Sybex CCNA Flash Cards #19

Daniel333

Alright, does this question make sense to anyone else?

#19) Which protocols are part of PPP?

Answer: HDLC, LCP, NCP

I always thought of HDLC as being a competing prococol for PPP. Anyone point me in the right direction of a document to explain this answer? Or is the answer wrong?

thanks as always

Netstudent

Sybex 4th edition...Talking about PPP in the WAN chapter


The basic purpose of PPP is to transport layer 3 packets across a Data Link layer point-to- point link. Figure 11.3 shows the protocol stack compared to the OSI reference model.


Figure 11.3: Point-to-point protocol stack
PPP contains four main components:



EIA/TIA-232-C, V.24, V.35, and ISDN

A Physical layer international standard for serial communication.

HDLC

A method for encapsulating datagrams over serial links.

LCP

A method of establishing, configuring, maintaining, and terminating the point-to- point connection.

NCP

A method of establishing and configuring different Network layer protocols. NCP is designed to allow the simultaneous use of multiple Network layer protocols. Some examples of protocols here are IPCP (Internet Protocol Control Protocol) and IPXCP (Internetwork Packet Exchange Control Protocol).

Think of PPP being nothing more than HDLC with a few more bells and whistles.

Netstudent

I actually have the same question in my "Do I know this Quiz" in Cisco press ICND Chapter 9.

But the answer choices are:

HDLC
LCP
LAPD
IPCP

And Wendell says the answer is LCP and IPCP

WTH is IPCP? I'm getting so frustrated with all this Cisco inconsistency crap. So my previous post may be wrong so who the hell knows. IP control protocol or something like that so i dunno.

HOLY HELL it's 5:30 I gatta go home. I'v been so submerged in Cisco that I forgot what time it was.

Daniel333

I guess that is where I am confused. How can PPP just be th same thing as HDLC except with more bells and whistles. When HDLC is a part of PPP?

If it's a part of PPP when why do I have to set my encap on my serial links? HDLC seems to operate at layer 3, while PPP layer 2. Am I right in that?

elegua

Daniel333 wrote:

I guess that is where I am confused. How can PPP just be th same thing as HDLC except with more bells and whistles. When HDLC is a part of PPP?

If it's a part of PPP when why do I have to set my encap on my serial links? HDLC seems to operate at layer 3, while PPP layer 2. Am I right in that?

Hi Daniel333;

HDLC protocol resides with Layer 2 of the OSI model.

Hope this help.

Daniel333

DarbyWeaver wrote:

PPP uses HDLC as the "encapsulating protocol" along with the LCP and the NCP.

Wow, that makes sense to me! Thanks!