The MPLS WG Archive

["James R. Leu" <jleu@laurelnetworks.com>]

On Thu, Jun 22, 2000 at 06:19:37PM -0400, Robert Streijl wrote:
> 
> 
> Hi,
> 
> I am fairly new to MPLS and I am currently reading through the produced drafts.
> I bumped into Type Length Values used for encoding.
> I started with the architecture and then started reading the LDP spec, but I
> still don't get it.
> 
> I understand that LDP PDUs can contain multiple messages. I also understand that
> there are different message types, but I don't understand the role of TLVs.
> The TLVs show byte allocations, so I am wondering if it goes in the LDP PDU or
> LDP messages. First I thought it is appended to the LDP PDU header, then I
> thought it is one of the fields in each of the messages. However, the TLV
> messages are bigger than the reserved space in the LDP messages.
> 
> Is this encoding information somehow stored in a different way, not in the LDP
> messages/PDUs?
> 
> Can somebody please help me understand this?

Each PDU contains an LDP Message.  Each LDP Message contains an LDP Message
header and some LDP TLVs.  The LDP Message header dictats which type of LDP
Message it is, and that determins which LDP TLVs will follow.

If your looking for a sample implementation look at MPLS for Linux at

http://nero.doit.wisc.edu/mpls-linux/

It utilizes LDP PDU encode and decode functions from Nortel Networks.

Jim
-- 
James R. Leu
Software Engineer
Laurel Networks, Inc
jleu@laurelnetworks.com