Data Communication & Networking

 Data Components -

A data communication system has five components.

1.  Receiver 

2. Sender

3. Message 

4. Transmission media- Path by which message travels. Ex Twisted pair wires, Coaxial cable,fibre optic cable and radio waves

5. Protocol 

Protocol is set of rules used by computers to communicate with each other across network. 

Protocols can be classified as

Proprietary Protocol ( specific make)

Open source Protocol ( Any make).

Bandwidth- 

It is defined as amount of data that can be transmitted into a fixed amount of time.

Usually expressed in bps ( bits per  second)

Fundamental Characteristics of Data Communication 

1. Delivery- System must deliver data to correct destination 

2. Accuracy- System must deliver data accurately 

3. Timeliness- System must deliver data in a timely manner 

4. Jitter- Jitter refers to variation in packet arrival time. It is uneven delay in the delivery of audio and video packets,which results in degradation of the quality.Hence Jitter is to be minimized.

5. Data flow- Communication between two devices can be unidirectional,half duplex or full duplex.

Simplex- 

Only one of Two devices can transmit,the other can receive only. Key board and traditional monitor are examples of Simplex.  Keyboards can only  introduce digital input and monitor can accept output.

Simplex mode can use entire channel capacity to send data in one direction.

Half duplex- 

Both devices can transmit and receive but not at same time. Entire channel capacity is taken over by whichever of the two devices is transmitting at a time. Ex. Walkie Talkie

Full Duplex- 

Also called Duplex.  Both can transmit and receive simultaneously.Channel capacity is shared between two devices.

Ex. - Telephone network 

Data Transmission-

There are two types

Parallel and Series

In parallel mode multiple bits are sent with each clock tick. In serial mode ,1 bit is send with each clock tip.

Parallel- 

1) Fast Transfer Rates

2) Used for short Distance only

3) Multiple bits are sent.

Serial-

1) Slow transfer rate

2) Used for long distance  

3) Single bit is sent

Serial Communication has two sub classes 

1. Asynchronous                          2. Synchronus 

Asynchronous Transmission:-

We send One start bit at  Beginning and one or more stop bit at end of each byte.Suitable for slow speed.Does not contain error detection information,and is susceptible to errors.

Additional bits are required be sent.So this method is inefficient mean of sending large data.

Synchronous Transmission:-

No start or stop bits or gaps. We send bits one after another.Greater efficiency. User data is prefixed with a header field and suffixed with a tailor field which includes a checksum value.

Network:-

Network is a set of devices ( often referred as nodes) connected by communication link. A node can be a computer, printer or other device capable of sending and receiving data generated by other nodes of network.

Main advantage of Network is sharing of resources.  Resources can be hardware or software.

Categories of network-

1. LAN

2. WAN

3. Intranet and Internet 

LAN :-

A group of computers and network communities devices interconnected within a geographically limited area,such as building or campus.

Transfer data at high rate ( higher bandwidth)

Can be in single building or in multiple buildings in a campus area.

WAN :-

WAN is collection of many seperate networks.

They exist in unlimited geographical area.

Interconnect multiple LANs.

Linkup of LANs is often shown as cloud.

Transfer data at lower speeds ( lower bandwidth)

Intranet:-

Multiple PCs are connected to each other.

These PCs are not available to world outside the intranet. 

Each organization has its own Intranet network and members/employees of that organization can access the computers in the intranet.

Each computer in intranet is identified by an unique  IP Address.

Internet:-

Internet is network of networks.It is worldwide collection of multiple computer networks.

Speed is very fast.

Accessible to every user in world.

Similarities between Intranet and Internet 

Intranet uses internet protocols such as TCP/IP and FTP.

In intranet, own instant messengers can be used as similar to Yahoo messenger/gtalk over internet.

Difference between Intranet and Internet 

Internet is not safe as intranet. Intranet can be safely privatized as per need.

Security in internet is low,configured under 0 security level in firewall. Security in Intranet is high, configured under 100 security levels in  firewall.

Internet is regulated by Internet Architecture Board ( IAB).Intranet is regulated by an organization.

Topology 

A network in which terminals are interconnected with each other for inter communication within and outside the network is called as Topology.

1. Mesh topology 

2. Star topology 

3. Bus topology 

4. Ring topology 

Mesh topology -

In Mesh topology every device has a dedicated point to point connectivity to every other device. Each device must has (n-1) I/O ports.

