Practical advantages:encapsulation HDLC vs PPP

Answered Question
Aug 18th, 2010

Folks, is there any reason one should be using HDLC as layer 2 encapsulation these days?


I know that PPP provides authentication and information I have is that when it comes to overhead, they are very similar.


In case you see practical reasons or advantages of using HDLC please let me know.

Correct Answer by Giuseppe Larosa about 6 years 6 months ago

Hello Marlon,

I agree also PPP provides for loopback detection with the PPP magic number, link quality monitor and it is standards based.


only disadvantage:

you need to add encapsulation ppp in interface configuration




Hope to help

Giuseppe

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (3 ratings)
Loading.
Correct Answer
Giuseppe Larosa Wed, 08/18/2010 - 13:39

Hello Marlon,

I agree also PPP provides for loopback detection with the PPP magic number, link quality monitor and it is standards based.


only disadvantage:

you need to add encapsulation ppp in interface configuration




Hope to help

Giuseppe

news2010a Wed, 08/18/2010 - 14:15

Great.


One more point:
HDLC  was developed by Cisco and therefore it is proprietary, right?


So I would pick PPP if using open standard (in case other router brand is ever introduced) is to be considered.

news2010a Thu, 08/19/2010 - 08:27

Thanks for all good answers.


Just a correction on my own assumption:Juniper does support HDLC as well.

Peter Paluch Thu, 08/19/2010 - 08:36

Marlon,


The HDLC is a standard and many vendors should support it. The question is whether they also support the slightly changed Cisco version of the HDLC. The original HDLC did not have a protocol ID field so an HDLC circuit could transport only a single protocol. Cisco improved this limitation at the expense of making its own cHDLC incompatible with the standard. Actually, the "HDLC" run by default on Cisco serial and ISDN interfaces is the cHDLC, not the plain basic HDLC.


You may find more details here:


http://en.wikipedia.org/wiki/Cisco_HDLC


Best regards,

Peter

Giuseppe Larosa Thu, 08/19/2010 - 08:44

Hello Marlon,

Juniper supports also Cisco HDLC


Peter is right about what makes the difference between Cisco HDLC and original HDLC


Hope to help

Giuseppe

Peter Paluch Wed, 08/18/2010 - 14:15

Marlon, Giuseppe,


I completely agree with Giuseppe, adding features like support for compression (though Cisco HDLC supports it, too), multilink PPP with optional LFI mechanism, extensible authentication and probably others.


An irony is that the PPP datagrams themselves are encapsulated in HDLC-like framing RFC 1662 describes the gory details.


Best regards

Peter

CSCO11717902 Wed, 08/18/2010 - 17:36

I prefer to use ppp, this is very common in the industry, I work in a ISP, and everything is PPP I didn't see HDLC.

Actions

This Discussion