HDLC Vs PPP

Discussion in 'Cisco' started by answers, Sep 10, 2006.

  1. answers

    answers Guest

    what are the major differences between HDLC and PPP? How are they
    mainly used?
     
    answers, Sep 10, 2006
    #1
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  2. answers

    answers Guest

    answers wrote:
    > what are the major differences between HDLC and PPP? How are they
    > mainly used?


    And forgot to mention...what are the differences between PPP and Frame
    relay ?
     
    answers, Sep 10, 2006
    #2
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  3. answers

    Merv Guest

    answers wrote:
    > answers wrote:
    > > what are the major differences between HDLC and PPP? How are they
    > > mainly used?

    >
    > And forgot to mention...what are the differences between PPP and Frame
    > relay ?



    Perhaps you could post the results of your own research so far and then
    we can comment
     
    Merv, Sep 10, 2006
    #3
  4. answers

    answers Guest

    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..
     
    answers, Sep 10, 2006
    #4
  5. answers

    Merv Guest

    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.
     
    Merv, Sep 10, 2006
    #5
  6. answers

    Steinar Haug Guest

    > 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.

    Steinar Haug, Nethelp consulting,
     
    Steinar Haug, Sep 10, 2006
    #6
  7. answers

    Merv Guest

    I thought PPP has a 2 byte protocol field in addition to the flag,
    control and address fields
     
    Merv, Sep 10, 2006
    #7
  8. answers

    Steinar Haug Guest

    > I thought PPP has a 2 byte protocol field in addition to the flag,
    > control and address fields


    Yes, so does Cisco HDLC. See

    http://www.nethelp.no/net/cisco-hdlc.txt

    for a description of the format.

    Steinar Haug, Nethelp consulting,
     
    Steinar Haug, Sep 11, 2006
    #8
  9. answers

    James Guest

    If you ever want to run VoIP over your data networks always run PPP or
    Frame Relay. HDLC does not handle fragmentation well, jitter can be
    controlled and is more predictable with PPP and Frame Relay .

    James

    Steinar Haug wrote:
    > > I thought PPP has a 2 byte protocol field in addition to the flag,
    > > control and address fields

    >
    > Yes, so does Cisco HDLC. See
    >
    > http://www.nethelp.no/net/cisco-hdlc.txt
    >
    > for a description of the format.
    >
    > Steinar Haug, Nethelp consulting,
     
    James, Sep 11, 2006
    #9
  10. answers

    Steinar Haug Guest

    > If you ever want to run VoIP over your data networks always run PPP or
    > Frame Relay. HDLC does not handle fragmentation well, jitter can be
    > controlled and is more predictable with PPP and Frame Relay .


    Um, Cisco HDLC does not handle fragmentation *at all* - but that's okay
    as long as IP does it. If you want your link layer protocol to handle
    fragmentation I agree that PPP may be a better choice.

    On the other hand, for basic, non-fragmented packets PPP, Cisco HDLC and
    Frame Relay all give you mostly the same functionality (with the addition
    of an extra multiplexing field, the DLCI, for Frame Relay).

    Steinar Haug, Nethelp consulting,
     
    Steinar Haug, Sep 11, 2006
    #10
  11. answers

    dinesh3663

    Joined:
    Aug 6, 2007
    Messages:
    2
    Encapsulation

    We have configured PPP on one serial interface and HDLC on another serial interface.

    We have given 2 default routes for 2 serials.

    If i Trace route one destination IP it always takes the Default path of serial interface the encapsulation is PPP.

    Any issue.
     
    dinesh3663, Aug 6, 2007
    #11
  12. answers

    theapplebee

    Joined:
    Jun 19, 2009
    Messages:
    67
    Location:
    USA
    Frame-relay is enhanced from X.25. It doesn't have error checking scheme on layer 2. It uses large frame size. Still many tier 1 ISP is using frame-relay protocol.

    HDLC is simple and easy to use. However, Cisco that is one of leader in telecom market modified HDLC and made non-compatible HDLC(another word, Cisco propriatary). Meaning to use Cisco HDLC, devices at both end should be Cisco routers. Still heavily used for point-to-point topology and circuit testing.

    PPP is common WAN protocal. 70% of ISP links (not T1s.... ) that are above Multi-links, DS3 and OCs. As you know, it provides authentication for secure scheme.

    Sharing Cisco Expertise : www.ipBalance.com
     
    Last edited: Apr 17, 2010
    theapplebee, Nov 4, 2009
    #12
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