Review of WAN Protocol Basics
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Lesson 1 - Agenda
Data Communications Fundamentals
Introduction to Network Protocols
Physical Interfaces
Bit Oriented Protocols
Basic Analysis with the Internet
Advisor
1-2
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Lesson 1 - Objectives
On Completion of this lesson you will be able to:
 List and explain data communications fundamentals as they
apply to wide area networks.
 Define the term network protocol.
 Explain the OSI seven-layer protocol model, peer-to-peer
communications and protocol encapsulation.
 Explain bit oriented protocol and give examples.
 Identify and describe the different interfaces and components of
the Internet Advisor.
 Demonstrate how to connect the Internet Advisor to a network
under test.
1-3
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Data Communications Fundamentals
Communications Modes
DTE/DCE Terminology
Wide Area Analog/Digital Transmission
Multiplexing
Private Leased Lines
Public Switched Data Networks
1-4
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Communication Mode
one direction always
alternate one direction
Simplex
and then the other
both directions always
Half Duplex
Full Duplex
1-5
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
DTE/DCE Terminology
Data Circuit-Terminating
Equipment (DCE)
Data Terminal
Equipment (DTE)
Line (DCE)
EQPT (DTE)
Full Duplex
Customer Premise
Wide Area Network
1-6
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Wide Area Analog/Digital Transmission
analog transmission
typically asynchronous
typically low speed (<=56kbps)
modem
modem
digital transmission
typically synchronous
typically high speed (>=56kbps)
DSU/CSU
DSU/CSU
1-7
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Multiplexing
Transmission of more than one signal on
a single communications line
Increases the number of
communications sessions that can be
maintained at one time
Various types
– Time Division Multiplexing
– Frequency Division Multiplexing
1-8
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Time Division Multiplexing
A
B
C
D
B
A
B
B
A
1-9
C
A
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Private Leased Lines
Point to Point
Point to Multipoint
Fully Meshed
1-10
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Public Switched Data Networks
X.25
Frame Relay
ATM
SMDS
ISDN
1-11
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Summary of Data Communications
Fundamentals
Binary communications
Most often serial in networks
Full duplex communications occurs in both directions
DTE on customer site while DCE on WAN
Multiplexing allows more than one communications
channel on the same line
Time division multiplexing
WAN cover large distances
1-12
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Introduction to Network Protocols
Definition
Protocol Functions
ISO Reference Model
Peer to Peer Communications
Data Encapsulation from Higher
Layers
1-13
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Definition of Communications Protocol
Set of communications rules
Defines addressing
Defines syntax and semantics
Allows communications between
disparate systems
– Communication rules
– Connection control
1-14
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Radio Communications Protocol
HQ, One Adam 12.
One Adam 12, HQ.
What’s your 10-22?
Over.
I’m going 10-22 at
DD for a cuppa java.
Over.
1-15
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
ISO Reference Model
Application
Presentation
Session
Transport
Provides access to the network for the end user or
software application.
Responsible for format and code conversion. Includes
formatting the syntax of data.
Responsible for establishing, maintaining and terminating
logical connections.
Responsible for moving data between nodes; providing
reliable or unreliable data transfer. Includes packet
fragmentation, error detection, and retransmission.
Network
Responsible for end-to-end connectivity through the
network. Includes routing and flow control.
Data Link
Responsible for ensuring error-free, reliable flow of data
acrossa physical link.
Physical
Responsible for the transmission of bits. Includes the
mechanical, electrical and functional physical interface.
