This document discusses various WAN protocols including Frame Relay, ISDN, HDLC, PPP, and DDR. Frame Relay is a packet-switched protocol that uses DLCIs and LMI frames. ISDN provides digital telephony and data services. HDLC is a data link protocol that specifies encapsulation. PPP is used for dial-up connections and supports authentication. DDR allows routers to dial an ISDN connection on demand.

1. WAN Protocols
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2. Objectives
• Understand advantages of WAN.
• Understand the different ways to connect computer
within a WAN.
• Understand different protocols used in WAN.
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3. Introduction
• A Wide Area Network (WAN) spans a large physical
distance.
• A network device called a router connects LANs to a
WAN.
• In IP networking, the router maintains both a LAN
address and a WAN address.
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4. Importance and Advantages of WANs
Two great advantages of WAN are allowing secure and fast
data transmission between the different nodes in the
network.
WAN Connection Types
• Point-to-Point Connection or Dedicated Connection
• Circuit Switching
• Packet Switching
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5. WAN Connection Types contd..
Point-to-Point Connection or Dedicated
Connection
Dedicated connections are point-to-point serial connections
that offer fixed, permanent connections to remote networks.
Data can be transmitted through the connection in two
different ways:
• Datagram transmission: Data is transmitted packet by
packet.
• Data stream transmission: Data is transmitted byte by byte.
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6. WAN Connection Types contd..
Circuit Switching
The circuit switching method occupies phone lines only
during communication.
ISDN is one of the protocols used in this method.
Packet Switching
Packet switching is considered the foundation of most
telecommunications networks.
Packet switching links together all the nodes in a WAN with
the use of a physical link.
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7. Devices Used in WAN
A router is commonly used in the frame relay of T1-based
WANs.
Routers are also beneficial when linking WANs to the
Internet, as they can monitor security policies within a WAN.
When two routers are far apart, a multiport device, called
a WAN switch can link them together within the network.
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8. WAN Protocols
In this section we introduces various protocols and used in
Wide Area Network (WAN) environments. These are as
follows:
Frame Relay: A packet-switched technology that emerged
in the early 1990s, Frame Relay is a Data Link and
Physical layer specification that provides high performance.
Integrated Services Digital Network (ISDN): It is a set of
digital services that transmit voice and data over existing
phone lines.
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9. WAN Protocols contd..
Link Access Procedure, Balanced (LAPB): It was created
to be used as a connection-oriented protocol at the Data Link
layer for use with X.25. It can also be used as a simple Data
Link transport.
High-Level Data Link Control (HDLC): It was derived from
Synchronous Data Link Control (SDLC), which was created
by IBM as a Data Link connection protocol.
Point-to-Point Protocol (PPP): It is an industry-standard
protocol.
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10. Frame Relay
Frame Relay is a high-performance WAN protocol that
operates at the physical and data link layers of the OSI
reference model.
Frame Relay originally was designed for use across
Integrated Services Digital Network (ISDN) interfaces.
Frame Relay Devices
Devices attached to a Frame Relay WAN fall into the two
general categories:
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11. Frame Relay contd..
Data terminal equipment (DTE): DTEs generally are
considered to be terminating equipment for a specific
network and typically are located on the premises of a
customer
Data circuit-terminating equipment (DCE): DCEs are
carrier-owned internetworking devices.
The link layer component defines the protocol that
establishes the connection between the DTE device, such as
a router, and the DCE device, such as a switch.
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12. Frame Relay contd..
Frame Relay Terminology
To understand the terminology used in Frame Relay
networks, first you need to know how the technology works.
The user's network device sends a frame out on the local
network.
The router picks up the frame, extracts the packet, and
discards the frame.
The router then forwards the data out the interface that it
thinks can find the remote network.
The CO receives the frame and sends it through the Frame
Relay "cloud' to its destination.
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13. Frame Relay contd..
Frame Relay Frame Formats
To understand much of the functionality of Frame Relay, it
is helpful to understand the structure of the Frame Relay
frame.
Three primary components make up the Frame Relay
frame: the header and address area, the user-data portion,
and the frame check sequence (FCS).
This identifier commonly is referred to as the data-link
connection identifier (DLCI).
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14. Frame Relay contd..
Local Management Interface (LMI) Frame
Format
LMI was developed in 1990 by Cisco Systems, StrataCom,
Northern Telecom and Digital Equipment Corporation and
became known as the Gang-of-Four LMI or Cisco LMI.
LMI DLCI – Identifies the frame as an LMI frame instead of
a basic Frame Relay frame. The LMI-specific DLCI value
defined in the LMI consortium specification is DLCI = 1023.
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15. Local Management Interface (LMI) Frame Format contd..
Protocol Discriminator – Always contains a value
indicating that the frame is an LMI frame.
Frame Check Sequence (FCS) – Ensures the integrity
of transmitted data.
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16. Local Management Interface (LMI) Frame Format contd..
Frame Relay Encapsulation
When configuring Frame Relay on Cisco routers, you need
to specify it as an encapsulation on serial interfaces.
You'd opt for the IETF-type encapsulation if you needed to
connect a Cisco device to a non- Cisco device with Frame
Relay.
