Cisco Networking Academy Program
Youngstown State University
Cisco Regional Academy
Curriculum Review
Semester 4, v.2.1.2
Chapter 2: WANs
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Disclaimer
This presentation is intended for review
purposes by Cisco Networking Academy Program
teachers and students only.
This presentation is not a substitute for careful
study of the Cisco Academy curriculum.
Most of the text and graphics have been copied
directly from the on-line curriculum, and remain
the copyrighted property of Cisco Systems.
CCNA 640-507 objectives are used for reviews.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Contents
 Part 1: WAN Technology
 Part 2: WAN Devices
 Part 3: WANs and the OSI Model
 Part 4: WAN Encapsulation
 Part 5: WAN Link Options
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Chapter Learning Objectives
 You will be able to:
– Define a WAN.
– Describe the types of available
WAN services.
– Describe WAN devices and
their interfaces.
– Explain the OSI layers of
WAN operation.
– Describe PPP and HDLC WAN
encapsulations.
– Describe common WAN link options.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 1
WAN Technology
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN – Wide Area Network
 WAN:
– Data network that operates beyond a LAN's
geographic scope.
– Subscribes to an outside
WAN service provider,
such as a regional Bell
operating company (RBOC)
to use WAN carrier services.
– Uses data links, such as
Integrated Services
Digital Network (ISDN) and
Frame Relay, that are provided by carrier services.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Technologies
 WAN technologies function at the three lowest
layers of the OSI reference model:
– network,
– data link,
– physical.
 The main focus is
on the physical and
data link layers!
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Services
 Examples of WAN Services are:
– ISDN Integrated Services Digital Network.
• Permits telephone networks to carry data, voice,
and other traffic over copper lines.
– Frame Relay
• Industry-standard,
switched data link
layer protocol.
• Handles multiple
virtual circuits using
HDLC encapsulation
between connected devices.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Service Types
 Time-division multiplexing (TDM)
– Information from many sources has bandwidth
allocation on a single medium.
– Multiplexed traffic in fixed time slots, avoids
congested facilities.
– Used by basic
telephone service
and ISDN.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Service Types
 Call setup
– Sets up and clears calls between users.
 Frame Relay
– Information contained in frames shares
bandwidth with other WAN Frame Relay
subscribers.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Service Provider Terms
 Provider gives connection and equipment
requirements used to receive services.
 Commonly used terms with WAN services:
– Customer premises equipment (CPE)
• Devices physically located
at the subscriber's site.
• Devices may be owned
by the subscriber and/or
leased from the service
provider.
– Demarcation (demarc)
• The point at which the CPE ends
and the local loop portion of the service begins.
• Often occurs at the POP of the building.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Service Provider Terms
– Local loop (or "last-mile")
• Cabling (usually copper) that extends from the demarc to
the WAN service provider's central office.
– CO switch
• A switching facility that
provides the nearest point
of presence for the
provider's WAN service.
– Toll network
• The collective switches and
facilities (called trunks) inside the WAN provider's cloud.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Subscriber to Provider Interface
 The key interface in the customer site is
between the Data Terminal Equipment (DTE)
and the Data Circuit-terminating Equipment
(DCE).
– The DTE device is usually the customer router.
– The DCE device converts the user data from the
DTE into an acceptable WAN service.
• CSU/DSU – Channel Service Unit/Data Service Unit
• Modem
• TA NT1 -Terminal Adapter/
Network Termination 1
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Virtual Circuits
 A virtual circuit is a logical circuit created to
ensure reliable communication between two
network devices.
– Switched Virtual Circuits (SVCs)
• Dynamically established on demand and terminated
when transmission is complete.
– Permanent Virtual Circuits (PVCs)
• A permanently established virtual circuit that consists of
one mode: data transfer.
• Frame Relay and X.25
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Data Lines
 WAN links can be ordered from a provider at various
speeds stated in bits per second (bps) capacity.
– T1 1.544 Mbps (United States)
– E1 2.048 Mbps (Europe)
 Special note:
– In countries that use T1 lines, ISDN service utilizes 23 B-channels
and 1 D-channel for a total bandwidth of 1.544 Mbps.
