EduDivision-DATACOM NETWORKING

CommServ – Education Division Datacom NetworkingIntroduction-1
Data Communication Transport

Introduction
• Name, Company and Location
• Job Title and Responsibilities
• Related Work Experience
• Course Expectations

Course Prerequisites
• There are no prerequisites for this course.

Course Materials
• Course Manual
• Evaluation Form
• Reference Materials

Course Objectives
• To gain a solid understanding of modern data
communications technologies and concepts
• Technologies covered:
– TCP/IP, Ethernet, ATM, Frame Relay, X.25, PPP, Modems,
ISDN, xDSL, SDH/SONET, Packet-over-SONET, MPLS

Course Schedule
•Day 1: PRE-TEST, Standards, Physical Media, Datacom Concepts
& Traffic Cases
•Day 2: Ethernet Concepts, Ethernet Frame Types & Devices
Fast & Gigabit Ethernet
•Day 3: WAN Concepts, ATM and Frame Relay
•Day 4: WAN Concepts, X.25, Point-to-Point Protocol, Modems,
ISDN, xDSL, PDH/SDH/SONET, Packet-Over-SONET, MPLS
•Day 5: Internet Architecture & Applications, Transport Layer,
Protocols, Internet Protocol & IP Addressing, Internet Routing &
Dynamic Routing
POST TEST

Modern Datacom Networking

CommServ – Education Division Datacom NetworkingStandard-8
Datacom Networking
2. Standardization and the OSI Model
Chapter Objectives
–Identify the standards bodies associated with data
communications
–Describe in detail the OSI reference model

Standard Bodies
Frame Relay Forum
IEEE
ITU
ISO
ANSI
IETF
ATM Forum
ETSI

International Telecommunications Union (ITU)
ITU-R
Study Group Study Group
ITU-T ITU-D
ITU

ITU-T Recommendations
FunctionSeries
Public data communication networkX-
Digital communication over the telephone networkV-
Telephone switching and signalling networksQ-
ISDNI-
International telephone connections and circuitsG-
Telephone network and ISDNE-

Standards Organizations
• International Telecommunications Union
– www.itu.int
• International Standards Organisation
– www.iso.ch
• American National Standards Institute
– www.ansi.org
• European Telecommunications Standards Institute
– www.etsi.org
• Electronic Industries Alliance
– www.eia.org
• Internet Engineering Task Force
– www.ietf.org

Standards Organizations
• Frame Relay Forum
– www.frforum.com
• Institute of Electrical and Electronics Engineers
– www.ieee.org
• International Multimedia Teleconferencing Consortium
– www.imtc.org

OSI Reference Model
• The Open System Interconnection (OSI) Reference Model is a concept
that describes how data communications should take place
• It divides the process into seven groups, called layers
• Protocol standards developed by the ISO and other standards bodies
are fitted into these layers
• The OSI model is not a single definition of how data communications
actually takes place in the real world, Numerous protocols may exist at
each layer
• The OSI model is old, but it’s important because modern functionality is
defined using the language of the OSI model, for example “layer 2
forwarding”

OSI Reference Model Layers
Transmits and receives on the network mediumPhysical1
Transfers units of information to the other end
of the physical link
Data Link2
Switches and routes information to the
appropriate network device
Network3
Provides end-to-end data integrity and reliable
delivery of data
Transport4
Co-ordinates interaction between end-to-end
application processes
Session5
Provides code conversion and data
reformatting
Presentation6
Interfaces directly with application programs
running on the devices
Application7

The Physical Layer
TDM / FDM / WDMMultiplexing
Baseband
Broadband
Bandwidth Usage
Asynchronous
Synchronous
Bit
Synchronisation
Current StateSignalling
Bus, Ring, CellularPhysical Topology
P-2-P , P-2-MPConnection Types
Physical
MethodsFunctionLayer

The Datalink Layer
DLC
Physical
device
Addressing
Contention
Token passing
Media access
services
Bus
Ring
Logical topology
MAC
Flow control
Error control
Connection services
Asynchronous
Synchronous
Transmission
Synchronisation
LLC
MethodsFunctionSub layer

Network Layer
Static
Dynamic
Route Selection
Distance Vector
Link State
Route Discovery
Packet SwitchingSwitching
Logical Network
Services
Addressing
Network
MethodFunctionLayer

Routing
6 5
4
3
2
3
3 2
1 1
1
3
2
3 2 4
5 6 1
4
5
6

Transport Layer
Service requester
initiated
Address/Name
Resolution
Segment sequencing
Error control
End-2-End flow control
Connection services
Segmentation and
Reassembly (SAR)
Segment development
Connection identifier
Transaction identifier
Addressing Methods
Transport
MethodFunctionLayer

Session Layer
• Session layer facilitates and controls communication sessions between service
providers and service requesters
• The session layer has functions to establish maintain, synchronise and manage
communication sessions
• Often, it also helps the upper layers identify and connect to the services
available on the network.
• The two main session layer tasks are:
• Dialogue control
• Session administration
• This includes the control and management of multiple bidirectional messages
so that the application can be notified if only some of a series of messages are
completed.
• For example, an Automated Teller Machine transaction in which you get cash
out of your checking account should not debit your account and fail before
handing you the cash, and then record the transaction even though you did not
receive money.
• RPC, SQL, NFS, NetBios names, AppleTalk ASP, DECnet SCP

Presentation Layer
• This layer’s main purpose is defining data formats, such as ASCII text,
EBCDIC text, binary, BCD, and JPEG.
• Encryption is also defined by OSI as a presentation layer service.
• For example, FTP allows you to choose binary or ASCII transfer. If
binary, the sender and receiver do not modify the contents of the file. If
ASCII is chosen, the sender translates the text from the sender’s
character set to a standard ASCII and sends the data. The receiver
translates back from the standard ASCII to the character set used on
the receiving computer.
• Example: TIFF, GIF, JPEG, PICT, ASCII, EBCDIC, encryption, MPEG,
MIDI, HTML

Presentation Layer
The presentation layer’s main functions are:
• Translation
• Code conventions
• Bit/Byte order
• File syntax
• Encryption / Decryption

Application Layer
• Provides interface to end user process and applications
• Takes care of all the requests made by the running applications
• An application that communicates with other computers is
implementing OSI application layer concepts. The application layer
refers to communications services to applications. For example, a word
processor that lacks communications capabilities would not implement
code for communications, and word processor programmers would not
be concerned about OSI Layer 7. However, if an option for transferring
a file were added, then the word processor would need to implement
OSI Layer 7 (or the equivalent layer in another protocol specification).
• Examples: FTP, WWW browsers, Telnet, NFS, SMTP gateways
(Eudora, CC:mail), SNMP, X.400 mail, FTAM

Data Transmission
Bits
S-Data unit
T-Data unit
Packet
Frame
Bits
P-Data unit
A-Data unitDataA
Data
Physical
Data Link
Network
Transport
Session
Presentation
Application
DataAP
DataAPS
S DataAPT
T S DataAPN
N T S DataAPD D
101101111000101011010010101010
ProtocolStack
Data unit

Example: HTTP
Web Browser
Physical
Data Link
Network
Transport
Session
Presentation
Application
Ethernet
IP
TCP
HTTP
Web Server
Ethernet
IP
TCP
HTTP

OSI and Network Devices
Physical
Data Link
Network
Transport
Session
Presentation
Application
Physical
Data Link
Network
Transport
Session
Presentation
Application
Repeater
Bridge
Router
Hub
Switch
Router
User
Application
User
Application

OSI and Network Devices

OSI Layers: Network Interaction
Physical
Data Link
Network
Transport
Session
Presentation
Application
Physical
Data Link
Network
Transport
Session
Presentation
Application
User
Application
User
Application

OSI Model Summary
Concerned with transmission of unstructured bit stream over physical
medium; deals with the mechanical, electrical, functional and procedural
characteristics to access the physical medium.
1) Physical
Provides for the reliable transfer of information across the physical link.
Establishes a physical link, sends blocks of data (frames) in the proper
format, along with the necessary synchronization, error control, and flow
control.
2) Data Link
Provides upper-layers with independence from the data transmission and
switching technology used to connect systems. Concerned with routing
packets, congestion control, fragmentation, and reassembly.
3) Network
Provides reliable, transparent transfer of data between end points.
Provides end-to-end error recovery and flow control.
4) Transport
Provides the control structure for communication between applications.
Establishes, manages and terminates connections (sessions) between
applications.
5) Session
Provides data representation (Syntax) independence to the
application process.
6) Presentation
Access to the OSI environment for user applications and processes.7) Application

CommServ – Education Division Datacom NetworkingPhysical Media
Datacom Networking
3. Physical Media
Chapter Objectives
–Describe the characteristics of coaxial cable, UTP, STP and optical fiber
–Describe the terms DCE and DTE
–Describe the characteristics of RS232, RS422, V.35, V.36 and X.21

Physical Media
• Co-axial
• Twisted Pair
– Unshielded
– Shielded
• Optical Fiber
– Single Mode
– Multimode

Typical Coaxial Cable
BNC Connectors

BNC T-Connector

Characteristics of Coax
• Medium cable costs
• Simple to install
• Moderate installation costs
• Moderate EMI
• High bandwidth
• Often used as backbone cable

Unshielded Twisted Pair

Characteristics of UTP
• Lowest cost
• Very simple to install
• Low installation costs
• Highest electromagnetic interference (EMI)
• Lowest in bandwidth
• Used in more than 99% of LANs

Categories of UTP for Networks
• Category 3 (Cat 3)
– Bandwidth 16 Mhz
– Data transmission function
– 11.5 dB attenuation
– 100 ohms Impedience
– Used with 10baseT (10Mbps), IBM token ring (4Mbps), ARCnet, 100VG-
AnyLAN (100 Mbps)
– 20 MHz Bandwidth
– Data transmission function
– 7.5 dB Attenuation
– 100 ohms Impedance
– Used with 10baseT (10Mbps), IBM Token ring, ARCnet, 100VG-AnyLan
(100 Mbps)