Data Link Connection Identifiers (DLCIs)
DLCI numbers, used to identify a PVC, are typically
assigned by the provider and start at 16.
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17. Local Management Interface (LMI) Frame Format contd..
Dynamic or Static Address Mapping
Dynamic address mapping uses Frame Relay Inverse ARP
to request the next-hop protocol address for a specific
connection, given its known DLCI.
Inverse ARP is enabled by default for all protocols it
supports, but can be disabled for specific protocol-DLCI
pairs.
Configure LMI
Our Frame Relay software supports the industry-accepted
standards for addressing the Local Management Interface
(LMI), including the Cisco specification.
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18. Local Management Interface (LMI) Frame Format contd..
Frame Relay Subinterfaces
Frame Relay subinterfaces provide a mechanism for
supporting partially meshed Frame Relay networks.
By configuring Frame Relay subinterfaces, a single
physical interface is treated as multiple virtual interfaces.
Subinterfaces address these limitations by providing a way
to subdivide a partially meshed Frame Relay network into
a number of smaller, fully meshed (or point-to-point)
subnetworks
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19. Local Management Interface (LMI) Frame Format contd..
Configure Frame Relay Subinterface
To configure subinterfaces on a Frame Relay network,
perform the following task:
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20. Local Management Interface (LMI) Frame Format contd..
Mapping Frame Relay
For IP devices at the ends of virtual circuits to
communicate, their addresses must be mapped to the
DLCIs.
There are two ways to make this mapping happen:
• Use the frame-relay map command.
• Use the inverse-arp function.
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21. Local Management Interface (LMI) Frame Format contd..
Monitoring Frame Relay
The show frame relay lmi command will give you the LMI
traffic statistics exchanged between the local router and the
Frame Relay switch.
Integrated Services Digital Network (ISDN)
ISDN is comprised of digital telephony and data-transport
services offered by regional telephone carriers.
The emergence of ISDN represents an effort to
standardize subscriber services, user/network interfaces,
and network and internetwork capabilities.
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22. Local Management Interface (LMI) Frame Format contd..
ISDN Devices
ISDN devices include terminals, terminal adapters (TAs),
network-termination devices, line-termination equipment,
and exchange-termination equipment.
ISDN Terminals
Devices connecting to the ISDN network are known as
terminal equipment (TE) and network terminator (NT)
equipment.
ISDN Channel
There are several types of ISDN channels, the two main
being the 64 Kilobits per second B-channel for data, and the
D-channel for control information.
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23. Local Management Interface (LMI) Frame Format contd..
ISDN Services
There are two types of services associated with ISDN:
1. Basic Rate Interface (BRI)
2. Primary Rate Interface (PRI)
ISDN Protocols
ISDN protocols are defined in ITU protocols that operates on
the Physical, Data Link and Network layer of the OSI model.
Configure ISDN and BRI Interfaces
Here you will configure routers 804A and 804B to dial ISDN
between the networks 172.16.30.0 and 172.16.50.0, using
network 172.16.60.0 on the ISDN BRI interfaces.
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24. High-Level Data Link Control (HDLC)
The HDLC is a popular ISO-standard, bit-oriented Data Link
Layer protocol.
HDLC specifies an encapsulation method for data on
synchronous serial data links using frame characters and
checksum.
HDLC Operation Modes
Normal Response Mode (NRM): This mode is used in
unbalanced configurations.
In this mode, slave stations (or secondary) can only transmit
when specially instructed by the master (primary station).
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25. High-Level Data Link Control (HDLC) contd..
Frame Classes
In the HDLC protocol, three classes of frames are used.
• Unnumbered frames
• Information frames
• Supervisory frames
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26. Point-to-Point Protocol (PPP)
PPP is a protocol for communication between two
computers using a serial interface, typically a personal
computer connected by phone line to a server.
PPP uses the Internet protocol (IP).
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27. Point-to-Point Protocol (PPP) contd..
PPP Frame Format
The PPP frame format appears in the following figure.
Field
length, in
bytes 1 1 1 2 Variable 2 or 4
Flag Address Control Protocol Data FCS
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28. Point-to-Point Protocol (PPP) contd..
PPP Components
PPP provides a method for transmitting datagrams over
serial point-to-point links.
Configure PPP on Cisco Routers
PPP encapsulation must be enabled on both interfaces
connected to a serial line to work, and there are several
additional configuration options available by using the help
command.
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29. Point-to-Point Protocol (PPP) contd..
Authentication Types (CHAP/PAP) on
PPP Links
Authentication is an optional phase, but it is highly
recommended on all dial connections.
Configuring PPP Encapsulation and
Authentication
By default, Cisco routers use High-Level Data Link Control
(HDLC) as a point-to-point encapsulation method on serial
links.
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30. Dial-on-Demand Routing (DDR)
DDR is used to allow two or more Cisco routers to dial an
ISDN dial-up connection on an as-needed basis.
Configuring DDR
To forward traffic across the ISDN link, you configure static
routes in each of the routers. You certainly can configure
dynamic routing protocols to run on your ISDN link, but then
the link will never drop.
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