Greenfield Access Network

Colton Conor colton.conor at
Thu Jul 31 13:23:20 UTC 2014

If a new operator or city is building a greenfield access network from the
ground up, what software and hardware is needed in the core network to
provide and manage residential and business internet services similar to
the likes of AT&T, Comcast, and Google Fiber? Television and Telephone
services are not to be considered only internet.

Assume hypothetically the operator already has the following in place:
10 GPON OLTs Chassis from an access vendor in 10 POPs around town (each POP
has 1 Chassis). Each OLT Chassis has 4 10G Uplinks back to the core.
Dark fiber going from the POP locations back to the core location
Assume a 32:1 way split, and each OLT chassis has enough ports populated to
serve the area.
10,000 GPON ONTs. The ONTs can be put in routed gateway or bridged mode.
Assume you are building a network designed to serve 10,000 subs
All the fiber splitters, ducts, fiber, etc connecting the OLTs to the ONTs
is already in place
/20 of IPv4 space and /32 of IPv6 space from ARIN
4 burstable 10G internet connections from 4 tier 1 internet providers

Questions are:

What is the ideal way to aggregate the 40 10G connections from the uplinks
of the chassis? I would guess a 10G switch since 10G ports on a router
would be much more expensive?
Which router is recommended to handle 4 10G internet connections with full
tables, and then at least 4 10G ports going back to the 10G aggregation
How do you handle IP address management? a /20 is only 4096 IP addresses,
but the network would have potentially 10,000 customers. Assume that
getting more space from ARIN is not an option. Is CGN an option? Dynamic IP
addresses? DHCP?
How do you separate users and traffic? VLANs, Service VLANs, Per Customer
VLANs, Usernames? Passwords? PPPoE? MAC Separation?
Is a BRAS or BGN functionally really needed or are these older concepts?
If CGNAT or DHCP is needed, what will host the CGNAT or DHCP service? The
core router, a linux box, or something else?
What about DNS?
Is a firewall needed in the core?
What else is needed?

Is there a guide out there somewhere? I know many cities are looking at
building their own network, and have similar questions. Access vendors are
willing to sell gear all day long, but then they leave it up to the
operator/city to answer these harder questions.

How would you build a access network from the ground up if you had the
resources and time to do so? Would you even use GPON? Even if GPON was not
used and another access technology like AE, VDSL2, or wireless was used I
think many of these questions would be the same.

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