Eg . If 5 computers are to be connected in Mesh Topology,  each computer must have 4 input/output ports.

Each link can carry its own data load.

It has privacy or secrecy. Fault identification is easy.

It's disadvantages are large no of cables and I/O ports.

Star topology -

Each device has a dedicated point, which links to central controller only.This controller is called HUB  . All the devices are connected through HUB only. 

Generally used in LAN only.

Easy to install and reconfigure.

Each device needs only one link.Hence it is less expensive.

If a link fails,only that link to be attended.

Easy to identify fault.

Bus topology -

Bus topology is multipoint 

One long cable acts as backbone to link all devices in a network.

Installation is easy.

Generally used in LAN network.

Disadvantages- Difficult in fault isolation and reconnection.  Difficult to add device in an existing system.A fault or break in bus cable stop all transmission.

Ring Topology :-

Each has a dedicated point to point connection only with two devices on either side of it.Data is passed along the ring in one direction, from device to device until it reaches its destination.Each device acts as repeater.

Generally used in LAN.

Easy to install and configure.

Unidirectional traffic and a break in the ring can disable entire network.

Standard Organisations :-

ISO ( International Organization for Standards)

Non Government Organization

Based in Geneva

Maintain standard for Quality assurance.

Most significant activities are its work on open System, which define Protocols.

ÌTUT ( International Telecommunication Unions)

Agency of United Nations

Sets standard for Modems and Switching network.

Co ordinates international communications and recommend standard interface.

ÀNSI ( American National Standard Institute)

Represents a number of US Standards organizations

Private Agency 

Sets up standard for FDDI and ASCEE.

OSI Model:-

Established in 1947,by ISO.

Purpose of OSI is to facilitate communication between different systems without requiring changes to the logic of the underlying hardware and software.

Seven layer framework that allows communication between all types of computer systems.

It is a theoretical model.Not a protocol,technology, program or software.

1) Physical Layer :-

It is responsible for transmission of digital data bits from physical layer of Sending device to physical layer of receiving device.

At physical layer,  data is transmitted using type of signaling supported by physical mediam : electric voltage,radio frequencies,or pulses of infrared or ordinary light.

Physical  layer provides the means to transmit the web page request to the default gateway.

Physical layer provides a physical mediam through which bits are transmitted.

2) Data link layer :-

After physical layer ,Data link layer

1) checks physical transmission error like CRC Checks.

2) Packages bits into data frames.This layer is responsible for moving frames from one node to next.

4) At data link layer, the web request is inserted inside a network request to the default gateway.

5) It is used for error free transfer of data frames.

Trqditional simple LAN and VLAN operate in Data link layer.

3) Network Layer :-

When data arrives at Network layer,source and destination addresses contained inside each frame are examined to determine if data has reached its final destination.

Formats data into packets delivered upto transport layer.

Network layer maintains logical addresses such as IP address for device on Network.

The network layer also manages mapping between logical address and physical address.

It is responsible for moving the packets from source to destination.

Router operates primarily on the network layer of OSI Model.

Eg - IP( internet protocol)

Data units in networking are called packets.

Functions of network layer

1) Logical addressing 

2) Path determination ( Finding the correct path)

3) Routing 

4) Transport Layer:-

It delivers data across network connections.

It helps in error control.TCP and UDP are used.

TCP is most common example.TCP connection breaks up the web page  into manageable chunks,levels them numbers so they can be reassembled in correct order and transport the pieces.

It provides reliable message delivery from process to process.

Process to process delivery of the entire message is the responsibility of the Transport layer.

Transport layer does

Segmentation 

Flow control 

Error control

5) Session Layer :-

It helps in setting and managing connections. It manages sequence and flow of events.

It is built to support multiple types of connections that can be created dynamically and run over individual networks.

Session layer keeps track of a file that are downloaded.

Session layer helps in session management. 

6) Presentation Layer :-

It handles syntax  processing of message such as format conversations ( like ASCII to EBCDIC ) and encryption/descryption needed to support the application layer above it.

Sender side data is encrypted and receiver side data is decrypted.

Conversation of data from one form to another is the job of Presentation layer.

SSL ( secured socket layer) protocol is used in this process 

7) Application Layer :-

It supplies network services to end user's applications. Network services are protocols that work with user's data. 

