For MPLS overview and RouterOS supported MPLS features see MPLS Overview.
MPLS RSVP TE tunnels are a way to establish unidirectional label switching paths. In general RSVP TE serves similar purpose as label distribution using LDP protocol - establishing label switched path that ensures frame delivery from ingress to egress router, but with additional features:
- possibility to establish label switching path using either full or partial explicit route;
- constraint based LSP establishment - label switching path is established over links that fulfill requirements, such as bandwidth and link properties.
MPLS RSVP TE is based on RSVP protocol with extensions introduced by RFC 3209 that adds support for explicit route and label exchange.