Hi,

This is Ankitha from Bangalore, India.
As I am doing my project on PPP protocol, I require necessary documents.
I am requesting you to send me HLD document link for PPP protocol.
Thank you.

Cheers,
Ankitha

I'm going to assume when you mention "HLD" and "High Level Design" you do not mean you are asking for a high level document that you can use as is for your own project work, but are either asking for docs that generally describe the PPP protocol, or are actually referring to the HDLC link layer protocol that often encapsulates PPP.

For the raw technical specs, best see the relevant RFCs:

RFC 1661 (rfc1661) - The Point-to-Point Protocol (PPP)
RFC 1662 (rfc1662) - PPP in HDLC-like Framing


And for a more abstract and general discussion, perhaps the Wikipedia articles:

Point-to-Point Protocol - Wikipedia, the free encyclopedia
High-Level Data Link Control - Wikipedia, the free encyclopedia


At any rate, these links should give you a good starting point. Hope this helps.