Application layer provides the service to user.Mail services are available to network users through the application layer.

Application layer provides file transfer,web surfing Emails etc.

Eg. - Web browser  such as Internet Explorer or Netscape,HTTP,FTP,Telnet

Data and Signal -

Both data and signal can be Analog and Digital.

Baseband Transmission-

Data is sent as digital signal through media as single channel that uses entire bandwidth of the media.

Bi directional 

Broadband Transmission-

Sent in the form of Analog signal,which flows as electromagnetic waves or optical waves.

Each transmission is assigned to a portion of bandwidth.

Hence multiple transmissions are possible at the same time.

Unidirectional 

Frequency division multiplexing is possible.

Transmission Impairment -

Signal at Beginning of the medium is not same at the end of medium.What is sent is not what is received.Three causes of Impairment are Attenuation,Distortion and noise.

Attenuation -

It means loss of energy in overcoming the resistence of the medium.To compensate this loss,amplifiers are uses to amplify the Signal.

Signal loses strength due to different propogation speeds of each frequency that makes up the Signal.

The decibel ( DB) measures

i) Relative strength of two signals at a point.

ii) Relative strength of one  signals at two points

dB = 10 log P2/P1

If this value is negative- Signal is attenuated.

If this value is positive- Signal is Amplified.

Distortion -

Distortion means that signal changes its form and shape.

Noise -

Signal to noise ratio (SNR)-

SNR =  Signal Power/ Average Noise Power

In decibel

SNR ( In db) = 10 log SNR

High SNR means signal  less corrupted by noise.

Nyquist Bit Rate( noiseless channel)

For a noiseless channel,  the nyquist Bit Rate is the theoretical maximum bit rate is

Bit rate = 2× bandwidth of channel × log L base 2.

L is the number of signal levels used to represent data

Shannon capacity ( noisy channel)

The theoretical maximum bit rate of a noisy channel 

   Bit rate = Bandwidth of channel × log (1 + SNR)

Baud Rate-

Baud rate refers to signal ( symbol) rate,how many signal changes are transmitted per second.

Goal of data communication is to increase the data rate while decreasing signal rate.

Increase data rate -- Increase the speed of transmission

Decrease the Signal rate ----- decreases bandwidth requirement.

Bit rate ---- No of bits per second 

Baud rate ---- No of signal elements per second.

(Bit per Second)BPS = Baud per second × the no of bits per Baud.

Digital to Analog conversion -

There are three types of D to A conversion techniques

1. Amplitude Shift Keying(ASK)

2. Frequency Shift Keying(FSK)

3.  Phase Shift Keying(FSK)

Analog to Analog conversion -

1. Amplitude Modulation 

2. Frequency Modulation 

3. Phase Modulation 

Transmission Media-

Two basic categories 

a. Un guided transmission media

Wireless communication,  transports electromagnetic waves without using a physical conductor.

Three types

Radio waves - used in wireless LANs

Microwave- used for Terrestrial and satellite communication 

Infrared waves - used for controlling devices like remote control

b. Guided transmission media

Open wire

Coaxial wire

Optical Fibre

Twisted pair

Open wire - not used in data communication.

Coaxial cable - 

Thick net ( RG -8 and RG - 11)

Thin net ( RG -58)

Optical Fibre Cables 

High speed alternative to Copper wire

Uses glass or plastic filaments to move data.

Provides greater bandwidth.

Twisted Pair Cables

LAN cables are generally called twisted pair.

Two types-

UTP - Unshielded Twisted pair - Indoor areas

STP - Shielded Twisted pair - Outdoors Areas

Error Detection & Correction-

Data can be corrupted during transmission. Some applications required that errors to be detected and corrected. 

Single bit Error-

Only one bit of data changes during transmission.

Burst Error- 

Two or more bits of data have changed during transmission

To detect errors we need to send Extra( redundant) bits with data.

Popular methods of Error detection methods are Parity checking,Block coding, CRC( Cyclic Redundancy Check) and Checksum.

Checksum uses ones complement arithmetic.

Simple Parity Check - 

Basic error detection technique used to identify single error in data transmission.

It adds an extra bit, called an Parity bit to the data to ensure that total no of 1s or 0s in the data meets a specific condition.

Even Parity  - Ensures that total no of 1s in data is even.

Odd Parity - Ensures that total no of 1s in data is odd.