Categories of UTP for Networks (2)
– Used for high-speed data transmission
– Used with 10BaseT (10 Mbps), IBM Token ring, Fast Ethernet, (100 Mbps),
Gigabit Ethernet (1000 Mbps), ATM (155 Mbps)
• Category 5 Enhanced (Cat 5E)
– Transmits high-speed data
– Used with 10BaseT (10 Mbps), IBM Token Ring, Fast Ethernet (100 Mbps),
Gigabit Ethernet (1000 Mbps), ATM (155 Mbps)

Categories of UTP for Networks (3)
– Used with 10BaseT (10 Mbps), IBM Token Ring, Fast Ethernet (100 Mbps), Gigabit
Ethernet (1000 Mbps), ATM (155 Mbps)
• Category 6 Enhanced (Cat 6E)
– Used with 10BaseT (10 Mbps), IBM Token Ring, Fast Ethernet (100 Mbps), Gigabit
Ethernet (1000 Mbps), ATM (155 Mbps)
• Category 7 (Cat 7-NOT YET APPROVED)

Shielded Twisted Pair

Characteristics of STP
• Medium cable costs expense
• Simple to moderate installation difficulty
• Moderate installation costs
• Moderately low EMI
• Moderate band width
• Usually found in older networks

Optical Fiber

Single Mode and Multimode Fiber
• Single Mode Fiber
– Small core diameter which only allows one mode (ray) of light to propagate
through the fiber
– Used for applications with long transmission distances (carrier core
networks)
• Multimode Fiber
– Larger core diameter which allows many modes of light to propagate
through the fiber
– Larger core diameter facilitates use of cheaper components
– Used primarily for applications with short (<2Km) transmission distances
(campus backbones)

Characteristics of Fiber
• Highest cable costs
• Difficult to install
• Highest installation costs
• No EMI
• Very high bandwidth
• Uses light rather than electrical signals

DCE Vs DTE
DCE DCE
DTE DTE
V.24,
V.28,
Client/Calling Server/Called/
Modem Answer Modem
PSTN
V.24,
V.28,
V.90/V.34/V.32
V.42/V.42bis

Physical Layer Standards
RS-232C (EIA) / V.24 (ITU)
generator receiver
A
Bcommon ground pin 7
RS232C (V.24, V.28)

Physical Layer Standards (contd)
generator receiver
A
B
RS422 (V.11, X.27) R
RS-422 (EIA) / V.11 (ITU)

Data Rate vs. Cable Length
100
1k
10k
cable
length
(feet)
50
10
Data Rate - bps
100 1k 10k 100k 1M 10M
RS-232
4k
RS-422

V.24/V.28, RS232c Interface
ISO 2110 Connector
1 13
14 25

9 - 25 pin D Cable
PC 9 Pin Modem 25 Pin Function in the PC
3 2 TxD Transit Data
2 3 RxD Receive Data
7 4 RTS Request to Send
8 5 CTS Clear to Send
6 6 DSR Data Set Ready
5 7 SG Signal Ground
1 8 DCD Carrier Detect
4 20 DTR Data Terminal Ready
9 22 RI Ring Indicator

V.24 Interface Circuits
Pin V.24 RS232c DTE DCE EIA Description
1 101 AA FG Protective Ground
2 103 BA X TxD Transmit Data
3 104 BB X RxD Receive Data
4 105 CA X RTS Request to Send
5 106 CB X CTS Clear to Send
6 107 CC X DSR Data Set Ready
7 102 AB SG Common Return / Signal
Ground
8 109 CF X DCD Data Carrier Detect
15 114 DB X TC Transmit Timing Clock
17 115 DD X RC Receive Timing Clock
20 108 CD X DTR Data Terminal Ready
22 125 CE X RI Ring Indicator
24 113 DA X TC External Transmit Timing
Clock
Other pins not shown used used in some modem circuits only.

Null Modem Cable 25 pin to 25 pin D
Pin Signal
7 Signal
Ground
2 Transmit
3 Receive
4 RTS
5 CTS
20 DTR
6 DSR
8 DCD
Signal Pin
Signal Ground
7
Transmit 2
Receive 3
RTS 4
CTS 5
DTR 20
DSR 6
DCD 8

Pin Signal
5 Signal
Ground
3 Transmit
2 Receive
7 RTS
8 CTS
4 DTR
6 DSR
1 DCD
Signal Pin
Signal Ground
5
Transmit 3
Receive 2
RTS 7
CTS 8
DTR 4
DSR 6
DCD 1
Null Modem Cable 9 pin to 9 pin D

V.35 Interface
KK EE AA W S M H C
MM HHCC Y U P K E A
LL FF BB X T N J D
DDJJNN Z V R L F B
ISO 2593 Connector

V.35 Interface (contd)
ITU-T No. Circuit Pin Number Source Source Designation
DTE DCE
102 GND B Signal Ground
103 TXD P , S X Transmit Data a,b
104 RXD R , T X Receive Data a,b
105 RTS C X Request to Send
106 CTS D X Clear to Send
107 DSR E X Data Set Ready
108.1 DTR H X Data Terminal Ready
109 DCD F X Data Carrier Detect
113 TCX U , W X Transmit Signal timing a,b from DTE
114 TXC Y , AA X Transmit Signal timing a,b to DTE
115 RXC V , X X Receive Signal timing a,b to DTE
140 RL N X Remote Digital Loop
141 LL L X Local Loop
142 TST NN X Test Indicator

V.36 Interface
1 19
3720
ISO 4902 Connector

X.21 Interface
1 8
9 15
ISO 4903 Connector
ITU-T. Pin Number Source Source Designation
circuit DTE DCE
G 8 Signal Ground
T 2, 9 X Transmit Data a,b
R 4, 11 X Receive Data a,b
C 3, 10 X Control a, b
I 5, 12 X Indication a, b
S 6, 13 X Signal element timing a, b

RJ 45 Ethernet
Pin Name Description 568A 568B
1 TD + Transmit Data + White/Green White/Orange
2 TD - Transmit Data - Green Orange
3 RD + Receive Data + White/Orange White/Green
4 n/c Not connected Blue Blue
5 n/c Not connected White/Blue White/Blue
6 RD - Receive Data - Orange Green
7 n/c Not connected White/Brown White/Brown
8 n/c Not connected Brown Brown
Note 1 Cable has four pairs. White/Green and Green are a pair etc.
Note 2 TD & RD are swapped on Hub's.

Pin Function Required
TE NT
1 Power source 3 + Power sink + No
2 Power source 3 - Power sink - No
3 Transmit +
4 Receive +
5 Receive -
6 Transmit -
7 Power sink 2 - Power source 3 - No
8 Power sink 2 + Power source 3 + No
Note: Power source 2 and 3 are not mandatory and may only be
available from some NT or TE devices.
RJ 45 ISDN BRI s/t Interface

RJ 48c
Pin Description
1 Receive Ring
2 Receive Tip
3 Not connected
4 Transmit Ring
5 Transmit Tip
6 Not connected
7 ground for transmit screen
8 ground for receive screen
E1 / T1 Balanced/Unbalanced

SC Connectors

ST Connectors

LC FC
MTRJ
Mini-Gbic plus LC, MRTJ and FC Connector
Mini-Gbic

CommServ – Education Division Datacom NetworkingFundamental -
Datacom Networking
4. Datacom Fundamental
Chapter Objectives
–Define LANs and WANs
–Identify multiplexing, transmission, and error control methods
–Describe common network topologies

Network Definition - LAN / WAN
Local Area Networks
(LANs)
Router A
Router B
Wide Area Network
(WAN)
Token
Ring

Bandwidth Usage
• Baseband
all the available bandwidth is used to derive a single transmission path
• Broadband
the total available bandwidth of the cable is divided into a number of lower bit
rate channels, which can transmit many simultaneous signals

Modulation / Demodulation
• Amplitude Modulation
where the Amplitude of the signal is varied
• Frequency Modulation
where the Frequency of the signal is varied
• Phase Modulation
where the Phase of the signal is shifted

Digitization
• Is the Process of Converting an Analog Signal to Digital Format
• A COder-DECoder performs this operation by applying Pulse Code
Modulation algorithm
• The CODEC may be placed at any point
• A logarithmic (com-panding) scale is used to map the amplitude to its
digital value
• The PCM companding rules define:
255 amplitude levels, -law, in USA, Canada
and Japan
256 amplitude levels, A-law, almost rest of
the world

Multiplexing Techniques
• Time Division Multiplexing (TDM)
– Conventional
• Bit-Interleaved
• Byte-Interleaved
– Statistical (STDM)
T S - 1
t
f
T S - 2 T S - 3 T S - 4 T S - 1 T S - 2 T S - 3 T S - 4 T S - 1 T S - 2 T S - 3 T S - 4
TDM

Multiplexing Techniques
• Frequency Division Multiplexing (FDM)
(CATV is a good example)
• Wavelength Division Multiplexing (WDM)
(often used in optical data transmission)
t
f
F C - 1
F C - 2
F C - 3
F C - 4
FDM

Communication Modes
• Simplex
– data is transmitted in one direction only
• Half Duplex
– Data can be transmitted in both directions, but only in one direction at any
given time
• Full Duplex
– Data is transmitted in both directions simultaneously

Transmission Modes
SYN character Bit stream of many characters
Asynchronous
Synchronous
SYN character
Stop bit Character Start bit

Asynchronous communications

Synchronous Transmission
• The complete block of data is transmitted as a contiguous bit stream in
frames
• To enable the receiving device to stay in sync data is carefully encoded
(bit sync)
• frames are preceded by a reserved byte to ensure correct interpretation
on byte boundaries (byte sync)
• frames are preceded by synchronization bytes (frame sync)

Error Control
• Parity Bit Method
– an additional bit is added to each tansmitted character to detect single bit
errors
• Even / Odd parity
• Block sum check algorithms
– two additional bits are added (row / column) to detect errors
– two bit errors that escape the row parity checking, will be detected by this
method

Error Control
Frame to be transmitted
Calculated CRC value
fInput data Output data
Inputpolynomial

Data Compression
• Packed Decimal
– Reduce the number of transmitted data (numbers 0-9 all have 011 in msb
position)
• Relative Encoding
– Data that has only small differences between successive values, (send only
the d-magnitude)
• Character Suppression
– Used for more general case
• Huffman Coding
– Statistical coding

Network Topologies

Protocols
• A protocol is a set of rules that govern the behaviour of communicating
parties
• Protocols handle:
 Format of the exchanged data
 Type and order of the information
 Timing
 Sequencing
 Error control
 Flow Control

CommServ – Education Division Datacom NetworkingTraffic Case-82
Datacom Networking
5. Traffic Case
Chapter Objectives
–Describe at a high level the path a packet may take through a
network

So, what happens when you do this?

