ECE 6TH SEMESTER CHAPTER1. NETWORKING CONCEPTS …
Transcript of ECE 6TH SEMESTER CHAPTER1. NETWORKING CONCEPTS …
COMPUTER NETWORKS
ECE 6TH SEMESTER
CHAPTER1. NETWORKING CONCEPTS
Learning objectives
To know about uses, applications, disadvantages of network
To elaborate various types of network
To elaborate various types of topologies
Discuss switching techniques
Definition
A computer network is defined as the interconnection of two or more computers. It is done to enable the computers to communicate and share available resources.
Applications
Sharing of resources such as printers
Sharing of expensive software's and database
Communication from one computer to another computer
Exchange of data and information among users via network
Sharing of information over geographically wide areas.
Uses of computer networks
sharing information
sharing of hardware and software
Reduced cost
Improved security
Centralized software managements
Electronic mail
Flexible access
Increased speed
Components of computer networks
Two or more computers
Cables as links between the computers
A network interfacing card(NIC) on each computer
Switches
Software called operating system(OS)
Disadvantages of computer networks
High cost of installation
Requires time for administration
Failure of server
Types of Networks
LAN(Local Area Network)
LAN is a network which is designed to operate over a small physical area such as an
office, factory or a group of buildings.
LAN’s are easy to design and troubleshoot
Exchange of information and sharing of resources becomes easy because of LAN. In LAN all machines are connected to a single cable.
Different types of topologies such as star, tree, bus, ring, etc Can be used
It is usually a privately owned network.
MAN(Metropolitan Area Network)
It is in between LAN & WAN technology that covers the entire city.
It uses similar technology as LAN.
It can be a single network such as cable TV network, or a measure of connecting a number of
LAN’s o a large network so that resources can be shared LAN to LAN as well as device to
device.
WAN(Wide Area Network)
When network spans over a large distance or when the computers to be connected to each
other are at widely separated locations a local area network cannot be used. A wide area network(WAN) is installed.
The communication between different users of WAN is established using leased telephone lines, satellite links and similar channels.
It is cheaper and more efficient to use the phone network for the link.
Most WAN networks are used to transfer large blocks of data between its users.
Peer to Peer Network
In peer to peer network each computer is responsible for making its own resources available
to other computers on the network.
Each computer is responsible for setting up and maintaining its own security for these resources.
Also each computer is responsible for accessing the required network resources from peer to peer relationships.
Peer to peer network is useful for a small network containing less than 10 computers on a single LAN .
In peer to peer network each computer can function as both client and server.
Peer to peer networks do not have a central control system. There are no servers in peer networks.
Peer networks are amplified into home group.
Client Server Network
In client-server network relationships, certain computers act as server and other act as clients. A server is simply a computer, that available the network resources and provides service to other computers when they request it. A client is the computer running a program that requests the service from a server.
Local area network(LAN) is based on client server network relationship. A client-server network is one n which all available network resources such as files,
directories, applications and shared devices, are centrally managed and hosted and then are accessed by client.
Client serve network are defined by the presence of servers on a network that provide security and administration of the network.
Topologoies
BUS Topology
Bus topology is a network type in which every computer and network device is connected to
single cable. When it has exactly two endpoints, then it is called Linear Bus topology.
Features of Bus Topology
It transmits data only in one direction.
Every device is connected to a single cable
Advantages of Bus Topology
It is cost effective.
Cable required is least compared to other network topology.
Used in small networks.
It is easy to understand.
Easy to expand joining two cables together.
Disadvantages of Bus Topology
Cables fails then whole network fails.
If network traffic is heavy or nodes are more the performance of the network decreases.
Cable has a limited length.
It is slower than the ring topology.
RING Topology
It is called ring topology because it forms a ring as each computer is connected to another
computer, with the last one connected to the first. Exactly two neighbours for each device.
Features of Ring Topology
A number of repeaters are used for Ring topology with large number of nodes, because if
someone wants to send some data to the last node in the ring topology with 100 nodes, then
the data will have to pass through 99 nodes to reach the 100th node. Hence to prevent data
loss repeaters are used in the network.
The transmission is unidirectional, but it can be made bidirectional by having 2 connections
between each Network Node, it is called Dual Ring Topology.
In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction
in them. Also, if one ring fails, the second ring can act as a backup, to keep the network up.
Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to pass
through each node of the network, till the destination node.
Advantages of Ring Topology
Transmitting network is not affected by high traffic or by adding more nodes, as only the
nodes having tokens can transmit data.
Cheap to install and expand
Disadvantages of Ring Topology
Troubleshooting is difficult in ring topology.
Adding or deleting the computers disturbs the network activity.
Failure of one computer disturbs the whole network.
STAR Topology
In this type of topology all the computers are connected to a single hub through a cable. This hub
is the central node and all others nodes are connected to the central node.
Features of Star Topology
Every node has its own dedicated connection to the hub.
Hub acts as a repeater for data flow.
Can be used with twisted pair, Optical Fibre or coaxial cable.
Advantages of Star Topology
Fast performance with few nodes and low network traffic.
Hub can be upgraded easily.
Easy to troubleshoot.
Easy to setup and modify.
Only that node is affected which has failed, rest of the nodes can work smoothly.
Disadvantages of Star Topology
Cost of installation is high.
Expensive to use.
If the hub fails then the whole network is stopped because all the nodes depend on the hub.
Performance is based on the hub that is it depends on its capacity
MESH Topology
It is a point-to-point connection to other nodes or devices. All the network nodes are connected
to each other. Mesh has n(n-1)/2 physical channels to link n devices.
Types of Mesh Topology
1. Partial Mesh Topology : In this topology some of the systems are connected in the same
fashion as mesh topology but some devices are only connected to two or three devices.
2. Full Mesh Topology : Each and every nodes or devices are connected to each other.
Features of Mesh Topology
Fully connected.
Robust.
Not flexible.
Advantages of Mesh Topology
Each connection can carry its own data load.
It is robust.
Fault is diagnosed easily.
Provides security and privacy.
Disadvantages of Mesh Topology
Installation and configuration is difficult.
Cabling cost is more.
Bulk wiring is required.
TREE Topology
It has a root node and all other nodes are connected to it forming a hierarchy. It is also called
hierarchical topology. It should at least have three levels to the hierarchy.
Features of Tree Topology
Ideal if workstations are located in groups.
Used in Wide Area Network.
Advantages of Tree Topology
Extension of bus and star topologies.
Expansion of nodes is possible and easy.
Easily managed and maintained.
Error detection is easily done.
Disadvantages of Tree Topology
Heavily cabled.
Costly.
If more nodes are added maintenance is difficult.
Central hub fails, network fails.
HYBRID Topology
It is two different types of topologies which is a mixture of two or more topologies. For example
if in an office in one department ring topology is used and in another star topology is used,
connecting these topologies will result in Hybrid Topology (ring topology and star topology).
Features of Hybrid Topology
It is a combination of two or topologies
Inherits the advantages and disadvantages of the topologies included
Advantages of Hybrid Topology
Reliable as Error detecting and trouble shooting is easy.
Effective.
Scalable as size can be increased easily.
Flexible.
Disadvantages of Hybrid Topology
Complex in design.
Costly.
Switching Techniques
Circuit switching: it is a technique that directly connects the sender and the receiver in an
unbroken path.
• Telephone switching equipment, for example, establishes a path that connects the caller's
telephone to the receiver's telephone by making a physical connection.
• With this type of switching technique, once a connection is established, a dedicated path
exists between both ends until the connection is terminated.
• Routing decisions must be made when the circuit is first established, but there are no decisions
made after that time
• Circuit switching in a network operates almost the same way as the telephone system works.
• A complete end-to-end path must exist before communication can take place.
• The computer initiating the data transfer must ask for a connection to the destination.
• Once the connection has been initiated and completed to the destination device, the destination
device must acknowledge that it is ready and willing to carry on a transfer.
Advantages:
• The communication channel (once established) is dedicated.
Disadvantages:
• Possible long wait to establish a connection, (10 seconds, more on long- distance or
international calls.) during which no data can be transmitted.
• More expensive than any other switching techniques, because a dedicated path is required for
each connection.
• Inefficient use of the communication channel, because the channel is not used when the
connected systems are not using it.
Packet Switching:
Packet Switching
• Packet switching can be seen as a solution that tries to combine the advantages of message and
circuit switching and to minimize the disadvantages of both.
• There are two methods of packet switching: Datagram and virtual circuit.
• In both packet switching methods, a message is broken into small parts, called packets.
• Each packet is tagged with appropriate source and destination addresses.
• With current technology, packets are generally accepted onto the network on a first-come, first-
served basis. If the network becomes overloaded, packets are delayed or discarded (``dropped'').
• In packet switching, the analog signal from your phone is converted into a digital data stream.
That series of digital bits is then divided into relatively tiny clusters of bits, called packets.
• Datagram packet switching is similar to message switching in that each packet is a self-
contained unit with complete addressing information attached.
• This fact allows packets to take a variety of possible paths through the network.
• So the packets, each with the same destination address, do not follow the same route, and they
may arrive out of sequence at the exit point node (or the destination).
• Reordering is done at the destination point based on the sequence number of the packets.
• It is possible for a packet to be destroyed if one of the nodes on its way is crashed momentarily.
Thus all its queued packets may be lost.
• In the virtual circuit approach, a preplanned route is established before any data packets are
sent.
• A logical connection is established when a sender send a "call request packet" to the receiver
and the receiver send back an acknowledge packet "call accepted packet" to the sender if the
receiver agrees on conversational parameters.
• The conversational parameters can be maximum packet sizes, path to be taken, and other
variables necessary to establish and maintain the conversation.
• Virtual circuits imply acknowledgements, flow control, and error control, so virtual circuits are
reliable. That is, they have the capability to inform upper-protocol layers if a transmission
problem occurs
• In virtual circuit, the route between stations does not mean that this is a dedicated path, as in
circuit switching.
• A packet is still buffered at each node and queued for output over a line.
Advantages:
• Packet switching is cost effective, because switching devices do not need massive amount of
secondary storage.
• Packet switching offers improved delay characteristics, because there are no long messages in
the queue (maximum packet size is fixed).
• Packet can be rerouted if there is any problem, such as, busy or disabled links.
•The advantage of packet switching is that many network users can share the same channel at the
same time. Packet switching can maximize link efficiency by making optimal use of link
bandwidth.
Disadvantages:
• Protocols for packet switching are typically more complex.
• It can add some initial costs in implementation.
• If packet is lost, sender needs to retransmit the data. Another disadvantage is that packet-
switched systems still can’t deliver the same quality as dedicated circuits in applications
requiring very little delay - like voice conversations or moving images.
Message Switching
• With message switching there is no need to establish a dedicated path between two stations.
• When a station sends a message, the destination address is appended to the message.
• The message is then transmitted through the network, in its entirety, from node to node.
• Each node receives the entire message, stores it in its entirety on disk, and then transmits the
message to the next node.
• This type of network is called a store-and-forward network.
A message-switching node is typically a general-purpose computer. The device needs sufficient
secondary-storage capacity to store the incoming messages, which could be long. A time delay is
introduced using this type of scheme due to store- and-forward time, plus the time required to
find the next node in the transmission path.
Advantages:
• Channel efficiency can be greater compared to circuit-switched systems, because more
devices are sharing the channel.
• Traffic congestion can be reduced, because messages may be temporarily stored in route.
• Message priorities can be established due to store-and-forward technique.
• Message broadcasting can be achieved with the use of broadcast address appended in the
message
Disadvantages
• Message switching is not compatible with interactive applications.
• Store-and-forward devices are expensive, because they must have large disks to hold
potentially long messages
VERY SHORT QUESTIONS
1. Define network?
2. What is full form of LAN?
3. Define star topology?
4. What is a server?
5. Name various elements of computer network?
6. What are the 3 phases of circuit switching?
7. Name four network topology?
SHORT QUESTIONS
1. Explain packet switching?
2. What is message switching?
3. Explain tree and star topology?
4. Discuss mesh topology?
5. What are the uses of computer network?
6. What is peer to peer network?
7. What is Ring topology?
8. What do you mean by email?
LONG QUESTIONS
1. Explain various topologies in detail?
2. Explain switching techniques?
3. What is peer to peer and client server model?
4. What is computer network and what are its applications?
2. NETWORKING MODELS
Learning objectives
OSI model
Established in 1947, the International Standards Organization(ISO) is a multinational body
dedicated to world wide agreement on international standards .An ISO standard that covers all
aspects of network communications is the Open Systems Interconnection model. It was first
introduced in the late 1970s .An open system is a set of protocols that all owes any two different
system to communicate regardless of the underlying architecture. The purpose of the OSI mode
list show how to facilitate communication between different systems without requiring changes
to the logic of the underlying hardware and software
Layer 7: Physical Layer
The lowest layer of the OSI model is concerned with data communication in the form of
electrical, optic, or electromagnetic signals physically transmitting information between
networking devices and infrastructure. The Physical Layer is essentially responsible for the
communication of unstructured raw data streams over a physical medium. It defines a range of
aspects associated with the electrical, mechanical, and physical systems and networking devices
that include the specifications; e.g. cable size, signal frequency, voltages, etc.; topologies such as
Bus, Star, Ring, and Mesh; communication modes such as Simplex, Half Duplex, and Full
Duplex; data Transmission Performance e.g. Bit Rate and Bit Synchronization; as well as
modulation, switching, and interfacing with the physical transmission medium as described here.
Common protocols include Wi-Fi, Ethernet, and others as listed here. The hardware includes
networking devices, antennas, cables, modem, intermediate devices such as repeaters and hubs.
Layer 6: Data Link Layer
The second layer of the OSI model concerns data transmission between the nodes within a
network and manages the connections between physically connected devices such as switches.
The raw data received from the physical layer is synchronized and packaged into
data frames that contain the necessary protocols to route information between appropriate nodes.
The Data Link Layeris further divided into two sublayers: Logical Link Control (LLC) sublayer
responsible for flow controls and error controls that ensure error-free and accurate data
transmission between the network nodes; and the Media Access Control (MAC) sublayer
responsible for managing access and permissions to transmit data between the network nodes.
The data is transmitted sequentially and the layer expects acknowledgement for the encapsulated
raw data sent between the nodes.
Layer 5: Network Layer
The third layer of the OSI model organizes and transmits data between multiple networks. This
layer is responsible for routing the data via the best physical path based on a range of factors
including network characteristics, best available path, traffic controls, congestion of data packets,
and priority of service, among others. The network layer implements logical addressing for data
packets to distinguish between the source and destination networks. Other functions at the
Network Layer include encapsulation and fragmentation, as well as congestion controls and error
handling. The outgoing data is divided into packets and incoming data is reassembled into
information that is consumable at a higher application level. Network Layer hardware includes
routes, bridge routers, 3-layer switches, and protocols such as Internet (IPv4) Protocol version 4
and Internet Protocol version 6 (IPv6).
Layer 4: Transport Layer
The fourth layer of the OSI model ensures complete and reliable delivery of data packets.
The Transport Layer provides mechanisms such as error control, flow control, and congestion
control to keep track of the data packets, check for errors and duplication, and resend the
information that fails delivery. It involves the service-point addressing function to ensure that the
packet is sent in response to a specific process (via a port address). Packet Segmentation and
reassembly ensure that the data is divided and sequentially sent to the destination where it is
rechecked for integrity and accuracy based on the receiving sequence. Common protocols
include the Transmission Control Protocol (TCP) for connection-oriented data transmission
and User Datagram Protocol (UDP) for connectionless data transmission.
Layer 3: Session Layer
The Session Layer manages sessions between servers to coordinate the communication – as the
first of the top three OSI model layers that deal with the software level. Session refers to any
interactive data exchange between two entities within a network. Common examples include
HTTPS sessions that allow Internet users to visit and browse websites for a specific time period.
The Session Layer is responsible for a range of functions including opening, closing, and re-
establishing session activities, authentication and authorization of communication between
specific apps and servers, identifying full-duplex or half-duplex operations, and synchronizing
data streams. Common Session Layer protocols include Remote procedure call protocol (RPC),
Point-to-Point Tunneling Protocol (PPTP), Session Control Protocol (SCP), and Session
Description Protocol (SDP) as described here.
Layer 2: Presentation Layer
The sixth layer of the OSI model converts data formats between applications and the networks.
Responsibilities of the Presentation Layer include data conversion, character code
translation, data compression, encryption and decryption. The Presentation Layer, also called the
Syntax Layer, maps the semantics and syntax of the data such that the received information is
consumable for every distinct network entity. For example, the data we transfer from our
encryption-based communication app is formatted and encrypted at this layer before it is sent
across the network. At the receiving end, the data is decrypted and formatted into text or media
information as originally intended. The presentation layer also serializes complex information
into transportable formats. The data streams are then deserialized and reassembled into original
object format at the destination.
Layer 1: Application Layer
The Application Layer concerns the networking processes at the application level. This layer
interacts directly with end-users to provide support for email, network data sharing, file transfers,
and directory services, among other distributed information services. The upper most layer of the
OSI model identifies networking entities to facilitate networking requests by end-user requests,
determines resource availability, synchronizes communication, and manages application-specific
networking requirements. The Application Layer also identifies constraints at the application
level such as those associated with authentication, privacy, quality of service, networking
devices, and data syntax. The most common Application Layer protocols include File Transfer
Protocol (FTP), Simple Mail Transfer Protocol (SMTP) and Domain Name System (DNS).
2.2 TCP/IP
Layer 4: Application layer
is the top most layer of four layer TCP/IP model. Application layer is present on the top of
the Transport layer. Application layer defines TCP/IP application protocols and how host
programs interface with Transport layer services to use the network.
Application layer includes all the higher-level protocols like DNS (Domain Naming
System), HTTP (Hypertext Transfer Protocol), Telnet, SSH, FTP (File Transfer Protocol), TFTP
(Trivial File Transfer Protocol), SNMP (Simple Network Management Protocol), SMTP (Simple
Mail Transfer Protocol) , DHCP (Dynamic Host Configuration Protocol), X Windows, RDP
(Remote Desktop Protocol) etc.
Layer 3: Transport Layer
Transport Layer is the third layer of the four layer TCP/IP model. The position of the Transport
layer is between Application layer and Internet layer. The purpose of Transport layer is to permit
devices on the source and destination hosts to carry on a conversation. Transport layer defines
the level of service and status of the connection used when transporting data.
The main protocols included at Transport layer are TCP (Transmission Control
Protocol) and UDP (User Datagram Protocol).
2. In OSI model the transport layer guarantees 2. In TCP/IP model the transport layer doe
Layer 2: Internet Layer
Internet Layer is the second layer of the four layer TCP/IP model. The position of Internet
layer is between Network Access Layer and Transport layer. Internet layer pack data into data
packets known as IP datagrams, which contain source and destination address (logical address or
IP address) information that is used to forward the datagrams between hosts and across networks.
The Internet layer is also responsible for routing of IP datagrams.
Packet switching network depends upon a connectionless internetwork layer. This layer is known
as Internet layer. Its job is to allow hosts to insert packets into any network and have them to
deliver independently to the destination. At the destination side data packets may appear in a
different order than they were sent. It is the job of the higher layers to rearrange them in order to
deliver them to proper network applications operating at the Application layer.
The main protocols included at Internet layer are IP (Internet Protocol), ICMP (Internet Control
Message Protocol), ARP (Address Resolution Protocol), RARP (Reverse Address Resolution
Protocol) and IGMP (Internet Group Management Protocol).
Layer 1: Network Access Layer
Network Access Layer is the first layer of the four layer TCP/IP model. Network Access
Layer defines details of how data is physically sent through the network, including how bits are
electrically or optically signaled by hardware devices that interface directly with a network
medium, such as coaxial cable, optical fiber, or twisted pair copper wire.
The protocols included in Network Access Layer are Ethernet, Token Ring, FDDI, X.25, Frame
Relay etc.
2.4 Comparison between OSI and TCP/IP model
SI(Open System Interconnection)
TCP/IP(Transmission Control Protocol / In
1. OSI is a generic, protocol independent
standard, acting as a communication gateway
between the network and end user.
1. TCP/IP model is based on standard prot
the Internet has developed. It is a communi
which allows connection of hosts over a ne
the delivery of packets. delivery of packets. Still the TCP/IP model is more reliabl
3. Follows vertical approach. 3. Follows horizontal approach.
4. OSI model has a separate Presentation layer
and Session layer.
4. TCP/IP does not have a separate Presentation layer or
Session layer.
5. Transport Layer is Connection Oriented. 5. Transport Layer is both Connection Oriented and
Connection less.
6. Network Layer is both Connection Oriented
and Connection less.
