The document provides an overview of fundamentals of enterprise networks including types of communication networks, communication layers and protocols, network design and management, and future trends. It defines communication networks and describes layering concepts and standard organizations. It also discusses personal area networks (PANs), local area networks (LANs), metropolitan area networks (MANs), and wide area networks (WANs).

1. Fundamentals of
Enterprise Networks
M.N.A.DELOVE

2. OUTLINE
• Overview
• Types of Communication Networks
• Communications Layers and Protocols
• Network Design and Management
• Future Trends

3. OVERVIEW
• Definition of Communications Networks
• Layering Concept in Communication Networks
and Protocols
• Standard Organizations
• Brief History of Communication Networks

4. Definition of Communications
Networks
• A communication network is a collection of
elements connected by using transmission
facilities to provide end-users with the capability
of exchanging messages and information in a
variety of formats, for example, voice, data, and
video
• The elements could be computers, workstation,
routers, switches, private branch exchanges
(PBXs) and multiplexers, etc.
• Formally called Network Element or the node

5. • Transmission links may be twisted wire pairs,
co-axial cables, and optical cables, radio links,
satellite links, or infrared connections.
• Operations systems
 Operate
 Monitor
 Manage network resources
• People
• Network categorization based on geographical
dispersion of its components
- PAN, LAN, MAN, WAN

6. LAYERING CONCEPT IN
COMMUNICATION NETWORKS AND
PROTOCOLS
• To facilitate the exchange of information, each network
element and user equipment must provide a set of
comprehensive functions so that they can
communicate with each other in an unambiguous way.
• Could be complex to implement and maintain in one
package
• Breaking up into smaller and more manageable
components
• Termed layering model
 Each model contains a group of related communication
functions

7. • A protocol is an implementation of a set of
unambiguous rules and procedures used in exchanging
information via messages among network elements
and end-user devices
Advantage of layering approach
 Easy to develop specialized protocols for each layer
 Allows for the mixing and matching of many different
protocols
Disadvantage
 Places burden on industry to standardize
• Two most important layering approaches
- Open Systems Interconnection model
- Internet Model

8. Standard Organizations
• Formal standards are typically developed by industry consortia, professional
associations, and government organizations.
• ISO
• ITU-T
• ITU-R
• IEEE
• IETF
• 3GPP
• 3GPP2
• CableLabs
• DMTF
• OMA
• TIA
• TM Forum
• W3C

9. BRIEF HISTORY OF COMMUNICATION
NETWORKS
• The evolution of communications networking
is tied to the invention of telegraph,
telephony, radio, and computers.
• Telephone networks used to connect
computers together.
• Low speed( data rate)
• Telephone lines became quickly insufficient.
• Need for dedicated transmission lines thus
packet switching.

10. • ARPANET in the early 1970s and the Internet
in the 1980s
• PC revolution in 1980
• LAN associated equipments routers and
bridges were developed
• Wireless voice communication in 1970s

11. TYPES OF COMMUNICATION
NETWORKS
• PAN
• LANs
• MANs
• WANs

12. PAN
• Personal Area Network
• The use of Bluetooth and infra red radiation to
create a network
• IEEE 802.15 (Bluetooth) provides a so-called
wireless PAN by connecting a number of
devices around a person
• Devices e.g. PDAs, laptops, cellular phones,
headphones, mouse, keyboard, and so on.

13. • short range communications (1–100 m) based on low-
cost tiny transceivers.
• A Bluetooth network, referred to as a piconet
• consists of up to eight simultaneously communicating
devices
• a piconet can have up to 125 Bluetooth enabled
devices, only eight can be active at the same time.
• The devices in a piconet can dynamically and in an ad
hoc fashion form a network by first choosing a master
device that can control other devices, called slaves.
• The master acts like an AP
-selecting frequencies to be used
-controlling the access to these frequencies by the
slaves.

14. • Devices share the same frequency range
• Uses FHSS for media access control.
• Frequency range (2.4000–2.4835 MHz)
• Divided into 79 separate 1-MHz channels
• Bluetooth version 1.2 provides a data rate of 1
Mbps, while Bluetooth version 2.0 can provide
up to 3 Mbps
• Interconnection of piconets is called a
scatternet.

