3Com 4500G Family Configuration Manual page 850

Figure 1-2 A scenario for the Enhanced DLDP mode
GE1/0/50
(up)
Device A
Ethernet
optical port
Fiber link
In normal DLDP mode, only fiber cross-connected unidirectional links (as shown in
be detected.
In enhanced DLDP mode, two types of unidirectional links can be detected. One is fiber
cross-connected links, and the other refers to fiber pairs with one fiber not connected or broken as
shown in Figure 1-1. To detect unidirectional links that are of the latter type, you need to configure
the ports to operate at specific speed and in full duplex mode. Otherwise, DLDP cannot take effect.
When a fiber of a fiber pair is not connected or is broken, the port that can receive optical signals is
in Disable state; the other port is in Inactive state.
DLDP authentication mode
You can prevent network attacks and illegal detect through DLDP authentication. Three DLDP
authentication modes exist, as described below.
Non-authentication. In this mode, the sending side sets the Authentication field and the
Authentication type field of DLDP packets to 0. The receiving side checks the values of the two
fields of received DLDP packets and drops the packets with the two fields conflicting with the
corresponding local configuration.
Plain text authentication. In this mode, before sending a DLDP packet, the sending side sets the
Authentication field to the password configured in plain text and sets the Authentication type field to
1. The receiving side checks the values of the two fields of received DLDP packets and drops the
packets with the two fields conflicting with the corresponding local configuration.
MD5 authentication. In this mode, before sending a packet, the sending side encrypts the user
configured password using MD5 algorithm, assigns the digest to the Authentication field, and sets
the Authentication type field to 2. The receiving side checks the values of the two fields of received
DLDP packets and drops the packets with the two fields conflicting with the corresponding local
configuration.
DLDP implementation
1) On a DLDP-enabled link that is in up state, DLDP sends DLDP packets to the peer device and
processes the DLDP packets received from the peer device. DLDP packets sent vary with DLDP
states. Table 1-4
GE1/0/50
(down)
Tx end Rx end
Unconnected or broken fiber
lists DLDP states and the corresponding packets.
Device B
1-5
Figure 1-1 ) can