Question: tlvs are mandatory in lldp advertisements?
Answer: Each LLDP frame starts with the following mandatory TLVs: Chassis ID, Port ID, and Time-to-Live. The mandatory TLVs are followed by any number of optional TLVs. The frame ends with a special TLV, named end of LLDPDU in which both the type and length fields are 0. According to IEEE Std 802.1AB, §9.6.