[j-nsp] Junos BNG PPPoE inside a VPLS

[Caillin Bathern]

There are two ways I know of load-sharing PPPoE across BNGs.

PADO delay being configure manually on each BNG achieves this but this is a poor way of doing it.  If the BNG a client has established with fails then the client holds the PPPoE session up until its timeout and then tries to re-establish to another BNG.

The other is a cool feature that the SmartEdge does where you can actually make the PADO only go out if you are the VRRP master (and the PPPoE packets have a source MAC of the VIP).  This way when your VRRP fails over and G-ARPs are sent out by the backup BNG it attracts the PPPoE traffic from the client.  For an unknown session the backup BNG then immediately sends a PADT which causes the client to re-establish its PPPoE session with the new BNG.  I wish this was a feature mirrored by other vendors as it is a nice way of providing backup in case your stateful VC fail-over doesn't work for whatever reason.

As mentioned before, if you used PWHT on Juniper you can always dual-home the PW to multiple BNGs but even so the risk is that you have to wait for the CPE to notice a timeout on the PPPoE session before it will try to re-establish with the new BNG.

Of course all this says is that you should have a physically diverse VC for each BNG and a redundant path from each MSAN to multiple BNG VCs in case the whole VC dies (failed ISSU anyone?).

Cheers,
Caillin

-----Original Message-----
From: juniper-nsp [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Terebizh, Evgeny
Sent: Friday, 27 September 2013 5:34 PM
To: Paul Stewart; William Jackson
Cc: juniper-nsp at puck.nether.net
Subject: Re: [j-nsp] Junos BNG PPPoE inside a VPLS

I've seen a similar scenario.

Yes, I guess it's up to client's machine which PADO to use. Typically host machine answers to the first PADO it gets.
It could be assumed that the load would be split between two redundant NAS boxes as the least loaded NAS is gonna serve clients first (I mean it would send PADO back to the client first).
I believe same applies to IPoE; the least loaded NAS would send DHCP offer faster and the client would use first offer it gets just like in PPPoe scenario. 

HTH
/ET





On 9/27/13 4:24 AM, "Paul Stewart" <paul at paulstewart.org> wrote:

>I'm curious on the load sharing you mentioned here...
>
>So you have a VPLS path from DSLAM going to two different BNG nodes at 
>the same time?  How does the PPPOE session setup work - first one to answer?
>(presuming you are referring to PPPOE)
>
>Love to hear more about this as we have talked about scenarios like I 
>believe you are referring to...
>
>Thanks,
>
>Paul
>
>
>
>On 2013-09-26 5:39 PM, "William Jackson" <william.jackson at gibtele.com>
>wrote:
>
>>The reason for the VPLS use is that we have multiple BNG nodes that 
>>load share the PPPoE sessions. And to mitigate single points of failure.
>>
>>I believe Juniper might just be looking into this scenario as well.
>>
>>
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