Label Switched Paths; Label Advertisement Modes - Extreme Networks BlackDiamond 6800 MPLS Installation And User Manual

Configuring the MPLS Module
Table 3-1: MPLS Terms and Acronyms (continued)
Term or Acronym
TLS Tunnel
Tunnel LSP
VC
VC Tunnel
VPLS
VPN

Label Switched Paths

Protocols that use label switching are connection-oriented. In MPLS, the connections are
called Label Switched Paths (LSPs) and are unidirectional in nature.
LSPs are established using the LDP or RSVP-TE. Once established, an LSP can be used
to carry IP traffic or to tunnel other types of traffic, such as bridged MAC frames. The
tunnel aspects of LSPs, which are important in supporting virtual private networks
(VPNs), result from the fact that forwarding is based solely on labels and not on any
other information carried within the packet.

Label Advertisement Modes

MPLS provides two modes for advertising labels:
• Downstream-on-demand (DoD)
• Downstream unsolicited (DU)
Using DoD mode, label bindings are only distributed in response to explicit requests. A
typical LSP establishment flow begins when the ingress LER originates a label request
message to request a label binding for a particular FEC (for a particular IP address
prefix or IP host address). The label request message follows the normal routed path to
the FEC. The egress LER responds with a label mapping message that includes a label
3-4
Description
A specific type of VC tunnel that carries only VLAN tagged Ethernet
traffic.
Any active RSVP-TE LSP used to forward IP traffic through an MPLS
network.
Virtual Circuit. A logical point-to-point connection.
A two label stack LSP used to tunnel a specific type of traffic. The
type of traffic carried over the VC tunnel is negotiated when VC
tunnel is established.
Virtual Private LAN Services.
that has the property that all VC tunnels within a VPN are
signaled with the same vcid, where the vcid represents the
VPN identifier.
Virtual Private Network. A logical private network domain that spans
a public or service provider network infrastructure.
A multipoint Layer-2 VPN service
MPLS Module Installation and User Guide