MPLS technical advantages and problems (1)

1. Today's Internet

As the Internet continues to grow, various emerging businesses and vpcs that cater to their needs are also evolving, however, the operation methods targeting different businesses and handling multiple network connections at the same time have bound the development of enterprises. They hope to provide a variety of hybrid services through a single and flexible access device, in the future, uniform access protocols, such as IP addresses, will be implemented. However, different services (such as voice, data, and multimedia applications) have different requirements on network transmission quality, if the ISP still develops a large-scale IP network based on a traditional router, related issues (such as the software operation of the router forwarding component, to construct the overhead of the high-speed Router component, the traditional routing path finding mechanism will become increasingly acute in terms of unpredictable network performance during transmission, and the network cannot provide QoS for specific services.

Compared with IP routing technology, the fast exchange technology based on ATM and frame relay can use multiple forwarding algorithms (essentially the label Exchange Algorithm ). Because these forwarding algorithms are simple and effective, they are directly solidified into the switch hardware. Compared with the traditional IP routing mechanism, the L2 layer fast switching technology has a high price-performance ratio.

To solve the problems existing in the above IP networks, each ISP is eager to seek a network solution that can combine the advantages of the fast exchange technology and IP routing technology. Therefore, the label exchange technology emerged. The label exchange technology is committed to the optimal attributes of L2 layer switching technology (usually implemented by ATM or frame relay) and the optimal attributes of L2 layer routing technology (implemented by IP addresses) multi-Protocol Label Switching (MPLS) is currently the most unified and promising label switching technology. MPLS was developed by the Internet Engineering Task Team (IETF) and started in early 1997. It was designed to meet the various attributes that must be followed by large-scale telecom-grade networks. The goal is to achieve fast QoS switching through ATM, frame relay, and other media in a large-scale IP network. Therefore, the emergence of MPLS will be of revolutionary significance for the development of the network.

II. Key concepts in MPLS Technology

Because MPLS technology can be applied to any network layer protocol, it is called multiprotocol. Currently, it is mainly used to transmit IP services. At the same time, multiple protocols also show that the application of MPLS technology is not limited to a specific link layer media, that is, the MPLS technology is used, network layer data packets can be transmitted based on a variety of physical media, such as ATM, frame relay, leased line/PPP. The key element in the MPLS network is the label exchange router (LSR), which has the ability to understand and participate in IP routing and L2 layer switching. MPLS requires LSR to participate in IP routing. The forwarding mechanism is very different from the traditional hop-by-hop routing decision mechanism. Using the preceding transmission technologies and a single operation mode, MPLS can avoid problems arising from mutual operations between L2 and L3 layers, at the same time, ensure that the two mechanisms run independently. LSR uses the standard routing protocol (such as OSPF) on the L3 to perform path search. In this way, the topology of the entire network is obtained, and the learned routing information is used to assign corresponding labels to specific IP packets ). From an end-to-end perspective, labels are used to determine the transmission path of IP packets between endpoints. This path is called the label switching path (LSP ). LSP is established between LSR Peer through MPLS core protocol label assignment protocol (LDP), which is essentially similar to the VC connection defined by the exchange technology. When transmitting IP packets, the MPLS Label Edge Router (LER) uses a specific decision mechanism to encapsulate the packets, packets that carry specific tags are then forwarded to the upgraded switch (such as the ATM-LSR or LSR) within the network, after receiving the corresponding IP packets through the internal label information library (LIB) query and exchange tags and forward packets along the LSP.