15. • The data rate calculations in wLANs are similar to
those discussed under the wired LANs section.
• transmission errors play a greater role in wLANs
data calc.
• interference on the air.
• Also the errors cause retransmissions, which, in
turn, lower the data rates
• 802.11b results in about 85% average efficiency,
whereas IEEE 802.11a and 802.11g would give us
about 75% average efficiency.
• Also consider thePCF, which introduces more
delays.

16. wLAN Technologies Standardized by the IEEE
802.11a 802.11b 802.11g 802.11n Bluetooth
Maximum 54 11 54 200+ 3
data
rate (Mbps)
Frequency 5 2.4 2.4 2.4/5 2.45
(GHz)
Modulation OFDM DSSS OFDM MIMO FHSS
Range (ft) ~100 ~300 ~120 ~750 ~30

17. LANs
• A LAN is used to connect a number of computers and
other devices in a small, local, area such as a room, a
floor, or a building.
• Computers could be
- servers (Web server, e-mail server, file
server, or print server)
-client (which shares the files, printers, and servers with
other client computers in the same LAN)
• hub/ switches for connecting servers and client
• Network Interface Card (NIC) in each node
-provides the physical layer and data link layer
functions

18. • Network Operating System (NOS)
- handles all network functions
-performs data link
-network
-application layer functions
- acts as the application software
e.g. NOS are MS Windows Server and Linux
Server

19. • Ethernet, specified in the IEEE 802.3 is the commonly
used standards in LAN technology
• Two different implementation of Ethernet
- Traditional (or shared) using CSMA/CD
-Switched using Forwarding Table
• In putting together a LAN, perhaps the most important
aspect to watch for is the effective data rate
- which is the maximum speed in bits that the
hardware layers (i.e. physical and data link layers) can
provide.

20. • Three major components of the effective data
rate :
- The nominal data rate that depends on the
physical layer properties. E.g. the nominal rate for
a 100Base-T Ethernet is 100 Mbps
- The error rate of the circuit, which is a critical
factor in determining retransmissions, therefore
reducing the transmission efficiency
- The efficiency of data link layer protocol
• The packet size, which plays an important role in
these calculations, depends on the type of the
traffic on the LAN

21. • LAN traffic include
-number of small Web application specific (i.e.,
Hypertext Transfer Protocol, HTTP)
- the e-mail application-specific (i.e., SMTP, or
Simple Mail Transfer Protocol) messages
- followed by a large number of larger packets
• This results in about 97% efficiency for the
Ethernet frames with 33 bytes overhead
• Calculating the effective data rate for a whole
LAN
- consider the efficiency of the media access
control

22. • The Ethernet’s media access mechanism
works well in low-traffic LANs
-resulting typically in a 50% capacity utilization.
• The total effective data rate for a 100Base-T
will be calculated as follows:
-50% capacity × 97% efficiency × 100 Mbps rate
= 485 Mbps (for the whole LAN)
• With 10 computers in the LAN, each
computer’s effective data rate would be
485/10 = 48.5 Mbps.

23. • The effective rates for switched Ethernets are
much higher due to the significant
improvements (up to 95%) in capacity
utilization
- since there is no sharing in this architecture
NB: switched Ethernet is not affected by the
traffic due to the availability of dedicated
circuits for each computer

24. Improving LAN performance
• There needs to be continuous monitoring and,
if necessary, to make changes to improve
performance
• The two bottleneck
-server
- circuit.

25. Server Bottleneck
• A key indicator to determine whether the server
is a bottleneck is the utilization of the server
-say over 70%, then it is likely the server is the
bottleneck.
• Eliminate bottleneck by upgrading
-hardware (CPU, memory, storage, etc.)
- software (operating system, applications, etc.)
• If the server utilization is low, then the bottleneck
is the circuit

26. Circuit Bottleneck
• Improving the circuit capacity, say from
100Base-T to 1000Base-T may help
• The are other methods of improving
performance of a LAN
-dividing a LAN into two or more segments,
-reducing the network demand by scheduling
certain applications during off hours

27. WIRELESS LANS
• When the computers on a LAN are connected
via unguided media, eliminating the cables,
the resulting LAN is called a wireless LAN
(wLAN).
• LAN technologies based on the radio
transmission
• The IEEE 802.11 series of standards, also
referred to as the Wi-Fi technology

28. • Earliest version IEEE 802.11b
• Later IEEE 802.11a after commercialisation of
802.11b even though preceded it
• Followed by IEEE 802.11g
• Now IEEE 802.11n
• IEEE 802.15 – (PAN) limited range and data rate.
• Each new version improves
 Data rates
 Security