Upper Layer Protocol into IP
• This is the File Transfer Protocol (FTP), which is a higher-
layer protocol (layers 5,6 & 7 of OSI model)
• FTP is carried within an Internet Protocol (IP) packet

Local Area Network Technologies
• Your PC is connected to your office Local Area Network
(LAN), through a Network Interface Card (NIC)
• Typically, the LAN technology used is Ethernet

Adapting IP to Ethernet
• The information (IP) needs to be adapted to the network technology
• In this case the information must be transmitted in Ethernet frames

The Hub
• Likely the first device your frame will encounter is a hub – an Ethernet
repeater
• This hub simply repeats the signal and sends it on

The LAN Switch
• Likely the next device your frame will encounter is an Ethernet switch,
also called a LAN switch
• This LAN switch forwards on your Ethernet frame intelligently on the
basis of it’s Ethernet address

A Typical Office Network

The Router
• A router’s job is to take in IP packets and work out the next
best hop for that packet based on the router’s internal
routing tables

IP Forwarding

Layer 3 – Layer 2 Interaction
• Consider a router with Ethernet and ATM interfaces

Destination Server
The final router knows
that the destination
IP device is directly
connected to it
The server will return
the requested files to
the source – the same
process in reverse

CommServ – Education Division Datacom NetworkingEthernet
Datacom Networking
7. Ethernet Concept
Chapter Objectives
–Describe naming conventions used with Ethernet
–Describe the structure of a MAC address
–Describe the CSMA/CD principle

LAN Technologies
• Ethernet
– By far the most widely used LAN technology today (95%+)
– Available in 10Mbps, 100Mbps and 1000Mbps flavours
• Token Ring
– Old IBM standard
– Workstations connected to rings, token passing concept
– Rings were available at speeds of 4Mbit/s and 16Mbit/s
• Fiber Distributed Data Interface (FDDI)
– LAN Fiber backbone technology, used 100Mbit/s ring
– No longer likely to be implemented in a new network
• Asynchronous Transfer Mode (ATM)
– Extensively deployed WAN technology, can be deployed in LANs
– However, Ethernet is a far more cost effective LAN technology

Ethernet Evolution
Ethernet Design Goals
– Simplicity
– Efficient use of shared resources
– Ease of reconfiguration and
maintenance
– Compatibility
– Low cost
1972 1996
Gigabit
standard
(802.3z)
VLANs
(802.1Q)
1000BaseT
(802.3ab)
198
0
Ethernet
V1 DIX -
V2 in 82
1983 1990
10Base-T
(802.3i)
10BaseF
(Fiber)
1993
802.3z study
group formed
to standardize
Gigabit
Ethernet
19981985
IBM
ships
first
Token
Ring LAN
IEEE
802.3
Standard
81-83
Fast
Ethernet
(802.3u)
1995 1997
Full
Duplex
(802.3x)
1973
Invention
accredited
to Robert
Metcalfe-
Patent
1977

IEEE 802 Family Architecture
IEEE 802.3 IEEE 802.4 IEEE 802.5 IEEE 802.6 Physical
IEEE 802.2
Internet
Transport
Upper
IEEE 802.x
Link
802.1 Internetworking
802.2 Logical Link Control (LLC)
802.3 CSMACD
802.4 Token Bus
802.5 Token Ring
802.6 Metropolitan Area
Networks
802.7 Broadband Tech Advisory Group
802.8 Fiber Optic Tech Advisory Group
802.9 Integrated Voice&Data Networks
802.10 Network Security
802.11 Wireless Networks
802.12 Demand Priority Access LAN's

Ethernet Naming Conventions

10BaseT Specifications
• 10BaseT
– 2 pairs of Cat 3 UTP
– By far the most widely used specification
• 10BaseF
– 2 strands of MMF
• 10Base2
– Thin coaxial or “Thinnet” (Dead)
• 10Base5
– Thick coaxial or “Thicknet” (Dead)
• 10Broad36
– Coaxial (Dead)

MAC Address Format
7 0- 7 0- 7 0- 7 0- 7 0- 7 0-
octet order bit order

Ethernet Principle – CSMA/CD
• CS = Carrier Sense
– Listen until no carrier is sensed, then transmit after a delay
• MA = Multiple Access
– Designed for a broadcast environment
– Every station hears every frame
• CD = Collision Detection
– Listen for a collision while you transmit

Ethernet Operation – CSMA

Ethernet Operation – CD

Ethernet Collisions – More Detail
The adapters have to hear the collision while they
are still transmitting
They then transmit a 32-bit jam signal
They wait a random time before retransmission
If there are repeated collisions the adapter tries
again, up to a a maximum of 16 times
– Uses ―truncated binary exponential backoff‖ algorithm

Ethernet, Logical vs Physical

Datacom Networking
8. Ethernet Frame
Chapter Objectives
–Identify the characteristics of the following Ethernet frame types:
•Ethernet Version 2
•IEEE 802.3 Novell Raw
•IEEE 802.3 Standard (with LLC)
•IEEE 802.3 SNAP

Chapter Objectives
• After completing this chapter you will be able to:
– Identify the characteristics of the following Ethernet frame types:
• Ethernet Version 2
• IEEE 802.3 Novell Raw
• IEEE 802.3 Standard (with LLC)
• IEEE 802.3 SNAP

Ethernet Version 2 Frame (DIX)
Network
Data Link Control
Physical

Examples of Ethernet Types
E-Type Value
NetWare 8137
XNS 0600, 0807
IP 0800
IP (VINES) 0BAD, 80C4
ARP 0806
RARP 8035
DRP 6003
LAT 6004
LAVC 6007
ARP (ATalk) 80F3

IEEE 802.3 Frame - Novell ―RAW‖

IEEE 802.3 Frame – with LLC (Standard Frame)
Network
Logical Link Control
Physical
Media Access Control

IEEE 802.3 Frame – SNAP
Network
SNAP
Physical
LLC
MAC

Ethernet Frames Compared

Determining Ethernet Frame Types

Datacom Networking
9. Ethernet Device
Chapter Objectives
–Describe collision domains and broadcast domains
–Describe how a hub, bridge and switch operate
–Identify where a crossover cable is used
–Describe the concept of Virtual LANs (VLANs)

Chapter Objectives
• After completing this chapter you will:
– Describe collision domains and broadcast domains
– Describe how a hub, bridge and switch operate
– Identify where a crossover cable is used
– Describe the concept of Virtual LANs (VLANs)

Broadcasts
Ethernet inherently supports broadcasts
Broadcast mechanism is used frequently
 Example ARP – Address Resolution Protocol
A Broadcast Domain is all devices that will see a
broadcast frame

Ethernet Devices

Hubs
A hub is a simple OSI layer 1 device: a hub just
repeats the incoming signal

Crossover Cables
A ―crossover‖ or ―crossed‖ cable may be used to
directly connect two Ethernet devices
– Transmit/Receive reversed at one end
– Crossover cables can be made or bought

Connecting Hubs
Hubs may be connected or ―cascaded‖
– Connected hubs behave like one ―big‖ hub

Transparent Bridging

Bridges and Switches

LAN Switch Operation
• Flooding
• Learning
• Forwarding
• Filtering
• User filtering

LAN Switch Operation
• Having learned about destination addresses on the network the switch
will forward frames intelligently on the basis of their MAC address

Full-Duplex Ethernet

Virtual LANs (VLANs)
• A VLAN is a logical grouping of nodes (clients and servers) residing in
a common broadcast domain
• The broadcast domain has been artificially created within a LAN switch
– standard 802.3ac
LAN Switch
OFF
ON
OFF
ON
VLAN #1 - 5 workstations or repeaters

VLAN Example -1

VLAN Example -2

CommServ – Education Division Datacom NetworkingFast Ethernet-
Datacom Networking
10. Fast Ethernet
Chapter Objectives
–Identify the physical specifications for Fast Ethernet
–Define auto-negotiation
–Understand how to interwork 10Mbit/s Ethernet and Fast Ethernet

Fast Ethernet Essentials
• 10BaseT and 100BaseT
– Both use CSMA/CD
– Frame formats and frame lengths the same
– Usually deployed over Category 5 UTP
– Interconnections made with hubs, switches, routers etc.
– Standard defined by IEEE 802.3u

Fast Ethernet vs 10BaseT Ethernet
• 10BaseT vs 100BaseT
– Transmits 10 times as much data in the same time
– New physical standards
– Interframe gap .96 microseconds instead of 9.6 microseconds (unchanged
at 96 bit times)

