PLANET XGS3-24042 - Manual (Page 656)

80-10
TLV Encoding
LDP encapsulates parameters in LDP messages via TLV (Type-Length-Value). The LDP TLV format is as
follows:
Figure 80-2 The TVL Format of LDP
 U bit：Unknown flag, I bit. If the U flag is 0, LSR should notify the source LSR of the packet and
ignore the whole message; otherwise, ignore this TLV parameter and analyze other ones normally.
 F bit：Forwarding unknown TLV flag, 1bit. This flag only applies to LDP messages with unknown TLV
and a U bit set as 1. If the F flag is 0, stop forwarding unknown TLV parameters; otherwise, forward
them;
 Type：Type, 14 bits.
 Length：Length, 1 byte. The length of TLV value segment.
 Value：The Value segment, whose length is defined by the parameter of “Length”.
 The Value segment of TLV can also contain TLV parameters, meaning that, TLV are embeddable.
The first byte of TLV doesn’t need alignment.
Currently defined TLV types:
TLV Type
FEC 0x0100
Address List 0x0101
Hop Count 0x0103
Path Vector 0x0104
Generic Label 0x0200
ATM Label 0x0201
Frame Relay Label 0x0202
Status 0x0300
Extended Status 0x0301
Returned PDU 0x0302
Returned Message 0x0303
Common Hello Parameters 0x0400
IPv4 Transport Address 0x0401
Configuration Sequence Number 0x0402
IPv6 Transport Address 0x0403