On 6/9/21 8:16 PM, Mark Leonard wrote:
Not so long ago I learned about Open Access Fiber Networks. I'm quite
curious about how these are actually implemented. I'm able to find
boatloads of marketing material and management-targeted boilerplate, but
I've not yet been able to find any technical resources.
My first thoughts were:
* Are these just massive VPLS networks?
* Are they just giant L2 networks?
I can't imagine that either of the above would scale particularly well.
I'm looking for any books / papers / config guides / magic tomes / etc
on the subject.
Can anyone point me in the right direction?
I think part of why you're not finding a lot of technical information is
that things built under the name "open access network" come in all
shapes, colors, and sizes.
Things I've seen:
* Fully open glass: Point-to-point fiber from central location(s) to
each individual service point. Providers co-lo at the central
location(s) and bring their own backhaul to them (which the open network
operator may offer turnkey separately) and buy usage of the fiber from
the open network operator. They can run whatever they want on it. CPE
is provided by the service provider. Multiple strands can enable
multiple service providers simultaneously at the same customer prem, but
the number of fibers grows reeeally fast.
* Central split open PON: Each service point has one or two fibers to
central split cabinets in the field, and service providers buy customer
glass to the splitter cabinet, space in the splitter cabinet for
passives, and backhaul glass to each cabinet in areas they want to
serve. They run whatever they want on it via co-location in central
PoPs which need not be active for everyone in the facility (could be
another layer of a hierarchical split), but the cost/availability of the
baukhaul glass generally implies a PON architecture (but it could be
e.g. WDM-PON since you can put whatever you want at the field split
locations). CPE is provided by the service provider. Multiple strands
between the field split and customer prem, if available, enables the
customer to buy service from multiple providers with each provider
having their own glass path and CPE.
* Open L2 access: Could be active-E, xPON, or some mix. The open
network operator hands off customer services on either a
VLAN/VLL-per-customer basis or just adds customers to your VLAN/VPLS(s)
on demand. Service providers establish either a central NNI (open
network operator handles regional backhaul) or co-locates with their own
backhaul as above. This architecture favors customers being able to buy
service from multiple provides at once via a multi-port CPE ONT handled
by the open network operator, but sometimes that responsibility gets
delegated out to the service provider. The open network operator is
responsible for bandwidth management, etc.
* Private label of central services: There's fundamentally just one
network (per type of service, e.g. IP, linear video, voice, etc.), and
service providers just private label it. They may or may not even get
separate blocks of number resources. The open network operator is
really responsible for everything except maybe end-user billing.
Most people seem to be focusing on open L2 type systems as it provides
the most rapid deployment of service with lots of "providers", but it
requires you have a competent administrator of the open-access network
which is often not the case. I've also seen open glass (of both forms)
especially with geographically larger deployments. I've had munis and
HOAs inquire about all types. I'm not sure I've ever seen anyone
actually deploy the private label only variety since it doesn't actually
provide much beyond just directly selling the whole-stack service
yourself, but it's been talked about.
A lot of DSL got deployed back in the day on a similar basis with
service providers either co-locating in COs and buying dry pairs or
re-selling someone else's DSL product (could be the ILEC or someone who
already co-lo'd DSLAMs) with backhaul over ATM on a VPI-per-customer
basis to a central NNI.
Linear video has proven to be problematic on them since it's
difficult/expensive to get retrans rights for small geographic areas
which can make it tough to get providers willing to come in and offer it
without some exclusivity arrangements. Thankfully, demand for linear
video is rapidly dropping as people abandon it entirely or switch to
over-the-top alternatives.
My general "favorite" where someone does want to do open access is the
central split open PON model with ample excess fiber on both the
backhaul and customer legs, but it is situational of course.
--
Brandon Martin
