Ericsson ECN330 Manuel d'utilisateur télécharger pdf (Page 29)

modest broadband data rates. The new services bring more variables to be

taken into consideration when building next generation networks. The two

new architectures that are now emerging are centralized architecture and

distributed architecture. Figures 15 and 16 represent a centralized architec-

ture and a distributed architecture. [12]

The centralized model is very similar to existing old broadband edge archi-

tectures. In this model, the network is centralized around the BRAS prod-

ucts. They aggregate the output from DSLAMs, provide end users with point-

to-point protocol or IP-over ATM and enforce quality of service. Also, they

route traffic to an internet service provider’s backbone network. The architec-

ture is called “centralized” because BRAS is the centralized control point for

QoS policies for all services. This model is a simple-minded Layer 2 aggre-

gation network. Figure 15 represents a centralized architecture.

Figure 15, Centralized Architecture [12]

Figure 15 above represents the centralized architecture. The broadband ac-

cess network has a limited visibility into the access link bandwidth and also

into the available DSLAM capacity. Furthermore, it has a limited integration

with end to end policy control. This extends from broadband access network

to the broadband aggregation network. In the aggregation network, the port

density of GigE/10-GigE is also limited. The edge network relies on high-cost

BRAS routers. There are potential scaling issues in the network when it has

large amounts of IPTV and VOD traffic. Because this model focuses on high

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Ericsson ECN330 Manuel d'utilisateur Page 29