100BaseT Specifications
• 100BaseTX
– 2 pairs of Cat 5 UTP or Cat 1 STP
– By far the most widely used
specification (95%+)
• 100BaseFX
– 2 strands of SMF or MMF
• 100BaseT4
– 4 pairs of Cat 3/4/5 UTP
• 100BaseT2
– 2 pairs of Cat 3/4/5 UTP

Matching Interfaces

Auto-Negotiation
10 or 100?
Full or half?
Then,
AUTO-NEGOTIATE!
Useful if unsure what
you‘re plugging in to
- AND when
upgrading to a
100BASE-T hub
??
Switch or
Hub
Algorithm used to negotiate common data service
Common RJ-45 connector for 1 of 8 services
Fast link pulses (FLP) similar to link integrity (LI)
Hub/NIC adjust speed to highest common mode
Order:
1. 1000BaseT FDX
2. 100BaseT2 FDX
3. 100BaseT2 HDX
4. 100BaseTX FDX
5. 100BaseT4
6. 100BaseTX
7. 10BaseT FDX
8. 10BaseT

Flow Control
HDX - Switch generates collision
FDX - Switch generates pause
frame

CommServ – Education Division Datacom NetworkingGigabit
Datacom Networking
11. Gigabit Ethernet
Chapter Objectives
–Identify the physical specifications for Gigabit Ethernet
–Describe carrier extend
–Describe frame bursting

Gigabit Ethernet Essentials
• Latest extension to Ethernet
• 1000 Mbit/s - 10 times faster than fast Ethernet
• Compatible with existing Ethernet

Gigabit Carrier Extend
P DA SA L/T Data FSSDS LLC Carrier Extend 448 bytes
64 previous minimum
+ 448 carrier extend
= 512 minimum frame size
Minimum frame size = 512 bytes

Frame Bursting
• Frame Bursting is a means to reduce the Inefficiency of Carrier
Extension
• The first frame is transmitted using the normal procedures for gigabit
Ethernet.
• A frame burst timer is started to allow transmissions of up to 64 Kbits.
• If additional frames are queued for transmission and the 64 Kbit timer
has not expired, two things happen
– The first frame is followed by carrier extend
– The next frame is transmitted

Gigabit Ethernet Specifications
• 1000BaseLX
– 2 strands of SMF or MMF
• 1000BaseSX
– 2 strands of SMF
• 1000BaseCX
– 2 pairs of twinax
• 1000BaseT
– 4 pairs of Cat 5 UTP

Ethernet Comparison
512 Bytes64 Bytes64 BytesMin Frame
Size
1518 Bytes1518 Bytes1518 BytesMax Frame
Size
16 tries16 tries16 triesAttempt
Limit
96 bit times96 bit times96 bit timesInter Frame
Gap
Fast Ethernet
802.3u
Ethernet,
802.3
Parameter
Gigabit
Ethernet,
802.3z
48 bits48 bits48 bitsAddress
Size

CommServ – Education Division Datacom NetworkingWAN-157
Datacom Networking
13. WAN Concepts
Chapter Objectives
–Define circuit switching and packet switching
–Define SVCs and PVCs
–Identify HDLC protocols and describe where they are used

Circuit Switching and Packet Switching
• Circuit Switching
– In a circuit switched network, a dedicated communications path is
established between two terminals through the nodes of the network and
for information transfer
• Packet Switching
– In this case it is not necessary to dedicate transmission capacity along a
path through the network. Rather, data is sent out in a sequence of small
chunks, called packets. Each packet is passed through the network from
node to node along some path leading from the source to the destination.

A
B
A
B
A
B
A
B
A
B
A
B
A
B
Circuit Switching Packet Switching
Info
Info
Info
Info
CS vs. PS for different applications

Leased Line and Dial-up
• Leased line
– With a leased line connection, a data user has a permanent dedicated
transmission path which can be end to end across the network, locally,
nationally or internationally.
• Dial-up
– This method is used for modem to modem data communication over the
public switched telephone network (PSTN). Source and destination must
have compatible modems.

Virtual Circuits, PVC and SVC
• Virtual Circuit
– Appears to be a separate physical circuit to the user, but in fact is part of a
shared pool of resources
• Permanent Virtual Circuit (PVC)
– PVC is a continuously dedicated virtual circuit
• Switched Virtual Circuit (SVC)
– SVC is a temporary virtual circuit established and maintained only for the
duration of a data transfer session

Datalink Layer Review
• A data link layer protocol only provides services on a point-to-point,
physical link.
• It’s up to a higher layer protocol to provide end-to-end services.

HDLC, Derivatives and Variations
Used by Frame Relay
technology
LAPF
Error-correcting modems
(specified as part of V.42)
LAPM
ISDN D channel and Frame
Relay
LAPD
Current X.25 implementationsLAPB
Early X.25 implementationsLAP
UsesHDLC Subset

CommServ – Education Division Datacom NetworkingATM-164
Datacom Networking
14. ATM
Chapter Objectives
–Understand the concept of ATM
–Describe how an ATM switch works
–Describe where ATM is used in a Network

ATM Essentials
• Flexible bearer technology (2Mbit/s – 2.5Gbit/s)
• Connection-orientated
• Uses fixed-size cells
• Able to guarantee Quality of Service (QoS)
• A multiservice technology: both voice and data traffic can be carried on
an ATM network

ATM connections
• In ATM a connection must be set up from source to destination before
traffic can flow

The ATM Cell
• Fixed cell size
• ATM switches read the cell header only, any information in the payload
flows through the network transparently

channel
1
channel
5
channel
1
empty
cell
channel
1
channel
7
channel
1
channel
2
Cell
Labelled multiplexing

Asynchronous? Transfer Mode

The principle of ATM switching
ATM
payload A 2
payload B 7
payload B 14
payload A 18

ATM Multiplexing

Constant
bit rate
Data
bursts
Variable
bit rate
Segmentation Addressing Multiplexing
Cell buffers
Segmentation and Multiplexing of different Broadband Services

ATM Connections
• Many ways of setting up the connections:
– Permanent Virtual Circuit (PVC)
– Switched Virtual Circuit (SVC)
• Many types of connections:
– Constant Bit Rate (CBR)
– Variable Bit Rate (VBR)
– Available Bit Rate (ABR)
– Unspecified Bit Rate (UBR)
• Virtual connections can be of any bandwidth

ATM Connections
• Connections are virtual channels
– Permanent (PVC)
– Switched (SVC)

ATM‘s Physical Layer
ATM Layer
Physical
Layer
Adaptation
Layer
PMD
TC
SAR
CS
Layer two
Layer one

ATM Interface References Public
Networks
Private
Networks
Public
NNI
B-ICI
Public
NNI
Private
NNI
Public
UNI
Public
UNI
Private
UNI
Private
UNI
Public
UNI
Public
UNI

The Physical Interfaces Supported
• E1 2.048 Mbit/s, T1 1.544 Mbit/s
• E3 34 Mbit/s, DS3 45 Mbit/s
• UTP-25 25 Mbit/s
• STS-1 51.84 Mbit/s
• TAXI 100 Mbit/s
• UTP- 5 I55.52 Mbit/s
• STM-1, OC3 155.52 Mbit/s
• STM-4, OC12 622.08 Mbit/s
• STM-16, OC48 2.488 Gbit/s
• STM-64, OC192 10 Gbit/s - work in progress

SDH/SONET
• The base standard defined to support ATM is:
– European/world standard
• Synchronous Digital Hierarchy (SDH)
– American standard
• Synchronous Optical Network (SONET)
• The two systems are identical at transmission rates of 155 Mbps and
above

SONET / SDH Topology
Section
ADM
Line
Path
ADM ADM
Repeaters
Inserted
Data
Dropped
Data
Repeaters
Inserted
Data
Dropped
Data

Physical Implementation of SDH
• Physical aspects of SDH/SONET
– Fibre
• single mode
– Preferred connection to operator connection
• multimode
– Used for private ATM networks, for example, a university campus
– UTP
• Category 5
– Used among workgroups
– To replace traditional LANs with ATM

ATM Layer
ATM Layer
Physical Layer
Adaptation
Layer
PMD
TC
SAR
CS
Layer two
Layer one

ATM Cell Format
VPI (high order)
VCI - 1VPI (low order)
VCI - 2
VCI - 3 Payload type CLP
Header error control
Payload (48 octets)
bit order

UNI Cell Header
48-octet data field
GFC VPI
VPI VCI
VCI
VCI PTI
HEC
8 1
1st Octet
2nd Octet
3rd Octet
4th Octet
5th Octet
Bits
CLP

NNI Cell Header
48-octet data field
VPI
VPI VCI
VCI
VCI PTI CLP
HEC
8 1
1st Octet
2nd Octet
3rd Octet
4th Octet
5th Octet
Bits

Generic Flow Control
• Locally significant only (at UNI)
– Any value will be overwritten by the switch
• Two modes of operation:
– Controlled mode
– Uncontrolled mode
• Currently only uncontrolled mode is defined
– Uncontrolled GFC = 0000
48-octet data field
VPI
VPI VCI
VCI
VCI PTI CLP
HEC
GFC

Virtual Path Identifier
• Identifies this cell’s path
• 8 bits available at the UNI
• 12 bits available at the NNI
– 256/4096 possible simultaneous paths
– Maximum number of usable bits is negotiable between user and network
48-octet data field
VCI
VCI
VCI PTI CLP
HEC
VPI
VPI
GFC
‘Real’ physical link
VPI 57
VPI 68

Virtual Channel Identifier
• Identifies this cell’s channel
• 16 bits available at the UNI & NNI
– 65,536 possible simultaneous channels per path
– Maximum number of useable bits is negotiable on a per-path basis
VPI 57
VPI 68
VCI 39
VCI 40
VCI 38
VCI 39
VPI 68
VPI 68
VCI 39
VCI44
VCI 40
VCI 41
Physical Interfaces 4- octet data field
PTI CLP
HEC
VPI
VPI
GFC
VCI
VCI
VCI