The party bit is calculated based on type of Parity.  Parity bit may be 0 or 1.The data and Parity bit are transmitted together. 

The receiver checks the data and Parity bit.If the Parity condition is not met, an error is detected.

This method is used for just one redundant bit per data unit.

Cyclic Redundancy Check (CRC)-

CRC is robust error detection method to ensure data integrity during transmission. 

It uses polynomial division to generate checksum,which is appended to data. Receiver uses same polynomial to verify data's integrity.

LAN Protocols-

For data transmissions on LAN, protocols are used to form frames. Basically there are two types of protocols are used.

There are two types of protocols 

● Character Oriented protocols 

● Bit Oriented protocols 

For the purpose of sending data on link, there are two types of stations.

■ Primary Station( Issue Commands)

■ Secondary Station ( Responds to commands)

NIC ( Network interface Card)-

Computer hardware component that connects a computer to a network.

Located on motherboard.

It provides physical connection between networking cable and computer internal bus. NIC comes in three basic varieties,8 bit,16 bit and 32 bit. 

Two types of NICs.

Wired and wireless. 

MAC - Media Access Control

MC is unique identifier assigned to a network interface card.

■  The IEEE 802.3 MAC is Physically located in the ROM of the Network Interface Card.

■ Link between Data link layer and physical layer.

Most popular IEEE 802.3 MAC Protocol is Ethernet Protocol.

Ethernet -

It is a protocol in TCP/IP stack,describing how networked device can format data for transmission to other network segments and how to put tht data on Network connection.

 IEEE 802.3  is standard of Eathernet.

Eathernet LAN can support data rates  1 to 100 Mbps.

Cables used for Eathernet for LAN are generally called twisted pair cables. There are of two types UTP and STP.

UTP for indoor areas 

STP for outdoor and special areas.

PoE ( Power over Eathernet)

It allows a single cable to provide data connection and electrical power to the devices.

This technology is applicable for network products such as Accesss points, Routers, Modems ,switches,etc.

Power over Eathernet is defined by Standard IEEE 802.3 af/ 15.4 W.

IEEE 802.3 is standard of Eathernet.

IEEE 802.11 is standard of wifi or wireless LAN.

IEEE 802.15 is standard of Bluetooth.

Networking Devices-

(HUBs, Switches, Routers  & Gateways)

Repeater -

It is an electronics device that receives a signal and retransmits it.Its job is to regenerate the signal over the same network before signal becomes two weak or corrupted.

Hubs -

It is a multiport repeater.

Connects multiple wires coming from different branches.

HUBs come in three types.

Passive 

Active

Switching.

HUBs are used in star Technology.

Bridge-

It connects two LANs working on same network protocols so that they can exchange data.

Switches-

Switch is multiport bridge. The switch can perform error checking before forwarding data . It forwards good packets selectively to correct port.

Computer networking device that connects network segments.

Switches may operate at one or more OSI layers,including physical, data link,network or transport.

A device that operates simultaneously at more than of these layers is called multilayer switch.

Switches provide many facilities not offered by old devices such as HUBS and Bridges.

Router -

Router is networking device that forwards data packets between computer networks.

Gateway - 

It acts as an entrance between two different networks. Gateway device is used to connect two different networks.

Gateway in organization is the computer that routes traffic from a work stn to outside network that is sending web pages.

It is passage to connect two networks together that may work upon differernt networking models.

VLAN ( Virtual LAN)-

VLAN has same attributes as a physical LAN,but it allows for end stations to grouped together even if they they are not located on same network switch.

Network configuration can be done through software instead of physically relocating them.

VLAN 0 and  VLAN 1 -

VLAN 0 and VLAN 1 are two different networks on Eathernet network.

VLAN 0 is often used for  management and traffic.Access to VLAN 0 is usually restricted for security reasons.VLAN ID  is 0.

VLAN 1 is standard VLAN with a VLAN ID 1. Default VLAN for new connections.

WAN- 

WAN can be intranet or internet otherwise called Private or public network.

Majority of applications use TCP( transmission control protocol) and Internet Protocol ( IP) together.

WAN is established with the help of Routers & long distance communication links and suitable for Network layer protocol ( Ex . IP)

Data units are packets.

Packets are routed through networks with help of IP routing,static and Dynamic.

