MPLS concept
MPLS is a label mechanism package switching technology that integrates IP Routing control by simple Layer 2 exchange. Improvements to IPOA (IP Over ATM) are the source power generated by MPLS. At present, MPLS has not become the final formal standard. In the process of MPLS, many companies have launched their own marking technology, such as Cisco's TAG switching technology. MuPLs involved a lot of basic concepts: 1. FEC (Forward equivalence class) MPLS is actually a classification forwarding technology that will have the same forwarding processing mode (the same destination, the same forwarding path is the same, with the same service level, etc.), This kind of category is called forwarding equivalents. A group that belongs to the same forwarding equivalence class will obtain exactly the same processing in the MPLS network. During the LDP (later), various equivalents correspond to different tags, in the MPLS network, each node will identify the forwarding equivalence of the packet through the packet. 2. Multi-protocol marker exchange (1) Multi-protocol MPLS is located between the traditional second and third layer protocols, which can be various protocols in the current network. Such as: IPX, AppleTalk, etc. (2) Marking a length fixed, only the local meaning. It is used to uniquely represent the FEC to which a packet belongs, determines the forwarding method of tag packet. (3) Exchange The distribution of the FEC and the distribution of the mark, MPLS's mark exchanges in the network, and establish a virtual circuit. 3. The marker stack is a set of marked cascades. 4. The marker group contains a packet of the MPLS tag package. Marking can use a dedicated package format, or the existing link layer is encapsulated such as: ATM VCI and VPI. 5. Marking Switch Router (LSR) Supports the MPLS protocol router that is the basic element in the MPLS network. 6. The Mark Switch Path (LSP) uses the MPLS protocol established packet forwarding path, and the link between the label packet source LSR and the destination LSR and the link between them, similar to the virtual circuit in the ATM. 7. Upstream LSR and downstream LSR, when a packet is sent by a router to another router, the sender's router is an upstream router, the recipient is a downstream router. 8. The marker information library (LIB) is similar to the routing table, which contains various forwarding information corresponding to each tag. 9. Mark Distribution Protocol (LDP) This protocol is MPLS control protocol, which is equivalent to a signaling protocol of traditional networks, responsible for FEC's classification, marking allocation, and transmission of the resulting result and the establishment and maintenance of LSP. 10. The LDP peers is labeled to distribute the LDP * to the LDP * as the other entity. 11. Mark the merge group packets for a certain FEC, replace different entry marks with the same process of continuing forwarding, reducing the consumption of marking resources. 12. Subrostructure in the TLV (Type Length Value) MPLS message is similar to the objects in various messages in other protocols.
MPLS (MULTIPROTOCOL LABEL SWITCH) was originally used to increase the protocol proposed by the router's forwarding speed, but because MPLS is performing in the current IP network, it is very critical in the current IP network, MPLS It has become increasingly important criteria for expanding the scale of IP networks. The key to the MPLS protocol is to introduce the concept of label (label). It is a short easy-to-hand, does not contain topology information, with only local meaning information. Label is short of easy processing, usually can be directly referenced by indexing. Only local significance is to facilitate access. People who are familiar with ATM may naturally think of VPI / VCI in ATM. It can be said that the VPI / VCI in the ATM is a label, so the ATM is actually a label exchange. In the MPLS network, the IP package is encapsulated by the label when entering the first MPLS device. The MPLS edge router analyzes the contents of the IP package and selects the appropriate label for these IP packets, and the MPLS is not only analyzing the destination address information in the IP cladding relative to the traditional IP routing. It also analyzes other information in the IP header, such as TOS. The nodes in all MPLS networks after all MPLS networks are based on this short tag as a forwarding judgment basis. When the IP package finally leaves the MPLS network, the label is separated by the edge router. MPLS's protocol development process In 1996, IPSilon launched an IP Switching protocol and immediately caused great vibration in the data communication world. Ipsilon has become a well-known company in the data communication world, and thus triggered a revolution in router technology, and companies have launched their own three-layer exchange programs, which has a key role in the development of MPLS protocols. There are some protocols: 1) ip switching. It was proposed in 1996 by IPSilon and launched commercial products that support the agreement. The protocol enables an ATM switch to have a router, thereby having high performance of the ATM switch, thereby breaking through the performance limitations of traditional routers. The basic purpose of IP exchange is to use the abandoned ATM control plane method to efficiently integrate the ATM switch IP router. IP Switching labels are built by data streaming. IPSILON defines a set of protocols, including label binding protocols (called IPSILON Flow Management Protocol or IFMP, RFC) and Switch Management Protocol (called General Switch Management Protocol or GSMP, RFC). GSMP is only used to control a single ATM switch and those virtual links across the switch. 2) Tag switching is a method of label (Cisco called Cisco) developed by Cisco. Unlike IP Switching, Tag Switch does not trust the driver of data streams to establish label forwarding items, which is trusted to control drive (there is a control plane equivalent to the ATM protocol), Tag Switching Network by Tag Edge Routers and Tag Switching Routers composition. The IP package is labeled on Tag Edge Routers, and the route determination trust standard routing algorithm (such as OSPF, BGP, etc.). The binding and distribution of tags uses the Tag Distribution Protocol (TDP). 3) AGGREGATE ROUTE-BASED IP SWITCH (ARIS) is a label switching scheme for IBM.
