Figure 23 depicts an LDP LSP being tunneled through an RSVP LSP. (For definitions of label operations, see Label Description.) The shaded inner oval represents the RSVP domain, whereas the outer oval depicts the LDP domain. RSVP establishes an LSP through routers B, C, D, and E, with the sequence of labels L3, L4. LDP establishes an LSP through Routers A, B, E, F, and G, with the sequence of labels L1, L2, L5. LDP views the RSVP LSP between Routers B and E as a single hop.
When the packet arrives at Router A, it enters the LSP established by LDP, and a label (L1) is pushed onto the packet. When the packet arrives at Router B, the label (L1) is swapped with another label (L2). Because the packet is entering the traffic-engineered LSP established by RSVP, a second label (L3) is pushed onto the packet.
This outer label (L3) is swapped with a new label (L4) at the intermediate router (C) within the RSVP LSP tunnel, and when the penultimate router (D) is reached, the top label is popped. Router E swaps the label (L2) with a new label (L5), and the penultimate router for the LDP-established LSP (F) pops the last label.
Figure 23: Swap and Push When LDP LSPs Are Tunneled Through RSVP LSPs
Figure 24 depicts double push label operation (L1L2), which is used when the ingress router (A) of the LDP and the RSVP are the same router. Note that Router D is the penultimate hop for the LDP-established LSP, so L2 is popped from the packet by Router D.
Figure 24: Double Push When LDP LSPs Are Tunneled Through RSVP LSPs
 | Copyright © 2009, Juniper Networks, Inc. All rights reserved. Trademark Notice. | |