IEEE standard of WAN is 802.11

TCP-

Responsible for end to end delivery of segments. Segments are terms that is used to describe the data that is transmitted and received at transport layer of OSI model where TCP resides.

User Datagram protocol ( UDP)-

1) Unreliable and contactless.Uses random path in network channel.

2) Operate at  transport layer of the OSI model for providing internet service.

3) No acknowledgement is received.

Major uses of this protocol are DNS and TFTP.

Session Initiation Protocol ( SIP) -

1) A protocol used for initiating ,maintaining and terminating communication session that include voice,video and message.

2) A set of rules that allows users

to make and manage voice,video and messaging calls over the internet.

3) Used in internet telephony,mobile calling over LTE ( VoLTE).

4) Protocol of Application layer.

Internet Protocol (IP)

A piece of software that operates at Network Layer and provides the following.

Unique Addresses

Connectionless communication 

Routing 

Data Transmission on IP

There are three types of data transmission on Internet Protocol.

1) Unicast - Communication from single host to another single host.

2) Broadcast - Single device transmitting a message to all other devices in a given address range.

3) Multicast- Single device to communicate with specific sets of hosts.

IP Addresses-

Computer gets its address one of Two wayes. Either the computer administrator enters it into computer manually(Static  IP address) or it is learned by computer dynamically using a protocol called DHCP ( Dynamic IP).

DHCP( Dynamic host Configuration Protocol)

Network management Protocol used to automate the process of assigning IP address and other network configuration details on a network.

Information provided by DHCP are-

IP address

Subnet mask

Default gateway 

DNS service. 

 

IP address are of two types

IPv4 ( IP version 4) and IPv6 ( IP Version 6)

IPv4 Address 

An IP Address is a number used to identify the logical connection of computer to a physical network.

IPv4 is 32 bit binary address ( Composed by four,8 bit binary numbers).

IP address is represented as four decimal numbers ( between 0 and 255) seperated by dots.It is called dotted decimal notation.Eg. 199.232.66.20

These addresses are always unique and software configured.

It is easy to move hosts from one network to another simply by changing the IP address or the Network Mask. This process is called Renumbering.

Network and Host Portion of an IP Address-

Left most portion of address- Which network the machine (Host) belongs to.

Right most portion - Address of Host itself. 

Eg IP address- 199.233.66.20 then 

Network Address- 199.233.61

Host Address - 20

All the computers on same local network - Same network number in their address. Host Portion will be different and unique for each host on the network.

Classes of IP Address -

IP Addresses are divided into classes : A,B,C,D and E.

Classful-

First addressing scheme developed. Wasted a lot of address space so new scheme was developed called CLASSLESS.

Source Address- IP address of HOST sent on DATAGRAM.

Destination Address- IP address of host

Mask - 

Mask is a value that is stored in the configuration of a computer along with IP address. 

Mask gives the computer a simple way to figure out whether the IP address of another computer is on same local network or on a different local network.

 Subnet Mask-

A subnet mask is a 32 bit number used in networking to divide an IP address into network and its host Portion.It is primarily used to determine which part of an IP Address represents the network and which part represents the devices( host) within the network.

Written in dotted decimal notation,similar to an IP Address.(e.g 255.255.255.0)

Each octet ( 8 bits) can range from 0 to 255.

Subnet mask ANDed with IP address gives the Network address.

E.g.

IP Address: 192.168.1.10

Subnet mask: 255.255.255.0 (Default)

Network Address: 192.168.1.0

Classes of IP Addresses -

The entire IP address is between-  0.0.0.0 to 255.255.255.255

The different classes of IP Addresses are Class A, Class B,Class C,Class D & Class E. Example

Class A - 0.0.0.0 to 127.255.255.255

Class B - 128.0.0.0 to 191.255.255.255

Class C - 192.0.0.0 to 223.255.255.255

Class D - 224.0.0.0 to 239.255.255.255

Class E - 224.0.0.0 to 255.255.255.255

Class A B and C used for Host purpose.

Class A - 

No of networks 256, No of hosts 16777214

Class B - 

No of networks 65536, No of hosts 65536

Class C -

No of networks 16777216, No of hosts 256

Subnetting- 

Subnetting is process used in networking to divide a large network into smaller manageable sub networks.

This is done to improve the efficiency of IP address allocation,enhance network performance and improve security. 

Subnet mask determines how the IP address is divided into Network and host Portion.

