Tutorial

Advanced MPLS Signaling
(continued)

RSVP, with features added to accommodate MPLS traffic engineering, is called RSVP-TE. The traffic-engineering functions allow for the management of MPLS labels or colors.

Figure 6:  RSVP-TE Path Request

In Figures 6 and 7, we see how a call or path is set up between two endpoints. The target station requests a specific path, with detailed traffic conditions and treatment parameters included in the path-request message.  This message is received, and a reservation message, reserving bandwidth on the network, is sent back to the target. After the first reservation message is received at the target, the data can start to flow in explicit paths from end to end.

Figure 7: RSVP-TE Reservation

This call set-up, or signaling, process is called “soft state,” because the call will be torn down if it is not refreshed in accordance with the refresh timers. In Figure 8, we see that the path-request and reservation messages continue for as long as the data is flowing.

Figure 8: RSVP-TE Path Set Up

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