LDP messages

LDP mainly uses the following types of messages:

• Discovery messages—Declare and maintain the presence of LSRs, such as Hello messages.

• Session messages—Establish, maintain, and terminate sessions between LDP peers, such as Initialization messages used for parameter negotiation and Keepalive messages used to maintain sessions.

• Advertisement messages—Create, alter, and remove FEC-label mappings, such as Label Mapping messages used to advertise FEC-label mappings.

• Notification messages—Provide advisory information and notify errors, such as Notification messages.

LDP uses UDP to transport discovery messages for efficiency, and uses TCP to transport session, advertisement, and notification messages for reliability.