1-16
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Protocol Functions
Addressing
Segmentation and
reassembly
Ordered delivery and Encapsulation
(control plus data)
sequencing
Multiplexing
Flow control
– Message
Error control
– Other protocols
Connection control
1-17
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Peer-to-Peer Communications
Application
Application
Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Network
Data Link
Data Link
Data Link
Physical
Physical
Physical
1-18
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Each Protocol Layer Encapsulates Data from the
Layer Above
U
s
e
r
o
r
u
s
e
r
p
r
o
g
r
a
m
A
H
U
s
e
r
D
a
t
a
P
H D
a
t
a
S
H
T
H
N
H
D
L
H
F
l
a
g
D
a
t
a
D
a
t
a
D
a
t
a
L
7
A
p
p
l
i
c
a
t
i
o
n
L
6
P
r
e
s
e
n
t
a
t
i
o
n
L
5
S
e
s
s
i
o
n
L
4
T
r
a
n
s
p
o
r
t
L
3
N
e
t
w
o
r
k
F
C
S
F
l
a
g
L
2
D
a
t
a
L
i
n
k
D
a
t
a
B
i
t
S
t
r
e
a
m
1-19
L
1
P
h
y
s
i
c
a
l
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Protocol Layers and Stacks
WAN protocol analysis focuses on the
lower three layers
– Physical, Data Link and Network
Different protocol stacks often share the
same lower three layers
– For example, IP, IPX and SNA over
Frame Relay
1-20
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Protocol Summary
Protocols are sets of rules that allow computer
with different characteristics to communicate
with one another
Protocol stacks share common lower layers
for actual communication
Peer-to-Peer communication occurs between
upper layers
Lowest three layers often involved in network
analysis and troubleshooting
1-21
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Physical Interfaces
Physical interfaces are hardware components that
attach to the physical media that transmit and
receive network signals
Physical interfaces are associated with one or more
protocols that utilize the interface to perform the
function of the lower layers of the ISO reference
model
Physical interface standards are sets of common
features that manufacturers use to produce products
that operate with one another
1-22
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Typical WAN Physical Interfaces
RS-232/V.24
V.35
RS-449/V.36
T1
E1
ISDN Basic Rate Interface (BRI)
ISDN Primary Rate Interface (PRI)
1-23
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Introduction to Bit-Oriented Protocols
Definition
Data Communications Today: Bit-
Oriented Protocols
Examples of Bit-Oriented Protocols
The Control Field Specifies the Frame
Type
Point-to-Point Protocol
Bit-Oriented Protocols Summary
1-24
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Data Communications Today:
Bit-Oriented Protocols
01
Flag
Address
E3
The quick brown fox...
Control
Data
1-25
FCS
FCS
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Flag
Examples of Bit-Oriented Protocols
 SDLC (Synchronous Data Link Control)
 HDLC (High-level Data Link Control)
 LAP-B (Link Access Procedure-Balanced)
 ADCCP (Advanced Data Communications Control Procedures)
 And many others
Flag
Address
Control
FCS
Data
01111110
8 bits
Flag
01111110
8 or 16 bits
8 or 16 bits
optional (multiple of 8 bits)
16 bits
8 bits
payload (next protocol)
Frame
delineation
frame type identification, frame numbering
link level addressing
1-26
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Point-to-Point Protocol (PPP)
 Synchronous PPP
 Asynchronous PPP
 Multilink PPP
Synchronous PPP frame format:
Flag
Address
Control
01111110
11111111
00000011
8 bits
8 bits
8 bits
Type Field
FCS
Information
Flag
01111110
16 bits
optional (multiple of 8 bits)
next protocol type field
16 bits
8 bits
payload (next protocol)
03 hex identifies PPP information frame
not used (FF hex)
1-27
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Bit-Oriented Protocol Summary
Bit oriented protocols can transmit
more types of data than can character
oriented protocols
Fields within the protocols (not control
characters) manage network overhead
and physical layer maintenance
1-28
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Connecting the Agilent Technologies Internet
Advisor to the Network Under Test
Asynchronous
modem
RS-232C/V.24
(RS-449/V.36
or V.35)
modem
RS-232C/V.24
(RS-449/V.36
or V.35)
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Connecting the Agilent Technologies Internet
Advisor to the Network Under Test
T1 network,
CEPT - E1
or DDS 4-wire
Synchronous
R
R
DSU/CSU
DSU/CSU
T1 DSX
CEPT - E1
RS-232C/V.24
RS-449/V.36
X.21
or V.35
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Interface Configuration
V-series interfaces include:
RS-232C/V.24
RS-449/V.36
V.35
Interface configuration:
 DTE clock source: DTE or DCE (default)
 Data sense: normal, inverted, NRZI-external
or
 Bits/second
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Agilent Technologies Internet Advisor
Configuration Menu
 Interface/Protocols
– Data source
– Monitor options
– Protocols
 Decode Table
 Filters/Counters
 Log
– Disk logging options
– Disk logging configuration
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0
Lesson 1 - Review
You should be able to:
 List and explain data communications fundamentals as they
apply to wide area networks.
 Define the term network protocol.
 Explain the OSI seven-layer protocol model, peer-to-peer
communications and protocol encapsulation.
 Explain bit oriented protocol and give examples.
 Identify and describe the different interfaces and
components of the Internet Advisor.
 Demonstrate how to connect the Internet Advisor to a
network under test.
1-33
© Agilent Technologies
Copyright 2000
H7211A+212, Rev. 2.0