29. • IEEE 802.11b designed to connect easily to Ethernet.
• The physical layer specifications are based on the spread
spectrum technology where the energy carrying the signal
is spread over a rather large band of the frequency
spectrum
• There are two versions:
-Direct Sequence Spread Spectrum (DSSS)
-Frequency Hopping Spread Spectrum (FHSS)
• A wLAN architecture has a simple star topology where the
computers equipped with wireless NICs are connected
through an access point
• Uses Access Points (AP) or Ad-doc mode
• Devices using AP must use same channel

30. • IEEE 802.11b has 3 channels for AP
• APs connected through Ethernet LANs
• Roaming between APs
• APs installation
 geographical needs
 traffic needs
• IEEE 802.11b uses a scheme to avoid collisions for
accessing the medium
• Uses CSMA/CA.
• uses two complementary MAC methods together:
-the mandatory Distributed Coordination Function (DCF),
a.k.a., Physical Carrier Sense Method
- the optional Point Coordination Function (PCF), a.k.a.,
Virtual Carrier Sense Method

31. DCF
• A node listens to the medium to make sure
that an existing transmitting node has
finished, before transmission
• Uses the stop-and-wait Automatic Repeat
Request (ARQ)
• The ACK/NAK (Acknowledgment/Negative
Acknowledgment) frames are sent a short
time

32. PCF
• Solves the famous hidden node problem in wireless
networks
• two devices may not be able to detect each other’s
signals, even though both can hear the AP.
• Node sends Request-To-Send signal to the AP,
requesting allocation of a channel in a time period.
• The AP responds with a Clear-To-Send signal containing
the duration that the channel is reserved.
• The device starts transmitting its messages

33. • IEEE 802.11a completed after IEEE 802.11b
standardised and commercialised
• IEEE 802.11a operates in so called unlicensed
information infrastructure
• Total bandwidth of 300 MHz
• 4-12 channels (20MHz each) depending on
configuration
• Faster data rates up to 54Mbps
• However, limited range
 50m (150ft)

34. • Advantages of IEEE 802.11a
• Capacity of LAN is increased
• IEEE 802.11a combined with IEEE 802.11b can support
more users with higher data rates
• Disadvantages of IEEE 802.11a
• Range is considerably limited. i.e., more IEEE 802.11a
APs to cover the same area covered by one IEEE
802.11b AP.
• Although packet format are very similar, physical layer
schemes and frequency bands are quite different. i.e.,
802 .11a and 802.11b are not compatible.

35. • IEEE 80.11g created to solve interoperability problem
• Combines 802.11a and 802.11b
• 802.11g offers data rate up to 54Mbps with 50m
• 802.11b and 802.11g all operate in 2.4GHz band
• All 802.11g devices downgraded to 802.11b, when
802.11g APs detects 802.11b device in a network
• 802.11g Provides 3-6 channels depending on
configuration
• Employs Orthogonal Frequency Division Multiplexing
(OFDM)

36. • Newer version, 802.11n allows the use of
multiple antennas simultaneously
• Uses Multiple Input Multiple Output (MIMO)
• More efficient and reliable scheme
• Supports up to 300Mpbs data.

37. Data Rate Calculation
• The data rate calculations in wLANs are similar to those
discussed under the wired LANs section
• However, in wLANs, transmission errors play a greater
role in the data rate calculations due to the potential
interference on the air
• 802.11b results in about 85% average efficiency
• IEEE 802.11a and 802.11g would give us about 75%
average efficiency.
• Based on the assumption that a typical 802.11
overhead is about 51 bytes and the average packet
length is a mix of short and full length packets.

38. • PCF introduces more delays.
• As a result, MAC in wLANs operates with
about up to 85–90% of capacity
• The effective data rate for a network based on
the 802.11b NICs and APs can be calculated
as: 85% efficiency × 85% capacity × 11 Mbps =
9.6 Mbps
• With 10 devices, each device would get 9.6
Mbps/10 devices = 960 Kbps.
• For 802.11a and 802.11g, we would get about
34.4 Mbps data rate total.

