MPLS: IP and ATM Fusion Model

To solve the problems faced by the Internet-based IP backbone network, the IETF proposed Multi-Protocol Label Switching (MPLS ). MPLS can greatly improve IP Forwarding performance on the backbone network, and provide service classification (CoS) and QoS Assurance. MPLS can be used on a considerable number of existing trunk ATM networks to implement high-performance IP services on these networks.
The multi-protocol tag exchange proposed by IETF is similar to tag exchange. It tags data packets and forwards data packets through the ing relationship between the fixed length tag and the forwarding direction. Unlike traditional IP Forwarding, MPLS does not need to perform the longest matching on the destination address in the data packet header. Instead, it only needs to use a simple algorithm to search tags, which improves forwarding efficiency, this tag matching operation can also be completed using swap hardware with similar functions, such as an ATM switching network. When MPLS is used in an ATM network, it can achieve efficient IP Forwarding, and does not require the address resolution process of the traditional IPoA. It is an integrated model integrating IP and ATM.

MPLS network structure

MPLS is a layer-3 switching technology. After the tag-based mechanism is introduced, it separates routing and forwarding, and uses tags to specify the path of a group through the network. MPLS networks are composed of the core label exchange router (LSR) and the edge Label Edge Router (LER. The role of LSR can be seen as the combination of an ATM switch and a traditional router. It consists of a control unit and a switching unit. The role of LSR is to analyze IP headers, it is used to determine the corresponding transfer level and label transformation path (LSP ). MPLS network.
LSR is an ATM switch that implements MPLS functions. LER can be an ATM switch with MPLS functions or a router with MPLS functions. The process of tag switching is divided into three steps. One is to create a route table and a tag ing table in LSR together with LDP (TAG Distribution Protocol) and traditional routing protocol (OSPF, etc. Second, the LER receives the IP packet, completes the layer-3 function, and adds a tag to the IP packet. On the LER at the MPLS egress, remove the tag from the group and continue forwarding. Third, LSR no longer processes the group by Layer 3, but forwards the Group through the switch unit based on the group tag.