Next Generation DSL

DSL is in a transition, and Riverstone Networks is in prime position to lead service providers into a future that is both service-rich and profitable. No longer the domain of early adopters and best effort Internet access, DSL will soon enter 'main-street', the mass market, by providing the triple play of voice, video, and data services.

Carriers are looking for ways to enhance their DSL offerings to provide these advanced content services, while converging on a single service infrastructure where possible. This infrastructure must support higher bandwidths, QoS, IP multicast, while at the same time it must be quicker and less expensive to deploy and manage. And, the transition is global, given that the majority of DSL subscribers are in fact located outside of North America (Figure 1).

Top 20 DSL countries by total number of subscribers
30 September 2003

 
Country
Total Subscribers ('000)
 
Country
Total Subscribers ('000)
1
Japan
9,228.6
11
UK
1,414.7
2
USA
8,243.5
12
Brazil
837.7
3
China
7,817.4
13
Belgium
706.0
4
South Korea
7,069.4
14
Hong Kong
660.0
5
Germany
4,252.0
15
Netherlands
643.6
6
France
2,429.5
16
Sweden
508.0
7
Taiwan
2,374
17
Denmark
416.5
8
Canada
2,027.7
18
Switzerland
383.0
9
Italy
1,672.0
19
Israel
358.0
10
Spain
1,433.4
20
Australia
333.0

Traditionally, DSLAMs connect to the carrier's ATM aggregation network at speeds of 155 Mbps and below. Permanent Virtual Circuits are nailed up between the DSLAM and either ISP-controlled subscriber management systems or L2TP tunnel switches in the carrier's core. This architecture, suitable for best-effort Internet access, does not scale for more demanding, advanced, services.

Carriers require a new solution more in line with their evolving MPLS and Ethernet deployments. Recently, the DSL Forum has defined a set of service architectures that support these new requirements.

Instead of an ATM uplink, DSLAMs equipped with GE connect to the carrier's Ethernet equipped aggregation network. This aggregation network may take two forms (Figure 2). The first is where the carrier trunks the DSLAM via GE (over fiber) to a Riverstone router located at an aggregation PoP or even co-located with the DSLAM itself in a large installation.

An alternative topology relies on a Next Generation SONET or SDH infrastructure capable of mapping the DSLAM's GE trunk across the access network and then into a PoP for handoff to the router. In both cases, the combination of greater bandwidth, IP multicast capability on the router, and more advanced QoS support permits the carrier to offer a host of new, revenue generating services.