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The ppp-max-payload trap Highlighted

Latest reply: Apr 28, 2021 14:18:13 590 25 9 0 0

             When you are configuring a BNG gateway, one of the biggest concerns is with de payload length that our subscribers will have available to use on each packet.

 

                Why this is a concern?

 

              With the growth of the use of streaming applications, the traffic tries to use the maximum MTU available on the path. But as you know, on the IPv4 protocol this attribute considers the MTU negotiated by the two ends of the session, and sometimes, if we have a hop with the MTU smaller than what was negotiated between the two ends of the session, we will have fragmentation on the communication.

This fragmentation requires space on buffer to reconstruct the original packets, but to streaming, unfortunately is normal that we have an overflow and discard some content.

 

                When I have to have this concern?

 

             We have to worry about MTU in some points of our network, for example on my MPLS structure, on my transportation contracts, on my subscriber access, etc.

 

                But why the title of this post is “The ppp-max-payload trap”?

 

             One of the points where we must make attention to MTU on our structure is when we use PPPoE to our subscriber's access.

               When we use PPPoE as the protocol to control the connection, we have to add 6 Bytes of the header on the original packet, then the MRU (Maximum Receive Unit) cannot be greater than 1494 Bytes.


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            The default configuration of Huawei´s BNG considers that is not necessary to negotiate the MRU of the connection during the link discovery phase of PPPoE process. If MRU of PPPoE connection is not negotiated during link discovery, the device directly forwards packets smaller than the negotiated MTU and fragments packets that are longer in length.

                In some environments, I already saw administrators changing the default behavior of BNG using the below command:

 

    [HUAWEI] pppoe ppp-max-payload enable

 

           With this command, during the link discovery phase of PPP process, the MRU of the connection will be limited by the smaller value between MTU, and Max Payload value defined by the administrator.

         Studying all the theories of this process, we cannot saw any problem, because in a perfect world all manufacturers correctly follow all RFC and other standards. In this perfect world, we can use any BNG product interacting with any CPE equipment and all of that we read until now works perfectly.

               Unfortunately, we only see a perfect world at the end of Fairy Tales. In our real world the biggest concern of the administrators is to solve a lot of interoperability issues found between the different manufacturers.

             Sometimes I am approached by ISP administrators asking about problems with your subscribers when trying to access streaming contents. This normally is a symptom of problems during the MTU negotiation. More than 80% of the ISPs that ask me about this problem are using this command and experimenting problems with low-cost CPE.

             What I’ve already discovery is that there is some problem during the negotiation phase between Huawei and some low-cost CPEs and for this the MRU set to a wrong value.

          All clients where I deactivate this command, turning the BNG to default configuration do not have this symptom anymore.


              If you need to know more about the PPPoE process, you can use the HCIA-Datacom Training Material using this link. https://e.huawei.com/en/talent/ - /cert/product-details?certifiedProductId=287&authenticationLevel=CTYPE_CARE_HCIA&technicalField=IIC&version=1.0


    To learn more about the command “pppoe max-payload” you can access this link https://support.huawei.com/hedex/hdx.do?docid=EDOC1100169782&id=EN-US_CLIREF_0314069563&lang=en


                  If you have more information to aggregate to this discussion, please, send to us commenting.

 

#HuaweiEntrepriseCommunity

#MVE


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vagkaefer
MVE Created Apr 14, 2021 13:36:39

Nice post, thanks for sharing The ppp-max-payload trap-3882863-1 The ppp-max-payload trap-3882863-2
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LuizPuppin
LuizPuppin Created Apr 14, 2021 13:42:50 (1) (0)
Tks dear @vagkaefer
I know that some cases came to you about this...
Hope that can be useful.  
andersoncf1
andersoncf1 Created Apr 14, 2021 17:10:46 (1) (0)
 
A%20computer%20engineer%20working%20in%20Fiber%20X%20(Brazil).%20HCIA%20(R%26S)%2C%20HCIP%20(R%26S)%2C%20HCPA-IP%20Network%2C%20HCPP-IP%20Network%20and%20HCIA%20(Cloud).
Faridrami
Created Apr 14, 2021 16:09:08

thanks for sharing The ppp-max-payload trap-3883059-1
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LuizPuppin
LuizPuppin Created Apr 14, 2021 16:34:38 (0) (0)
 
andersoncf1
andersoncf1 Created Apr 14, 2021 17:10:55 (0) (0)
 
shakeela
shakeela Created Apr 14, 2021 17:43:54 (0) (0)
 
shakeela
shakeela Created Apr 14, 2021 17:44:00 (0) (0)
 
KleitonSilva
Created Apr 14, 2021 16:58:00

One more time a big contribution to comuunity, awesome!
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LuizPuppin
LuizPuppin Created Apr 14, 2021 17:08:11 (0) (0)
Thanks, dear friend.  
andersoncf1
Moderator Created Apr 14, 2021 17:10:20

Great job! Congrats teacher
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LuizPuppin
LuizPuppin Created Apr 14, 2021 17:41:08 (0) (0)
 
Network%20Engineer%2C%20Post-Graduation%20in%20Computer%20Networks%20and%20Security%2C%20Possessing%20Certifications%20of%20Huawei%3A%20HCIE-R%26S%20(Written)%2C%202x%20HCIP-R%26S%20and%20Security%20and%203x%20HCIA-R%26S%2C%20Security%20and%20WLAN.
shakeela
Created Apr 14, 2021 17:43:29

Good
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LuizPuppin
LuizPuppin Created Apr 14, 2021 18:18:04 (0) (0)
 
shakeela
Created Apr 14, 2021 17:43:35

The ppp-max-payload trap-3883155-1
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LuizPuppin
LuizPuppin Created Apr 14, 2021 18:18:12 (0) (0)
 
rosivaldocs
Created Apr 14, 2021 19:55:41

Thanks for sharing
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LuizPuppin
MVE Author Created Apr 15, 2021 11:19:31

Thanks dear. I hope that can help someone.
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I%20have%2020%20years%20working%20with%20telecom%20market.%20On%20all%20this%20time%20I%20worked%20always%20in%20great%20projects.%20The%20biggest%20was%20the%202014%20World%20Cup%20Command%20and%20Control%20Centre%2C%20where%20I%20was%20the%20Soluction%20Architect%20and%20Implementation%20Manager%20of%20Network%20and%20security%20Solution.%3Cbr%2F%3EI%20work%20with%20Huawei%20s%20products%20to%20ISP%20Market%20since%202015%20and%20in%202017%20started%20to%20present%20trainnings%20customized%20to%20this%20market%2C%20focused%20in%20BGP%20and%20MPLS%20solution.%20I%20had%20more%20than%20400%20students%20and%20more%20than%20100%20ISP%20on%20my%20classes%20on%20last%2018%20mount
Unicef
MVE Created Apr 15, 2021 11:55:48

Very good and well done
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LuizPuppin
LuizPuppin Created Apr 15, 2021 11:57:23 (0) (0)
Thanks dear freind  
Live%20Lead%20Love%20%3A)
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