For Eg. in IPv4,the subnet mask 255.255.255.0 means the first 24 bits are for the network ,  and remaining 8 bits are for hosts.

Purpose of Subnetting-

Reduces waste of IP address by allocating only necessary number of IPs for each subnet.

Limits the size of Broadcast domains,reducing network congestion.

Super netting-

Process of combining multiple smaller networks into a larger network.

Reverse of Subnetting.

IP Routing-

IP Routing is the process of moving data packets from one network to another based on their destination addresses.

It involves determining best path for data to travel across interconnected networks using Routers.

Static Routing -

Routers are manually configured by the network administrator.

Used in small or simple networks where topology does not change frequently.

Dynamic Routing-

Routers automatically discover and maintain routes in network using Routing Protocols.

It adapts changes in Network Topology,such as link failures or new routes without manual intervention.

Routing Protocols are of two types. Intra domain and Inter domain.

Intra domain(Interior Gateway Protocol) has two types.

1) Distance Vector, e.g. RIP, IGRP - calculate the best path based on number of hops.

2) Link State e.g. OSPF,IS-IS - Use complex algorithm to calculate the shortest path to a destination.

RIP - Routing information Protocol 

1) RIP is Intra domain Distance Vector Protocol based on hop count matrix.

2) The maximum hop count allowed for RIP is 15.

IGRP - Interior Gateway Routing Protocol 

1) IRGP Protocol is Cisco proprietary protocol.

2) Distance Vector Routing protocol.

3) It supports max 100 hops. 100 Routers can be connected.

4) Products data security and data reliability.

5)  Classful Routing protocol 

6) consumes more bandwidth than EIGRP.

7) Supports only IP Routing.

OSPF - Open Shortest Path First

1) Routing Protocol

2) Standard protocol- works with any company router.

3) Link State Protocol 

4) Unlimited hop count ( Unlimited Routers can be connected)

5) Classless routing protocol

6) Used in UTS Network 

IS-IS - Intermediate System to Intermediate System

Another link state protocol that operates similarly to OSPF.

EIGRP - Enhanced Interior Gateway Routing protocol 

1) Hybrid Routing protocol 

2) It has both characteristics,distance Vector and link state

3) Cisco proprietary protocol

4) Successor of IGRP

5) Classless Routing protocol 

Exterior ( Inter domain)-

BGP ( Border gateway Protocol)

Router-

Router is specialized computer connected to more than one network. Router receive data packets from one network, read their destination IP address and forward them to appropriate next address.

Uses Routing Protocols like RIP,OSPF or BGP is used.

Router operates at layer 3 ( Network layer) of OSI model.

Gateway -

Gateway is a device that acts as a gate between two different networks.

It is used to connect networks that use different network protocols ensuring that data can flow smoothly between them.

Gateway operates at layer 4 of OSI Model.

Network Address Translation-

A technique used in networking to modify the source or destination IP Address of packets as they pass through a router or firewall.

Very important aspect of firewall security.It conserves the number of public addresses used within an organization. 

MPLS( Multi Protocol Label Switching)-

It is a a networking technology used to improve the speed,efficiency and management of network traffic.

Key features-

Label Switching: Instead of solely relying on IP address for Routing, MPLS assigns short path labels to packets,enabling faster and most efficient forwarding.

In MPLS data packets are assigned labels.

Designs to work in large complex networks.

Works with various network protocols, Eg. IPv4,IPv6, Eathernet. 

Commonly used to create VPN for secure communication.

MPLS header - 32 bits

Comparison of MPLS versus IP-

MPLS uses labels for forwarding packets,bypassing traditional Routing while IP Routing uses IP Addresses for packet forwarding.

Speed in MPLS is faster than IP Routing. 

MPLS is ideal for large scale network which needs high performance while IP Routing is simpler and more cost effective.

VPN ( Virtual Private Network)-

It extends a private network across public network and enable users to send and receive data across shared or public network.

VPN allows users to securely access a private network and share data remotely through public network.

VPN protects your data on line.

It uses two security protocols.

PPTP - point to point tunneling protocol

L2TP

Modem -

A hardware device that enables computers or other devices to connect to the internet by converting digital data into signals that can be transmitted over telephone lines,cable systems etc.

LAN extender-

A device or technology used to expand LAN beyond its Normal physical or geographical limitations. It enables users to connect to LAN over greater distances than would be possible with standard Eathernet or wireless connections.

