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1. Network Devices and Technologies
Chapter 4

2. Network Technology
Network Technology means a combination of both network
hardware and software in data communication or network architecture.
Technology generally mostly consider the
 Data rate at speed of data transmission per a second
 Way of using bandwidth
 Security and ways of accessing information
 Device configuration and connectivity etc.
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3. 3
Network Devices -Hub
 is simple network device and is reflected in their low cost.
 Small hubs with four or five ports (often referred to as
workgroup hubs).
 Hubs with more ports are available for networks that require greater
capacity.
 Figure 4.1 shows an example of the type of hub you might see on a
corporate network
Figure 4.1 Hub

4. 4
Hub…
Advantages of Hub:
 As an active hubs regenerate signals, it increases the distance that can
be spanned by the LAN (up to 100 meters per segment).
 Hubs can also be connected locally to a maximum of two other hubs,
there by increasing the number of devices
 Active hubs are usually used against attenuation, which is a decrease in
the strength of the signal over distance.

5. 5
Disadvantages of Hub:
Bandwidth is sharing among all hosts i.e. 10Mbs shared by 25
ports/users.
Can create bottlenecks when used with switches.
Bottleneck: is a point in the enterprise where flow of data impaired or
stopped entirely.
 Broadcasting: the method of sending data to all systems regardless of
the intended recipient is referred to as broadcasting.

6. 6
Switches
Figure 4.3: switch works
 Switch looks much like a hub.
 Switches are far more efficient than hubs and are far more desirable
for today’s network environments.
 Figure 4.3 shows an example of a 32-port Ethernet switch.
 If you refer to Figure 4.1, you’ll notice few differences in the
appearance of the high-density hub and this switch.

7. 7
Switches…
Switches

8. 8
Switches…
Rather than forwarding data to all the connected ports, a switch forwards
data only to the port on which the destination system is connected.
 It looks at the Media Access Control (MAC) addresses of the devices
connected to it to determine the correct port.
 A MAC address is a unique number that is stamped into every NIC. By
forwarding data only to the system to which the data is addressed,
 The switch decreases the amount of traffic on each network link
dramatically.
In effect, the switch literally channels (or Switches , if you prefer) data
between the ports.

9. 9
 Switches divide a network into several isolated channels
 Packets sending from 1 channel will not go to another if not specify
 Each channel has its own capacity and need not be shared with
other channels
10Mbps
10Mbps
10Mbps
10Mbps
Switch
Hub 3.3Mbps
3.3Mbps
3.3Mbps
Switches…

10. 10
Repeaters
 Bus-based Ethernet LANs operating by means of baseband
transmission (i.e. 10Base2 and 10Base5) are restricted to segment
lengths of 185 m, or 500 m, respectively.
 Two, or more, such LANs could be interconnected to extend this
length limitation by means of a device known as a repeater.
 A repeater operates at layer 1 of the OSI Reference Model.
 It is primarily concerned with the transmission of electrical signals at
bit level. A repeater, in its simplest form, simply reshapes and retimes
data and then retransmits them.

11. 11
Bridge
 Bridges are used to connect separate LANs together,
 It performs ‘filtering’ function.
 MAC frame addresses are examined and only those frames
containing addresses which indicate that they are intended to pass
between networks are accepted by a bridge.
 All other intra-network frames are rejected by the bridge.
 In order to perform such filtering, frames are first buffered before
any possible onward transmission to enable examination of
destination addresses.
 Such processing can add a delay to frames passing between
networks via a bridge

12. 12
Bridge…
 Has one input and one output
 Used to isolate network traffic and
computers
 Has the intelligent to examine
incoming packet source and
destination addresses
 But cannot interpret higher-level
information
 It cannot filter packet according to
its protocol

13. 13
Routers
 Repeaters and bridges are used for internetworking of LANs at layers
1 and 2, respectively.
 However, to permit an internet operation, end-systems
must support internet-based addressing, which is a layer 3 function.
 A key building block of the Internet is a router which is a device
operating at the OSI layer 3, the network layer, and running a layer 3
protocol such as the IP to route traffic in the form of packets, based
upon network-wide addresses.
 A router makes use of network layer addresses rather than the MAC
addresses used by a bridge to interconnect similar, or possibly
dissimilar, networks.

14. 14
Routers…
 The destination address of each packet may then be examined,
normally on a first-in–first-out (FIFO) basis.
 The router uses the routing table to determine the output port to be
used and the packet passed to an output buffer associated with the
required port.
 Each network has a router. A set of routing tables, one for each
router, are shown below.

