D-Link DGS-6600-48TS Configuration Guide - Page 353

Volume 5-Multiprotocol Label Switching / Chapter 33-Multiprotocol Label Switching (MPLS) MPLS Configuration Commands port is set to 3503. The corresponding label is pushed to the label stack of the echo request. The TTL in the outmost label is set to 255. The labeled echo request is forwarded via the LSP. When the echo request arrive the egress, it is sent to control plane of the egress LSR. The egress LSR validates the echo request and sends reply packet to R1. The MPLS echo reply is a UDP packet. The source IP address is the replier; the source port is 3503. The destination IP address and UDP port are copied from the source IP address and UDP port of the echo request. The IP TTL is set to 255. Step 1 2 3 4 5 Router R1 R2 R4 R4 to R2 R1 Action Initiates an LSP ping request for an FEC at the target router R4 and sends an echo request to R2. Receives the echo request packets and forwards it through transit router R3 to the penultimate router R4. Receives the IP packet, processes the echo request, and sends an MPLS echo reply R1. Receives the echo reply and forwards it back towards R1, the originating router. Receives the MPLS echo reply in response to its MPLS echo request. Table 33-2 LSP ping example LSP Traceroute LSP traceroute also uses MPLS echo request and reply packets to test an LSP. The TTL in the outmost label of the MPLS echo requests is set successively to 1, 2, 3, and so on. It force the echo request expired at each successive LSR along the LSP. The LSR returns an MPLS echo reply containing information about the successive LSR in response to the TTL-expired MPLS packet. FEC A Echo request R1 R2 R3 R4 Ingress Step 1 Step 2 Step 3 Step 6 Step 5 Step 4 Step 7 Step 9 Echo reply Egress Step 8 FEC B Figure 33-3 LSP traceroute DGS-6600 Configuration Guide 353