Virtual Paths
Multiple channels
destined for a common
location can be quickly
and simply switched by
the network if they share
a common VPI
channels
131
145
117
channels
131
145
117

Reserved Virtual Connections
• The following VPI/VCI combinations have been reserved:
– VPI = 0 VCI = 0 to 15 ITU-T
– VPI = 0 VCI = 16 to 31 ATM Forum
– VPI = ALL VCI = 1 to 5
• In practice, carriers regard VCIs 0 to 31 as reserved for all VPIs

Payload Type Identifier
PTI Coding
(MSB first)
Interpretation
User data cell, congestion not experienced, SDU type = 0
User data cell, congestion not experienced, SDU type = 1
User data cell, congestion experienced, SDU type = 0
User data cell, congestion experienced, SDU type = 1
Segment OAM F5 flow-related cell
End-to-end OAM F5 flow-related cell
Resource management cell
Reserved for future functions
000
001
010
011
100
101
110
111
48-octet data field
VPI
VPI VCI
VCI
VCI CLP
HEC
GFC
PTI

Congestion Control
• Bit 2 of the PTI may be used to indicate to the destination that
congestion has taken place in the network
• The bit is called Explicit Forward Congestion Indicator (EFCI)
• This will occur when switches are discarding cells with CLP =1
48-byte data field
VPI
VPI VCI
VCI
VCI CLP
HEC
GFC
PTI
EFCI

Cell Loss Priority
• CLP operates independently on each active VPI/VCI
• A switch may flip CLP from 0 to 1, for example, if traffic on
a VPI/VCI exceeds the maximum agreed sustainable cell
rate
CLP = 0
CLP = 0 CLP = 1 CLP = 1
Private UNI Private NNI Public UNI Public NNI
48-octet data field
VPI
VPI VCI
VCI
VCI
HEC
GFC
PTI CLP

Header Error Check
• The HEC is performed on the header only
– Supports forward correction of single-bit errors
– Supports detection of multiple-bit errors
• Faulty cells are discarded
– At the UNI:
• Error detection is mandatory
• Error correction is optional
• The HEC is generated/verified at the TC part of the physical layer
48-octet data field
VPI
VPI VCI
VCI
VCI CLP
GFC
PTI
HEC

Virtual Paths and Channels
ATM Switch
Virtual Channel Switch
Virtual Path Switch
VCI1 VCI2 VCI3 VCI4
VCI1
VCI2
VCI3
VCI4
VCIa
VCIb
VCIa
VCIb
VPI1
VPI2
VPI3
VPI1
VPI2
VPI4
VPI5
VPI5

The Switch Map
ATM Cell ATM Cells
VPI/VCI = A/B VPI/VCI = X/Y
1 2
Switch Map (1)
VPI VCI Interface VPI VCI
A B 2 X Y
- - - - -
VPI/VCI is of
LOCAL Significance
Only

ATM Switching
• ATM cells are being switched along a predefined connection

The Adaptation Layer
ATM Layer
Physical Layer
Adaptatio
n Layer
PMD
TC
SAR
CS
Layer two
Layer one

QoS Service Catagories
• CBR Constant Bit Rate
• VBR-RT Variable Bit Rate - Real Time
• VBR-NRT Variable Bit Rate - Non-Real Time
• ABR Available Bit Rate
• UBR Unspecified Bit Rate
• GFR Guaranteed Frame Rate (later)

ATM Service Classes
• Classes as defined by ITU-T rec. I 362
Class A Class B Class C Class D
Timing between
source and destination Required Not required
Bit rate Constant Variable
Connection mode Connection-oriented Connectionless
AAL 1 AAL 2 AAL 3 AAL 4
AAL 5
Relevant
Adaptation Layer

General Principles of Adaptation
Adaptation
Layer
SAR
CS
Higher layer data
H H
The use of a CS
is not required by
all AALs Etc.
H T H T H T

Usage of Adaptation Layer
• AAL is used to adapt a source application to ATM
– ATM switching takes place in the ATM Layer.

AAL1 Segmentation and Reassembly sublayer
Protocol Data Unit (SAR PDU)
Payload, 47 bytes (376 bits) Header, 5 bytes
SNP SN
44
SN, Sequence Number, 3 bits are used
to detect loss of cells
SNP, Sequence Number Protection

ATM Adaptation Layer type 1
Payload
Information for:
•Lost cell detection
•Synchronization
•Support of structured Circuit Emulation
1 octet47 octets
Real time, constant bit rate stream (e.g. PCM Speech)

AAL 1

AAL 2

AAL2 Segmentation And Reassemble sublayer
Protocol Data Unit (SAR PDU)
Header, 5 bytes
LI CID
8
CID, Channel Identity
LI, Length Indicator
UUI, User-to-user Indicator
HEC, Header Error Control
PayloadPayloadPayload
UUIHEC
8
STF
655
STF, Start Field

AAL2 demultiplexed to AAL2U
Header, 5 bytesPayloadPayloadPayload
Payload
Payload
Payload
AAL2
AAL 2U

AAL5 (SEAL)

AAL5, variable bit rate

AAL5 Trailer

AAL5 Transmission
• AAL5 makes use of the PTI field in ATM cell header
– Bit 1 = 1 indicates this cell carries the AAL5 trailer
48-byte data field
VPI
VPI VCI
VCI
VCI CLP
HEC
GFC
PTI

The use of AALs
ATM
AAL1
ATM
AAL5
PCM (voice)
IP (64KB max.)
48 octet
ATM SDUs 53 octet
ATM PDUs
AAL1
ATM
AAL5
AAL
ATM ATM ATM
AAL
ATM

ATM Applications – Large Core Networks

Site 2Site 1
Transport Layer
Network Control Layer
Signaling
User Plane
RNC
TDM
Network
PCM
64 kbps
AMR coding
12 kbps
WCDMA Transport
• Aggregation of server nodes in the Control Layer
TSC
Server
MSC
Server
Q.BICC
N-ISUP
RANAP
Iu
MGW
GCPGCP
TRA
• M-MGw build the Transport Layer
AAL2
Switch
AAL2
Switches
Q.AAL2
Q.AAL2
• Bandwidth efficient transport using “Codec at the edge”
• Local Switching
TDM
Network

ATM Based Signaling
MAP-ATM
TCAP
MAP/CAP
SCCP
MTP3b
SSCF-NNI
ATM
L1
AAL5
SSCOP
SGSN <---> HLR
3G MSC <--> HLR
HLR <--> VLR
MSC <--> MSC
RANAP-ATM
RANAP
SCCP
MTP3b
SSCF-NNI
ATM
L1
AAL5
SSCOP
MSC MA <--> RNC
MSC server <--> RNC
SGSN <---> RNC
Q.AAL2-ATM
Q.AAL2
MTP3b
SSCF-NNI
ATM
L1
AAL5
SSCOP
GCP-ATM
GCP
MTP3b
SSCF-NNI
ATM
L1
AAL5
SSCOP
MSC server <---> MGW
BICC/ISUP-ATM
BICC/ISUP
MTP3b
SSCF-NNI
ATM
L1
AAL5
SSCOP
MSC server <---> MSC server
TSC server <--> PSTN
MSC MA <---> RNC
C-MGw <--> RNC
C-MGw <--> C-MGw
RNC <--> RNC
RNSAP-ATM
RNSAP
SCCP
MTP3b
SSCF-NNI
ATM
L1
AAL5
SSCOP
RNC <---> RNC

CommServ – Education Division Datacom NetworkingFrame Relay-
Datacom Networking
15. Frame Relay
Chapter Objectives
–Understand the concept of Frame Relay
–Describe how a Frame Relay switch works
–Describe where Frame Relay is used in a Network

Frame Relay Essentials
• WAN packet switching technology, preceded ATM
• Typically implemented at speeds from 56kbit/s to 2Mbit/s (Can go to
speeds of 45Mbit/s)
• Supports PVCs (SVCs are supported, but generally not used)
• Uses variable-length frames to transfer data
• Has some built in traffic control mechanisms

Frame (LAPF) Format

CommServ – Education Division Datacom Networking
Frame Relay Terms
DLCI 21
DLCI 23
DLCI 22
DLCI 31
DLCI 32
DLCI 33
S 0
Frame Relay
Switch
Token
Ring
SDLC
FRAD
Definitions
DLCI: Data Link Connection Identifier
CIR : Committed Information Rate
Bc : Committed burst in bits
Be : Excess burst in bits
FECN: Forward Explicit Congestion Notify
BECN: Backward Explicit Congestion Notify
DE: Discard Eligible
Router
Frame Relay Switch
Maps DLCIs to form a PVC
Controls each PVC‘s CIR, Bc, Be
Congestion Notification: FECN, BECN
Provides Accounting and Monitoring
Router

Frame Relay Switching
• Frame Relay Frames are being switched along a predefined
connection

Congestion Control
• FECN – Forward Explicit Congestion Notification
• BECN – Backward Explicit Congestion Notification
• DE – Discard Eligibility
8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1
Byte 1 Byte 2
DLCI(msb) DLCI(lsb)C/R EA EADE
F
E
C
N
B
E
C
N

Congestion Notification

Network Congestion Recovery
Committed
Information
Rate (CIR)
Maximum
Information
Rate
Guaranteed
transmission
Transmit if
possible DE =
1
Discard
all excess

Frame Relay Illustration
• Committed Information Rate (CIR)
• Port speed (PIR)
• Permanent Virtual Circuits (PVCs)
Free if
Available
Traffic
Time
Peak
CIR
What
You Pay
for
{
{

Performance Model
Frame 1
DE=0
Frame 2
DE=0
Frame 3
DE=0
Frame 1
DE=0
Frame 2
DE=0
Frame 3
DE=0
Frame 4
DE=1
Frame 1
DE=0
Frame 2
DE=0
Frame 3
DE=1
Frame 4
DISCARDED
Time Time Time
Number of
bits
transmitte
d
Number of
bits
transmitte
d
Number of
bits
transmitte
d
Discard region
DE = 1 region
DE = 0 region
Discard region
DE = 1 region
DE = 0 region
Discard region
DE = 1 region
DE = 0 region
Bc+Be
Bc
Bc+Be
Bc
Bc+Be
Bc

FR Applications – Corporate LAN Interconnect

interface s 0
encapsulation frame-relay
!
interface s 0.1 point-to-point
ip address 172.16.1.1 255.255.255.0
frame-relay interface-dlci 42
!
ip address 172.16.4.1 255.255.255.0
!
Interface s 0.3 point-to-point
ip address 172.16.2.10 255.255.255.0
interface s 0
!
ip address 172.16.2.18 255.255.255.0
!
ip address 172.16.3.25
Frame Relay Configuration Example
DLCI 36
Frame Relay
Network
172.16.3.0
BA
DLCI 42
172.16.1.0
DLCI 59
172.16.2.0
DLCI 53
172.16.4.0
DLCI 46

interface s 0
!
interface s 0.1 multipoint
ip address 172.16.1.1 255.255.255.0
interface s 0
!
ip address 172.16.1.18 255.255.255.0
Frame Relay
BA
172.16.1.2
172.16.1.3
D
C
DLCI 36
Frame Relay Multipoint Example

CommServ – Education Division Datacom NetworkingX25-235
Datacom Networking
16. X25
Chapter Objectives
•Understand the concept X.25
•Describe the structure of a LAPB frame
•Describe the structure of an X.25 packet

X.25 Essentials
 Old WAN packet switching technology, preceded both
Frame Relay and ATM
 Designed to run over error-prone physical links so
contains extensive error checking mechanisms
 X.25 typically implemented over low speed links <64K
- (low speed by today‘s standards)
 X.25 used extensively with older proprietary systems
- banking terminals, control links for telephone exchanges

X.25 and OSI Reference Model
Application
Presentation
Session
Transport
Network
Data Link
Physical Physical
Frame
Packet
X.25 Protocol
Suite
Upper
Layer
Protocols

X.25 Interface
User
Process
Packet
Link
Access
Link
Access
PhysicalPhysical
User
Process
Packet
Multi-channel
Logical Interface
LAPB Link Level
Logical Interface
Physical Interface
Physical
DLC
Network
OSI-RM
User Data
User Data
Layer 3
Header
X.25 Packet
LAPB
Header
Layer 3
Header
User Data FCS
LAPB Frame
10101110111......
Node-A Node-B
Flag

X.25 WAN
DTE
DCE DCE
Packet Switching Network
Leased line
Physical DTE
Physical DCE

X.25 WAN (contd)
DTE
Packet Switching Network
X 25 context is between
DTE and Packet switched network (DCE)
DTE
DTE
X 25
X 25
Logical DCE
at layer 2 / 3
Logical DTE
at layer 2 / 3
DCE DCE
Transparent at layer 2 / 3
Logical DTE
at layer 2 / 3

Flag Address Information FCS FlagControl
0 1 1 1 1 1 1 0 0 1 1 1 1 1 1 0
Flag
Flags

Flag Address Information FCS FlagControl
0N(R) N(S) I:
7 6 5 4 3 2 1 0
F
P
S:N(R) 0 1
7 6 5 4 3 2 1 0
U:P
F X X 1 1
7 6 5 4 3 2 1 0
P
F
X X X
X X
01 or 03
Address and Control

Information frames
I Information nr p ns 0
Supervisory frames
RR Receiver Ready nr p/f 0 0 0 1
RNR Receiver Not Ready nr p/f 0 1 0 1
REJ Reject nr p/f 1 0 0 1
Unnumbered frames
SABM Set asynchronous balanced mode 0 0 1 p 1 1 1 1
UA Unnumbered acknowledgement 0 1 1 f 0 0 1 1
DISC Disconnect 0 1 0 p 0 0 1 1
DM Disconnected mode 0 0 0 f 1 1 1 1
FRMR Frame Reject 1 0 0 f 0 1 1 1
LAPB Commands and Responses

LAPB Operation 1
SABM
SABM
UA
UA
Info nr=0 ns=0
Info nr=0 ns=0
Info nr=1 ns=0
Info nr=1 ns=2
Info nr=1 ns=1
Info nr=1 ns=0
Info nr=1 ns=1
Info nr=1 ns=3
Info nr=1 ns=2
Info nr=1 ns=3
RR nr=4
RR nr=4
Info nr=4 ns=1
Info nr=4 ns=1
DCE
DTE
Info nr=2 ns=4
Info nr=2 ns=4

LAPB Operation 2
Info nr=2 ns=7
Info nr=2 ns=7
REJ nr=6
DCE
DTE
Info nr=2 ns=5
Info nr=2 ns=4
Info nr=2 ns=6
Info nr=2 ns=5
Info nr=2 ns=4
Ignored as
CRC incorrect
Info nr=2 ns=0
Info nr=2 ns=0
REJ nr=6
Info nr=2 ns=6
Info nr=2 ns=6
Info nr=2 ns=7
Info nr=2 ns=0
Info nr=2 ns=0
Info nr=2 ns=7
Info nr=1 ns=2
Info nr=1 ns=2
REJ frame
acknowledges
up to frame 5
XX

LAPB Operation 3
Info nr=2 ns=7 p=0
Info nr=2 ns=7 p=0
DCE DTE
Info nr=2 ns=5 p=0
Info nr=2 ns=4 p=0
Info nr=2 ns=6 p=0
Info nr=2 ns=5 p=0
Info nr=2 ns=4 p=0
Info nr=2 ns=4 p=1
Info nr=2 ns=4 p=1
T1
timer
T1
timer
Info nr=2 ns=4 p=1
Info nr=2 ns=4 p=1
Info nr=2 ns=4 p=1
Info nr=2 ns=6 p=0
T1
timer
N 2 times Info nr=2 ns=4 p=1

Logical Channel Numbers (LCNs)
LCN LCN
LCN LCN
Logical DTE
Logical DCE
Logical DTELogical DTE
Logical DCE
Logical DTE

LCNs (contd)
LCN 5 LCN 8
LCN 45
LCN 19
LCN 9 LCN 9

General Format Identifier
Q D
01 Modulo 8
10 Modulo 128
11 Extensions
00 Reserved
8 7 6 5 4 3 2 1Bits
Byte 1 LCGNModulo
GFI normal
L D
Long Address indicator
Call Request packets only
8 7 6 5 4 3 2 1Bits
Byte 1 LCGNModulo
GFI Extended addressing

Byte 1
2
3
12345678
Logical Channel Number
GFI
Bits
Packet Type Identifier
Logical Channel Group Number
Packet Layer Header
16 Logical Channel Group Numbers
256 Logical Channel Numbers in each group
A Logical channel may be identified by LCN or by LCGN + LCN
Logical channel 0 = LCGN 0 , LCN 0
Logical channel 1025 = LCGN 4 , LCN 1

Packet Header
Call request / incoming call 0 0 0 0 1 0 1 1
Call accept / call connected 0 0 0 0 1 1 1 1
Clear request / Clear indication 0 0 0 1 0 0 1 1
Clear confirmation 0 0 0 1 0 1 1 1
Data pr m ps 0
RR pr 0 0 0 0 1
RNR pr 0 0 1 0 1
REJ pr 0 1 0 0 1
Interrupt 0 0 1 0 0 0 1 1
Interrupt confirmation 0 0 1 0 0 1 1 1
Reset request / Reset indication 0 0 0 1 1 0 1 1
Reset confirmation 0 0 0 1 1 1 1 1
Restart request/restart indication 1 1 1 1 1 0 1 1
Restart confirmation 1 1 1 1 1 1 1 1
Diagnostic 1 1 1 1 0 0 0 1

Call Setup
Call request Incoming Call
Call AcceptCall connected

General Format Identifier Logical Channel Group Number
Logical Channel Number
Packet Type Identifier
Calling DTE Address Length Called DTE Address Length
Called DTE Address Field
BCD - 2 digits / octet
Variable length (15 digits max)
Facility Field Length
12345678Bits
Call Request, Incoming call, Call Accepted, Call Connected
Facility Field codes and values
Variable length
Calling DTE Address Field
BCD - 2 digits / octet
Variable length (15 digits max)

X.25 Operation
DTE A DTE B
A Initiates a
virtual call to B
Incoming Call
Call Accepted
Data pr=0 ps=0
Data pr=0 ps=1
Data pr=2 ps=0
RR pr = 1
Call Request
Call Connected
Data pr=0 ps=0
Data pr=0 ps=1
Data pr=3 ps=0
Network
RR pr=1
RR pr=2
Data pr=1 ps=3
Data pr=1 ps=2
Data pr=1 ps=3
Data pr=1 ps=2
Acknowledgement
from local DCE
Acknowledgement
from local node
Call established
Data transfer stage
Acknowledgement
changed by local
node for packet
with ps=2
Packet delayed at local node
until ACK has been received
from remote DTE

X.121 Addressing
DNIC Data Network Identification Code (DCC + NI)
DCC Data Country Code (3 digits)
NI Network Identifier (1 digit)
NTN Network Terminal Number (max10 digits incl SA)
SA Sub-address
234 2 19201005
234 2 19201004 74
240 2 00451
272 4 30000200
310 6 000715
DNIC NI NTN SA

CommServ – Education Division Datacom NetworkingPPP-256
Datacom Networking
17. PPP
Chapter Objectives
–Describe how a PPP frame structure
–Describe the function of the Link Control Protocol (LCP)
–Describe the function of the Network Control Protocol (NCP)
–Describe where PPP is used in a Network

PPP Essentials
• Very widely-used standard for transporting layer 3 datagrams
(especially IP) over point-to-point links (rfc 1661)
• PPP replaces the older Serial Line Interface Protocol (SLIP)
• PPP is comprised of:
– Encapsulation method
– Link Control Protocol (LCP)
– Network Control Protocol (NCP)
• Often referred to as “self-configuring”

PPP Frame Format

Link Control Protocol (LCP) Functions
• Determine encapsulation format options
• Negotiate optimal packet size
• Terminate the link
• Authenticate the identity of the peer on the link [ PAP or CHAP ]
(optional)
• Negotiate PPP Multilink data compression (optional)
• Link quality monitoring (optional)

Network Control Protocols (NCPs)
• NCPs are a series of independently-defined protocols that
encapsulate network layer protocols
• Examples: TCP/IP, DECnet, AppleTalk, IPX…

PPP Logical Flow
LCP
Link DEAD
Start
Up State
NCPNegotiate Options
Bind NCP
Last
Last
Terminate Data Exchange
Fail authentication
OpenLCP phase
NCP phase
Open State

PPP Applications

CommServ – Education Division Datacom NetworkingModems-267
Datacom Networking
18. Modems
Chapter Objectives
–Describe the function of a modem
–Identify modem standards and associated speeds
–Describe where modems are used in a Network

Chapter Objectives
• After completing this chapter you will be able to:
– Describe the function of a modem
– Identify modem standards and associated speeds
– Describe where modems are used in a Network

Modem – MOdulation and DEModulation

Modem Standards
Rec. Speed (bit/s) Transmission
Mode
PSTN LL
2W
LL
4W
Back-up
via PSTN
Mod.
Method
V.21 300 Asynchronous (A) FD FD FSK
V.23 1200/600 A and S HD HD FD * FSK
V.22 1200/600 A and S FD FD * DPSK
V.22bis
V.22f.bk
2400/1200 A and S FD FD * QAM
V.26bis 2400/1200 Synchronous (S) HD HD FD * DPSK
V.26ter 2400/1200 A and S FD FD * DPSK
V.27ter
V.26bisf.bk
4800/2400 S HD HD FD * DPSK
V.29 9600/7200/4800 A and S FD QAM
V.32 9600/4800 A and S FD FD * QAM/TCM
V.33 14400/12000 S FD QAM/TCM
V.34 28800 S FD TCM
V.34bis 28800/31200/33600 S FD TCM
Baseband 2400/1800/1200
7200/4800/3600
19200/14400/9600
A and S HD FD
V.90 56000 to the end user
33600 from the end user
S Asymetric PCM

LAPM Frame Format

Modem Applications

CommServ – Education Division Datacom NetworkingISDN-273
Datacom Networking
19. ISDN
Chapter Objectives
–Describe the concept of ISDN
–Identify the reference points in an ISDN network
–Identify the differences between primary and basic rate ISDN
–Describe where ISDN is used in network

ISDN Essentials
• Full services, digital, end-to-end network
• Narrowband ISDN and Broadband ISDN (B-ISDN is ATM-based)
• ISDN based on 64Kbit/s channels
• Two channel types: Bearer (B) Channel and Data (D) Channel
– B channel for user traffic, uses PPP
– D channel signalling and control, uses LAPD

ISDN BRI Reference Model
TE1
NT2 NT1
Terminal
Adapter
U
Interface
T
Interface
S
Interface
R
Interface
To Telco
To Telco
TE2

PRI Frame Format for E1/T1
7 6 5 4 3 2 1 07 6 5 4 3 2 1 00
B1 D-Channel B31Framing
7 6 5 4 3 2 1
256 bits/125 microseconds (2.048Mbps)
E1
Signaling
+31+0 +1 +16
Data Data
F
7 6 5 4 3 2 1 07 6 5 4 3 2 1 0
B1 B2 B23 D-Channel
24th Channel
193 bits/125 microseconds (1.544Mbps)
T1

Basic Rate Interface (BRI)
B1
B2
D
64Kbs
64Kbs
16Kbs
2B + 1D

Primary Rate Interface (PRI)
64Kbs
64Kbs
:
:
B1
64Kbs
64Kbs
64Kbs
:
B2
D
23B + 1D (USA)
30B + 1D
(EISDN)
B22 or
29B23 or
30

LAPD Format

Types of ISDN Connections
• Circuit Switched
• Packet Switched
• Frame Mode
• Semi-permanent

ISDN Applications

CommServ – Education Division Datacom NetworkingxDSL-282
Datacom Networking
20. xDSL
Chapter Objectives
–Describe the concept of xDSL
–Identify the speeds of common xDSL standards
–Describe where xDSL is used in a network

Copper Access

xDSL Technologies
• Asymmetric Digital Subscriber Line (ADSL)
• Rate Adaptive Digital Subscriber Line (RADSL)
• High-bit-rate Digital Subscriber Line (HDSL)
• Symmetrical Digital Subscriber Line (SDSL)
• Very-high-data-rate Digital Subscriber Line (VDSL)

DSL Types
Technology Data Rate Mode Distance (ft) Distance (m)
ISDL/ISDN 128Kbps Duplex 18000 5400
HDSL 2.048Mbps
1.544Mbps
Duplex
Duplex
12000 3600
SDSL 2.048Mbps
1.544Mbps
Duplex
Duplex
10000 3000
ADSL 6.144Mbps
640Kbps
Downstream
Upstream
12000 3600
RADSL 0.32-9Mbps Downstream Depends on data
rate
VDSL 12.96Mbps
25.92Mbps
51.84Mbps
1.5 – 6Mbps
Downstream
Upstream
4500
3000
1000
1350
900
300

ADSL standards and bandwidth
8,1 / 1,5 Mbps
Annex A (POTS)
8,1 / 1,8 Mbps
Annex B (ISDN)
8 / 3.4 Mbps
‗Annex J‘ (POTS)
Scenario
...
ADSL ADSL2 ADSL2+
ADSL2++
VDSL1/2 DMT
13,4 / 1,6 Mbps
Annex A (POTS)
11,5 / 1,9 Mbps
Annex B (ISDN)
5,7 / 1,0 Mbps
Annex L (POTS)
11,5 / 3,5 Mbps
Annex M (POTS)
28,7 / 1,6 Mbps
Annex A (POTS)
26,8 / 1,9 Mbps
Annex B (ISDN)
26,8 / 3,5 Mbps
Annex M (POTS)

ITU G.992.1 - ADSL
• ITU G.992.1 (ADSL) is implemented from EDA 1.1
• The following ADSL annexes are available:
ISDN DS
ADSL
Annex B f
[kHz]
ADSL
Annex A f
[kHz]
DS
POTS
US
US
Variable frequency spectrum
POTS
f
[kHz]
DS
ADSL
Annex M
US
25 80 138 276 1104552

ITU G.992.3 - ADSL2
• ITU G.992.3 (ADSL2) is implemented from EDA 1.3
• The following ADSL2 annexes are available:
ISDN DS
ADSL2
Annex B f
[kHz]
ADSL2
Annex A f
[kHz]
DS
POTS
US
US
POTS
f
[kHz]
DS
ADSL2
Annex M
US
25 80 138 276 1104
DS
POTS
US
552
f
[kHz]
ADSL2
Annex L

ITU G.992.5 - ADSL2+
• ITU G.992.5 (ADSL2+) is implemented from EDA 2.0
• New frequency spectrum compared with G992.1 & G992.3
• The following ADSL2+ annexes are available:
ISDN DS
ADSL2+
Annex B f
[kHz]
POTS
f
[kHz]
ADSL2+
Annex A f
[kHz]
DS
DS
POTS
US
ADSL2+
Annex M
US
25 80 138 276 2208
US

ADSL2/ADSL2+ Facts
• ADSL2 Boosts performance
– 13 Mbps / 3 Mbps (DS/US)
• ADSL2 provides service over longer loop lengths
– Approx. 500 m more compared with G992.1
– Annex L even more on long loop lengths
• ADSL2+ Boosts performance even more
– 28 Mbps / 3 Mbps (DS/US)
• ADSL2+ relevant for loop lengths up to 2 km
Length, Km1 Km 2 Km 3 Km 4 Km 5 Km 6 Km
8
13
ADSL2
ADSL2+
28
Data Rate, Mbps
Annex L is
relevant here
7 Km
ADSL

xDSL Applications

Multiple downstream
tunnels with same content
Video service via PPP tunnels
Channel 1
Channel 2
Set-top Box
Channel 1
Set-top Box
Channel 2
Set-top Box
Channel 2
Router/
BRAS
Video
Service
Provider
IP
DSLAM

Video service via IGMP
Supports
IGMP snooping
Supports
IP Multicast
Only one downstream
for each channel
Channel 1
Channel 2
Set-top Box
Channel 1
Set-top Box
Channel 2
Set-top Box
Channel 2
Router/
BRAS
Video
Service
Provider
IP
DSLAM

CommServ – Education Division Datacom NetworkingSDH SONET-
Datacom Networking
21. SDH & SONET
Chapter Objectives
–Describe the differences between PDH and SDH/SONET
–Identify the speeds associated with SDH/SONET
–Describe where SDH/SONET is used in a Network

PDH Systems
DS0 @ 64k
1.5Mb 6Mb 45Mb 274MbX 4 X 7 X 6
2Mb 8Mb 34Mb 565Mb140Mb
X30
X 4 X 4 X 4

PDH Multiplexing and Demultiplexing
• With PDH everything must be de-multiplexed to extract a single signal!
– Motivation for development of SDH/SONET

PDH/SDH and SONET
SDH/SONET
– Higher bandwidth, easier to manage, backwards-
compatible with PDH

SONET and SDH Frames

SONET and SDH Frames – Overhead

Overhead Layers
ADM
or
DCS
REGREG PTEPTE
Section SectionSection Section
Line Line
Path
Path
Termination
Section
Termination
Line
Termination
Section
Termination Path
Termination
Service (DS1, DS3 ..)
Mapping and
Demapping
Service
Mapping and
Demapping
PTE Path Terminating Element
REG Regenerator
ADM Add-Drop Multiplexer
DCS Digital Cross-Connect System

SDH Multiplexing Structure
Pointer
SOH
SOH
STM-1
VC-4
C-4
260
9
P
O
H
140 Mbit/sC-4VC-4STM-1

SDH Multiplexing Structure
x 1
x 3
x 1
x 7
x 3
x 1x N
STM-N
AUG AU4 VC4 C4
C3
C2
C12
C11
139,264
kbit/s
44,736
34,368
kbit/s
6,312
kbit/s
2,048
kbit/s
1,544
kbit/s
VC3
VC2
VC12
VC11
TU3
TU2
TU12
TUG2
TUG3
Aligning
Mapping
Multiplexing
STM Synchronous Transport Mode
AUG Administrative Unit Group
AU Administrative Unit
TUG Tributary Unit Group
TU Tributary Unit
VC Virtual Container
C Container
AU3 VC3
x 3
x 7
TU11TU11
x 4

SDH/SONET Equipment
• Add-drop multiplexer
– A multiplexer capable or extracting or inserting lower rate signals from a
higher rate multiplexed signal without completely demultiplexing the signal
• Digital Cross Connect
– An electronic cross-connect which has access to lower-rate channels in
higher-rate multiplexed signals and can cross-connect those channels
• Regenerator (Repeater)
– Device that restores a degraded digital signal for continued transmission

SDH / SONET Acronyms
This Graphic is the Property
of Quill Training Services
9953.280
2488.320
622.080
155.520
51.840
STS-192
STS-48
STS-12
STS-3
STS-1
OC-192
OC-48
OC-12
OC-3
OC-1
STM-64
STM-16
STM-4
STM-1
SDH-64
SDH-16
SDH-4
SDH-1
Format
Frame
Level
SDH
( Mbps )
Line Rate
Format
Frame
Carrier Level
Optical

Applications of SDH/SONET

CommServ – Education Division Datacom NetworkingPOS-311
Datacom Networking
22. POS
Chapter Objectives
–Describe the concept of Packet Over SONET (POS)
–Describe where POS is used in a Network

Packet Over SONET (POS) Essentials
• POS = Packet over SONET or Packet over SDH
• A standard for transmitting packets (primarily IP) over high speed
SONET/SDH links
• Consists of PPP over SONET or SDH
– IP is carried within PPP
• Works with all speed of SONET/SDH
• Attractive solution for large ISP cores

IP over PPP over SDH/SONET

POS Applications – Large Core ISP Networks

CommServ – Education Division Datacom NetworkingMPLS-319
Datacom Networking
23. MPLS
Chapter Objectives
–Describe the concept of Multiprotocol Label Switching (MPLS)
–Describe how MPLS devices work
–Identify how MPLS is implemented with different technologies
–Describe where MPLS is used in a Network

Multiprotocol Label Switching Essentials
• MPLS is an Internet Engineering Task Force (IETF) forwarding
standard
• Concept:
– Packets entering the network are analysed and put into a forward
equivalence class (FEC)
– Forward equivalence classes are mapped to connections through the
network
– The packet is labelled according to which path it should take through the
network
– Packet is transferred though the network by switching on the label

MPLS Network Components
Label Switching Router (LSR) deployed in
the core of the network to perform high
speed label switching
Label Edge Router (LER) deployed at the
edge of the network for connectivity to user
networks. Also called ingress and egress
LSRs.

MPLS in Operation

LER Functions

LSR Functions

MPLS Implementation
• MPLS can be implemented as:
• A Layer 3 (or “Pure IP”) solution
– The Label is extra information attached to the IP header
– LERs are edge routers running MPLS software
– LSRs are core routers running MPLS software
• An ATM solution
– The Label is the VPI/VCI
– LERs are edge routers running MPLS software
– LSRs are ATM switches running MPLS software

MPLS Label in a ―Pure IP‖ Solution

MPLS Label in an IP over ATM Solution

MPLS Applications – Large Backbone
Networks

CommServ – Education Division Datacom NetworkingInternet
Datacom Networking
25. Internet Architecture
Chapter Objectives
–Describe the structure of the TCP/IP protocol suite

Internet Protocols
TCP
IP
Transport
Layer
RARP
UDPOSPF EGP
BGP
ICMP IGMP
RIP
TELNET, FTP, TFTP, BOOTP, SMTP, HTTP, SNMP, NFS, NTP, , ,
Internet
Layer ARP
Type Code
Protocol Number
Port Number
IEEE 802.2, PPP, LAPB, Ethernet, RS232, 802.3, 802.5,
Upper
Layer
Link/Physical
Layer

Upper-Layer Protocols: End User and Utility
Functions
TCP
IP
Transport
Layer
RARP
UDPOSPF EGP
BGP
ICMP IGMP
RIP
TELNET, FTP, TFTP, HTTP, SMTP
SNMP, BOOTP/DHCP, DNS, NTP, RADIUS
Internet
Layer
ARP
Type Code
Protocol Number
Port Number
Upper
Layer
Link/Physical
Layer

Transport Layer Protocols
TCP
IP
Transport
Layer
RARP
UDPOSPF EGP
BGP
ICMP IGMP
RIP
SNMP, BOOTP/DHCP, DNS, NTP, RADIUS, , , ,
Internet
Layer
ARP
Type Code
Protocol Number
Port Number
Upper
Layer
Link/Physical
Layer

Internet Layer Protocol: Internet Protocol
TCP
IP
Transport
Layer
RARP
UDPOSPF EGP
BGP
ICMP IGMP
RIP
Internet
Layer
ARP
Type Code
Protocol Number
Port Number
Upper
Layer
Link/Physical
Layer

Anomalies
TCP
IP
Transport
Layer
RARP
UDPOSPF EGP
BGP
ICMP IGMP
RIP
Internet
Layer ARP
Type Code
Protocol Number
Port Number
Upper
Layer
Link/Physical
Layer

Sending and Receiving a Message
Application specify:
Upper Layer Protocol
Internet address
Upper Layer protocol:
Build header for peer to describe format
Specify Port number to select Application
Transport Layer protocol:
Build Header for peer to describe format
Specify Protocol number to select proper
Internet Layer (IP):
Source and destination IP addresses
Link Layer (unique for physical connection):
Identify IP stack with Type Code number
at IP address
Transport Layer protocol

Internet Society (ISOC) Specifications
• All Internet standards specified by the IETF, a division of ISOC
• Standards are called Request for Comments (RFCs) and are
sequentially numbered
• All standards available free from http://www.ietf.org
• RFC search facility available at http://www.rfc-editor.org/

CommServ – Education Division Datacom NetworkingInternet Apps-
Datacom Networking
26. Internet Applications
Chapter Objectives
–Describe how the Hypertext Transfer Protocol (HTTP) works
–Describe how the Domain Name Service (DNS) works
–Describe how the Simple Network Management Protocol (SNMP) works
–Describe how the File Transfer Protocol (FTP) works
–Describe how Telnet works

Hypertext Transfer Protocol
Architecture
HTTP
TCP
IP
Protocol 6
HTTP
TCP
IP
Protocol 6
ServerClient
Port 80 Port 80

HTTP Operation
Web client
browser TCP port 80
hypertext
links
Web
server

Uniform Resource Locator (URL)
scheme = http://, ftp://, telnet://,
news:, mailto: , , , , ,
http://server.name/file.type
scheme
path=domain name
or IP address
search object

Domain Name Service (DNS)
rootunnamed
intorgnetmilgoveducom ukau us
geographically based domains:
2-letter country codes
defined in ISO 3166
organizationally based domains:
defined by Internet Registry (IR)
IP
Physical network
DNS
UDP
Protocol 17
port 53

File Transfer Protocol
IP
Physical network
FTP
TCP
Protocol 6
port 21

Telnet
IP
Physical network
Telnet
TCP
Protocol 6
port 23

Simple Network Management Protocol
Architecture
SNMP
UDP
IP
Protocol 17
SNMP
UDP
IP
Protocol 17
ManagerAgent
Port 169 Port 169

SNMP Management
Manager
Managed
Resources
Managed Node
Agent
MIB
SNMP
SNMP Operations
Set, Get, GetResponse,
GetNext, Trap

CommServ – Education Division Datacom NetworkingTransport
Datacom Networking
27. Transport Layer Protocol
Chapter Objectives
–Describe how connection may be multiplexed
–Define ports and sockets
–Describe the differences between TCP and UDP
–Describe the operation of TCP and UDP

Multiplexing Connections
Internet
client
server
SMTP
FTP
HTTP
SMTP
FTP
HTTP
IP address
X
IP address
Y
destination
port 25
source
port 3000
destination
port 21
source
port 3001
destination
port 80
source
port 3002

Connection Components
Internet
client
server
SMTP
FTP
HTTP
SMTP
FTP
HTTP
IP address
X
IP address
Y
destination
port 25
source
port 3000
destination
port 21
source
port 3001
destination
port 80
source
port 3002
socketsocket
connection

Transport Layer Protocols
UDP
IP
TCP
Upper Layer Protocols
Physical network
ports
617 protocols

Transmission Control Protocol (TCP)
Segment Format
TCP Data
+0
+4
bit order
01234567012345670123456701234567
octet +0 octet +1 octet +2 octet +3
octet order
+8
+16
+20
source port destination port
sequence number
acknowledgement number
check sum urgent pointer
options (if any) padding
window+12
hdr
length reserved
code
bits

EduDivision-DATACOM NETWORKING

EduDivision-DATACOM NETWORKING

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