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DSL and Cable Modem Networks

Chapter Description

Before committing to a DSL or cable-modem, learn exactly what these technologies consist of and what kind of service they can provide for you.

Case Study

HB & J, Inc. is an organization with a corporate campus and several remote SOHO users. HB & J, Inc. has outsourced file storage to a server farm hosted by an off-site data center company. HB & J, Inc. decided to forego traditional Frame Relay service and implemented an IP-VPN, with the public Internet as the transport medium. The topology of the HB & J, Inc. network is illustrated in Figure 7-8.

Figure 7-8 Figure 7-8 HB & J, Inc.


HB & J, Inc. is using SDSL between their two campus buildings—the main building and the annex building. SDSL is implemented by the deployment of a pair of SDSL modems on each side of an existing copper facility. The main building of the HB & J, Inc. campus is using HDSL, provided by the local NSP, to connect to the Internet.

HB & J, Inc.'s SOHO users have deployed cable modem access (where available) for connectivity to the Internet. These SOHO users are using a virtual private network (VPN) client to establish a secure communications tunnel across the Internet to the HB & J, Inc. Corporate Campus and the Data Center server farms. The VPN client must interoperate and be supported by the Corporate Campus and the Data Center in order to establish the secure tunnel across the Internet.

The Data Center has deployed a dedicated service to the Internet (likely DS3 or higher) to meet the demands of their large, high-volume customer base.

DSL and cable modem service provide HB & J, Inc. a more cost-efficient connectivity method than traditional dedicated service. For new locations where DSL or cable modem service may not be available, HB & J, Inc. will need to install dedicated Internet service.

If HB & J, Inc. decides at some time to add traditional Frame Relay or ATM service to support remote users, the Corporate Campus also will need to implement a Frame Relay/ATM connection so that connection can be established with these users as well.