Greenfield Access Network

Robert Drake rdrake at
Fri Aug 1 11:12:22 UTC 2014

On 7/31/2014 12:07 PM, Colton Conor wrote:
> 1. The article mentioned DHCP doesn't do the other part of what PPPoE or
> PPPoA does, which is generate RADIUS accounting records that give us the
> bandwidth information. So that’s one of the main challenges in switching to
> a DHCP based system. So, how do you handle bandwidth tracking in an all
> DHCP environment then? If I want to track how many GB a customer used last
> month, or the average Mbps used how do you do so?
A medium sized NMS could do 95th percentile usage on 10k ports. Normally 
I wouldn't want to use an NMS for billing usage but the capability is there.
> 2. I liked your option 82 example, and that works well for DSL networks
> where one port is tied to one customer. But how does option 82 work when
> you have multiple customers hanging off a GPON port? What does GPON use a
> subport identifier?
The ONT can put an option-82 header on the packet and tag whichever port 
the DHCP request came from.

> 3. You mentioned, DHCP is again, not a authentication protocol. So what
> handles authentication then if only DHCP is used, and there are no
> usernames and passwords? I guess for DSL networks you can enable or disable
> the port to allow or disallow access, and Option 82 for identification? I
> assume you wouldn't want to shut off the GPON OLT port if one customer
> wasn't paying their bill as it would affect the other customers on that
> port. I assume access vendors allow you to shut down the sub port or ONT in
> this situation for GPON? Still that seems messy having to login to a shelf
> or EMS system or API to an EMS system especially if you have multiple
> access vendors in a network. Is there a way to do authentication with DHCP?
> What about open networks like wifi where anyone can connect, so you don't
> have the ability to turn of the port or disable the end device?
Most GPON vendors either support TR-69 or some other means to remote 
provision the ONTs.  You can use the DHCP option-82 to identify who a 
customer is and then send their ONT a specific config.  Like DOCSIS you 
could make a disable profile, or you could make them hop on a different 
VLAN that redirects all traffic to a billing page or something.  There 
is also DPoE/DPoG (DOCSIS Provisioning of EPON/GPON) that converts 
DOCSIS provisioning into something PON can use.

> 4. I don't think anyone is buying a BRAS anymore, but looks like Cisco,
> Juniper, and ALU have what they call BGN, Broadband Subscriber Management,
> and other similar software. How are these different from BRAS functionality?
I've got no experience with BRAS so I'm not sure.  I think the ASR1k can 
do pppoe termination if you want a Cisco solution.
> So it looks like there are open source and commercial solutions for DHCP
> and DNS. Some providers like Infloblox seems to integrate all these into
> one.

Infoblox, Bluecat, 6connect, Incognito, Promptlink, VitalQIP, Cisco BAC

There are a bunch of vendors and they all have their ups and downs. A 
DHCP system can be an expensive part of your network and it's a very 
critical one, so you might want to look at multiple offerings before 

> So if we have a core router that speaks BGP, a 10G aggregation switch to
> aggregate the the chassis, and a device like Infloblox or the other
> commercial solutions you mentioned that do DHCP/DNS, is there anything else
> that is needed besides the access gear already mentioned in the
> assumptions?  Are these large and expensive commercial BGN/Broadband
> Subscriber management products a thing of the past or still very relevant
> in todays environment?
Make sure you've got your provisioning system planned out and working 
before you run with it.  Your DHCP systems will tie heavily into your 
OSS so you'll need to work that piece out.  If you use an NMS for 
billing reasons then that will need to tie into the OSS as well.  It's 
always possible to roll out a network that just works, turn up a bunch 
of devices and then realize a critical piece is broken or badly 
designed.  You don't want to be in a position where everything works 
except.... and you can't take it down because everyone is using it.

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