PLANET XGS3-24042 User 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