Figure 8-16 highlights some of the choices for connecting to the WAN.
Figure 8-16 WAN Choices
Leased Line:
Packet Switching:
Circuit Switching:
Metro Ethernet:
Broadband:
PPPoE, PPPoA, Ethernet
Internet
Service
Provider
Telco
Service
Provider
POTS or ISDN
Service
Provider
Ethernet
PPP, HDLC
Frame Relay, X.25, ATM
PPP, HDLC
Telco
Service
Provider
DSL,
Cable
Provider
316 Chapter 8: Extending the Network into the WAN
The following are typical WAN protocols:
?– High-Level Data Link Control (HDLC): The Cisco default encapsulation type on
point-to-point connections, dedicated links, and circuit-switched connections. You
typically use HDLC when two Cisco devices are communicating across a point-topoint
connection. HDLC is a bit-oriented synchronous data link layer protocol.
?– PPP: Provides router-to-router and host-to-network connections over synchronous
and asynchronous circuits. PPP was designed to work with several network layer
protocols, including IP. PPP also has built-in security mechanisms, such as Password
Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol
(CHAP).
?– Frame Relay: A successor to X.
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