Use fibre optics,DSL ( Digital Subscriber line) or wireless connections.

Media Converter-

Media converter is a networking device used to connect two different type of media or transmission technologies.such as copper ( Ethernet) and fibre optics within a LAN.

WLAN -( Wireless Local Area Network)

Uses wireless communication to connect devices within a limited area such as Home,office or school.

Devices connect using Radio waves instead of Physical cables.

Wi fi ( Wireless fidelity) belongs to WLAN.

Access points are specially configured nodes on WLAN.  They act as central transmission and receiver of WLAN radio signals.Access points support Wi Fi wireless communication standards.

IEEE standard of WLAN is 802.11

Bandwidth available in 802.11a WLAN is 54 Mbps.

Access protocol for WLAN is CSMA/CA.

RF band used in WLAN is 2.4 GHz.

WAP ( Wireless Access Point)-

Hardware device that allows Wi Fi devices to  to a wired device.

Acts as bridge between wired  and wireless devices,providing connectivity

IPv6 Address-

Latest version of Internet Protocol. 

Developed by Internet Engineering Task Force (IETF)

Most recent version of Internet Protocol.

IPv6 addresse is represented by 8 groups of 16 bit value.(128 bit addresses).

IPv6 addresses are represented by Colon Hex notation.

Leading zeros in the Quartet are omitted to simplify the representation of the address.

Consucative sections of zeros are omitted using Double colon (::) 

Provides better support for Mobile devices.

Uses hexadecimal numbers in address format while IPv4 uses Decimal numbers.

IPv6 Address Classification 

IPv6 Address are classified as Unicast Addressing,  Anycast addressing and Multicast addressing.

Dual Stack Deployment -

Strategy used to enable the co existence of IPv4 and IPv6. It allows devices and applications to communicate using both IPv4 and IPv6 protocols,ensuring a smooth transition to IPv6 while maintaining compatability  with IPv4 systems.

Tunneling Approaches -

Techniques used to facilitate communication between IPv4 and IPv6 networks during transition to IPv6.

Manual Tunnneling -

Network administrator manually configure tunnel between specific IPv4 and IPv6 end points.

Automatic Tunnneling-

Tunnels are dynamically created as needed without requiring manual configuration of each end point.

QOS( Quality of Service)-

Ability of network to provide better service to selected traffic over various technologies.It is essential for applications requiring consistent and reliable performance, such as video streaming,  VoIP, online gaming etc.

Bluetooth-

Bluetooth is open wireless protocol designed for short range data exchange between devices.

Operates at 2.4 GHz ISM

Typical range - 10 m

Quick sharing of files between devices.

Data transfer speed is slower compare to Wi Fi.

Radio over IP- 

Radio over internet protocol is a method of transmitting and receiving radio communications via Internet Protocol.

RoIP is similar to  VoIP. It uses standard VoIP techniques to transfer analog audio.

This provides a method of linking two or more radios.

Connectors & Interfaces 

EIA RS 232- C- Standard 

This standard is used to connect serial devices like Modem to Personal Computer.

25 pin connector

V.35 Interface -

Standard for Synchronus data transmission.

Commonly used in WAN.

High speed Synchronus data transmission.

34 pin rectangular connector.

Speed is upto 2 Mbps.

Used in past. Have been phased out in favor of Eathernet based solution due to advancement in technology.

E1 Interface-

Digital transmission format for transmitting voice and data.

Data rate of E1 is 2.048 Mbps.

Transmission medium is Coaxial, twisted pair or optical fibre.

BNC connector is used for Coaxial cable

RJ 45 connctor  for twisted pair. 

Being replaced by Broadband and IP based technology.

Data Communication Equipment ( DCE) 

Device or hardware that establish a connection between Data source and its destination.

Fitted with 25 pin female connector. 

Examples are Modems,Network switches and Multiplexers

Data Communication Equipment ( DTE) 

Device or equipment that serves as source or destination data in a communication system.

Originate or terminate data communication.

Interfaces with DCE to transmit or receive data over a network.

Example- Computer, printer etc

RJ 45 Connector-

Standard type of physical connector commonly used  for Eathernet networking.

8 pin connector designed to connect computers,Modems,Routers and other networking devices Via Ethernet cables.

