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MPLS: Multiprotocol Label Switching (Multiprotocol label forwarding)

Works at the network layer and is responsible for forwarding packets. (fast packet switching and packet forwarding)

Talk about the exchange of data packets

Process switching: look up the table based on each route. Consume the resources of CPU.

Fast switching: based on the classification of data streams, and then define the forwarding strategy of data streams.

CEF: turn it on before running the MPLS protocol (above the cisco device), and get the CEF table by learning the routing entries.

When the router starts the CEF process, the router automatically generates LDP,TDP, two tables.

Label for MPLS Fram

The MPLS is encapsulated between a layer 2 Ethernet frame and a layer 3 packet.

Distribution of MPLS frame format

Lable:20 bytes, adding a label for each entry. The label number of 0-15 is an exception and is used as a logical label.

TC: 3 bytes, mainly used in QOS.

S: 1 byte, mainly used on the stack.

A TTL value of TTL:8 bytes, which prevents loops.

Interpretation of MPLS protocol terms

The router in the LSR:MPLP domain is not the router at the edge of the MPLS domain.

The router in the ELSR:MPLS domain that is connected to the client exit, that is, the edge router.

LSP: the path of the MPLS, single item.

TDP:LDP: the main thing is to tag data. Transport layer protocol

LIB: tag information database, with LSR router tags, neighbor tags, and their own tags are mapped.

LFIB: tag forwarding information base, which is queried only when the tag is forwarded.

CEF contains FIB and neighbor packages.

FIB: save the tag information and check the tag on the transmitted shock router.

Ages Table: neighbor tabl

On a link, you cannot send the same label for different routers.

The label of MPLS

Label pressing: label pressing occurs on the ELSR route. When the router learns the customer's routing information, it will put a local label on the route entry. When the ELSR wants to transmit the tagged route entry, it will send the locally tagged route entry to the next-hop LSR router. When the LSR router receives the tagged data, it will check the FIB. Check to see if the accepted label is in the acceptance table. If the accepted route entry is not in my LSB, it will be discarded directly. If it is in my LIB, I will delete the label of the route entry, then add the local tag of LSR to it, and then forward it to the startled LSR.

Label pop-up: when a local router sends a tagged routing entry to a startled router, the source tag carried by the routing entry is deleted and a startled local label is added. (the condition is that the tags at both ends are mapped in the FIB.)

Transmission of data packets of MPLS

When the edge router learns the routing information on the access side through the IGP protocol, it will check whether the routing information is to be forwarded by label.

If you want to forward the label of the MSPL protocol, then deploy the MPLS protocol on the intranet of the ISP operator. After the establishment of the MPLS neighbor of the private network is completed, the data will be forwarded.

When ELSR accepts an external route entry, it needs to add the local label number to the accepted route entry, and then check the local FIB table to find the router that accepts the label in the next hop. When the next-hop router receives the tagged route entry, it will remove the label and check the LFIB when it is labeled as the next-hop router of this router until the route entry is transmitted to the ELSR router. At this point, you will find that the entry corresponding to the corresponding tag is unntagged to remove all the tags. Restore the route.

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