6. Network Layer is Connection less.
7. OSI is a reference model around which the
networks are built. Generally it is used as a
guidance tool.
7. TCP/IP model is, in a way implementation of the OSI
model.
8. Network layer of OSI model provides both
connection oriented and connectionless service.
8. The Network layer in TCP/IP model provides
connectionless service.
9. OSI model has a problem of fitting the
protocols into the model.
9. TCP/IP model does not fit any protocol
10. Protocols are hidden in OSI model and are
easily replaced as the technology changes.
10. In TCP/IP replacing protocol is not easy.
11. OSI model defines services, interfaces and
protocols very clearly and makes clear
distinction between them. It is protocol
independent.
11. In TCP/IP, services, interfaces and protocols are not
clearly separated. It is also protocol dependent.
12. It has 7 layers 12. It has 4 layers
VERY SHORT QUESTIONS
1. What is the full form of OSI?
2. Name the seven layers of OSI model?
3. Name the four layers of TCP model? 4. Draw the diagram of OSI model?
5. Which layer consist of data in form of packets? 6. Name the two protocols used in Transport layer?
SHORT QUESTIONS
1. what is the function of data link layer?
2. what is the function of presentation and session layer?
3. what is OSI reference model? 4. Write the function of transport layer of TCP model? 5. Write the function of application layer of OSI model?
LONG QUESTIONS
1. What is an OSI model? Explain in detail.
2. What is TCP/IP model? Explain in detail.
3. TCP/IP ADDRESSING
Learning Objectives
To know about IP addressing
Elaborate classful and classless addressing
Discuss subnetting and supernetting
Know about IPV4 and IPV6 header formats
Elaborate comparison between them
IP Addressing
IP address is an address having information about how to reach a specific host, especially outside
the LAN. An IP address is a 32 bit unique address having an address space of 232.
Generally, there are two notations in which IP address is written, dotted decimal notation and
hexadecimal notation.
Dotted Decimal Notation
Hexadecimal Notation
Some points to be noted about dotted decimal notation :
1. The value of any segment (byte) is between 0 and 255 (both included).
2. There are no zeroes preceding the value in any segment (054 is wrong, 54 is correct).
Classful Addressing
The 32 bit IP address is divided into five sub-classes. These are:
Class A
Class B
Class C
Class D
Class E
Each of these classes has a valid range of IP addresses. Classes D and E are reserved for
multicast and experimental purposes respectively. The order of bits in the first octet determine
the classes of IP address.
IPv4 address is divided into two parts:
Network ID
Host ID
The class of IP address is used to determine the bits used for network ID and host ID and the
number of total networks and hosts possible in that particular class. Each ISP or network
administrator assigns IP address to each device that is connected to its network.
Note: IP addresses are globally managed by Internet Assigned Numbers Authority(IANA) and
regional Internet registries(RIR).
Note: While finding the total number of host IP addresses, 2 IP addresses are not counted and are
therefore, decreased from the total count because the first IP address of any network is the
network number and whereas the last IP address is reserved for broadcast IP.
Class A:
IP address belonging to class A are assigned to the networks that contain a large number of hosts.
The network ID is 8 bits long.
The host ID is 24 bits long.
The higher order bit of the first octet in class A is always set to 0. The remaining 7 bits in first
octet are used to determine network ID. The 24 bits of host ID are used to determine the host in
any network. The default sub-net mask for class A is 255.x.x.x. Therefore, class A has a total of:
2^7= 128 network ID
2^24 – 2 = 16,777,214 host ID
IP addresses belonging to class A ranges from 1.x.x.x – 126.x.x.x
Class B:
IP address belonging to class B are assigned to the networks that ranges from medium-sized to
large-sized networks.
The network ID is 16 bits long.
The host ID is 16 bits long.
The higher order bits of the first octet of IP addresses of class B are always set to 10. The
remaining 14 bits are used to determine network ID. The 16 bits of host ID is used to determine
the host in any network. The default sub-net mask for class B is 255.255.x.x. Class B has a total
of:
2^14 = 16384 network address
2^16 – 2 = 65534 host address
IP addresses belonging to class B ranges from 128.0.x.x – 191.255.x.x.
Class C:
IP address belonging to class C are assigned to small-sized networks.
The network ID is 24 bits long.
The host ID is 8 bits long.
The higher order bits of the first octet of IP addresses of class C are always set to 110. The
remaining 21 bits are used to determine network ID. The 8 bits of host ID is used to determine
the host in any network. The default sub-net mask for class C is 255.255.255.x. Class C has a
total of:
2^21 = 2097152 network address
2^8 – 2 = 254 host address
IP addresses belonging to class C ranges from 192.0.0.x – 223.255.255.x.
Class D:
IP address belonging to class D are reserved for multi-casting. The higher order bits of the first
octet of IP addresses belonging to class D are always set to 1110. The remaining bits are for the
address that interested hosts recognize.
Class D does not posses any sub-net mask. IP addresses belonging to class D ranges from
224.0.0.0 – 239.255.255.255.
Class E:
IP addresses belonging to class E are reserved for experimental and research purposes. IP
addresses of class E ranges from 240.0.0.0 – 255.255.255.254. This class doesn’t have any sub-
net mask. The higher order bits of first octet of class E are always set to 1111.
Range of special IP addresses:
169.254.0.0 – 169.254.0.16 : Link local addresses
127.0.0.0 – 127.0.0.8 : Loop-back addresses
0.0.0.0 – 0.0.0.8 : used to communicate within the current network.
Summary of Classful addressing :
Problems with Classful Addressing:
The problem with this classful addressing method is that millions of class A address are wasted,
many of the class B address are wasted, whereas, number of addresses available in class C is so
small that it cannot cater the needs of organizations. Class D addresses are used for multicast
routing, and are therefore available as a single block only. Class E addresses are reserved.
Since there are these problems, Classful networking was replaced by Classless Inter-Domain
Routing (CIDR) in 1993
3.2.3 Classless Addressing
To reduce the wastage of IP addresses in a block, we use sub-netting. What we do is that we use
host id bits as net id bits of a classful IP address. We give the IP address and define the number
of bits for mask along with it (usually followed by a ‘/’ symbol), like, 192.168.1.1/28. Here,
subnet mask is found by putting the given number of bits out of 32 as 1, like, in the given
address, we need to put 28 out of 32 bits as 1 and the rest as 0, and so, the subnet mask would be
255.255.255.240.
3.3. Subnetting
Subnetting: Dividing a large block of addresses into several contiguous sub-blocks and
assigning these sub-blocks to different smaller networks is called subnetting. It is a practice that
is widely used when classless addressing is done.
Supernetting
Supernetting is the opposite of Subnetting. In subnetting, a single big network is divided into
multiple smaller subnetworks. In Supernetting, multiple networks are combined into a bigger
network termed as a Supernetwork or Supernet.
Supernetting is mainly used in Route Summarization, where routes to multiple networks with
similar network prefixes are combined into a single routing entry, with the routing entry pointing
to a Super network, encompassing all the networks. This in turn significantly reduces the size of
routing tables and also the size of routing updates exchanged by routing protocols.
More specifically,
When multiple networks are combined to form a bigger network, it is termed as super-
netting
Super netting is used in route aggregation to reduce the size of routing tables and routing
table updates
IPV4 Header Format
Base Header
Version: It defines the version number of IP, i.e., in this case, it is 4 with a binary value of 0100.
Header length (HLEN): It represents the length of the header in multiple of four bytes.
Service type: It determines how datagram should be handled and includes individual bits such as
level of throughput, reliability, and delay.
Total length: It signifies the entire length of the IP datagram.
Identification: This field is used in fragmentation. A datagram is divided when it passes through
different networks to match the network frame size. At that time each fragment is determined
with a sequence number in this field.
Flags: The bits in the flags field handles fragmentation and identifies the first, middle or last
fragment, etc.
Fragmentation offset: It’s a pointer that represents the offset of the data in the original datagram.
Time to live: It defines the number of hops a datagram can travel before it is rejected. In simple
words, it specifies the duration for which a datagram remains on the internet.
Protocol: The protocol field specifies which upper layer protocol data are encapsulated in the
datagram (TCP, UDP, ICMP, etc.).
Header checksum: This is a 16-bit field confirm the integrity of the header values, not the rest of
the packet.
Source address: It’s a four-byte internet address which identifies the source of the datagram.
Destination address: This is a 4-byte field which identifies the final destination.
Options: This provides more functionality to the IP datagram. Furthermore can carry fields like
control routing, timing, management, and alignment.
IPv4 is a two-level address structure (net id and host id) classified into five categories (A, B, C,
D, and E).
IPV6 Header Format
An IPv6 address is a 128-bit binary value, which can be displayed as 32 hexadecimal digits.
Base Header
Version: This four-bit field specifies the version of the IP, i.e., 6 in this case.
Priority: It defines the priority of the packet concerning traffic congestion.
Flow label: The reason for designing this protocol is to facilitate with special controlling for a
certain flow of data.
Payload length: It defines the total length of the IP datagram excepting the base header.
Next header: It’s an eight-bit field describe the header that trails the base header in the datagram.
The next header is one of the optional extension headers which IP uses or the header for an upper
layer protocol such as UDP or TCP.
Hop limit: This eight-bit hop limit field assists with the same functions at the TTL field in IPv4.
Source address: It is a 16 bytes internet address identifies the source of the datagram.
Destination address: This is 16-byte internet address that generally describes the final destination
of the datagram.
Comparison Between IPV4 and IPV6
BASIS OF
COMPARISON
IPV4
IPV6
Address Configuration Supports Manual and DHCP Supports Auto-configuration an
configuration. renumbering
End-to-end connection Unachievable Achievable
integrity
Address Space It can generate 4.29 x
109 addresses.
It can produce quite a large num
addresses, i.e., 3.4 x 1038.
Security features Security is dependent on IPSEC is inbuilt in the IPv6 prot
application
Address length 32 bits (4 bytes) 128 bits (16 bytes)
Address Representation In decimal In hexadecimal
Fragmentation performed
by
Sender and forwarding routers Only by the sender
Packet flow identification Not available Available and uses flow label field in the
header
Checksum Field Available Not available
Message Transmission
Scheme
Broadcasting Multicasting and Anycasting
Encryption and
Authentication
Not Provided Provided
VERY SHORT QUESTIONS
1. Define IP address.
2. Masking is used in subnetting(T/F)?
3. Name the five class of classfull addressing?
4. Mention the range of addresses included in each class of IP address?
5. What is the full form of IPV4 and IPV6?
6. Which address is used for loop back test?
7. What is TCP/IP
SHORT QUESTIONS
1. Explain the various types of ip address? 2. What is subnetting?
3. What is supernetting?
4. Draw the table for various address class of IP address?
5. What is the disadvantage of classful addressing and why classless addressing was opted?
LONG QUESTION
1. Explain IPV4 Header format?
2. Explain IPV6 header format?
3. Compare IPV4 and IPV6 header format?
4. Explain IP addressing in detail?
4. CABLES AND CONNECTORS
Learning Objectives
Ethernet
Ethernet
Ethernet is the most popular physical layer LAN technology in use today. It defines the number
of conductors that are required for a connection, the performance thresholds that can be
expected, and provides the framework for data transmission. A standard Ethernet network can
transmit data at a rate up to 10 Megabits per second (10 Mbps). Other LAN types include Token
Ring, Fast Ethernet, Gigabit Ethernet, 10 Gigabit Ethernet, Fiber Distributed Data Interface
(FDDI), Asynchronous Transfer Mode (ATM) and LocalTalk.
Ethernet is popular because it strikes a good balance between speed, cost and ease of installation.
These benefits, combined with wide acceptance in the computer marketplace and the ability to
support virtually all popular network protocols, make Ethernet an ideal networking technology
for most computer users today.
The Institute for Electrical and Electronic Engineers developed an Ethernet standard known as
IEEE Standard 802.3. This standard defines rules for configuring an Ethernet network and also
specifies how the elements in an Ethernet network interact with one another. By adhering to the
IEEE standard, network equipment and network protocols can communicate efficiently.
Ethernet Specification and Standardisation
Fast Ethernet
The Fast Ethernet standard (IEEE 802.3u) has been established for Ethernet networks that need
higher transmission speeds. This standard raises the Ethernet speed limit from 10 Mbps to 100
Mbps with only minimal changes to the existing cable structure. Fast Ethernet provides faster
throughput for video, multimedia, graphics, Internet surfing and stronger error detection and
correction.
There are three types of Fast Ethernet: 100BASE-TX for use with level 5 UTP cable; 100BASE-
FX for use with fiber-optic cable; and 100BASE-T4 which utilizes an extra two wires for use
with level 3 UTP cable. The 100BASE-TX standard has become the most popular due to its
close compatibility with the 10BASE-T Ethernet standard.
Network managers who want to incorporate Fast Ethernet into an existing configuration are
required to make many decisions. The number of users in each site on the network that need the
higher throughput must be determined; which segments of the backbone need to be reconfigured
specifically for 100BASE-T; plus what hardware is necessary in order to connect the 100BASE-
T segments with existing 10BASE-T segments. Gigabit Ethernet is a future technology that
promises a migration path beyond Fast Ethernet so the next generation of networks will support
even higher data transfer speeds.
Gigabit Ethernet
Gigabit Ethernet was developed to meet the need for faster communication networks with
applications such as multimedia and Voice over IP (VoIP). Also known as “gigabit-Ethernet-
over-copper” or 1000Base-T, GigE is a version of Ethernet that runs at speeds 10 times faster
than 100Base-T. It is defined in the IEEE 802.3 standard and is currently used as an enterprise
backbone. Existing Ethernet LANs with 10 and 100 Mbps cards can feed into a Gigabit Ethernet
backbone to interconnect high performance switches, routers and servers.
From the data link layer of the OSI model upward, the look and implementation of Gigabit
Ethernet is identical to that of Ethernet. The most important differences between Gigabit
Ethernet and Fast Ethernet include the additional support of full duplex operation in the MAC
layer and the data rates.
VERY SHORT QUESTIONS
1. What is Ethernet?
2. What are ethernet specifications?
3. What is the full form of IEEE?
4. Which cables are used in gigabit Ethernet?
5. Give examples of fast Ethernet?
SHORT QUESTIONS
1. What is fast Ethernet?
2. What is gigabit Ethernet?
LONG QUESTIONS
1. Explain different ethernet specifications and standards?
5. Network Connectivity
Learning Objectives
To know about various network connectivity devices like hub, switches, bridges, router,
gateways, NICs
Network Connectivity devices
Hub
Hub is one of the basic icons of networking devices which works at physical layer and hence
connect networking devices physically together. Hubs are fundamentally used in networks that
use twisted pair cabling to connect devices. They are designed to transmit the packets to the
other appended devices without altering any of the transmitted packets received. They act as
pathways to direct electrical signals to travel along. They transmit the information regardless of
the fact if data packet is destined for the device connected or not.
Hub falls in two categories:
Active Hub: They are smarter than the passive hubs. They not only provide the path for the data
signals infact they regenerate, concentrate and strengthen the signals before sending them to their
destinations. Active hubs are also termed as ‘repeaters’.
Passive Hub: They are more like point contact for the wires to built in the physical network.
They have nothing to do with modifying the signals.
5.2.2. Switches
Switches are the linkage points of an Ethernet network. Just as in hub, devices in switches are
connected to them through twisted pair cabling. But the difference shows up in the manner both
the devices; hub and a switch treat the data they receive. Hubworks by sending the data to all the
ports on the device whereas a switch transfers it only to that port which is connected to the
destination device. A switch does so by having an in-built learning of the MAC address of the
devices connected to it.
Bridges
A bridge is a computer networking device that builds the connection with the other bridge
networks which use the same protocol. It works at the Data Link layer of the OSI Model and
connects the different networks together and develops communication between them. It connects
two local-area networks; two physical LANs into larger logical LAN or two segments of the
same LAN that use the same protocol.
Types of Bridges:
There are mainly three types in which bridges can be characterized:
Transparent Bridge: As the name signifies, it appears to be transparent for the other
devices on the network. The other devices are ignorant of its existence. It only blocks or
forwards the data as per the MAC address.
Source Route Bridge: It derives its name from the fact that the path which packet takes
through the network is implanted within the packet. It is mainly used in Token ring
networks.
Translational Bridge: The process of conversion takes place via Translational Bridge. It
converts the data format of one networking to another. For instance Token ring to
Ethernet and vice versa.
Routers
Routers are network layer devices and are particularly identified as Layer- 3 devices of the OSI
Model. They process logical addressing information in the Network header of a packet such as
IP Addresses. Router is used to create larger complex networks by complex traffic routing. It has
the ability to connect dissimilar LANs on the same protocol. It also has the ability to limit the
flow of broadcasts. A router primarily comprises of a hardware device or a system of the
computer which has more than one network interface and routing software.
Gateways
Gateway is a device which is used to connect multiple networks and passes packets from one
packet to the other network. Acting as the ‘gateway’ between different networking systems or
computer programs, a gateway is a device which forms a link between them. It allows the
computer programs, either on the same computer or on different computers to share information
across the network through protocols. A router is also a gateway, since it interprets data from one
network protocol to another.
Others such as bridge converts the data into different forms between two networking systems.
Then a software application converts the data from one format into another. Gateway is a viable
tool to translate the data format, although the data itself remains unchanged. Gateway might be
installed in some other device to add its functionality into another.
Network card
Network cards also known as Network Interface Cards (NICs) are hardware devices that connect
a computer with the network. They are installed on the mother board. They are responsible for
developing a physical connection between the network and the computer. Computer data is
translated into electrical signals send to the network via Network Interface Cards.
They can also manage some important data-conversion function. These days network cards are
software configured unlike in olden days when drivers were needed to configure them. Even if
the NIC doesn’t come up with the software then the latest drivers or the associated software can
be downloaded from the internet as well.
VERY SHORT QUESTIONS
1. Name some connectivity devices?
2. What is the full form of NICs?
3. What are the types of types of hub?
4. What are the types of bridges?
5. Draw the diagram showing bridge connectivity?
SHORT QUESTIONS
1. What is hub?
2. What is router?
3. What is bridge?
4. What is the difference between bridge and hub?
5. What are gateways?
6. What are network interface card?
LONG QUESTIONS
1. Explain various network connectivity devices?
6. NETWORK ADMINISTRATION
Learning Objectives
Know about network security principals
Discuss cryptography
Elaborate troubleshooting tools
Discuss DHCP Server
Network Security Principles
The Three Primary Goals of Network Security
For most of today’s corporate networks, the demands of e-commerce and customer contact
require connectivity between internal corporate networks and the outside world. From a security
standpoint, two basic assumptions about modern corporate networks are as follows:
Today’s corporate networks are large, interconnect with other networks, and run both
standards-based and proprietary protocols.
The devices and applications connecting to and using corporate networks are continually
increasing in complexity
Because almost all (if not all) corporate networks require network security, consider the three
primary goals of network security:
Confidentiality
Integrity
Availability
Confidentiality
Data confidentiality implies keeping data private. This privacy could entail physically or
logically restricting access to sensitive data or encrypting traffic traversing a network. A network
that provides confidentiality would do the following, as a few examples:
Use network security mechanisms (for example, firewalls and access control lists [ACL]) to
prevent unauthorized access to network resources.
Require appropriate credentials (for example, usernames and passwords) to access specific
network resources.
Encrypt traffic such that an attacker could not decipher any traffic he captured from the
network.
Integrity
Data integrity ensures that data has not been modified in transit. Also, a data integrity solution
might perform origin authentication to verify that traffic is originating from the source that
should be sending it.
Examples of integrity violations include
Modifying the appearance of a corporate website
Intercepting and altering an e-commerce transaction
Modifying financial records that are stored electronically
Availability
The availability of data is a measure of the data’s accessibility. For example, if a server were
down only five minutes per year, it would have an availability of 99.999 percent (that is, “five
nines” of availability).
Here are a couple of examples of how an attacker could attempt to compromise the availability
of a network:
He could send improperly formatted data to a networked device, resulting in an unhandled
exception error.
He could flood a network system with an excessive amount of traffic or requests. This would
consume the system’s processing resources and prevent the system from responding to many
legitimate requests. This type of attack is called a denial-of-service (DoS) attack.
Cryptography
Cryptography involves creating written or generated codes that allow information to be kept
secret. Cryptography converts data into a format that is unreadable for an unauthorized user,
allowing it to be transmitted without unauthorized entities decoding it back into a readable
format, thus compromising the data.
Information security uses cryptography on several levels. The information cannot be read
without a key to decrypt it. The information maintains its integrity during transit and while being
stored. Cryptography also aids in nonrepudiation. This means that the sender and the delivery of
a message can be verified.
Cryptography is also known as cryptology.