15. 15
Routers…
 In this figure a link is defined in
the form (1,3) meaning the link
between network 1 and network 3
in this case for example:

16. 16
Gateway
 The terms gateway and router interchangeably, most of the literature
distinguishes between the two.
 A gateway is a computer that operates in all five layers of the Internet
or seven layers of OSI model.
 A gateway takes an application message, reads it, and interprets
 It can be used as a connecting device between two internetworks that
use different models.
 For example, a network designed to use the OSI model can be
connected to another network using the Internet model.

17. 17
Other Special network devices
 Multilayer switches
 Load balancer
 DNS server
 Bandwidth shaper

18. 18
Special network devices…
 Multilayer switches: it an integrated device that has capability to be
hub, switch, router bridge, repeater etc.
 It works at both layer 2 and 3 of OSI model.
 Load balancer: it is a device that used to share workload among
different servers which works as workhorses for network such as:
 Hold data
 Secure data
 Distribute data,
 Maintain backup etc
 So for this loads single server is becomes overloaded so load
balancer is important device:

19. 19
Special network devices…
 DNS: used to name resolution host name to IP address which also
used to communicate with other DNS servers to get necessary
information.
 Bandwidth shaper: a device that used to balance the bandwidth in
a given network administrations as shown in the figure below.
Fig: Bandwidth

20. 20
Special network devices…
 In the bandwidth shaper administrator balance the bandwidth
usability such as
 Who use bandwidth
 For what purpose it used
 What time of a day it used
 Establish priority of data traveling to in the internet from internet
 Channel service unit/data service unit(CSU/DSU): used for
conversion of data format between LAN technologies and WAN
technologies because LAN and WAN uses different technologies.

21. 1. LAN TECHNOLOGY:
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LAN is a group of computers and associated devices that share
common communication lines or wireless link and typically share the
resources of single protocols or server writhing small area.
To do network used different LAN technologies such as
 Ethernet
 Token Ring
 FDDI
 LocalTalk

22. 1. LAN TECHNOLOGY:
Ethernet: is a well-known and widely used LAN technology.
It used to expand network connectivity
On Ethernet networks, all computers share a common transmission
medium. Used IEEE802.3 standards.
Original Ethernet: is Ethernet technology that operates at 10 Mbps
data rate
Fast Ethernet: is second version operates at 100 Mbps
Gigabit Ethernet: is the most recent version, which operates at 1000
Mbps or 1 Gigabit per second (Gbps). 10Gbps: 22

23. Ethernet: CSMA
All computers attached to an Ethernet participate in a distributed
coordination scheme (or multiple media access) called Carrier Sense
Multiple Access (CSMA).
The scheme based on electrical signal activity on the cable to
determine status.
When no computer is sending a frame, the cable does not contain
electrical signals.
During frame transmission, a sender transmits electrical signals
used to carry encode bits.
We can determine whether the media is being used by detecting the
presence of a carrier.
If no carrier is present, the computer can transmit a frame.
If a carrier is present, the computer must wait for the sender to
finish before proceeding.
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24. Why CSMA?
No central control managing when computers transmit on Ethernet
Ethernet employs CSMA to coordinate transmission among multiple
attached computers.
Multiple access - multiple computers are attached and any can be
transmitter
Carrier sense - computer wanting to transmit tests ether for carrier
before transmitting
CSMA cannot prevent a computer from interrupting an ongoing
transmission (conflicts) without CSMA/CD and CSMA/CA
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25. Why CSMA?
25

26. Ethernet Communications Methods
How Ethernet transfers data on a network:
Carrier Sense Multiple Access with Collision Detection
(CSMA/CD)
Carrier Sense Multiple Access with Collision Avoidance
(CSMA/CA)
Both are contention-based access methods
Different nodes on the network segment compete to see which
node is able to send out its packet first
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27. Carrier Sense Multiple Access Collusion
Detection (CSMA/CD)
Ethernet interfaces include hardware to detect transmission
Monitor outgoing signal
Distorted signal is interpreted as a collision
After collision is detected, computer stops transmitting
So, Ethernet uses CSMA/CD to coordinate transmissions.
CSMA/CD is the formal name for access method that can
monitoring a cable during transmission to detect collisions.
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28. After a collision occurs, there will be a corrupted Ethernet frame and
the computer must wait for the cable to become idle again before
transmitting a frame.
The sender will send a noise burst to all stations to abort transmission
Carrier Sense Multiple Access Collusion
Detection (CSMA/CD)…
28