39. • wLAN requires a careful determination of the
number of APS and their placement
• The placement affects Coverage of area
• Number of APs important to handle traffic in
network
• A site survey to determine the potential location
of the APs should include the measurement of
potential interference from external sources
• Trial and error may be necessary for making sure
that the signal strength is acceptable in all areas

40. • directional antennas, instead of Omni
directional antennas, may be used
• 15% overlap between APs should be
engineered for
Smoothness
Transparent roaming

41. • Security is great concern in wLAN
 Transmitted in the air
 Easily captured and Jeopardized
Measures to counter insecurity
 Service Set Identifier
 Transmits in plain text and can easily be intercepted
 Security and privacy guaranteed by Wired Equivalent
Privacy (WEP)
 Require users to configure a key manually into the
device (NIC and APs)
 all messages will be encrypted by using this WEP key
 Key between 40 and 128 bits
 The longer the key, the harder to break if the
algorithm is the same

42.  The Extensible Authentication Protocol is an
advanced security feature that requires a login
and a password to a server.
 Wi-Fi Alliance, an industry group providing
certification for the 802.11-based equipment
• Wi-Fi Protected Access (WPA) used in the
certification process.
• IEEE 802.11i was designed to provide secured
communication of wLANs in a more
comprehensive way
• enhances the WEP in the areas of encryption,
authentication, and key management.

43. CAMPUS NETWORKS
• Bridges, routers, switches, and gateways are used for
connecting LANs together via higher speed circuits,
more commonly fiber optical cables.
• Bridges lost their place to switches
 Switches cheaper and powerful
• Router operate with different data link layer protocol
with the same network layer protocol
• Gateways operate at the network layer protocol
connecting LAN with different data link and Network
layer protocol
• Each LAN has its own subnet designation.

44. HUB ROUTER
ROUTER HUB
HUB ROUTER
ROUTER HUB
• A campus network with routers connecting its
LANs.

45. • The architecture of diagram above is easier to manage but it tends to
impose more delays than bridging due to the Layer 3 processing.
• Could be improved by connecting each hub of the LANs to a switch via a
separate circuit (and get rid of all the routers).
-Meaning more cables but less devices to worry about
• Switched operation will make performance improve significantly.
• The down side is that, the use of a single central switch introduces a
reliability problem
- when the switch fails, the whole network goes down.
• Improve the configuration even further
- higher performance and a more intelligent switch even
- eliminating the hubs
• Allowing us to create VLANs segment through software and assigning
computers to them.

46. • Computers can be assigned to any segment regardless of
location
• provides a more flexible network management
- creating project groups and assigning resources to them
• Multi-switch virtual LAN configurations are also possible by
using several switches
-complex and costly
- used for larger campus networks
• CAN largely data centric
• Additional software and/or hardware changes in the end-
user equipment
- can transmit voice and video as well

47. • Voice over IP (VoIP) and multimedia-specific
protocols and features that rely on a common
network layer protocol
• PBX (a.k.a. PABX)
• Latest trend in PBX development is IP PBX
• Switches calls between VoIP on Local line
• A single line for data access, VoIP and
traditional telephone

48. MANS AND WANS
• If network element are spanning from 3 to 30
miles, the network is typically called a MAN
• If covering a province, a country, or even
across countries, the network is called a WAN
• Typically, these networks are built by using
dedicated circuits leased from common
carriers.
• A WAN containing the dedicated circuits is
called a dedicated circuit WAN.

49. • The services provided by common carriers can
be classified as :
-circuit-switched services
- packet-switched services
• E.g. of dedicated digital circuits are T-Carrier
services, E-Carrier service, etc
• Lease organization charge a monthly flat fee
that depends on the capacity and length of
the circuit
• The line is dedicated to the customer with the
rights of unlimited use of the circuit.

50. • T-Carrier services most commonly in North America
• E-Carrier service in Europe and elsewhere.
- T1 circuits provide 1.544 Mbps data rate (equivalent of 24 voice
channels, 64 Kbps data rate)
- T3 circuits offer 44.376 Mbps data rate (28 T1 lines).
• For higher data rates, common carriers offer dedicated circuits
based on the Synchronous Optical Network (SONET) technology
-an ANSI standard in the United Sates for optical fiber transmission in
Gbps range
• Hierarchy of data rates in SONET starts with OC-1 (optical carrier
level 1) at 51.84 Mbps.
• OC-192 providing almost 10 Gbps data rate.