Cryptography is classified into symmetric cryptography, asymmetric cryptography and hashing.
Below are the description of these types.
Symmetric key cryptography –
It involves usage of one secret key along with encryption and decryption algorithms which
help in securing the contents of the message. The strength of symmetric key cryptography
depends upon the number of key bits. It is relatively faster than asymmetric key
cryptography. There arises a key distribution problem as the key has to be transferred from
the sender to receiver through a secure channel.
Asymmetric key cryptography –
It is also known as public key cryptography because it involves usage of a public key
along with secret key. It solves the problem of key distribution as both parties uses
different keys for encryption/decryption. It is not feasible to use for decrypting bulk
messages as it is very slow compared to symmetric key cryptography.
Hashing –
It involves taking the plain-text and converting it to a hash value of fixed size by a hash
function. This process ensures integrity of the message as the hash value on both, sender\’s
and receiver\’s side should match if the message is unaltered.
Troubleshooting Tools
Ping:
The most commonly used network tool is the ping utility. This utility is used to provide a basic
connectivity test between the requesting host and a destination host. This is done by using the
Internet Control Message Protocol (ICMP) which has the ability to send an echo packet to a
destination host and a mechanism to listen for a response from this host. Simply stated, if the
requesting host receives a response from the destination host, this host is reachable. This utility is
commonly used to provide a basic picture of where a specific networking problem may exist. For
example, if an Internet connection is down at an office, the ping utility can be used to figure out
whether the problem exists within the office or within the network of the Internet provider.
Tracert/traceroute
Typically, once the ping utility has been used to determine basic connectivity, the
tracert/traceroute utility can used to determine more specific information about the path to the
destination host including the route the packet takes and the response time of these intermediate
hosts. Figure below shows an example of the tracert utility being used to find the path from a
host inside an office to www.google.com. The tracert utility and traceroute utilities perform the
same function but operate on different operating systems, Tracert for Windows machines and
traceroute for Linux/*nix based machines.
Ipconfig/ifconfig
One of the most important things that must be completed when troubleshooting a networking
issue is to find out the specific IP configuration of the variously affected hosts. Sometimes this
information is already known when addressing is configured statically, but when a dynamic
addressing method is used, the IP address of each host can potentially change often. The utilities
that can be used to find out this IP configuration information include the ipconfig utility on
Windows machines and the ifconfig utility on Linux/*nix based machines.
Netstat
Often, one of the things that are required to be figured out is the current state of the active
network connections on a host. This is very important information to find for a variety of
reasons. For example, when verifying the status of a listening port on a host or to check and see
what remote hosts are connected to a local host on a specific port. It is also possible to use the
netstat utility to determine which services on a host that is associated with specific active ports.
Figure below shows an example of the netstat utility being used to display the currently active
ports on a Linux machine.
Wireshark
Wireshark is a network or protocol analyzer (also known as a network sniffer) available for free
at the Wireshark website. It is used to analyze the structure of different network protocols and
has the ability to demonstrate encapsulation. The analyzer operates on Unix, Linux and
Microsoft Windows operating systems, and employs the GTK+ widget toolkit and pcap for
packet capturing. Wireshark and other terminal-based free software versions like Tshark are
released under the GNU General Public License.
Wireshark shares many characteristics with tcpdump. The difference is that it supports a
graphical user interface (GUI) and has information filtering features. In addition, Wireshark
permits the user to see all the traffic being passed over the network.
Features of Wireshark include:
Data is analyzed either from the wire over the network connection or from data files that
have already captured data packets.
Supports live data reading and analysis for a wide range of networks (including Ethernet,
IEEE 802.11, point-to-point Protocol (PPP) and loopback).
With the help of GUI or other versions, users can browse captured data networks.
For programmatically editing and converting the captured files to the editcap application,
users can use command line switches.
Display filters are used to filter and organize the data display.
New protocols can be scrutinized by creating plug-ins.
Captured traffic can also trace Voice over Internet (VoIP) calls over the network.
Nmap
Nmap, short for Network Mapper, is a free, open-source tool for vulnerability scanning and
network discovery. Network administrators use Nmap to identify what devices are running on
their systems, discovering hosts that are available and the services they offer, finding open ports
and detecting security risks.
Nmap can be used to monitor single hosts as well as vast networks that encompass hundreds of
thousands of devices and multitudes of subnets.
Though Nmap has evolved over the years and is extremely flexible, at heart it's a port-scan tool,
gathering information by sending raw packets to system ports. It listens for responses and
determines whether ports are open, closed or filtered in some way by, for example, a firewall.
Other terms used for port scanning include port discovery or enumeration.
TCPDUMP
tcpdump is a most powerful and widely used command-line packets sniffer or package analyzer
tool which is used to capture or filter TCP/IP packets that received or transferred over a network
on a specific interface. It is available under most of the Linux/Unix based operating systems.
DHCP Server
A DHCP Server is a network server that automatically provides and assigns IP addresses, default
gateways and other network parameters to client devices. It relies on the standard protocol
known as Dynamic Host Configuration Protocol or DHCP to respond to broadcast queries by
clients.
A DHCP server automatically sends the required network parameters for clients to properly
communicate on the network. Without it, the network administrator has to manually set up every
client that joins the network, which can be cumbersome, especially in large networks. DHCP
servers usually assign each client with a unique dynamic IP address, which changes when the
client’s lease for that IP address has expired.
VERY SHORT QUESTIONS
1. What do you mean by network security?
2. What are network security principles?
3. What is cryptography?
4. What is hashing?
5. What is the full form of DHCP?
6. What is cryptology?
7. What is symmetric key cryptography?
8. What is asymmetric key cryptography?
9. What is TCPDUMP?
SHORT QUESTIONS
1. What is ping command?
2. What is DHCP server?
3. What is Tracert/traceroute?
4. What is ipconfig command?
5. Mention about wireshark?
6. Discuss about Nmap?
LONG QUESTIONS
1. What is network security principles?
2. What is cryptography?
3. Explain various troubleshooting tools?
7. INTRODUCTION TO WIRELESS NETWORK
Learning Objectives
Know about wireless lan
Discuss architecture of wireless lan
Discuss wimax and lifi
Elaborate Bluetooth architecture
Discuss its applications
Introduction to wireless Lan-802.11
A wireless LAN (WLAN or WiFi) is a data transmission system designed to provide location-
independent network access between computing devices by using radio waves rather than a
cable infrastructure
In the corporate enterprise, wireless LANs are usually implemented as the final link between
the existing wired network and a group of client computers, giving these users wireless access
to the full resources and services of the corporate network across a building or campus setting.
The widespread acceptance of WLANs depends on industry standardization to ensure product
compatibility and reliability among the various manufacturers.
The 802.11 specification [IEEE Std 802.11 (ISO/IEC 8802-11: 1999)] as a standard for
wireless LANS was ratified by the Institute of Electrical and Electronics Engineers (IEEE) in
the year 1997. This version of 802.11 provides for 1 Mbps and 2 Mbps data rates and a set of
fundamental signaling methods and other services. Like all IEEE 802 standards, the 802.11
standards focus on the bottom two levels the ISO model, the physical layer and link layer (see
figure below). Any LAN application, network operating system, protocol, including TCP/IP
and Novell NetWare, will run on an 802.11-compliant WLAN as easily as they run over
Ethernet.
IEEE 802.11 Architecture
Each computer, mobile, portable or fixed, is referred to as a station in 802.11 [Wireless Local
Area Networks].
The difference between a portable and mobile station is that a portable station moves from
point to point but is only used at a fixed point. Mobile stations access the LAN during
movement.
When two or more stations come together to communicate with each other, they form a Basic
Service Set (BSS). The minimum BSS consists of two stations. 802.11 LANs use the BSS as
the standard building block.
A BSS that stands alone and is not connected to a base is called an Independent Basic Service
Set (IBSS) or is referred to as an Ad-Hoc Network. An ad-hoc network is a network where
stations communicate only peer to peer. There is no base and no one gives permission to talk.
Mostly these networks are spontaneous and can be set up rapidly. Ad-Hoc or IBSS networks
are characteristically limited both temporally and spatially.
When BSS's are interconnected the network becomes one with infrastructure. 802.11
infrastructure has several elements. Two or more BSS's are interconnected using a Distribution
System or DS. This concept of DS increases network coverage. Each BSS becomes a
component of an extended, larger network. Entry to the DS is accomplished with the use of
Access Points (AP). An access point is a station, thus addressable. So, data moves between the
BSS and the DS with the help of these access points.
Creating large and complex networks using BSS's and DS's leads us to the next level of
hierarchy, the Extended Service Set or ESS. The beauty of the ESS is the entire network looks
like an independent basic service set to the Logical Link Control layer (LLC). This means that
stations within the ESS can communicate or even move between BSS′s transparently to the
LLC.
One of the requirements of IEEE 802.11 is that it can be used with existing wired networks.
802.11 solved this challenge with the use of a Portal. A portal is the logical integration
between wired LANs and 802.11. It also can serve as the access point to the DS. All data
going to an 802.11 LAN from an 802.X LAN must pass through a portal. It thus functions as
bridge between wired and wireless.
The implementation of the DS is not specified by 802.11. Therefore, a distribution system may
be created from existing or new technologies. A point-to-point bridge connecting LANs in two
separate buildings could become a DS.
While the implementation for the DS is not specified, 802.11 does specify the services, which
the DS must support. Services are divided into two sections
1. Station Services (SS)
2. Distribution System Services (DSS).
There are five services provided by the DSS
1. Association
2. Reassociation
3. Disassociation
4. Distribution
5. Integration
Wimax
WiMAX is one of the hottest broadband wireless technologies around today. WiMAX systems
are expected to deliver broadband access services to residential and enterprise customers in an
economical way.
Loosely, WiMax is a standardized wireless version of Ethernet intended primarily as an
alternative to wire technologies (such as Cable Modems, DSL and T1/E1 links) to provide
broadband access to customer premises.
More strictly, WiMAX is an industry trade organization formed by leading communications,
component, and equipment companies to promote and certify compatibility and interoperability
of broadband wireless access equipment that conforms to the IEEE 802.16 and ETSI
HIPERMAN standards.
WiMAX would operate similar to WiFi, but at higher speeds over greater distances and for a
greater number of users. WiMAX has the ability to provide service even in areas that are
difficult for wired infrastructure to reach and the ability to overcome the physical limitations of
traditional wired infrastructure.
WiMAX was formed in April 2001, in anticipation of the publication of the original 10-66 GHz
IEEE 802.16 specifications. WiMAX is to 802.16 as the WiFi Alliance is to 802.11.
Lifi
LiFi is a wireless optical networking technology that uses light-emitting diodes (LEDs) for data
transmission.
LiFi is designed to use LED light bulbs similar to those currently in use in many energy-
conscious homes and offices. However, LiFi bulbs are outfitted with a chip that modulates the
light imperceptibly for optical data transmission. LiFi data is transmitted by the LED bulbs and
received by photoreceptors.
LiFi's early developmental models were capable of 150 megabits-per-second (Mbps). Some
commercial kits enabling that speed have been released. In the lab, with stronger LEDs and
different technology, researchers have enabled 10 gigabits-per-second (Gbps), which is faster
than 802.11ad.
Benefits of LiFi:
Higher speeds than Wi-Fi.
10000 times the frequency spectrum of radio.
More secure because data cannot be intercepted without a clear line of sight.
Prevents piggybacking.
Eliminates neighboring network interference.
Unimpeded by radio interference.
Does not create interference in sensitive electronics, making it better for use in environments
like hospitals and aircraft.
7.3 Bluetooth
7.3.1Bluetooth Architecture
Bluetooth communication occurs between a master radio and a slave radio. Bluetooth radios are
symmetric in that the same device may operate as a master and also the slave. Each radio has a
48-bit unique device address (BD_ADDR) that is fixed.
Two or more radio devices together form ad-hoc networks called piconets. All units within a
piconet share the same channel. Each piconet has one master device and one or more slaves.
There may be up to seven active slaves at a time within a piconet. Thus, each active device
within a piconet is identifiable by a 3-bit active device address. Inactive slaves in unconnected
modes may continue to reside within the piconet.
A master is the only one that may initiate a Bluetooth communication link. However, once a link
is estBablished, the slave may request a master/slave switch to become the master. Slaves are not
allowed to talk to each other directly. All communication occurs within the slave and the master.
Slaves within a piconet must also synchronize their internal clocks and frequency hops with that
of the master. Each piconet uses a different frequency hopping sequence. Radio devices used
Time Division Multiplexing (TDM). A master device in a piconet transmits on even numbered
slots and the slaves may transmit on odd numbered slots.
Multiple piconets with overlapping coverage areas form a scatternet. Each piconet may have
only one master, but slaves may participate in different piconets on a time-division multiplex
basis. A device may be a master in one piconet and a slave in another or a slave in more than one
piconet.
Bluetooth Applications
Allows a transfer of images (or) word documents (or) applications (or) audio and video files
between devices without the help of cables.
Can be used for remote sales technology allowing wireless access to vending machines and
other commercial enterprises.
Provides inter accessibility of PDAs, palmtops and desktops for file and data exchanges.
It can be used to setup a personal area network (PAN) or a wireless personal area network
(WPAN).
VERY SHORT QUESTIONS
1. what is the full form of PAN?
2. What is the full form of WPAN?
3. Which technology us used in lifi?
4. What is the full form of TDM?
5. What is the full form of WLAN?
6. What does ESS and BSS stand for?
7. What does IEEE stand for?
8. What is the IEEE specification for WLAN?
SHORT QUESTIONS
1. Discuss about WLAN in brief?
2. What is Wimax?
3. What is lifi and what are its benefits?
4. What are the applications of Bluetooth?
5. What is piconet?
LONG QUESTIONS
1. Discuss about WLAN and its architecture in detail?
2. Mention about Bluetooth architecture?
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