29. CSMA/CA(Carrier Sense Multiple Access
Collusion Avoidance)
A method used by Ethernet to access a local area network
Most commonly used for wireless networks
Differs from CSMA/CD in that CSMA/CA first sends out a warning
message letting all the other computers on the network know that a
data packet is coming.
The basic idea is that the sender simulates the receiver into
outputting as short frame before transmitting data so that station
nearby can detect this transmission and avoid transmitting for the
duration of the upcoming (large) data frame.
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30. 10 Base-2 – Thin Ethernet
it is a less expensive technology.
It uses a lighter and thinner coaxial cable
10 Base-2 uses an RG-58A/U coaxial cable and is wired in a bus
topology.
Each device on the network is connected to the bus through a BNC
"T" adapter, and each end of the bus must have a 50 Ohm terminator
attached
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31. 10 Base-5 -- Thick Ethernet
10 Base-5 is laid out in a bus topology, with a single coaxial cable
connecting all nodes together.
At each end of the coaxial cable is a terminator.
Each node on the network physically connects to the coaxial cable
through a device called a transceiver and an AUI (Adapter Unit
Interface) cable is connected between the node and the transceiver.
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32. 32

33. Advantage of 10 Base-5(thick Ethernet)
Long Distances Possible:
Noise Immunity:
• 10 Base-5 uses a very heavily shielded cable, it can be used in
electrically noisy environments resistance which can cause other
network types to fail.
Conceptually Simple:
Since all devices on a 10 Base-5 network are simply chained together on a common
coaxial cable, it is a simple matter to plan the routing of the cable.
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34. Disadvantage of 10 Base-5…
Inflexible:
It can be very difficult to add or move a node once it is connected to
the coaxial cable
Fault Intolerant:
Since 10 Base-5 uses a common physical cable to interconnect all the
nodes, the failure of any part of the coaxial cable or any node has the
ability to cause the collapse of the entire network.
Very Difficult Troubleshooting:
failure anywhere on a 10 Base-5 segment has the ability to drop the
entire network.
It is very time consuming, and can be expensive if a company's
entire business relies on the network to be up
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35. 10 Base-T – Unshielded Twisted Pair
10 Base-T utilizes Category 3 (or higher) Unshielded Twisted Pair
(UTP) cable in a star topology.
Each node on the network has its own cable run back to a common
hub, and each of these cable runs may be up to 100 meters (330 feet) in
length.
RJ-45
35

36. 10 Base-F
10 Base-F is basically a version of Ethernet which runs over fiber
optic cable.
 In physical topology, it is very similar to 10 Base-T
It supports distances up to 2000 meters (6600 feet).
10 Base-F is wired in a star topology with all of the fiber optic runs
originating from a central hub.
It is also acceptable to connect a pair of 10 Base-F devices directly
together with a point to point link.
10 Base-FL is very useful for use in interconnecting buildings in a
campus environment where distances could be very long
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37. 100Base T
 Known as Fast Ethernet. Normally use Cat.5 cable
Use 4B5B encoding; every group of 5 clock period is used to send 4
bits. Hence the efficiency is 80%.
 For transmitting 100Mbps, the bandwidth need on the twisted pair
will be 125Mbps.
 4B5B encoding provide enough transitions to allow easy clock
synchronization and create unique patterns for frame delimiting; e.g.
“11111” means idle line.
 (Multilevel Transmit) MLT-3 coding is used to minimize EMI effect.
 In MLT-3, a transition occur for every binary 1 in 3 voltage levels37

38. 2. Token ring
Many LAN technologies that use ring topology use token passing for
synchronized access to the ring
Ring itself is treated as a single, shared communication medium
It implemented at layer two OSI model
Data can be sent simultaneously and able to reduce broadcast it
operates at 4 or 16 Mbps
It is self-healing technology devices can insert without disturbing
Hardware must be designed to pass token even if attached computer
is powered down
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39. 2. Token ring…
39
Transmission around a token ring
When a computer wants to transmit, it waits for the token
After transmission, computer transmits token on ring
Next computer ready to transmit receives token and then transmits
IBM token ring:
-Very widely used
-Originally 4mbps, now 16Mbps
-Uses special connector cable between computer
and ring interface

