backup tunnel—An MPLS traffic engineering tunnel used to protect another (primary) tunnel’s traffic when a link or node failure occurs.
Fast Reroute—Fast Reroute (FRR) is a mechanism for protecting MPLS traffic engineering LSPs from link and node failure by locally repairing the LSPs at the point of failure, allowing data to continue to flow on them while their headend devices attempt to establish end-to-end LSPs to replace them. FRR locally repairs the protected LSPs by rerouting them over backup tunnels that bypass failed links or nodes.
graceful restart—A process for helping an RP restart after a node failure has occurred.
ISSU—In Service Software Upgrade. Software upgrade without service interruption.
LSP—label switched path. A path that a labeled packet follows over several hops, starting at an ingress LSR and ending at an egress LSR.
LSR—label switch router. A Layer 3 device that forwards a packet based on the value of a label encapsulated in the packet.
mesh group—A set of label switch routers (LSRs) that are members of a full or partial network of traffic engineering label switched paths (LSPs).
MPLS—Multiprotocol Label Switching. A switching method that forwards IP traffic using a label. This label instructs the devices in the network where to forward the packets based on preestablished IP routing information.
NSF—nonstop forwarding. The ability of a device to continue to forward traffic to a device that may be recovering from a failure. Also, the ability of a device recovering from a failure to continue to correctly forward traffic sent to it by a peer.
primary tunnel—An MPLS tunnel whose LSP can be fast-rerouted if there is a failure.
SSO—stateful switchover. SSO refers to the implementation of Cisco software that allows applications and features to maintain a defined state between an active and standby RP. When a switchover occurs, forwarding and sessions are maintained. Along with NSF, SSO makes an RP failure undetectable to the network.
TE—traffic engineering. The techniques and processes used to cause routed traffic to travel through the network on a path other than the one that would have been chosen if standard routing methods had been used.
tunnel—A secure communication path between two peers. A traffic engineering tunnel is a label switched tunnel that is used for traffic engineering. Such a tunnel is set up through means other than a normal Layer 3 device.