Cisco Networking Academy Program
Youngstown State University
Cisco Regional Academy
Curriculum Review
Semester 4 , v. 2.1.2
Chapter 5: ISDN
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: ISDN
Part 2: ISDN and the OSI Model
Part 3: ISDN Uses
Part 4: BRI and PRI
Part 5: ISDN Configuration
Part 6: Dial on Demand Routing
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Chapter Learning Objectives
 You will be able to:
– Describe the operations and common uses of ISDN.
– Identify and describe the basic ISDN components,
reference points, and protocols.
– Explain the function of the first layers of the OSI and
the implementation of ISDN.
– Define the operation and bit rates of T1 and E1.
– List the important Cisco IOS commands for
configuring and maintaining an ISDN BRI interface.
– Explain the operation of DDR with ISDN lines.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 1
ISDN
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN
 Integrated Services Digital Network
– Telephone companies developed ISDN as a
totally digital network.
– Uses existing telephone wiring system.
– Designed to solve low bandwidth problems of
small offices or dial-in users.
– An alternative to leased lines.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Overview
 Benefits include:
– Circuit-switched access to digital data, video, and
phone services.
– Faster call setup (< 1 sec.) using D-channel
signaling.
– Faster data transfer using 64kBps B-channels.
– Clear data path for PPP negotiated links.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Design Considerations
 Security
– Crucial to design and confirm a robust security
model for protecting the network using PSTN.
 Cost
– Very important to evaluate data traffic profiles
and monitor ISDN usage patterns.
ISDN can be expensive!
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Basic ISDN Components
 ISDN components include:
–
–
–
–
–
Terminals,
Terminal adapters (TAs)
Network-termination (NT) devices
Line-termination equipment
Exchange-termination
equipment.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Components: TE
 Terminal Equipment and Terminal Adaptor
– TE1
• Directly compatible with ISDN.
• Connect to the ISDN network through a four-wire,
twisted-pair digital link.
– TE2
• Non-compatible with
ISDN and requires an
adaptor to connect.
– TA
• Can be a standalone
device or a board
inside the TE2.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Components: NT
 Network Termination
– NT1
• Connects the four-wire subscriber wiring to the
conventional two-wire local loop.
• A CPE device in North America only.
– NT2
• Complicated device,
typically found in digital
Private Branch exchanges
(PBXs).
• Performs Layer 2 and
Layer 3 protocol services.
• Intelligent device does switching and concentrating.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Reference Points
 Reference points are specifications that define
the connection between devices, depending on
their function.
 CPE device may support different reference
types.
 Reference points will determine what specific
equipment is required for purchase.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Reference Points: R & S
R
– Connection between non-ISDN device and a TA.
S
– Connection into the NT2 or customer switching
device.
– Enables calls
between various
parts of CPE.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Reference Points: T & U
T
– Electrically identical to S interface.
– Outbound connection from NT2.
U
– Connection between NT1 and ISDN provider
network.
– Used only in
North America.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Switches and SPIDS
 Service Profile IDentifiers
 ISDN service providers use a wide variety of
switch types for their services.
– ISDN carrier provides a SPID to identify the line
configuration of the service.
– Identifies user to the switch at the CO.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Protocols: E, I, Q
E
– Telephone network
standards.
I
– Concepts,
terminology,
general methods.
Q
– Switching and signaling standards.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 2
ISDN and the OSI Model
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ITU-T ISDN Standards
 Spans the first 3 OSI layers.
– Physical
• BRI Basic Rate Interface.
• PRI Primary Rate Interface.
– Data Link
• LAPD Link Access Procedure
on the D-channel.
– Network
• Specifies user-to-user, circuit-switched, and packetswitched connections.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Physical Layer
 ISDN physical-layer frame bits are:
– Framing bit - Provides synchronization.
– Load balancing bit - Adjusts average bit value.
– Echo of previous D channel bits - Used for
contention resolution.
– Activation bit - Activates devices.
– Spare bit-Unassigned.
– B1 channel bits.
– B2 channel bits.
– 8 Added channel bit counts bits.
– D channel bits - User data.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Data Link Layer
 LAPD is similar to HDLC.
– Used across D Channels to ensure control and
signaling information flow.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Network Layer
 Two layer-3 specifications.
– ITU-T I.450 (also known as ITU-T Q.930).
– ITU-T I.451 (also known as ITU-T Q.931).