– In countries using E1 lines, ISDN service provides transmission of
digital data over 30 B-channels (64 Kbps) and one D-channel (64
Kbps) plus one framing channel (64 Kbps) for a total bandwidth of
2.048 Mbps.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 2
WAN Devices
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Wan Devices
 Routers
– LAN and WAN interface ports.
 WAN switches,
– Connect to WAN bandwidth for voice, data,
and video.
– Modems,
• Interpret digital and
analog signals.
• Interfaces voice-grade services.
• Include CSUs/ DSUs and TA/NT1 devices that
interface ISDN services.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Leased Line Connections
 CSU/DSU adapts the physical interface on a
DTE device to the interface of a DCE device in
a switched-carrier network.
 CSUs/DSUs are sometimes integrated in the
router box.
 A WAN switch is NOT always necessary!
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 3
WANs and the OSI Model
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Physical Layer
 WAN physical-layer protocols describe:
– The electrical, mechanical, operational, and
functional connections for WAN services.
– Also the interface between the DTE and the DCE.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Data Link Layer
 WAN data link layer defines:
– How data is encapsulated for transmission.
– How frames are carried between systems on a
single data path.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Data Link Layer Protocols
 Frame Relay
– Simplified encapsulation with no error correction
using high-quality digital facilities.
 Point-to-Point Protocol (PPP)
 ISDN
– Digital services over existing phone lines for voice
and data.
 High-Level Data Link Control (HDLC)
– An ISO standard. Supports both point-to-point and
multipoint configurations.
– Vendor specific implementation.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 4
WAN Encapsulation
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Frame Encapsulation
 Each WAN connection uses a Layer 2 protocol
to encapsulate traffic while it is crossing the
WAN link.
– All serial line
encapsulations
share a common
frame format.
– Most common point-to-point WAN encapsulations
are HDLC and PPP.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
PPP Encapsulation
 PPP can:
– Check for link quality during connection
establishment.
– Support authentication through:
• Password Authentication Protocol (PAP).
• Challenge Handshake Authentication Protocol (CHAP).
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
HDLC Encapsulation
 Derived from the Synchronous Data Link
Control (SDLC) encapsulation protocol.
– HDLC is Cisco's default for serial lines.
– Only point-to-point connections are allowed.
 HDLC framing is not compatible with other
vendors' equipment.
– Use PPP with devices
that are not running
Cisco IOS software!
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 5
WAN Link Options
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
WAN Link Line Options
 Two basic line options are:
– Dedicated
– Switched
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Dedicated Lines
 Provide dedicated, full time service from WAN
provider via serial link.
 Point-to-point link provides a single, preestablished WAN path.
– T1 most widely used.
– Data, voice, video.
– Core WAN or
backbone connectivity.
 Also called “leased lines.”
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Packet Switched Option
 Network devices share a permanent virtual
circuit (PVC) with other WAN’s.
 Examples are:
– X.25
– Frame Relay
• Access is typically at:
– 56 kbps,
– 64 kbps,
– or 1.544 Mbps.
• Most widely used.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Circuit Switched
 Dedicated physical circuit is established on
demand only!
 Similar to regular telephone service.
 Low bandwidth
– Modem 28.8 to 56 Kbps
– ISDN 64 or 128 Kbps
 Dial on Demand Routing (DDR) uses this
system.
– Dynamically initiates and terminates WAN
connectivity as needed.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Summary
 WAN
– Interconnect LANs that are separated by a large
geographic distance.
– Provides a data path between routers and the
LANs that each router supports.
– Devices include WAN switches, modems, and
ISDN TAs.
– Mainly operates at the OSI physical and data link
layers.
 Many types of WAN services are available to
the WAN subscriber.
– Must interface to the provider's service.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Summary
 WAN encapsulation formats include PPP and
HDLC encapsulation.
 WAN link options include:
– Dedicated lines such as point-to-point links,
– Packet-switched connections such as Frame Relay,
– Circuit-switched connections such as DDR and ISDN.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
End
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor