Chapter 4. Gateway WAN/Metro Interfaces

This chapter discusses WAN and metropolitan-access approaches that differ from native switched Ethernet LAN infrastructures. You need to learn about these approaches because the majority of UNIX administrators are aware only of Ethernet network interfaces for connectivity of their beloved systems.

Note that the network access layer delivered to homes and business premises via access/edge metro architectures is either based (generally) on copper cabling or optical cables. In rural areas, the most commercially feasible solutions are dial/wireless access with rapid deployment of digital subscriber line (DSL) infrastructures operated by smaller regional Internet service providers (ISPs) and occasionally local cable networks. The information in this chapter is presented from the customer's (CPE = Customer Premises Equipment) point of view. This discussion considers CPE gateway functionality and not directly connected isolated clients.

In today's metropolitan areas, the following access solutions can be provided to customers:

• Dial services (analog/ISDN)

• Wireless solutions (laser, microwave, 802.11, GSM, GPRS, UMTS, satellite)

• Plain Ethernet services

• Metro cable access (Ethernet interfaces)

• Synchronous serial digital leased lines (DLLs)

• SDH/SONET links

• ATM or Frame Relay services

• Different flavors of DSL services

• Fiber/UTP/STP to the home (Ethernet offerings up to Gbps or shaped transmission rates)

• Ethernet via existing PSTN cabling with integrated telephony (LRE = Long Reach Ethernet)

• Powerline communications (Internet access via power lines)