08-18-2010 01:17 PM - edited 03-04-2019 09:28 AM
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.
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08-18-2010 01:39 PM
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
08-18-2010 01:39 PM
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
08-18-2010 02:15 PM
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.
08-18-2010 10:01 PM
Good post
08-19-2010 08:27 AM
Thanks for all good answers.
Just a correction on my own assumption:Juniper does support HDLC as well.
08-19-2010 08:36 AM
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
08-19-2010 08:44 AM
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
08-18-2010 02:15 PM
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
08-18-2010 05:36 PM
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.
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