3Com 5500-SI DLDP operating mode DLDP can operate in two modes: normal and enhanced.

DLDP Overview 91

DLDP operating modeDLDP can operate in two modes: normal and enhanced.DLDP implementation1If the link is up after DLDP is enabled on the port, DLDP sends DLDP packets to the peer device, and analyses and processes DLDP packets received from the peer device. DLDP in different status sends different packets..

Entry aging timer When a new neighbor joins, a neighbor entry is created, and the

corresponding entry aging timer is enabled.When an advertisement

packet is received from a neighbor, the neighbor entry is updated, and

the corresponding entry aging timer is reset.In normal mode, if no packet

is received from the neighbor when the entry aging timer expires, DLDP

sends an advertisement packet with RSY tag, and deletes the neighbor

entry.In enhanced mode, if no packet is received from the neighbor

when the entry aging timer expires, DLDP enables the enhanced

timer.The time interval set for the entry aging timer is three times of that

for the advertisement timer.

Enhanced timer In enhanced mode, if no packet is received from the neighbor when the

entry aging timer expires, DLDP enables the enhanced timer for the

neighbor. The timeout time for the enhanced timer is 10 seconds.The

enhanced timer then sends two probe packets every one second and

totally eight packets continuously to the neighbor.If no echo packet is

received from the neighbor when the Echo waiting timer expires, the

local end is set to unidirectional communication status and the state

machine turns into disable status. DLDP outputs log and tracking

information, sends flush packets. Depending on the user-defined DLDP

down mode, DLDP disables the local port automatically or prompt the

user to disable the port manually. DLDP deletes the neighbor entry.

Table73 DLDP operating mode and neighbor entry aging

DLDP operating

mode

Whether DLDP

probes neighbor

during neighbor

entry aging

Whether entry aging

timer is enabled during

neighbor entry aging

Whether enhanced

timer is enabled

when entry aging

timer expire

Normal mode No Yes (the neighbor entry ages

after the entry aging timer

expires)

Enhanced mode Yes Yes (the enhancement timer

is enabled after the entry

aging timer expires)

Yes (When the

enhanced timer expires,

the local end is set to

single pass status, and

the neighbor entry

ages)

Table72 DLDP timers (continued)

Timer Description

Table74 Types of packets sent by DLDP

DLDP status Packet types

Active Advertisement packets, including those with or without RSY tags

Advertisement Advertisement packets

Probe Probe packets