1-7Table 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.Table 1-6 The procedure to process a received DLDP packetPacket type Processing procedureIf the corresponding neighbor entry does not exist on thelocal device, DLDP creates the neighbor entry, triggersthe entry aging timer, and switches to the probe state.AdvertisementpacketExtracts neighborinformationIf the corresponding neighbor entry already exists on thelocal device, DLDP resets the aging timer of the entry.Flush packet Removes the neighbor entry from the local deviceCreates the neighbor entry if it does not exist on the localdevice.Probe packetSends echo packetscontaining bothneighbor and its owninformation to thepeerResets the aging timer of the entry if the neighbor entryalready exists on the local device.No Drops the echo packetNo Drops the echo packetSets the flag bit of the neighborto bidirectional linkEcho packetChecks tosee if thelocal deviceis in theprobe stateYesChecks tosee if theneighborinformationcontained inthe packet isthe same asthat on thelocal deviceYes If all neighbors are in thebidirectional link state, DLDPswitches from the probe state tothe advertisement state, andsets the echo waiting timer to 0.3) If no echo packet is received from the neighbor, DLDP performs the following processing:
