MPLS Fundamentals

Targeted LDP Session

Normally, LDP sessions are set up between directly connected LSRs. In a network in which the IGP routes need to be labeled, this is sufficient, because the label switching of packets is hop per hop. Therefore, if the label bindings are advertised hop per hop for the IGP routes, the LSPs are set up. However, in some cases, a remote or targeted LDP session is needed. This is an LDP session between LSRs that are not directly connected. Examples in which the targeted LDP session is needed are AToM networks and TE tunnels in an MPLS VPN network. In the case of AToM, an LDP session must exist between each pair of PE routers. The remote LDP session is set up when configuring the xconnect command on the PE routers of the AToM network. ...