1-7Figure 1-3 A case for Enhanced DLDP modez In normal DLDP mode, only fiber cross-connected unidirectional links (as shown in Figure 1-1 ) canbe detected.z In enhanced DLDP mode, two types of unidirectional links can be detected. One is fibercross-connected links (as shown in Figure 1-1). The other refers to fiber pairs with one fiber notconnected or disconnected (as shown in Figure 1-2). To detect unidirectional links that are of thelatter type, you need to configure the ports to operate at specific speed and in full duplex mode.Otherwise, DLDP cannot take effect.DLDP Implementation1) If the DLDP-enabled link is up, DLDP sends DLDP packets to the peer device, andanalyzes/processes the DLDP packets received from the peer device. DLDP packets sent indifferent DLDP states are of different types.Table 1-5 DLDP state and DLDP packet typeDLDP state Type of the DLDP packets sentActive Advertisement packets, with the RSY flag set or not set.Advertisement Advertisement packetsProbe Probe packets2) A DLDP packet received is processed as follows:z In authentication mode, the DLDP packet is authenticated and is then dropped if it fails theauthentication.z The packet is further processed, as described in Table 1-6.You can prevent network attacks and illegal detect through DLDP authentication. Three DLDPauthentication modes exist: non-authentication, plain text authentication, MD5 authentication.
