1-4DLDP StatusA link can be in one of these DLDP states: initial, inactive, active, advertisement, probe, disable, anddelaydown.Table 1-2 DLDP statusStatus DescriptionInitial Initial status before DLDP is enabled.Inactive DLDP is enabled but the corresponding link is downActive DLDP is enabled, and the link is up or an neighbor entry is clearedAdvertisementAll neighbors communicate normally in both directions, or DLDPremains in active state for more than five seconds and enters thisstatus. It is a stable state where no unidirectional link is foundProbeDHCP sends packets to check whether the link is a unidirectional. Itenables the probe sending timer and an echo waiting timer for eachtarget neighbor.DisableDLDP detects a unidirectional link, or finds (in enhanced mode) that aneighbor disappears. In this case, DLDP sends and receives onlyrecover probe packets and recover echo packets.DelayDownWhen a device in the active, advertisement, or probe DLDP statereceives a port down message, it does not removes thecorresponding neighbor immediately, neither does it changes to theinactive state. Instead, it changes to the delaydown state first.When a device changes to the delaydown state, the related DLDPneighbor information remains, and the DelayDown timer is triggered.After the DelayDown timer expires, the DLDP neighbor information isremoved.DLDP TimersTable 1-3 DLDP timersTimer DescriptionAdvertisementsending timerInterval between sending advertisement packets, which can be configuredon a command line interface.By default, the timer length is 5 seconds.Probe sending timer The interval is 0.5 seconds. In the probe state, DLDP sends two probepackets in a second.Echo waiting timerIt is enabled when DLDP enters the probe state. The echo waiting timerlength is 10 seconds.If no echo packet is received from the neighbor when the Echo waiting timerexpires, the state of the local end is set to unidirectional link (one-way audio)and the state machine turns into the disable state. DLDP outputs log andtracking information, sends flush packets. Depending on the user-definedDLDP down mode, DLDP disables the local port automatically or promptsyou to disable the port manually. At the same time, DLDP deletes theneighbor entry.
