SIP on FTTH systems cdel at
Thu Feb 6 09:56:45 UTC 2014

Time for users to consider splitting L2 services from IP ? 

Christian de Larrinaga

> On 6 Feb 2014, at 08:01, Mark Tinka <mark.tinka at> wrote:
> On Thursday, February 06, 2014 09:19:59 AM Måns Nilsson 
> wrote:
>> Or, one could make sure everything has a globally unique
>> IP address and is using reasonably secured
>> communications. The downside is that one then can't
>> defend the existence  of those empire-building
>> middleboxes. It is not the telco way, so is of course
>> unthinkable. Like anything beyond WAP was on cell phones
>> a decade ago.
> There are, typically, three topology models for modern FTTH 
> (wireline, really) networks that a service provider could 
> deploy:
>    1. SVLAN N:1 model
>    2. CVLAN 1:1 model
>    3. Hybrid of both
> The SVLAN (N:1) model is simple; just have a single VLAN for 
> each service (VLAN 10 for Internet/Unicast, VLAN 20 for 
> VoIP, VLAN 30 for IPTv/Multicast). This is simple and easy 
> to scale, but if one is using relatively "dumb" AN's (like 
> GPON's or MSAN's), it can be difficult to control how much 
> bandwidth customers need, and how they can roam between 
> services in the home (given CPE ties services to ports).
> The CVLAN (1:1) model is good for identifying services and 
> bandwidth requirements on a per-customer basis. The main 
> problem with this model is that Multicast traffic gets 
> treated like Unicast, because each customer has a unique 
> VLAN for themselves, and as such, the upstream PE router 
> ends up having to replicate the same linear video stream as 
> many times as there are customers down the line.
> The Hybrid model, where CVLAN's are used for all Unicast 
> traffic (Internet, VoIP and VoD, typically), and a single 
> SVLAN is used for all customers to handle Multicast traffic 
> (so-called MVLAN). The challenge here is if you're the type 
> of operator that likes to have a consistent set of address 
> per VLAN, it can become a little tricky if your VoIP service 
> is a walled-garden running on private IP space, given it 
> shares the same VLAN as Internet and VoD which would 
> normally run on public IP space.
> The N:1 SVLAN model is quite simple and scalable for 
> wholesale FTTH services. 
> There is product from some vendors, now, that is built with 
> FTTH in mind. 1U, dense switches (Active-E) that support 
> (reasonably) proper QoS and bandwidth management controls on 
> customer- and core-facing ports, at Layer 2. So that offers 
> you a lot more capability at the AN, and you can manage 
> bandwidth as close to the customer as possible, unlike 
> typical GPON deployments which may not have these features, 
> leaving you to apply bandwidth policy at the PE router - 
> much too far up the line.
> These new products can also support split horizons across 
> bridge domains (which GPON's and DSLAM's do today), meaning 
> that customers can use the same SVLAN's, but can only 
> communicate via the upstream router (Layer 3), eliminating 
> risk associated with Layer 2 visibility between customers 
> connected to the same bridge domain.
> Cheers,
> Mark.

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