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HDLC

what is HDLC and PPP
Asked by ARUN HR | Oct 14, 2010 |  Reply now
Replies (1)
View CCNA-Teacher T 's Profile
1. PPP and Frame Relay both are l2 protocols.
I know about PPP, about CHAP etc. I know a few things about FR
also..Like the packets are broken down into frames and transmitted, and
about DLCIs.. But I am not able to get the exact differences between
PPP and Frame Relay.

HDLC is used on point-to-pont serial links suc as T1s, DS3 and now
Packet-over-SONET (POS). It has a low overhead in terms of the
additional bytes required over and above the layer 3 payload. There is
no authentication protocol for HDLC.


PPP was and is heavily used in async dial-up and provide for
authentication using PAP or CHAP protocol. Now there is also PPP over
Ethernet (PPPoE).

A variation of PPP known as multi-link PPP (MLPPP) is quite popular for
loading balancing parallet circuit like T1's.

HDLC is used on point-to-pont serial links suc as T1s, DS3 and now
> Packet-over-SONET (POS). It has a low overhead in terms of the
> additional bytes required over and above the layer 3 payload. There is
> no authentication protocol for HDLC.
>
> PPP was and is heavily used in async dial-up and provide for
> authentication using PAP or CHAP protocol. Now there is also PPP over
> Ethernet (PPPoE).

PPP and Cisco HDLC has the *same* amount of overhead. PPP is the more
modern and probably better maintained protocol. PPP is also heavily used
on point-to-pont links.
Oct 20, 2010