51. Components in MANs/WANs
• There are special equipments such as
- Channel Service Unit
-Data Service Unit
• To be installed at the end of each dedicated
circuit
• routers and switches
- to create a network owned and maintained
by the organization itself

52. Architectural Decisions
• Network designers must determine the best
architecture that fits the application at hand
• factors to consider:
-delay, throughput, reliability, and the cost.
• Ways of connecting the locations via
dedicated lines.
-ring, star, and mesh topologies are the basic
dedicated circuit architectures

53. • ring and star architectures are most cost-effective
-result in less dedicated circuits to lease
• mesh architecture is more costly
-requires many more circuits
• performance (throughput, delay)
- mesh the best, followed by star and then ring
• From the reliability point of view
-mesh architecture is best
- ring worst since network relies on a central node

54. • To bring the down the cost of a mesh
-a partial mesh architecture can be used
- where only certain pair of nodes are
connected directly
• The nodes that are not directly connected
communicate with each other through other
nodes

55. • Enterprises that cannot afford to put together
their own dedicated circuit-based network
rely on switched services provided by the
common carriers
• end-user equipment are connected via
temporary, not dedicated,
• The connection is no longer available once
session is complete

56. • first leases a short connection from each of its
locations to the nearest Point of Presence
(POP) of the service provider
• An end-user equipment in the enterprise is
required to break its message to be
transmitted into smaller segments, called
packets and attach the address of the
destination equipment

57. • Packet-switching technologies
• X.25 is the oldest standardized packet-
switched protocol
-standardized by ITU-T (CCITT at the time)
• Frame relay
-operates at rates higher than those of X.25
up to 45 Mbps
• Asynchronous Transfer Mode (ATM).

58. The Internet
• The Internet is a network of networks
-an interconnection of thousands of LANs,
campus networks, MANs, and WANs
• Networks and computers connected to an
Internet Service Provider
• Many ISPs are connected to each other via
bilateral agreements and connections
• Networks connected in hierarchical structure.

59. • There is a payment-compensation scheme
established by the ISPs.
• ISPs are classified into three tiers:
-Tier 1 ISPs, the largest ones
-Tier 2 ISPs, buy connectivity from Tier 1 ISPs
-Tier 3 ISPs, buy connectivity from Tier 2 ISPs
• ISPs at the same level usually do not charge each
other for exchanging messages.
• This is called peering.

60. COMMUNICATIONS LAYERS AND
PROTOCOLS
• Write short notes on the following
• APPLICATION LAYER FUNCTIONS AND PROTOCOLS
• WWW Applications and Related Protocols
• E-Mail Applications and Related Protocols
• TRANSPORT LAYER FUNCTIONS AND PROTOCOLS
• NETWORK LAYER FUNCTIONS AND PROTOCOLS
• DATA LINK LAYER FUNCTIONS AND PROTOCOLS
• PHYSICAL LAYER FUNCTIONS AND PROTOCOLS

61. FUTURE TRENDS
• GIGABIT ETHERNET TRENDS
-The 10 Gbps Ethernet
-Sophisticated physical layer and required
several years of activities
-current 10 Gbps Ethernet applications are
mostly in WAN and carrier networks
-interconnect servers in data centers in
enterprise system

62. • The standardization activities for enterprise
networking is IEEE 802.3 HSSG.
• NEXT GENERATION INTERNET
- projects directed to develop the technologies
that will be part of the next generation of the
Internet
- Internet2, China’s Next Generation Internet,
CA*net
- common features include the use of IPv6
- a backbone in multiples of 100 Gbps data rates
- efficient multimedia transmission with adequate
QoS parameter values

63. -tools and protocols to facilitate new applications such as
videoconferencing
• Internet2 is a consortium that includes major U.S.
universities, corporations, government agencies and
laboratories, and international organizations
-focus on advanced network applications
-such as remote access to unique scientific instruments
-new network capabilities such as IPv6
-middleware
-high performance networks linking member institutions

64. • The purpose of CNGI project is to promote
China’s status in the Internet technology.
• A key aspect of CNGI is the immediate
adoption of IPv6 to solve the IPv4’s address
shortage problem
• China showcased CNGI at the 2008 Summer
Olympics in broadcasting the events
• CA*net is a Canadian approach to the next
generation Internet

65. • 4G CELLULAR NETWORKS
• 4G refers to a new type of wide area wireless
systems that will provide
- more bandwidth
- will use packet switching based on the IP
WIRELESS AD HOC NETWORKS AND WSNS
- include numbers of nodes (PDAs, laptops,
sensors, etc.) with varying functionalities and
power levels.