Datasheet

Book VII
Chapter 1
Wide-Area
Networking Basics
819
Introducing Digital Subscriber Line (DSL) Connections
✦ PPPoE (Point-to-Point Protocol over Ethernet): An OSI Layer 2 protocol
used to encapsulate PPP frames inside Ethernet frames. PPPoE is typically
used by Internet service providers (ISPs) to allow customers to log on to
DSL services using broadband modems. Based on the older Point-to-Point
Protocol (PPP), ISPs use PPPoE to track an IP address to a specific
customer’s authenticated username and password. This allows users
to establish a virtual point-to-point WAN “dialup” session over Ethernet
networks and securely transmit data between endpoints. PPPoE uses
tunneling for security purposes and is similar to the Point-to-Point
Tunneling Protocol (PPTP) found in virtual private networks. For this
reason, PPPoE consumes additional bandwidth and resources.
✦ Cisco Long Range Ethernet (LRE): A proprietary broadband Ethernet
protocol developed by Cisco Systems that connects LANs or individual
computers to LRE-enabled switches over POTS. LRE is based on VDSL
technology and supports distances up to 1.5 kilometers over standard
phone lines, enabling simultaneous voice, video, and data transfers.
Cisco LRE products are designed to share lines with analog, Integrated
Services Digital Network (ISDN), and digital private branch exchange
(PBX) switch telephones using the 0- to 700-kHz frequency range,
delivering data rates of 5–15 Mbps. This allows Cisco LRE to offer
Ethernet-like performance using lower quality and older Category 1/2/3
cabling. LRE is considered a metropolitan-area network protocol and is
easy to install and manage. Cisco LRE also provides huge speed advan-
tage over standard Internet dialup connections.
Figure 1-3:
ADSL setup.
Router
60-pin serial port
connector
Serial transition
cable
CSU/DSU
or other DCE
EIA/TIA-232, EIA/TIA-449, V.35,
X.21, or EIA-530 connector
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