MPLS Terms and Acronyms defines common MPLS terms and acronyms.
| Term or Acronym | Description |
|---|---|
| CSPF | Constrained Shortest Path First. Route selection determined by an algorithm based on available link bandwidth and path cost. |
| DoD | Downstream-on-Demand. Distribution of labels as a result of explicit upstream label requests. |
| DU | Downstream Unsolicited. Distribution of labels downstream without an explicit label request. |
| EXP bits | A three-bit experimental field in an MPLS shim header. |
| FEC | Forward Equivalence Class. A group of packets that are forwarded in the same manner (for example, over the same Label Switched Path). |
| Label | A short, fixed-length identifier used to forward packets from a given link. |
| Label stack | A set of one or more MPLS labels used by MPLS to forward packets to the appropriate destination. |
| Label swapping |
Lookup and replacement of an incoming label with the appropriate outgoing label. |
| LDP | Label Distribution Protocol. A protocol defined by the IETF used to establish an MPLS Label Switched Path (LSP). |
| LER | Label Edge Router. A Label Switch Router that is at the beginning (ingress) or end (egress) of an LSP. |
| LSP | Label Switched Path. The unidirectional MPLS connection between two routers over which packets are sent. LSPs are established using LDP or RSVP-TE. |
| LSR | Label Switch Router. A router that receives and transmits packets on an MPLS network. |
| MPLS | MultiProtocol Label Switching. A set of protocols defined by the IETF used to transmit information based on a label-switching forwarding algorithm. |
| NHLFE | Next Hop Label Forwarding Entry. The NHLFE represents the MPLS router next hop along the LSP. |
| PHP | Penultimate Hop Popping. A label stack optimization used for conserving the number of allocated labels. |
| PW | Pseudowire. A logical point-to-point connection. |
| RSVP | Resource ReSerVation Protocol (RSVP). A resource setup protocol designed for an integrated services network. |
| RSVP-TE | Resource ReSerVation Protocol-Traffic Engineering (RSVP-TE). The combination of RSVP and MPLS label signaling to provide traffic engineered LSPs as specified in RFC 3209RFC 3209, RSVP-TE: Extensions to RSVP for LSP Tunnels. |
| Shim header | MPLS-specific header information that is inserted between layer-2 and layer-3 information in the data packet. |
| SP | Service Provider. An entity that provides network services for individuals or organizations. |
| TE | Traffic Engineering. The provisioning of an autonomous flow along a specified network path. |
| Transport LSP | Any active LSP used to forward traffic through an MPLS network. |
| VPLS | Virtual Private LAN Service (VPLS). A multipoint Layer 2 VPN service that has the property that all PW tunnels within a VPN are signaled with the same vcid, where the vcid represents the VPN identifier. |
| VPN | Virtual Private Network (VPN). A logical private network domain that spans a public or service provider network infrastructure. |
| VPWS | Virtual Private Wire Service (VPWS). A point-to-point Layer 2 VPN service that operates over MPLS. |