40. 3.FDDI
Fiber Distributed Data Interconnect (FDDI) is another ring technology
Uses fiber optics between stations
Transmits data at 100Mbps
It is different from token ring because FDDI uses double ring as
follows and it and reliability than token ring
Primary ring used for transfer while second ring for backup
In case of fiber or station failure, remaining stations loop back and
reroute data through spare ring
FDDI network is also called self-healing because the hardware can
detect a catastrophic failure and recover automatically.
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41. 3. FDDI…
FDDI is a fiber-optic token ring LAN that offers a data rate of 100 Mbps,
max. length 2km between stations, 100km max: ring circumference and 500
stations per ring.
FDDI is fault-tolerant topology and it uses dual ring redundancy to
overcome failures
An FDDI is dual counter-rotating ring:
The primary ring is used to send data when everything is working correctly.
LocalTalk :implement at physical network interface for apple
Used a system of shielded pair cables plugging into self terminating
transceiver
Max rate 230 kbps
CSMA/CA was implemented as a random multiple access method. 41

42. 1. Point-to-Point technologies
Point-to-Point technologies (often called dedicated or leased lines)
are usually the most expensive form of WAN technology.
 Point-to-Point technologies are leased from a service provider, and
provide guaranteed bandwidth from location to another (hence
point-to-point).
Cost is determined by the distance of the connection, and the
amount of bandwidth allocated.
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43. Circuit-Switched technologies require call-setup to occur
before information can be transferred.
The session is usually torn down once data transfer is complete
(this is identified as an On-Demand Circuit).
low-speed compared to point-to-point lines.
Examples of circuit-switched technologies include:
Dial-up
ISDN: Integrated Services Digital Network (ISDN) is an example
of a circuit-switched WAN technology
2. Circuit switching…
43

44. Integrated Services Digital Network (ISDN) is a circuit-switching network
used for voice, data, and video transfer over plain copper telephone
lines.
ISDN is a bit similar to the normal telephone system but it is faster,
more reliable, and requires less time to setup a call.
An ISDN modem can be used to convert the signals of non-ISDN
equipment to ISDN signals.
44
2. Circuit switching…

45. 3. Packet Switching
In packet switching networks, data is segmented into packets that
each take a route independently based on the addressing information
their header regardless of type, content, or structure.
Each packet is given enough information to find its own path to its
intended destination.
Most large WANs are largely made up of packet switching
networks, the Internet being the most common example.
45

46. How Packet Switching Works?
Examples of Packet switching WAN technologies
 Frame Relay and ATM
 X.25 technologies
46

47. 3.1. X.25
 is a classic packet-switching standard from ITU-T that operates at
the Physical, Data Link, and Network layers of the OSI model.
 Not as widely used today; replaced by newer alternatives.
Automatic teller machine
Credit card verification networks
Because the older telephone lines were prone to error and
interference, X.25 is mainly concerned with error-Checking and
error-correction to allow a more reliable connection.
47

48. 3.2. Frame Relay
Frame Relay, one of today's most common examples of a packet-
switching network, is a high-performance WAN protocol that operates
at the physical and data link layers of the OSI model.
 is a newer and faster than X.25 and today’s common technology
Common use of Frame Relay is to interconnect LANs in a WAN
Greatly reducing network latency.
It also supports variable-length packet sizes for more efficient
utilization of network bandwidth.
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49. 3.2. ATM
ATM is short for Asynchronous Transfer Mode, a packet-switching
network that is commonly used for high-speed backbones in large
network environments such as the Internet, for voice, data and video
transfer.
Data is transmitted in small 53-byte fixed length cells , and that is why
ATM is also referred to as a cell-switching network .
Partly because of the fixed length cell approach, ATM is able to reach
data rates up to 622 Mbps.
49

50. ATM …
 Designed as single technology for voice, video, data, ...
 Low jitter (variance in delivery time) and high capacity
 Uses fixed size, small cells - 48 octets data, 5 octets header
 ATM switch uses integrated hardware circuits that switch cells
between incoming and outgoing ports which significantly increase data
throughput compared to software based switching.
50

51. ATM …
 ATM supports several innovative features such as Bandwidth on
demand and QoS (Quality of Service).
 The latter allows data to be prioritized based on the content.
 For example, real-time video transfer could have a higher priority than
file transfer, to allow the user to watch the video without interruptions.
 ATM uses its own reference model, which corresponds roughly to
both the OSI Data Link and the Physical Layer.
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52. Thank you!!!
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