 They support multiple connections:
– User to user.
– Circuit switched.
– Packet switched.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Encapsulation
 Two most common encapsulations are:
– HDLC (default)
– PPP (best choice)
• Uses LCP
– Establish, configure, maintain, and terminate a point-to-point
connection.
• PAP & CHAP authentication.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 3
ISDN Uses
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Uses of ISDN: 1. Remote Access
 Remote Access (most common)
– Connecting users located at remote locations
through dialup connections.
– Lowest speed links in the enterprise.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Uses of ISDN: 2. Remote Nodes
 Remote Node
– Users connect to the local LAN though the PSTN
for the duration of the call.
– Remote user appears as part of LAN.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Uses of ISDN: 3. SOHO
 Small office/home office (SOHO) connectivity
– A few users require a faster more reliable connection
than an analog dialup connection.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 4
ISDN Services
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Services: BRI
 Basic Rate Interface
– Two 8-bit (64Kbps) B channels.
• For voice, video, and data.
– One 2-bit (16Kpbs) D channel.
• For control and signaling information.
– Delivers a total bandwidth of a 144-kbps line.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
ISDN Services: PRI
 Primary Rate Interface
– T1 at 1.544 Mbps
• 23 8-bit channels and 1 8-bit D channel plus 1 framing
bit in North America and Japan.
– E1 at 2.048 Mbps
• 30 8-bit B channels plus one
8-bit D channel plus one 8-bit
Framing channel in Europe,
Australia, and elsewhere.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 5
ISDN Configuration
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Global Configuration Tasks
 Select Switch Type
– Must match provider’s switch at CO.
• Signaling specs differ regionally and nationally.
– Set Destination details.
• Indicate static routes from router to other ISDN
destinations.
• Establish criteria for “interesting packets” in the router
that will trigger an ISDN call.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Interface Parameters
 BRI interface
–
–
–
–
Port number.
IP and subnet mask.
DDR information and ID of service provider.
Define optional features.
• Time to wait for CO to respond to call.
• Idle time before time out and call drop.
– Switch type, and SPIDS.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
IOS Commands for BRI
 Before using ISDN BRI, select the ISDN switchtype from the global mode:
isdn switch-type switch-type
 To configure the BRI interface from global
mode:
interface bri number
• The number is assigned at the factory, and can be
displayed by using the show interfaces command.
• As an example, to configure the AT&T 5ESS switch type:
isdn switch-type basic-5ess
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Example
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Confirming BRI Status
 The show isdn status command shows:
– Layer 1 status
• active, inactive.
– Layer 2 status
• Terminal Endpoint Identifiers negotiated.
– Layer 3 status
• Readiness to make or receive calls.
 The show isdn active command:
– Lists the call in progress and its number.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Part 6
Dial in Demand Routing
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
DDR Considerations
 Dial on Demand Routing provides:
– Network routing and directory services.
– The illusion of full-time connectivity over circuitswitched connections.
 ISDN DDR is triggered
in a router by “interesting”
packets.
• For example, a router could
start ISDN web services if an
“interesting” packet has an Internet destination IP
address.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
DDR Troubleshooting
 The debug isdn q921 command:
– Troubleshoots SPID problems.
– Verifies a connection to the ISDN switch.
 The clear interface command:
– Clears a call in progress and the historical
statistics.
 Packets with unexpected protocols can cause
a router to dial up ISDN even if there are no
users accessing the network.
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Summary
 ISDN has integrated voice/data capability using
the public switched network.
 Components include terminals, TAs, NT
devices, and ISDN switches.
 Reference points define logical interfaces
between groups, such as TAs and NT1s.
 ITU-T standards cover the physical, data link,
and network layers of the OSI reference model.
 The two most common encapsulation choices
are PPP and HDLC (default.)
Robert E. Meyers CCNA, CCAI
Youngstown State University
Cisco Regional Academy Instructor
Cisco Networking Academy Program
Summary
 Uses include remote access, remote node, and
SOHO connectivity.
 There are two ISDN services: BRI and PRI.
 ISDN BRI delivers a bandwidth of 144 kbps
within three separate channels.
 ISDN PRI bandwidth is 1.544Mbps for T1, and
2.08MBps for E1.
 BRI configuration involves the configuration of
an interface, ISDN switch type, and SPIDs.
 DDR establishes and releases circuit switched
connections as needed.
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