Frame Relay and ATM-based forms are common and are already multi-protocol, making Layer 2 VPNs/MPLSs an easy transition for businesses and organizations now running traditional protocols. but intends to switch to an all-IP network in the near future. One of the important features of a Layer 2 VPN/MPLS is the ability to create a tunnel as an LSP route (illustrated in Figure 3). Another feature is the ability to use control protocols such as label distribution protocol LDP or BGP to establish virtual channels.
Example: flexibility for any organization
Benefits of MPLS to businesses and organizations
With the network using MPLS, there are many services provided with high quality such as: 1. Download for national data, Internet and voice networks. Voice traffic is gradually transferred to the national MPLS backbone network. This network will gradually replace the existing national TDM backbone network.2. Providing high-speed Internet access services in a number of key localities across the country. Initially forming the national backbone network on the basis of packet technology.3. Providing high-speed data transmission services for businesses and organizations such as banks and press agencies.4. Provide VPN virtual private network service to transnational companies and large enterprises and organizations. This is being considered as the most important service that affects the change of business structure and increases the competitiveness of operators.5. Provide Video Services.
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For businesses and organizations, the type of virtual private network on a wide area network is the most urgent need and shows clear benefits to the activities of these objects. For a company to achieve its business goals, the private network infrastructure must be spread out in all directions. MPLS networks are capable of supporting thousands of virtual private networks on just one The unique physical infrastructure, thanks to the feature of division of duties, reduces the need for a completely end-to-end peer-to-peer connection over the network. In terms of VPN support, traditional virtual private network infrastructures based on old technologies such as leased line, X25, ATM cannot meet the diversity of requirements and service quality of customers. a wide range of current customers. This will be the reason why these service providers have to switch to another more efficient delivery model.
The diversity of both requirements and quality can be illustrated by three groups of subjects with very different requirements as follows: