Networking Basics Overview

SKILLS FOR INDIA

Overview of Networking

Basics of Networking

An overview of computer networking which introduces
many key concepts and terminology. Sets the stage for
future topics.
2

A network consists of 2 or more computers connected
together, and they can communicate and share resources
(e.g. information)

3

 Communications – activity associated with distributing or exchanging
information
 Telecommunications – technology of communications at a distance that
permits information to be created any where and used everywhere with
little delay
 A network is a way to get “stuff” between 2 or more “things”
 Examples: Mail, phone system, conversations, railroad system,
highways and roads

4







Must have a message
Message must have a transmitter
Message must have a medium
Message must be understood
Message must have some level of security

Destination System

Source System

Source  Transmitter  Transmission  Receiver  Destination
1

2

Workstation/PC

3

Medium

4

5

Workstation/PC
5

Essentials for Network

1.
2.
3.
4.
5.
6.

Text input information
Input data digital bit stream
Transmitted analog signal
Received analog signal
Output data digital bit stream
Text output information

6

General Architecture of Computer Networks

External
nodes
(or stations)

Cloud

Internal nodes
(swithing devices)
7

Document Amendment History

S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

9

T H A N K Y O U. . .

All information, including graphical representations, etc provided in this presentation is for exclusive use of current Globsyn
Skills students and faculty. No part of the document may be reproduced in any form or by any means, electronic or otherwise,
without written permission of the owner.
10

Bus Topology

 Bus: each node is daisy-chained (connected one right after the other)
along the same backbone. Information sent from a node travels along
the backbone until it reaches its destination node. Each end of a bus
network must be terminated with a resistor to keep the

12

Ring Topology
 Similar to a bus network, rings have
nodes daisy chained, but the end of
the network in a ring topology comes
back around to the first node, creating
a complete circuit. Each node takes a
turn
sending
and
receiving
information through the use of a
token. The token along with any data
is sent from the first node to the
second node which extracts the data
addressed to it and adds any data it
wishes to send. Then second node
passes the token and data to the third
node, etc. until it comes back around
to the first node again. Only the node
with the token is allowed to send data
. All other nodes must wait for the
token to come to them.
13

Star Topology
 In a star network, each node is
connected to a central device called a
hub. The hub takes a signal that comes
from any node and passes it along to all
the other nodes in the network
 A hub does not perform any type of
filtering or routing of the data
 A hub is a junction that joins all the
different nodes together

14

Star-Bus Topology
 Prob. Most common topology
used today. Combines elements of
the star and bus topologies to
create a versatile network
environment
 Nodes in particular areas are
connected to hubs (and create star
topology), and hubs are connected
together along the network
backbone (like a bus network)
 Often you have stars nested
within stars

15

Mesh Topology

 It is also called a point-to-point
topology
 Each device is connected
directly to all other network
devices
 It provides fault tolerance
 It is only found in wide area
networks

16

Other network topologies








Some basic network topologies not previously mentioned:
One-to-one
Hierarchical
Hybrid
Client-server
Multiple nodes

17


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

18


19

SKILLS FOR INDIA

Types of Network

Network configuration

 Classification based on how computers behave in a network
 Two classifications are
 Peer-to-Peer network
 Server based network

21

Peer-to-Peer network








Nodes provide and request services
User in each node administers resources
No extra investment
Easy to setup
Very weak security
Additional load on nodes

22

Server based network






Designated computer to administer
Resources centralized
Supports larger networks
Strong security
Expensive

23

 Advantages of peer-to-peer networks:
Low cost
Simple to configure
User has full accessibility of the computer
 Disadvantages of peer-to-peer networks:
May have duplication in resources
Difficult to uphold security policy
Difficult to handle uneven loading
 Where peer-to-peer network is appropriate:
10 or less users
No specialized services required
Security is not an issue
Only limited growth in the foreseeable future
24

Clients and Servers
 Network Clients (Workstation)
Workstation
Computers that request network resources or services
Network Servers
Computers that manage and provide network resources and services to
clients
Usually have more processing power, memory and hard disk space than
clients
Run Network Operating System that can manage not only data, but also
users, groups, security, and applications on the network
Servers often have a more stringent requirement on its performance and
reliability

25

 Advantages of client/server networks
Facilitate resource sharing – centrally administrate and control
Facilitate system backup and improve fault tolerance
Enhance security – only administrator can have access to Server
Support more users – difficult to achieve with peer-to-peer networks

 Disadvantages of client/server networks
High cost for Servers
Need expert to configure the network
Introduce a single point of failure to the system

26


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

27


28

SKILLS FOR INDIA

Networking Media and Components

Coaxial cable
 Widely installed for use in business and corporation Ethernet and other
types of LANs.
 Consists of inter copper insulator covered by cladding material, and
then covered by an outer jacket
 Physical Descriptions:

 Inner conductor is solid copper metal
 Separated by insulating material
 Outer conductor is braided shielded (ground)
 Covered by sheath material
30

 Applications:
 TV distribution (cable tv); long distance telephone transmission;
short run computer system links
 Local area networks
 Transmission characteristics:
 Can transmit analog and digital signals
 Usable spectrum for analog signaling is about 400 Mhz
 Amplifier needed for analog signals for less than 1 Km and less
distance for higher frequency
 Repeater needed for digital signals every Km or less distance for
higher data rates
 Operation of 100’s Mb/s over 1 Km
31

Twisted Pair Cables
 Physical description:






Each wire with copper conductor
Separately insulated wires
Twisted together to reduce cross talk
Often bundled into cables of two or four twisted pairs
If enclosed in a sheath then is shielded twisted pair (STP) otherwise often
for home usage unshielded twisted pair (UTP). Must be shield from
voltage lines

 Application:
 Common in building for digital signaling used at speed of 10’s Mb/s
(CAT3) and 100Mb/s (CAT5) over 100s meters.
 Common for telephone interconnection at home and office buildings
 Less expensive medium; limited in distance, bandwidth, and data rate
32

Categories of Twisted Pairs Cabling System
Category

Maximum
data rate

Usual application

CAT 1

Less than 1
Mbps

analog voice (plain old
telephone service)
Integrated Services Digital
Network Basic Rate
Interface in ISDN Doorbell
wiring

CAT 2

4 Mbps

Mainly used in the IBM
Cabling System for token
ring networks

CAT 3

16 Mbps

Voice and data on
10BASE-T Ethernet (certify
16Mhz signal)

CAT 4

20 Mbps

Used in 16Mbps Token
Ring

Specs describe cable
Material, type of
Connectors, and
Junction blocks to
Conform to a category

Otherwise not used much
CAT 5

100 Mbps

100 Mbps TPDDI
155 Mbps asynchronous
transfer mode (certify 100
Mhz signal)

33

Optical Fibers
 Physical Description:
 Glass or plastic core of optical fiber = 2to125 µm
 Cladding is an insulating material
 Jacket is a protective cover
 Laser or light emitting diode provides transmission light source
 Applications:
 Long distance telecommunication
 Greater capacity; 2 Gb/s over 10’s of Km
 Smaller size and lighter weight
 Lower attenuation (reduction in strength of signal)
 Electromagnetic isolation – not effected by external electromagnetic
environment. Aka more privacy
 Greater repeater spacing – fewer repeaters, reduces line regeneration
cost
34

 Multimode fiber is optical fiber that is designed to carry multiple light
rays or modes concurrently, each at a slightly different reflection angle
within the optical fiber core. used for relatively short distances because
the modes tend to disperse over longer lengths (this is called modal
dispersion)
 For longer distances, single mode fiber (sometimes called monomode)
fiber is used. In single mode fiber a single ray or mode of light act as a
carrier

35

Wireless Transmission
 Frequency range (line of sight):
 26 GHz to 40 GHz: for microwave with highly directional beam as
possible
 30 MHz to 1 GHz: for omni directional applications
 300MHz to 20000 GHz: for infrared spectrum; used for point to
point and multiple point application (line of sight)
 Physical applications:
 Terrestrial microwave – long haul telecommunication service
(alternative to coaxial or optical fiber)
 Few amplifier and repeaters
 Propagation via towers located without blockage from trees, etc
(towers less than 60 miles apart)
36

 Satellite is a microwave relay station
 Geostationary orbit (22,000 miles) and low orbit (12000 miles)
 Satellite ground stations are aligned to the space satellite, establishes a
link, broadcast at a specified frequency. Ground station normally
operate at a number of frequencies – full duplex
 Satellite space antenna is aligned to the ground station establishes a
link and transmits at the specified frequency. Satellite are capable of
transmitting at multiple frequencies simultaneously, full duplex.
 To avoid satellites from interfering with each other, a 4 degree
separation is required for 4/6 GHz band and 3 degree for 12/14 GHz
band. Limited to 90 satellites
 Disadvantage: not satellite repair capability; greater delay and
attenuation problems

37

Wireless LAN
 Wireless LAN
 Hiper LAN (European standard; allow communication at up to 20
Mbps in 5 GHz range of the radio frequency (RF) spectrum
 Hiper LAN/2 operate at about 54 Mbps in the same RF band

38


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

39


40

SKILLS FOR INDIA

Network Components

Hubs
 A hub is the place where data converges from one or more directions
and is forwarded out in one or more directions.
 Seen in local area networks

42

Gateways

 A gateway is a network point that acts as an entrance to another
network. On the internet, in terms of routing, the network consists of
gateway nodes and host nodes
 Host nodes are computer of network users and the computers that serve
contents (such as Web pages)
 Gateway nodes are computers that control traffic within your
company’s network or at your local internet service provider (ISP)

43

Routers
 A router is a device or a software in a computer that determines the next
network point to which a packet should be forwarded toward its
destination
 Allow different networks to communicate with each other
 A router creates and maintain a table of the available routes and their
conditions and uses this information along with distance and cost
algorithms to determine the best route for a given packet
 A packet will travel through a number of network points with routers
before arriving at its destination

44

Bridge
 A bridge is a product that connects a local area network (LAN) to
another local area network that uses the same protocol (for example,
Ethernet or token ring)
 A bridge examines each message on a LAN, "passing" those known to
be within the same LAN, and forwarding those known to be on the
other interconnected LAN (or LANs)

45

Differences
 Bridge: device to interconnect two LANs that use the SAME logical
link control protocol but may use different medium access control
protocols
 Router: device to interconnect SIMILAR networks, e.g. similar
protocols and workstations and servers
 Gateway: device to interconnect DISSIMILAR protocols and servers,
and Macintosh and IBM LANs and equipment

46

Switches
 Allow different nodes of a network to communicate directly with each
other
 Allow several users to send information over a network at the same time
without slowing each other down

47


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

48


49

SKILLS FOR INDIA

IEEE Standards

Introduction
 IEEE 802 refers to a family of IEEE standards
 Dealing with local area network and metropolitan area network
 Restricted to networks carrying variable-size packets
 Specified in IEEE 802 map to the lower two layers
• Data link layer
– LLC sub layer
– MAC sub layer
• Physical layer
 The most widely used standards
 The Ethernet family, Token Ring, Wireless LAN
 Bridging and Virtual Bridged LANs
 An individual Working Group provides the focus for each area
51

IEEE 802 Working Groups
Active working groups
802.1

Inactive or disbanded working groups
802.2

Logical Link Control Working Group

Group
802.3

Higher Layer LAN Protocols Working

802.4

Token Bus Working Group

Ethernet Working Group

802.5

Token Ring Working Group

802.7

Broadband Area Network Working

802.11 Wireless LAN Working Group
802.15 Wireless Personal Area Network
(WPAN) Working Group
802.16 Broadband Wireless Access Working
Group

Group
802.8

Fiber Optic TAG

802.9

Integrated Service LAN Working
Group

802.17 Resilient Packet Ring Working Group

802.10 Security Working Group

802.18 Radio Regulatory TAG

802.12 Demand Priority Working Group

802.19 Coexistence TAG

802.14 Cable Modem Working Group

802.20 Mobile Broadband Wireless Access
(MBWA) Working Group
802.21 Media Independent Handoff Working Group

52

 Types
 Infrastructure based
 Ad-hoc
AP

 Advantages
 Flexible deployment
 Minimal wiring difficulties
 More robust against disasters
(earthquake etc)

AP

wired network

 Disadvantages
 Low bandwidth compared to wired networks (1-10 Mbit/s)
 Need to follow wireless spectrum regulations
 Not support mobility

AP: Access Point
AP

53


802.11

802.11

802.11a

802.11b

Protocol

Release
date

Op. Frequency

Legacy

1997

2.5~2.5 GHz

802.11a

1999

802.11b

802.11g

802.11n

Data rate
(Max)
2 Mbit/s

Range
(indoor)

Range
(outdoor)

5.15~5.35/5.47~5.725
/5.725~5.875 GHz

54 Mbit/s

~25 m

~75 m

1999

2.4~2.5GHz

11 Mbit/s

~35 m

~100 m

802.11g

2003

2.4~2.5GHz

54 Mbit/s

~25 m

~75 m

802.11n

2007

2.4GHz or 5GHz

540 Mbit/s

~50 m

~125 m
54

802.11n Working Group
 What is the 802.11n?
 Uses MIMO radio technology and OFDM as a basis
 Anywhere from 100Mbps to 600Mbps depending on implementation
 Support both 2.4 GHz and 5 GHz
 Use multiple stream

 802.11n increase transmission efficiency of MAC
 Cutting guard band time in half
 Reducing the number of pilot carrier, for data
 Aggregating frames and bursting
 Using a 40MHz instead of a 20MHz channel

30~50% => 70%

55

802.11n Working Group
Timeline

Draft 1.0 failed IEEE meeting ballot
IEEE record – 12,000 comments received
Draft 2.0 is now required – Orlando March 2007 IEEE
Meeting
Pre-N certification program start March 2007
Result – expect ratification in early 2008

56

802.15 Wireless Personal Area
Network(WPAN)
Working Groups summary
802.15

802.15.1

802.15.2

802.15.3

 802.15.1 : WPAN/Bluetooth
 802.15.2 : Coexistence Group
802.15.3a
 802.15.3 : High Rate(HR) WPAN Group
 802.15.3a : WPAN HR Alternative PHY Task
Group
 802.15.3b : MAC Amendment Task Group
 802.15.4 : Low Rate(LW) WPAN Group(Zigbee)
 802.15.4a : WPAN Low Rate Alternative PHY
 802.15.4b : Revisions and Enhancements
 UWB Forum

802.15.3b

802.15.4

802.15.4a

802.15.4b

57

802.16 Broadband Wireless Access(BWA)
 IEEE 802.16
 Be was established by IEEE Standards Board in 1999, aims to prepare
formal specifications for the global deployment of broadband Wireless
Metropolitan Area Network.
 A unit of the IEEE 802 LAN/MAN Standards Committee.
 A related technology Mobile Broadband Wireless Access(MBWA)
Mobile
(Vehicular)

WWAN
(IMT-2000)
cdma2000® 1xEV-DO,
cdma2000® 1xEV-DV
2G/2.5G

802.16e

Pedestrian
(Nomadic) Cellular
WCDMA HSDPA
802.15.1
(Bluetooth)

0.1

802.16a
(WiMAX)
802.15.3a
(UWB)

802.11
(WLAN)

1.0 3.1

10

100

58

802.16 Broadband Wireless Access
(BWA)
802.16

802.16.f

802.15.g

802.15.h

802.15.i

802.15.j

802.15.m

802.15.k

 802.16f : Management Information Base
 802.16g : Management Plane Procedures and Services
 802.16h : Improved Coexistence Mechanisms for License-Exempt
Operation
 802.16i : Mobile Management Information Base
 802.16j : Multihop Relay Specification
 802.16k : Bridging of 802.16
 802.16m : Advanced Air Interface.

59


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

60


61

Major Categories of Networks

Local Area Network
Metropolitan Area network
Wide area network
The internet
Personal Area Network

63

Local Area Network
A Local Area Network (LAN) is a relatively small network that is
confined to a small geographic area, such as a single office or a building.
Laptops, desktops, servers, printers, and other networked devices that
make up a LAN are located relatively close to each other. A key
characteristic is that all of the equipment that comprises a LAN, is owned
by a single entity.

64

Metropolitan Area Network

The term Metropolitan Area Network (MAN) is typically used to describe a
network that spans a citywide area or a town. MANs are larger than
traditional LANs and predominantly use high-speed media, such as fiber
optic cable, for their backbones. MANs are common in organizations that
need to connect several smaller facilities together for information sharing.
This is often the case for hospitals that need to connect treatment facilities,
outpatient facilities, doctor's offices, labs, and research offices for access to
centralized patient and treatment information. MANs share many of the
same security threats as LANs, but on a larger scale. The plight of an
administrator in a central location granting access to countless offices that
are scattered within a city is a difficult one that demands strict access
control mechanisms to protect against unauthorized information access.

65

Wide Area Network

A Wide Area Network (WAN) covers a significantly larger geographic area
than LANs or MANs. A WAN uses public networks, telephone lines, and
leased lines to tie together smaller networks such as LANs and MANs over
a geographically dispersed area. Connecting devices in different geographic
areas together for information sharing, WANs are an important piece of
enterprise networks. For example, consider the VisaNet global network used
by Visa International. The VisaNet network connects locations throughout
150 countries to validate and debit credit-card transactions at over 24
million locations. By providing security and simplicity over a standardbased WAN architecture, Visa International relies on their network
infrastructure to provide reliable access to merchants who accept Visa credit
cards for transactions.

67

Personal Area Network

A more recent term used to describe a type of network is a Personal Area
Network (PAN). PAN networks are usually wireless, established in an ondemand or ad-hoc fashion when needed to communicate between two or
more devices. PAN networks can be used between devices owned by two
different parties, or between two devices owned by one person, such as a
PDA and a laptop or mobile phone. These networks are usually characterized
as short-range, often limited to 10 meters or less in range.
An example of a PAN technology is Bluetooth wireless networking.
Bluetooth is designed as a cable-replacement technology, allowing users to
discard the serial and USB cables used by many of today's peripheral devices
and rely on a Bluetooth PAN for communication. Bluetooth PANs support up
to 7 devices in a single network and can be used for proprietary protocols
(such as PDA synchronization) or standards-based protocols, including
Internet access over IP and the Bluetooth Network Encapsulation Protocol
69
(BNEP).

Data Communications Through WANs
 WANs were developed to communicate over a large geographical area
(e.g. lab-to-lab; city-to-city; east coast-to-west coast; North America-toSouth America etc)
 WANs require the crossing of public right of ways (under control and
regulations of the interstate commerce and institute of telephone and data
communications established by the gov’t and international treaties).
 WANs around the world relies on the infrastructure established by the
telephone companies (“common carrier”) or public switched telephone
network (PSTN)
 WANs consists of a number of interconnected switching nodes (today =
computers). Transmission signals are routed across the network
automatically by software control to the specified destination. The
purpose of these nodes are to route messages through switching facilities
to move data from node to node to its destination
71

 WANs originally implemented circuit switching and packet switching
technologies. Recently, frame relay and asynchronous transfer mode
(ATM) networks have been implemented to achieve higher operating
and processing speeds for the message
 WAN are owned by the common carrier in the U.S. and government in
most foreign countries
 Interconnected devices, I.e. LANs or Personal Computers (PC) or
Workstation or Servers can be (usually are) privately owned by
companies

72


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

73


74

ISO/OSI Reference Model





Open Systems Interconnection
No one really uses this in the real world.
A reference model so others can develop detailed interfaces
Value: The reference model defines 7 layers of functions that take place
at each end of communication and with each layer adding its own set of
special related functions
 Flow of data through each layer at one

76

ISO/OSI Reference Model
File Transfer, Email, Remote Login 

ASCII Text, Sound (syntax layer) 

Establish/manage connection 
End-to-end control & error checking
(ensure complete data transfer): TCP 
Routing and Forwarding Address: IP 

Two party communication: Ethernet 
How to transmit signal; coding Hardware
means of sending an receiving data on a carrier
77

Layer 1: Physical layer
The physical layer defines electrical and physical specifications for devices.
In particular, it defines the relationship between a device and a transmission
medium, such as a copper or fiber optical cable.
The major functions and services performed by the physical layer are:
Establishment and termination of a connection to
a communications medium
Participation in the process whereby the communication resources are
effectively shared among multiple users. For example,
contention resolution and flow control

78

Modulation, or conversion between the representation of digital data in
user equipment and the corresponding signals transmitted over a
communications channel. These are signals operating over the physical
cabling (such as copper and optical fiber) or over aradio link
Parallel SCSI buses operate in this layer, although it must be remembered
that the logical SCSI protocol is a transport layer protocol that runs over this
bus. Various physical-layer Ethernet standards are also in this layer;
Ethernet incorporates both this layer and the data link layer. The same
applies to other local-area networks, such as token ring, FDDI, ITUT G.hn and IEEE 802.11, as well as personal area networks such
as Bluetooth and IEEE 802.15.4.

79

Layer 2: Data link layer
The data link layer provides the functional and procedural means to transfer
data between network entities and to detect and possibly correct errors that
may occur in the physical layer. Originally, this layer was intended for
point-to-point and point-to-multipoint media, characteristic of wide area
media in the telephone system. Local area network architecture, which
included broadcast-capable multi access media, was developed
independently of the ISO work in IEEE Project 802. IEEE work
assumed sub-layering and management functions not required for WAN
use. In modern practice, only error detection, not flow control using sliding
window, is present in data link protocols such as Point-to-Point
Protocol (PPP), and, on local area networks, the IEEE 802.2 LLC layer is
not used for most protocols on the Ethernet, and on other local area
networks, its flow control and acknowledgment mechanisms are rarely used.
Sliding window flow control and acknowledgment is used at the transport
layer by protocols such as TCP, but is still used in niches where X.25 offers
performance advantages.
80

The ITU-T G.hn standard, which provides high-speed local area
networking over existing wires (power lines, phone lines and coaxial
cables), includes a complete data link layer which provides both error
correction and flow control by means of a selective repeat Sliding
Window Protocol.
Both WAN and LAN service arrange bits, from the physical layer, into
logical sequences called frames. Not all physical layer bits necessarily
go into frames, as some of these bits are purely intended for physical
layer functions. For example, every fifth bit of the FDDI bit stream is
not used by the layer.

81

Layer 3: Network layer
The network layer provides the functional and procedural means of
transferring variable length data sequences from a source host on one network
to a destination host on a different network (in contrast to the data link layer
which connects hosts within the same network), while maintaining the quality
of service requested by the transport layer. The network layer performs
network routing functions, and might also perform fragmentation and
reassembly, and report delivery errors. Routers operate at this layer, sending
data throughout the extended network and making the Internet possible. This
is a logical addressing scheme – values are chosen by the network engineer.
The addressing scheme is not hierarchical.

82

Layer 3: Network layer
The network layer may be divided into three sub layers:
Sub network access – that considers protocols that deal with the interface to
networks, such as X.25;
Sub network-dependent convergence – when it is necessary to bring the
level of a transit network up to the level of networks on either side
Sub network-independent convergence – handles transfer across multiple
networks

83

An example of this latter case is CLNP, or IPv6 ISO 8473. It manages
the connectionless transfer of data one hop at a time, from end system
to ingress router, router to router, and from egress router to destination end
system. It is not responsible for reliable delivery to a next hop, but only for
the detection of erroneous packets so they may be discarded. In this scheme,
IPv4 and IPv6 would have to be classed with X.25 as subnet access
protocols because they carry interface addresses rather than node addresses.
A number of layer-management protocols, a function defined in the
Management Annex, ISO 7498/4, belong to the network layer. These
include routing protocols, multicast group management, network-layer
information and error, and network-layer address assignment. It is the
function of the payload that makes these belong to the network layer, not the
protocol that carries
84

Layer 4: Transport layer
The transport layer provides transparent transfer of data between end users,
providing reliable data transfer services to the upper layers. The transport
layer controls the reliability of a given link through flow control,
segmentation/desegmentation, and error control. Some protocols are stateand connection-oriented. This means that the transport layer can keep track
of the segments and retransmit those that fail. The transport layer also
provides the acknowledgement of the successful data transmission and
sends the next data if no errors occurred.

85

OSI defines five classes of connection-mode transport protocols ranging
from class 0 (which is also known as TP0 and provides the least features)
to class 4 (TP4, designed for less reliable networks, similar to the Internet).
Class 0 contains no error recovery, and was designed for use on network
layers that provide error-free connections. Class 4 is closest to TCP,
although TCP contains functions, such as the graceful close, which OSI
assigns to the session layer. Also, all OSI TP connection-mode protocol
classes provide expedited data and preservation of record boundaries.
Although not developed under the OSI Reference Model and not strictly
conforming to the OSI definition of the transport layer, the Transmission
Control Protocol (TCP) and the User Datagram Protocol (UDP) of the
Internet Protocol Suite are commonly categorized as layer-4 protocols
within OSI.
86

Layer 5: Session layer
The session layer controls the dialogues (connections) between computers.
It establishes, manages and terminates the connections between the local
and remote application. It provides for full-duplex, half-duplex,
or simplex operation, and establishes checkpointing, adjournment,
termination, and restart procedures. The OSI model made this layer
responsible for graceful close of sessions, which is a property of
the Transmission Control Protocol, and also for session check pointing and
recovery, which is not usually used in the Internet Protocol Suite. The
session layer is commonly implemented explicitly in application
environments that use remote procedure calls. On this level, InterProcess_(computing) communication happen (SIGHUP, SIGKILL, End
Process, etc.).

87

Layer 6: Presentation layer
The presentation layer establishes context between application-layer entities,
in which the higher-layer entities may use different syntax and semantics if
the presentation service provides a mapping between them. If a mapping is
available, presentation service data units are encapsulated into session
protocol data units, and passed down the stack.
This layer provides independence from data representation (e.g., encryption)
by translating between application and network formats. The presentation
layer transforms data into the form that the application accepts. This layer
formats and encrypts data to be sent across a network. It is sometimes called
the syntax layer.
The original presentation structure used the basic encoding rules of Abstract
Syntax Notation One (ASN.1), with capabilities such as converting
an EBCDIC-coded
text file to
an ASCII-coded
file,
or serialization of objects and other data structures from and to XML.
88

Layer 7: Application layer
The application layer is the OSI layer closest to the end user, which means
that both the OSI application layer and the user interact directly with the
software application. This layer interacts with software applications that
implement a communicating component. Such application programs fall
outside the scope of the OSI model. Application-layer functions typically
include identifying communication partners, determining resource
availability, and synchronizing communication. When identifying
communication partners, the application layer determines the identity and
availability of communication partners for an application with data to
transmit. When determining resource availability, the application layer must
decide whether sufficient network or the requested communication exist. In
synchronizing communication, all communication between applications
requires cooperation that is managed by the application layer.
89

Comparison with TCP/IP Model
In the TCP/IP model of the Internet, protocols are deliberately not as rigidly
designed into strict layers as in the OSI model. [10] RFC 3439 contains a
section entitled "Layering considered harmful (section link here )."
However, TCP/IP does recognize four broad layers of functionality which
are derived from the operating scope of their contained protocols, namely
the scope of the software application, the end-to-end transport connection,
the internetworking range, and the scope of the direct links to other nodes
on the local network.
Even though the concept is different from the OSI model, these layers are
nevertheless often compared with the OSI layering scheme in the following
way: The Internet application layer includes the OSI application layer,
presentation layer, and most of the session layer. Its end-to-end transport
layer includes the graceful close function of the OSI session layer as well as
the OSI transport layer.
90

The internetworking layer (Internet layer) is a subset of the OSI network
layer (see above), while the link layer includes the OSI data link and
physical layers, as well as parts of OSI's network layer. These comparisons
are based on the original seven-layer protocol model as defined in ISO
7498, rather than refinements in such things as the internal organization of
the network layer document.
The presumably strict peer layering of the OSI model as it is usually
described does not present contradictions in TCP/IP, as it is permissible that
protocol usage does not follow the hierarchy implied in a layered model.
Such examples exist in some routing protocols (e.g., OSPF), or in the
description of tunneling protocols, which provide a link layer for an
application, although the tunnel host protocol may well be a transport or
even an application layer protocol in its own right.
91


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

92


93

SKILLS FOR INDIA

Understanding Network Protocols

Protocols of Computer Communications and
Networks
 Protocol are used for communication between computers in different
computer networks. Protocol achieves:
 What is communicated between computers?
 How it is communicated?
 When it is communicated?
 What conformance (bit sequence) between computers?
 Key elements of a protocol are:
 SYNTAC: Data format and signal levels
 SEMANTICS: Control information for coordination and error
handling
 TIMING: Synchronization, speed matching, and sequencing
 Examples of protocols:
 WAN Protocol: TCP/IP
95

The Internet Protocol Suite and the OSI
Reference Model

96

TCP
The Transmission Control Protocol (TCP) is one of the core protocols of
the Internet Protocol Suite. TCP is one of the two original components of
the suite, complementing the Internet Protocol (IP), and therefore the entire
suite is commonly referred to as TCP/IP. TCP provides reliable, ordered
delivery of a stream of bytes from a program on one computer to another
program on another computer. TCP is the protocol used by major Internet
applications such as the World Wide Web, email, remote
administration and file transfer. Other applications, which do not require
reliable data stream service, may use the User Datagram Protocol (UDP),
which provides datagram service that emphasizes reduced latency over
reliability.

97

User Datagram Protocol
The User Datagram Protocol (UDP) is one of the core members of
the Internet Protocol Suite, the set of network protocols used for
the Internet. With UDP, computer applications can send messages, in this
case referred to as datagram, to other hosts on an Internet Protocol (IP)
network without requiring prior communications to set up special
transmission channels or data paths. The protocol was designed by David
P. Reed in 1980 and formally defined in RFC 768 .
UDP
uses
a
simple
transmission
model
without
implicit handshaking dialogues for providing reliability, ordering, or data
integrity. Thus, UDP provides an unreliable service and datagram may
arrive out of order, appear duplicated, or go missing without notice. UDP
assumes that error checking and correction is either not necessary or
performed in the application, avoiding the overhead of such processing at
the network interface level. Time-sensitive applications often use UDP
because dropping packets is preferable to waiting for delayed packets,
which may not be an option in a real-time system.
98

Internet Control Message Protocol

The Internet Control Message Protocol (ICMP) is one of the core
protocols of the Internet Protocol Suite. It is chiefly used by the operating
systems of networked computers to send error messages indicating, for
example, that a requested service is not available or that a host or router
could not be reached. ICMP can also be used to relay query messages. It is
assigned protocol number 1.
ICMP differs from transport protocols such as TCP and UDP in that it is
not typically used to exchange data between systems, nor is it regularly
employed by end-user network applications (with the exception of some
diagnostic tools like ping and trace route).
ICMP for Internet Protocol version 4 (IPv4) is also known as
ICMPv4. IPv6 has a similar protocol, ICMPv6.
99

Hypertext Transfer Protocol

Hypertext Transfer Protocol (HTTP) is an application protocol for
distributed, collaborative, hypermedia information systems. HTTP is the
foundation of data communication for the World Wide Web.
Hypertext is a multi-linear set of objects, building a network by using
logical links (the so-called hyperlinks) between the nodes (e.g. text or
words). HTTP is the protocol to exchange or transfer hypertext.
The standards development of HTTP was coordinated by the Internet
Engineering Task Force (IETF) and the World Wide Web
Consortium (W3C), culminating in the publication of a series of Requests
for Comments (RFCs), most notably RFC 2616 (June 1999), which defines
HTTP/1.1, the version of HTTP in common use.

100

Post Office Protocol
In computing, the Post Office Protocol (POP) is an applicationlayer Internet standard protocol used by locale-mail clients to retrieve email from
a
remote server over
a TCP/IP connection. POP
and IMAP (Internet Message Access Protocol) are the two most
prevalent Internet standard protocols for e-mail retrieval. Virtually all
modern e-mail clients and servers support both. The POP protocol has been
developed through several versions, with version 3 (POP3) being the current
standard.
Most webmail service
providers
such
as
Hotmail, Gmail and Yahoo! Mail also provide IMAP and POP3 service.

101

File
Protocol

Transfer

File Transfer Protocol (FTP) is a standard network protocol used to
transfer files from one host to another host over a TCP-based network,
such as the Internet. It is often used to upload web pages and other
documents from a private development machine to a public web-hosting
server. FTP is built on a client-server architecture and uses separate
control and data connections between the client and the server. FTP users
may authenticate themselves using a clear-text sign-in protocol, normally
in the form of a username and password, but can connect anonymously if
the server is configured to allow it. For secure transmission that hides
(encrypts) the username and password, and encrypts the content, SSH File
Transfer Protocol may be used.

102

Internet Message Control Protocol
Internet message access protocol (IMAP) is one of the two most
prevalent Internet standard protocols for email retrieval, the other
being the Post Office Protocol (POP). Virtually all modern e-mail
clients and mail servers support both protocols as a means of transferring
e-mail messages from a server.
The Internet Message Access Protocol (commonly known as IMAP) is
an Application Layer Internet protocol that allows a client to access email on a remote mail server. The current version, IMAP version 4
revision 1 (IMAP4rev1), is defined by RFC 3501. An IMAP server
typically listens on well-known port 143. IMAP over SSL (IMAPS) is
assigned well-known port number 993.

103

IPX/SP
X

IPX/SPX is a routable protocol and can be used for small and large
networks. It was created by Novell primarily for Novell NetWare networks,
but is popular enough that it is used on products that are not from Novell.
•NCP - NetWare Core Protocol provides for client/server interactions
such as file and print sharing. It works at the application, presentation, and
session levels.
•SAP - Service Advertising Protocol packets are used by file and print
servers to periodically advertise the address of the server and the services
available. It works at the application, presentation, and session levels.

104

IPX/SP
X
•SPX - Sequenced Packet Exchange operates at the transport layer
providing connection oriented communication on top of IPX.
•IPX - Internetwork Packet Exchange supports the transport and
network layers of the OSI network model. Provides for network
addressing and routing. It provides fast, unreliable, communication
with network nodes using a connection less datagram service.

105

Other Network Support

 ODI - Open Data-link Interface
operates at the data link layer allowing
IPX to work with any network interface
card
 RIP - Routing Information Protocol is
the default routing protocol for
IPX/SPX networks which operates at
the network layer. A distance-vector
algorithm is used to calculate the best
route for a packet
 MHS - Message Handling Service by
Novell is used for mail on Netware
networks

Network Level

Protocols

Application
Presentation

NCP

SAP

Session
Transport
Network
Data Link

IPX

SPX

NDIS/NIC
drivers

106

NetBIOS
NetBIOS is an acronym for Network Basic Input/Output System. It
provides services related to the session layer of the OSI model allowing
applications on separate computers to communicate over a local area
network. As strictly an API, NetBIOS is not a networking protocol.
Older operating systems ran NetBIOS over IEEE 802.2 and IPX/SPX using
the NetBIOS Frames (NBF) and NetBIOS (NBX) protocols, respectively.
In modern networks, NetBIOS normally runs over TCP/IP via the NetBIOS
over TCP/IP (NBT) protocol. This results in each computer in the network
having both an IP address and a NetBIOS name corresponding to a
(possibly different) host name.

107

NetBEUI (NetBIOS Extended User Interface
NetBEUI (NetBIOS Extended User Interface) is a new, extended version
of NetBIOS, the program that lets computers communicate within a local
area network. NetBEUI formalizes the frame format (or arrangement of
information in a data transmission) that was not specified as part of
NetBIOS. NetBEUI was developed by IBM for its LAN Manager
product and has been adopted by Microsoft for its Windows NT, LAN
Manager, and Windows for Workgroups products. Hewlett-Packard and
DEC use it in comparable products.
NetBEUI is the best performance choice for communication within a
single LAN. Because, like NetBIOS, it does not support the routing of
messages to other networks, its interface must be adapted to other
protocols such as Internetwork Packet Exchange or TCP/IP. A
recommended method is to install both NetBEUI and TCP/IP in each
computer and set the server up to use NetBEUI for communication
within the LAN and TCP/IP for communication beyond the LAN.
108

Difference between NetBIOS & NetBEUI
NetBIOS (Network Basic Input/Output System) isn't a network protocol.
It's an API (applications programming interface) for File and Printer
Sharing. NetBIOS names identify computers on the network. NetBIOS
broadcasts locate computers and shared disks and folders on the network
and allow them to appear in My Network Places and Network
Neighborhood.
NetBEUI (NetBIOS Extended User Interface) is a network protocol, like
TCP/IP and IPX/SPX. All three protocols support file and printer sharing
using the NetBIOS API.
Nothing in Windows networking requires the NetBEUI protocol. All
network functions are available using the TCP/IP and/or NW Link
IPX/SPX protocols.
NetBEUI is available as an un-supported protocol in Windows XP.
109

Apple Talk

AppleTalk is a proprietary suite of networking protocols developed
by Apple Inc. for their Mac computers. AppleTalk included a number of
features that allowed local area networks to be connected with no prior
setup or the need for a centralized router or server of any sort. Simply
connecting together AppleTalk equipped systems would automatically
assign addresses, update the distributed namespace, and configure any
required inter-networking routing. It was a true plug-n-play system.
AppleTalk was released for the original Macintosh in 1985, and was the
primary protocol used by Apple machinery through the 1980s and 90s.
Versions were also released for the IBM PC and compatibles, and the Apple
IIGS. AppleTalk support was also available in most networked printers
(especially laser printers), some file servers and a number of routers.
Through this period, AppleTalk was, by far, the most popular networking
system in the world.
110

Apple Talk..Continued
The rise of TCP/IP during the 1990s led to a re-implementation of most of
these types of support on that protocol, and AppleTalk became unsupported
as of the release of Mac OS X v10.6 in 2009. Many of AppleTalk's more
advanced auto-configuration features have since been introduced
in Bonjour.

111

Associated TCP/IP Protocols & Services
HTTP

This protocol, the core of the World Wide Web, facilitates
retrieval and transfer of hypertext (mixed media) documents.
Stands for the HyperText Transfer protocol

Telnet

A remote terminal emulation protocol that enables clients to log
on to remote hosts on the network.

SNMP

Used to remotely manage network devices. Stands for the Simple
Network Management Protocol.

DNS

Provides meaningful names like achilles.mycorp.com for
computers to replace numerical addresses like 123.45.67.89.
Stands for the Domain Name System.

SLIP/
PPP

SLIP (Serial Line Internet Protocol) and PPP (Point to Point
Protocol) encapsulate the IP packets so that they can be sent over
a dial up phone connection to an access provider’s modem.

112


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

113


114

SKILLS FOR INDIA

IP Addressing

What is an IP address?







IP (Internet Protocol) address
Device used by routers, to select best path from source to
destination, across networks and internetworks
Network layer address, consisting of NETWORK portion,
and HOST portion
Logical address, assigned in software by network
administrator
Part of a hierarchical ‘numbering scheme’ - unique, for
reliable routing
May be assigned to a host pc, or router port

116

Types of IP address
 Static address
 Dynamic address

117

Static IP address

 Manually input by network administrator
 Manageable for small networks
 Requires careful checks to avoid duplication

118

Dynamic IP address

Examples - BOOTP, DHCP
 Assigned by server when host boots
 Derived automatically from a range of addresses
 Duration of ‘lease’ negotiated, then address released back to server

119

Class A IP address
 1st octet = network address, octets 2-4 = host address
 1st bits of 1st octet set to 0
 up to (2^24 - 2) host addresses (16.8M)

121

Class A IP address

124. 224. 224.100

01111100

11100000

11100000

01100100

122

Class B IP address
 1st 2 octets = network address, octets 3-4 = host address
 1st 2 bits of 1st octet set to 10
 up to (2^16 - 2) host addresses (65534)

123

Class B IP address

129. 224. 224. 100

10000001

11100000

11100000

01100100

124

Class C IP address

 1st 3 octets = network address, octet 4 = host address
 1st 3 bits of 1st octet set to 110
 up to (2^8 - 2)

host addresses (254)

125

Class C IP address

193. 224. 224. 100

11000001

11100000

11100000

01100100

126

IP addresses and routing

 Routing tables
 Identifying source and destination
 IP packet routing

127

IP addresses and routing -Routing

Tables
 Created by router, held in memory, constantly updated
 Based on cross-referencing
 IP packet source address, and port on which received

128

IP addresses and routing Identifying source
and destination

 As part of a layer 3 packet, IP header contains source and destination
address
 Each address is 32 bits long, and unique to device or port
 Router reads destination IP address, checks against routing tables

129

IP addresses and routing - IP packet routing

 If destination address not on the same segment as receive port,
router sends packet to correct port for routing to destination
 If destination on same segment as receive port, packet not
forwarded

130

Networks and subnets
 Why subnet
 Subnet mask
 Restrictions on ‘borrowed’ bits

131

When an organization is granted a block of addresses, it can create
subnets to meet its needs. The prefix length increases to define the
subnet prefix length.

Why subnet
Reduce broadcast domain, improve network efficiency

Why subnet
Reduce broadcast domain, improve network efficiency

132

Subnet masks

 Extend NETWORK portion, borrow from HOST portion
 Allow external networks to route packets direct to subnet

133

Network Address Translation
Network Address Translation or NAT
Kinds of Network Address Translation
Operation of Network Address Translation
Security and Administration

135

IP Routing
When we want to connect two or more networks using different n/w
addresses then we have to use IP Routing technique. The router will
be used to perform routing between the networks. A router will
perform following functions for routing.
 Path determination
 Packet forwarding
 Path determination
The process of obtaining path in routing table is called path
determination. There are three different methods to which router can
learn path.
 Automatic detection of directly connected n/w.
 Static & Default routing
 Dynamic routing
136

IP Routing
 Packet forwarding
It is a process that is by default enable in router. The router will
perform packet forwarding only if route is available in the routing
table.

137

Routing Process
 The pc has a packet in which destination address is not same as the
local n/w address.
 The pc will send an ARP request for default gateway. The router will
reply to the ARP address and inform its Mac address to pc.
 The pc will encapsulate data, in which source IP is pc itself,
destination IP is server, source Mac is pc’s LAN interface and
destination Mac is router’s LAN interface.

138

Routing Process

R1

10.0.0.1
S. MAC
PC1
D. IP
S. IP

D. MAC
R1
172.16.0.5
10.0.0.6

172.16.0.5
139

The router will receive the frame, store it into the buffer. When obtain
packet from the frame then forward data according to the destination
IP of packet. The router will obtain a route from routing table
according to which next hop IP and interface is selected
 According to the next hop, the packet will encapsulated with new
frame and data is send to the output queue of the interface.

140

Static Routing
In this routing, we have to use IP route commands through which we
can specify routes for different networks. The administrator will analyze
whole internetwork topology and then specify the route for each n/w
that is not directly connected to the router.
Steps to perform static routing
Create a list of all n/w present in internetwork.
Remove the n/w address from list, which is directly connected to n/w.
Specify each route for each routing n/w by using IP route command.
Router(config)#ip route <destination n/w> <mask> <next hop ip>
Next hop IP it is the IP address of neighbor router that is directly
connected our router.
141

Advantages of static routing
(1) Fast and efficient.
(2) More control over selected path.
(3) Less overhead for router.
(4) Bandwidth of interfaces is not consumed in routing updates.
Disadvantages of static routing
(1) More overheads on administrator.
(2) Load balancing is not easily possible.
(3) In case of topology change routing table has to be change
manually.

142

Alternate command to specify static route

Static route can also specify in following syntax: Old
Router(config)#ip route 172.16.0.0 255.255.0.0 172.25.0.2
Or
Router(config)#ip route 172.16.0.0 255.255.0.0 serial 0

143

Backup route or loading static route
If more than one path are available from our router to destination then
we can specify one route as primary and other route as backup route.
Administrator Distance is used to specify one route as primary and
other route as backup. Router will select lower AD route to forward
the traffic. By default static route has AD value of 1. With backup
path, we will specify higher AD so that this route will be used if
primary route is unavailable.
Protocols
AD
Directly Connected
0
Static
1
BGP
20
EIGRP
90
IGRP
100
OSPF
110
RIP
120
144

Syntax: To set backup path Router(config)#ip route <dest. n/w>
<mask> <next hop> <AD>
Default Routing
Default routing means a route for any n/w. these routes are
specify with the help of following syntax: Router(config)#ip route 0.0.0.0 0.0.0.0 <next hop>
Or
<exit interface>
To display routing table
Router#sh ip route
145

To display routing table
Router#sh ip route
To display static routes only
Router#sh ip route static
S 192.168.10.0/28 [1/0] via 172.16.0.5
To display connected n/ws only
Router#sh ip route connected
To check all the interface of a router
Router#sh interface brief

146

Dynamic Routing
In dynamic routing, we will enable a routing protocol on router. This protocol
will send its routing information to the neighbor router. The neighbors will
analyze the information and write new routes to the routing table.
The routers will pass routing information receive from one router to
other router also. If there are more than one path available then routes are
compared and best path is selected. Some examples of dynamic protocol are: RIP, IGRP, EIGRP, OSPF
Types of Dynamic Routing Protocols
According to the working there are two types of Dynamic Routing Protocols.
(1) Distance Vector
(2) Link State

147

Dynamic Routing
According to the type of area in which protocol is used there are again two
types of protocol: (1) Interior Routing Protocol
(2) Exterior Routing Protocol
Interior Routing

Exterior Routing

RIP

BGP

IGRP

EXEIGRP

EIGRP
OSPF
148

Distance Vector Routing
The Routing, which is based on two parameters, that is distance and direction
is called Distance Vector Routing. The example of Distance Vector Routing is
RIP & IGRP.
Operation: (1) Each Router will send its directly connected information to the neighbor
router. This information is send periodically to the neighbors.
(2) The neighbor will receive routing updates and process the route
according to following conditions:  If update of a new n/w is received then this information is stored in
routing table.
 If update of a route is received which is already present in routing
table then route will be refresh that is route times is reset to zero.
149

 If update is received for a route with lower metric then the route, which is
already present in our routing table. The router will discard old route and
write the new route in the routing table.
 If update is received with higher metric then the route that is already
present in routing table, in this case the new update will be discard.
 A timer is associated with each route. The router will forward routing
information on all interfaces and entire routing table is send to the
neighbor. There are three types of timers associated with a route.
 Route update timer
It is the time after which the router will send periodic update to the
neighbor.
150

 Route invalid timer
It is the time after which the route is declared invalid, if there are no
updates for the route. Invalid route are not forwarded to neighbor routers
but it is still used to forward the traffic.
 Route flush timer
It is the time after which route is removed from the routing table, if there
are no updates about the router.

151

Metric of Dynamic Routing
 Metric are the measuring unit to calculate the distance of destination n/w. A
protocol may use a one or more than one at a time to calculate the distance.
Different types of metric are:  Hop Count
 Band Width
 Load
 Reliability
 Delay
 MTU

152

Hop Count
It is the no. of Hops (Routers) a packet has to travel for a destination n/w.
Bandwidth
Bandwidth is the speed of link. The path with higher bandwidth is preferred to
send the data.
Load
Load is the amount of traffic present in the interface. Paths with lower load
and high throughput are used to send data.
Reliability
Reliability is up time of interface over a period of time.
Delay
Delay is the time period b/w a packet is sent and received by the destination
153

MTU Maximum Transmission Unit
It is the maximum size of packet that can be sent in a frame mostly MTU is set
to 1500.
Problems of Distance Vector
There are two main problems of distance vector routing
•Bandwidth Consumption
•Routing Loops
Bandwidth Consumption
The problem of accessive bandwidth consumption is solved out with the help
of autonomous system. It exchanges b/w different routers. We can also
perform route summarization to reduce the traffic.
154

Routing Loops
It may occur b/w adjacent routers due to wrong routing information. Distance
Vector routing is also called routing by Rumor. Due to this the packet may
enter in the loop condition until their TTL is expired.
Method to solve routing loops
There are five different methods to solve or reduce the problem of routing
loop.
Maximum Hop Count
Flash Updates/Triggered Updates
Split Horizon
Poison Reverse
Hold Down
155

Maximum Hop Count
This method limits the maximum no. of hops a packet can travel. This method
does not solve loop problem. But it reduce the loop size in the n/w. Due to this
method the end to end size of a n/w is also limited.
Flash Updates/Triggered Updates
In this method a partial update is send to the all neighbors as soon as there is
topology change. The router, which receives flash updates, will also send the
flash updates to the neighbor routers.
Split Horizon
Split Horizon states a route that update receive from an interface can not be
send back to same interface.
156

Poison Reverse
This method is the combination of split Horizon and Flash updates. It
implements the rule that information received from the interface can not be
sent back to the interface and in case of topology change flash updates will be
send to the neighbor.
Hold Down
If a route changes frequently then the route is declared in Hold Down state and
no updates are received until the Hold Down timer expires.

157

Routing Information Protocol
Features of RIP:  Distance Vector
 Open standard
 Broadcast Updates
(255.255.255.255)
 Metric
Hop Count
Timers
Update 30 sec
Invalid 180 sec
Hold 180 sec

158

 Loop Control
 Split Horizon
 Triggered Updates
 Maximum Hop Count
 Hold Down
 Maximum Hop Count 15
 Administrative Distance 120
 Equal Path Cost Load Balancing
 Maximum Load path 6

Default 4
 Does not support VLSM
 Does not support Autonomous system
159

Configuring RIP
Router#conf ter
Router(config)#router rip
Router(config-router)#network <own net address>
Router(config-router)#network <own net address>
--------------------------Router(config-router)#exit
Router(config-router)#network 10.0.0.0
175.2.0.0 via 172.16.0.6

160

Configuring RIP

172.16.0.6

10.0.0.1

17

.5
.16.0
172

5. 2

R1

1
.1.

200.100.100.12

161

Display RIP Routers
Router#sh ip route rip
R 192.168.75.0/24 [120/5] via 172.30.0.2 00:00:25 serial 1/0
RIP Dest. n/w mask AD Metric Next Hop Timer own Interface

RIP advanced configuration
Passive Interfaces
An interface, which is not able to send routing updates but able to
receive routing update only is called Passive Interface. We can declare
an interface as passive with following commands: Router#conf ter
Router(config-router)#Passive-interface <type> <no>
Router(config-router)#exit
162

Neighbor RIP
 In RIP, by default routing updates are send to the address 255.255.255.255.
In some scenarios, it may be required to send routing updates as a unicast
from router to another. In this case, we have to configure neighbor RIP.
 For example: - in a Frame Relay n/w the broadcast update is discarded by
the switches, so if we want to send RIP updates across the switches then
we have to unicast updates using Neighbor RIP.

163

Unicast 10.0.0.2
255.255.255.255
10.0.0.1

Frame
Relay
Cloud

10.0.0.2

R1

R1
Router(config-router)#neighbor 10.0.0.2
neighbor

R2

R2
Router(config router)#
10.0.0.1

164

To change Administrative Distance
Router(config-router)#distance <value>
Router(config-router)#exit 95 or 100
To configure Load Balance
RIP is able to perform equal path cost Load Balancing. If multiple paths
are available with equal Hop Count for the destination then RIP will
balance load equally on all paths.
Load Balancing is enabled by default 4 paths. We can change the no. of
paths. It can use simultaneously by following command: Router(config)#router rip
Router(config-router)#maximum-path <1-6>
165

To display RIP parameters
Router#sh ip protocol
Or
Router#sh ip protocol RIP
This command display following parameters: (i) RIP Timers
(ii) RIP Version
(iii) Route filtering
(iv) Route redistribution
(v) Interfaces on which update send
(vi) And receive
(vii) Advertise n/w
(viii) Passive interface
(ix) Neighbor RIP
(x) Routing information sources
(xi) Administrative Distance

166

RIP version 2
RIP version 2 supports following new features: Support VLSM (send mask in updates)
Multicast updates using address 224.0.0.9
Support authentication

Commands to enable RIP version 2
We have to change RIP version 1 to RIP version 2. Rest all communication
will remain same in RIP version 2.
Router(config)#Router RIP
Router(config-router)#version 2

167

To debug RIP routing
Router#debug ip rip
To disable debug routing
Router#no debug ip rip
Or
Router#no debug all
Or
Router#undebug all

168

Interior Gateway Routing Protocol
Features:  Cisco proprietary
 Distance vector
 Timers
Update 90 sec
Invalid 270 sec
Hold time 280 sec
Flush 630 sec
 Loop control
All methods

169

Metric (24 bit composite)

Bandwidth (default)

Delay (default)

Load

Reliability

MTU

170







Broadcast updates to address 255.255.255.255
Unequal path cost load balancing
Automatic route summarization
Support AS
Does not support VLSM

171

Configuring IGRP
Router(config)#router igrp <as no>(1 – 65535)
Router(config-router)#network <net address>
Router(config-router)#network <net address>
Configuring Bandwidth on Interface for IGRP
By default the router will detect maximum speed of interface and use this
value as the bandwidth metric for IGRP. But it may be possible that the
interfaces and working at its maximum speed then we have to configure
bandwidth on interface, so that IGRP is able to calculate correct method

172

Router(config)#interface <type> <no>
Router(config-if)#bandwidth <value in kbps>
Router(config-if)#exit
Router(config)#interface serial 0
Router(config-if)#bandwidth 256
Configuring Unequal path cost load balancing
To configure load balancing, we have to set two parameters
(1) Maximum path (by default 4)
(2) Variance (default 1)
Maximum Path: - it is maximum no. of paths that can be used for load
balancing simultaneously.

173

Variance: - it is the multiplier value to the least metric for a destination n/w up
to which the load can be balanced.
Router(config)#Router igrp <as no>
Router(config-router)#variance <value>

174

Configuring IGRP
Configuring following options in IGRP as same as in case of RIP:  Neighbor
 Passive interface
 Timer
 Distance (AD)
 Maximum path

175

Network Address Translation
 RFC-1631
 A short term solution to the problem of the depletion of IP addresses
 Long term solution is IP v6 (or whatever is finally agreed on)
 CIDR (Classless Inter Domain Routing ) is a possible short term
solution
 NAT is another
 NAT is a way to conserve IP addresses
 Hide a number of hosts behind a single IP address
 Use:
• 10.0.0.0-10.255.255.255,
• 172.16.0.0-172.32.255.255 or
• 192.168.0.0-192.168.255.255 for local networks
176

Translation Modes
 Dynamic translation (IP masquerading)
 Large number of internal users share a single external address
 Static translation
 A block external addresses are translated to a same size block of
internal addresses
 Load balancing translation
 A single incoming IP address is distributed across a number of
internal servers
 Network redundancy translation
 Multiple internet connections are attached to a NAT firewall that
it chooses and uses based on bandwidth, congestion and
availability
177

Dynamic Translation (IP Masquerading )

 Also called Network Address and Port Translation (NAPT)
 Individual hosts inside the Firewall are identified based on of each
connection flowing through the firewall
 Since a connection doesn’t exist until an internal host requests a
connection through the firewall to an external host, and most
Firewalls only open ports only for the addressed host only that
host can route back into the internal network
 IP Source routing could route back in; but, most Firewalls block
incoming source routed packets
 NAT only prevents external hosts from making connections to internal
hosts.
 Some protocols won’t work; protocols that rely on separate
connections back into the local network
 Theoretical max of 216 connections, actual is much less
178

Static Translation
 Map a range of external address to the same size block of internal
addresses
 Firewall just does a simple translation of each address
 Port forwarding - map a specific port to come through the Firewall
rather than all ports; useful to expose a specific service on the internal
network to the public network

179

Load Balancing

 A firewall that will dynamically map a request to a pool of identical
clone machines
 often done for really busy web sites
 each clone must have a way to notify the Firewall of its current load
so the Fire wall can choose a target machine
 or the firewall just uses a dispatching algorithm like round robin
 Only works for stateless protocols (like HTTP)

180

Network Redundancy

 Can be used to provide automatic fail-over of servers or load balancing
 Firewall is connected to multiple ISP with a masquerade for each ISP
and chooses which ISP to use based on client load
 Kind of like reverse load balancing
 A dead ISP will be treated as a fully loaded one and the client will
be routed through another ISP

181

Problems with NAT

Can’t be used with:
 Protocols that require a separate back-channel
 Protocols that encrypt TCP headers
 Embed TCP address info
 Specifically use original IP for some security reason

182

Working of NAT & PAT

10.0.0.5

10.0.0.6

10.0.0.1

NAT

200.100.100.12

Internet

Switch

10.0.0.5
10.0.0.7

200.100.100.12
1080

10.0.0.8

10.0.0.6
200.100.100.12
1085
183

10.0.0.7
200.100.100.12

1100

Port Translation

1024

10.0.0.8
200.100.100.12
1024

184

Static NAT
This NAT is also used for servers. It provides port-based access to the servers
with the help of NAT.

Static NAT
200.1.1.5 = 192.168.10.6
Router

Internet
.1.5
200.1
Live

Local 192.168.10.6
185

Port Base Static NAT
This NAT is used for servers in which one Live IP is directly mapped to one
Local IP. This NAT will forward on the traffic for the Live IP to the Local
PC in the n/w.
200.1.1.5:80 -> 192.168.10.6
Router200.1.1.5:53 -> 192.168.10.7

Internet

Router

Web
192.168.10.6

DNS
192.168.10.7

186

Dynamic NAT using Pool
Dynamic NAT is used for clients, which want to access Internet. The
request from multiple client IPs are translated with the Live IP obtained
from the Pool. It is also called Pool Based Dynamic NAT.
Pool => 200.1.1.8 – 200.1.1.12/28
Internet
Local address => 172.16.X.X Except => 172.16.0.5
172.16.0.6
172.16.0.7
Pool allotted => 200.1.1.0 – 15/28
Server
Static => 200.1.1.3 = 172.16.0.7
Port Based Static NAT
200.1.1.4:53 = 172.16.0.6
200.1.1.4:80 = 172.16.0.5
187

Dynamic NAT using Pool
Client
Dynamic NAT
Pool => 200.1.1.8 – 200.1.1.12/28
Local address => 172.16.0.X
Except
172.16.0.5
172.16.0.6
172.16.0.7

188

Configuring NAT
Router#conf ter
Router(config)#int serial 0
Router(config-if)#ip nat outside
Router(config-if)#int eth 0
Router(config-if)#ip nat inside
Router(config)#ip nat inside source static 172.16.0.7 200.1.1.3
Router(config)#ip nat inside source static tcp 172.16.0.5 80 200.1.1.4
80
Router(config)#ip nat inside source static udp 172.16.0.6 53 200.1.1.4
53
Router(config)#access-list 30 deny 172.16.0.5
Router(config)#access-list 30 permit any
Router(config)#ip nat pool abc 200.1.1.8 200.1.1.12 netmask
189
255.255.255.240

Command for Basic NAT
Router(config)#ip nat inside source list 30 interface serial 0
<exiting interface name>
To display NAT translation
Router#sh ip nat translations
(after ping any address, it shows ping details)
To clear IP NAT Translation
Router#clear ip nat Translation *
190


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

191


192

SKILLS FOR INDIA

Remote Access Mode

Remote Access Service
Remote Access Services (RAS) refers to any combination of hardware and
software to enable the remote access tools or information that typically
reside on a network of IT devices. A RAS server is a specialized computer
which aggregates multiple communication channels together. Because these
channels are bidirectional, two models emerge: Multiple entities connecting
to a single resource, and a single entity connecting to multiple resources.
Both of these models are widely used. Both physical and virtual resources
can be provided through a RAS server: centralized computing can provide
multiple users access to a remote virtual operating system. Access Providers
often use RAS servers to terminate physical connections to their customers,
for example customers who get Internet through some form of modem.
Originally coined by Microsoft when referring to their built-in NT
remote access tools, RAS was a service provided by Windows
NT which allows most of the services which would be available on
a network to be accessed over a modem link.
194

The service includes support for dialup and logon, presents the same
network interface as the normal network drivers (albeit slightly slower). It is
not necessary to run Windows NT on the client - there are client versions for
other Windows operating systems.
A feature built into Windows NT enables users to log into an NTbased LAN using a modem, X.25 connection or WAN link. RAS works
with several major network protocols, including TCP/IP, IPX, and NBF.
To use RAS from a remote node, you need a RAS client program, which is
built into most versions of Windows, or any PPP client software. For
example, most remote control programs work with RAS.
Starting in the mid-1990s, several manufacturers such as U.S.
Robotics produced "modem terminal servers". Instead of having RS232ports, these would directly incorporate an analog modem. These devices
were commonly used by Internet service providers to allow consumer dialup. Modern versions interface to an ISDN PRI instead of having analog
modem ports.
195

Complete these steps to configure RAS on a Cisco ICM Logger.
Select Start > Settings > Control Panel
Double-click the Network Applet
Select Services
Double-click the Remote Access Service

196

Figure 1: Remote Access Setup

197

Click Configure. Figure 2: Configure Port Usage

198

Media Access Methods
An access method is a set of rules governing how the network nodes
share the transmission medium. The rules for sharing among
computers are similar to the rules for sharing among humans in that
they both boil down to a pair of fundamental philosophies:
 first come, first served and
 take turns.
These philosophies are the principles defining the three most
important types of media access methods:

199

Media Access Methods
Contention.
-(CSMA/CD Carrier Sense Multiple Access with Collision
Detection,
 -CSMA/CA Carrier Sense Multiple Access with Collision
Avoidance)
 Token passing.
 Demand Priority.

200

Contention
CSMA/CD Carrier Sense Multiple Access with Collision Detection
IEEE 802.3 Ethernet LANs use the Carrier Sense Multiple Access
with Collision detection(CSMA/CD) protocol to detect and handle
collisions on the network. However, WLANs can’t use CSMA/CD
because they can’t transmit and listen at the same time.
CSMA/CA Carrier Sense Multiple Access with Collision Avoidance
The IEEE 802.11b standard specifies the carrier sense multiple access
with collision avoidance (CSMA/CA) protocol for WLANs.
CSMA/CA tries to avoid collisions by using explicit packet
acknowledgment.
With CSMA/CA, an acknowledgment packet is sent by the receiving
station to confirm it has received a data packet. If the transmitting
station does not receive the acknowledgment, it assumes that a
collision has occurred and transmits the data packet again.
201

Token passing
IEEE 802.5 standard deals with Token Ring networks
Token passing is implemented on a token-ring network.
IEEE 802.5 Token Ring networks use a token-passing media access method. A
token is a special packet that gives permission to a device to transmit data on
to the network. When a device receives a token and transmits a frame, the
frame is forwarded around the ring by all attached devices.
When the frame reaches its destination, it is copied and processed by the
receiving device and placed back on the ring. Before placing the frame back on
the ring, the receiving device sets frame-status bits to indicate that the frame
was received. The frame circles the ring until it returns to the original
transmitting device.

202

Demand Priority

Demand priority is an access method used with the new 100Mbps
100VG-AnyLAN standard. Although demand priority is officially
considered a contention-based access method, demand priority is
considerably different from the basic CSMA/CD Ethernet. In demand
priority, network nodes are connected to hubs, and those hubs are
connected to other hubs. Contention, therefore, occurs at the hub.
(100VG-AnyLAN cables can actually send and receive data at the
same time.) Demand priority provides a mechanism for prioritizing
data types. If contention occurs, data with a higher priority takes
precedence

203

Collision & Broadcast Domains

MAC Address
Contains 48-bit destination address field.
Who is this frame for?
00-C0-F0-56-BD-97
“Hey Joe”

204

MAC Address

How will all other NICs handle
the frame?
Drop it (in the “bit bucket”)

205

Special MAC Address

Who is this frame for?
FF-FF-FF-FF-FF-FF
“Hey everybody”

206

Broadcast MAC Address

FF-FF-FF-FF-FF-FF
48 bits, all 1s
All NICs copy the
frame & send it up
the stack

207

Broadcast Frames
Necessary for network function
Used for
finding services: “Hey, is there a server out there?”
Advertising services: “Hey, I’m a printer you can use.”
Some Layer 3 (Network Layer) protocols use broadcasts
frequently:
Appletalk
IPX (older Novell protocol)
Networks that use these protocols must be limited in size, or
they will become saturated with broadcast frames.
TCP/IP (a Layer 3 protocol) uses broadcasts sparingly.
Therefore, networks that use TCP/IP can be made quite large
without broadcast problems. (They “scale” well.)
208

Collision Domain
Network region in which
collisions are propagated.
Repeaters and hubs propagate
collisions.
Bridges, switches and routers do
not.

Reducing Collisions
 Collision frequency can be kept low by breaking the network into
segments bounded by:
 bridges
 switches
 routers

Broadcast Domain
Network region in which
broadcast frames are propagated.
Repeaters, hubs, bridges, &
switches propagate broadcasts.
Routers either do or don’t,
depending on their configuration.

Reducing Broadcasts
Broadcasts are necessary for network function.
Some devices and protocols produce lots of broadcasts; avoid them.
Broadcast frequency can be kept manageable by limiting the LAN
size.
LANs can then be cross-connected by routers to make a larger
internetwork.

Shared Ethernet
A single segment that is shared among all connected NICs.
A single collision domain.
A logical “bus” (may be a physical star).
The segment includes repeaters and hubs.
Sometimes called a “single flat Ethernet”.

Switched Ethernet
Consists of a several segments, each of which is shared by NICs
attached to it.
The network is segmented into several collision domains.
Bridges, switches, and routers create the segment and collision
domain boundaries.
Segments may contain hubs and repeaters.

Switched Ethernet
Switch - 1 port per hub

Hub

Hub

Micro segmented Switched Ethernet
Each user NIC is connected directly to a
switch port.
Provides one switched segment to each
connected NIC.
No sharing.
No collisions.

Micro segmented Switched Ethernet
Switch - 1 port per PC

Summary
Term
LAN Segment
(Collision domain)
Entire LAN
(Broadcast domain)
Internetwork
(Group of LANs
cross-connected
by Routers)

Includes
Cable
Repeaters
Hubs

Boundary
Bridges
Switches
(Routers)

Everything
except
Routers

Edge of LAN
Routers

LANs &
Routers

Edge of
Internetwork

Example

switch

router

switch

Identify the collision domains
& broadcast domains
switch

hub

hub

& broadcast domains
hub

hub

& broadcast domains
switch

hub

& broadcast domains:

router
switch

Router connects separate networks.
One broadcast domain per router interface.

Application
First, complete Lab 7A
Then, on a printed copy of the “Teaching Topology” (curriculum
p7.5.5)
Circle each collision domain - use a solid line.
Circle each broadcast domain - use a dashed line.

Reminder
Collisions
spread throughout a LAN segment
spread across hubs & repeaters
are stopped by switches & bridges
Broadcasts
spread throughout an entire LAN
spread across hubs, switches, bridges
are stopped only by routers

225

LAN Switching
Ethernet switches are used in LAN to create Ethernet n/ws. Switches
forward the traffic on the basis of MAC address. Switches maintain a
Mac Addresse table in which mac addresses and port no.s are used to
perform switching decision. Working of bridge and switch is similar to
each other.

226

Classification of switches
Switches are classified according to the following criteria: Types of switches based on working
(1) Store & Forward
This switch receives entire frame then perform error checking and
start forwarding data to the destination.
(2) Cut through
This switch starts forwarding frame as soon as first six bytes of the
frame are received.
(3) Fragment-free
This switch receives 64 bytes of the frame, perform error checking
and then start forwarding data.
(4) Adaptive cut-through
It changes its mode according the condition. If it see there are
errors in many frames then it changes to Store & Forward mode from
Cut through or Fragment-free.

227

Classification of switches
Types of switches based on management
(1) Manageable switches
(2) Non-Manageable switches
(3) Semi-Manageable switches
Types of switches based on OSI layer
(1) Layer 2 switches (only switching)
(2) Layer 3 switches (switching & routing)
Types of switches based on command mode (only in Cisco)
(1) IOS based
(2) CLI based
Type of switches based on hierarchical model
(1) Core layer switches
(2) Distribution layer switches
(3) Access layer switches
228

Basic Switch Administration
IOS based switches are similar to the routers. We can perform following
function on switches in a similar manner as performed on router.
(1) Access switch using console
(2) Commands to enter & exit from different mode
(3) Commands to configure passwords
(4) Manage configuration
(5) Backup IOS and configuration
(6) Configuring and resolving hostnames
(7) Managing telnet
(8) Configuring CDP
(9) Configuring time clock
(10) Configuring Banners
(11) Command line shortcuts and editing shortcuts
(12) Managing history
(13) Configure logging
(14) Boot system commands
229

Basic Switch Administration
Following function and options are not similar in router and switch.
(1) Default hostname is ‘Switch’
(2) Auxiliary port is not present
(3) VTY ports are mostly 0 to 15
(4) By default interfaces are enabled
(5) IP address cannot be assign to interfaces
(6) Routing configuration mode is not present
(7) Interface no. starts from 1
(8) Web access is by default enabled
(9) Configuration registry is not present in similar manner
(10) Flash memory may contain multiple files and startup-configuration
is also saved in flash

230

Configuring IP and Gateway on switch
We can configure IP address on switch for web access or telnet IP
address is required for the administration of the switch. If we have to
access switch from remote n/w then we will configure default gateway
in addition to IP address.
IP address is assigned to the logical interface of switch with following
command:Switch(config)#interface vlan 1
Switch(config)#IP address <ip> <mask>
Switch(config)#no sh
Switch(config)#exit

231

Old Switches
Switch(config)#ip address <ip> <mask>
Switch(config)#exit
Configuring Gateway
Switch(config)#ip default-gateway <ip>
Switch(config)#exit

232

Breaking Switch Password
(1) Power off switch press mode button present in front of switch then
power on the switch.
(2) Keep mode button press until ‘Switch:’ prompt appears on console.
(3) In switch monitor mode, type following commands: flash_init
load_helper
rename flash:config.text flash:<anyname>
dir flash:
boot
(4) After booting switch will prompt to enter in initial configuration
dialog. Enter ‘no’ here and type.
Switch>enable
Rename flash:<anyname> Flash:config.text
Configure memory
Change password and save config. Then copy run start_config.
233


S.No

Description

Author

Version

Date

1
2
3
4
5
6
7
8

234


235

SKILLS FOR INDIA

Security Protocol

A security protocol (cryptographic protocol or encryption protocol) is
an abstract or concrete protocol that performs a security-related function and
applies cryptographic methods.
A protocol describes how the algorithms should be used. A sufficiently
detailed protocol includes details about data structures and representations,
at which point it can be used to implement multiple, interoperable versions
of a program.
Cryptographic protocols are widely used for secure application-level data
transport. A cryptographic protocol usually incorporates at least some of
these aspects:
Key agreement or establishment
Entity authentication
Symmetric encryption and message authentication material construction
Secured application-level data transport
Non-repudiation methods
237

Internet Key Exchange
Internet Key Exchange (IKE or IKEv2) is the protocol used to set up
a security association (SA) in the IPSec protocol suite. IKE builds upon
the Oakley protocol and ISAKMP. IKE uses X.509 certificates for
authentication which are either pre-shared or distributed
using DNS (preferably with DNSSEC), and a Diffie–Hellman key
exchange to set up a shared session secret from which cryptographic
keys are derived. In addition, a security policy for every peer which will
connect must be manually maintained

238

IPsec
Internet Protocol Security (IPsec) is a protocol suite for securing Internet
Protocol (IP) communications by authenticating andencrypting each IP
packet of a communication session. IPsec also includes protocols for
establishing mutual authentication between agents at the beginning of the
session and negotiation of cryptographic keys to be used during the session.
IPsec is an end-to-end security scheme operating in the Internet Layer of
the Internet Protocol Suite. It can be used in protecting data flows between a
pair of hosts (host-to-host), between a pair of security gateways (networkto-network), or between a security gateway and a host (network-to-host).[1]
Some other Internet security systems in widespread use, such as Secure
Sockets Layer (SSL), Transport Layer Security (TLS) andSecure
Shell (SSH), operate in the upper layers of the TCP/IP model. In the past,
the use of TLS/SSL had to be designed into an application to protect the
application protocols. In contrast, since day one, applications did not need to
be specifically designed to use IPsec.
239

Hence, IPsec protects any application traffic across an IP network. This
holds true now for SSL as well with the rise of SSL based VPN revolution
with implementations like OpenVPN.
IPsec originally was developed at the Naval Research Laboratory as part of
a DARPA-sponsored research project. ESP was derived directly from the
SP3D protocol, rather than being derived from the ISO Network-Layer
Security Protocol (NLSP). The SP3D protocol specification was published
by NIST, but designed by the Secure Data Network System project of
the National Security Agency (NSA), IPsec AH is derived in part from
previous IETF standards work for authentication of the Simple Network
Management Protocol (SNMP).
IPsec is officially specified by the Internet Engineering Task Force (IETF)
in a series of Request for Comments documents addressing various
components and extensions. It specifies the spelling of the protocol name to
be IPsec
240

Kerberos (protocol)
Kerberos is a computer network authentication protocol which works on
the basis of "tickets" to allow nodes communicating over a non-secure
network to prove their identity to one another in a secure manner. Its
designers aimed primarily at a client–server model, and it provides mutual
authentication—both the user and the server verify each other's identity.
Kerberos protocol messages are protected against eavesdropping and replay
attacks. Kerberos builds on symmetric key cryptography and requires
a trusted third party, and optionally may use public-key cryptography by
utilizing asymmetric key cryptography during certain phases of
authentication. Kerberos uses port 88 by default.
"Kerberos" also refers to a suite of free software published
by Massachusetts Institute of Technology (MIT) that implements the
Kerberos protocol.
241

Point-to-point protocol
In networking, the Point-to-Point Protocol (PPP) is a data
link protocol commonly used in establishing a direct connection between
two networking nodes. It can provide connection authentication,
transmission encryption (using ECP, RFC 1968), and compression.
PPP is used over many types of physical networks including serial
cable, phone line, trunk line, cellular telephone, specialized radio links, and
fiber optic links such as SONET. PPP is also used over Internet
access connections (now marketed as "broadband"). Internet service
providers (ISPs) have used PPP for customer dial-up access to the Internet,
since IP packets cannot be transmitted over a modem line on their own,
without some data link protocol. Two encapsulated forms of PPP, Point-toPoint Protocol over Ethernet (PPPoE) and Point-to-Point Protocol over
ATM (PPPoA), are used most commonly by Internet Service Providers
(ISPs) to establish a Digital Subscriber Line (DSL) Internet service
connection with customers.
242

PPP is commonly used as a data link layer protocol for connection
over synchronous and asynchronous circuits, where it has largely
superseded the older Serial Line Internet Protocol (SLIP) and telephone
company mandated standards (such as Link Access Protocol,
Balanced (LAPB) in the X.25 protocol suite). PPP was designed to work
with numerous network layer protocols, including Internet
Protocol (IP), TRILL, Novell's Internetwork Packet
Exchange (IPX), NBF and AppleTalk.

243

Networking Basics Overview

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to Networking Basics Overview

Similar to Networking Basics Overview (20)

Recently uploaded

Recently uploaded (20)

Networking Basics Overview

Editor's Notes