Use of PPP over frame-relay

Unanswered Question
Dec 21st, 2007

What is the use of using PPP on frame-relay link inspite of HDLC.



I have this problem too.
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Overall Rating: 3.5 (2 ratings)
Paolo Bevilacqua Fri, 12/21/2007 - 07:14

Underlying the frame-relay encapsulation, there is always HDLC. This is dictated by standards and cannot be changed.

But it is possible to run PPP encapsulation at VC level. Some people likes to do that for AAA purposes, interoperatbility in mixed environments, etc.

Normally, it is not necessary to do so.

Hope this helps, please rate post if it does!

mohindersingh Fri, 12/21/2007 - 09:00

Hi Bevilacqua,

Thanks for the reply...

I configured PPP in a test lab with OSPF as routing protocol with point to multipoint works fine..

Can you explain your tought of saying ppp can be used only on VC level in frame-relay..

Secondally I want to know the benefits which PPP can give over HDLC on frame relay or private circuits..



Paolo Bevilacqua Fri, 12/21/2007 - 09:17


Basically as said above, PPP Vs regular FR, gives you the advantages of AAA and nothing else.

wochanda Fri, 12/21/2007 - 17:08

The biggest use of PPPoFR that I've seen is for voice deployments over a FR<->ATM connection.

In the event your link is less than 768kb, it is necessary to do L2 fragmentation and interleaving to ensure good voice quality. This is built natively into both FR and ATM, but in hybrid FR/ATM circuits there is no way to achieve achieve fragmentation natively.

Since fragmentation is built into PPP multilink, it is common to deploy it over these FR<->ATM circuits to allow for fragmentation.

mohindersingh Fri, 12/21/2007 - 23:25

hi Wochanda,

Thanks for the reply...

Can you let me know the PPP multilink features use in load balancing which is not present in HDLC.

like in OSPF we don,t have more loadbalancing techniques except equal cost load balancing..

can we acheive some thing if we go with OSPF with PPP with multilink features?

i mean to say load balancing between two unequal cost links?

like set threshold on one link and if threshold of the link crosses traffic start flowing on other link?



Paolo Bevilacqua Sat, 12/22/2007 - 05:41

Not sure why the post above by wochanda has been low-rated.

It exposed an application about which I didn't thought or forgot about. All the information given is correct, and easily presented. My rating, a '5'.


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