HDMI ( High Definition Multimedia Interface) -

A standard for transmitting uncompressed video and audio data between devices.

Widely used for connecting audio visual equipment such as TV, monitor etc.

Supports High definition video resolutions

Combines audio and video transmission in a single cable.

19 pin connector is used.

HDMI cable is composed of four Shielded Twisted pair.

Syntax - 

Syntax refers to the structure or format of the data,meaning the order in which they are presented.

Header and trailer - 

Header and trailer added to data during network communications.

Header-

Header is added to the beginning of data by sending device.It contains control information such as-

Source Address 

Destination Address 

Protocol Information

Sequence number 

Error checking 

As data packets move from uppar to lower layers, Headers are added.

Trailer-

Trailer is added at end of the data by sending device.It contains following information 

Error checking code ( e.g. CRC)

Purpose of Header and trailer 

Ensure proper delivery

Data integrity 

Flow control and segmentation 

HDLC - High level data link Control

Dial up Modems are Asynchronous.

DSLAM- Digital subscriber line access multiplexer 

ADSL - Asymmetric digital subscriber line 

Link Local Address- 

It is a type of IP address that is automatically assigned to network interface for communication within single link or segment. It is used for local communication when there is no external router or DHCP server.

MAC address -

An identifier that every network device uses to identify itself on computer.No two devices will have same MAC address.

6 byte ( 48 bits)  number or 12 digit hexadecimal number.

First 6 hexadecimal will represent manufacturer,the next 6 digit hexadecimal represents NIC.

It is called physical or hardware address.

Used when two network devices communicate with each other.

IP address can be changed but MAC address can not be changed , it is decided by manufacturer.

IP address is used to find final destination while MAC address is used at each step on its way to final destination.

Switches have one MAC Address for each port.Switch controls flow of datadata using MAC address. 

Collision Domain-

It is a part of network where data packets can collide with each other.Collission can slow down network.Collission network is bound by Switches.

HUBs are Half duplex.Switch are better than hub.

Broadcast domain-

It is bound by Switches.

VTP - VLAN trunking protocol.

TCP Three way Handshake - there are three steps of Handshake 

Step 1. Client sends SYN( Synchronus) packets to the Server. This packet includes a sequence number that the Client chooses.

Step 2. Server sends SYN- ACK ( Synchronize- Acknowledge) packet  to the Client.This packets includes the server's sequence number and acknowledge client's sequence number.

Step 3. The client sends an ACK ( Acknowledge) packet  to Server.

Data Transmission on Internet Protocol-

Unicast -

Data Transmission from single host to another single host. There is one device transmitting a message to another receiver.

Broadcast-

Single device transmitting a message to all other devices in a given data range.

Broadcast represents one to many valid Eathernet transmissions.

Multicast-

Single device communicates with specific sets of hosts,not defined by any standard IP address and mask combination.

The speaker 's message is not broadcasted everywhere.

In TCP/IP max data packets length is 65535 bytes.

Collision Domain-

It is a network segment where data packets can collide with each other when being sent over a shared communication medium.

Collision can occur when data simultaneously on the same network segments.

Each port on a switch is a separate collision Domain,reducing network congestion.

Collision Domain is restricted by Switches.

ICMP ( Internet Control Message Protocol)

Network layer protocol used for sending error messages and operational information about network communications.

IP Routing-

Routing is the process of moving data from one network to another by forwarding packets via gateway.

With IP based networks,the Routing decision is based on the destination address in the IP packet header.

Routing is of two types

Static and Dynamic 

Static Routing -

Manual method used to set up Routing.

Administrator enters routes into the router using configuration commands.

This method is predictable and simple to set up.

Easy to manage small networks.

Does not scale well in large networks.

Dynamic Routing ( Using protocol)

Interior ( Intra Domain)

OSPF

IS -IS

IGRP

EIGRP 

Exterior ( Inter domain)

BGP

Default Administrative Distance (DAD) -

Value assigned to Routing protocol to determine the trustworthiness of a route.

Lower value indicates higher performance.

Default Administrative Distance of Static Route is 1

Routing Protocol-

Routing protocol is a set of rules used by by Routers to determine best path for forwarding data packets in a network.

Types of Routing Protocols 

1. Distance Vector Routing protocol 

Routes are selected based on hop count I.e. number of route between source and distance 

2. Link State Routing protocol 

Uses short path algorithm 

3. Hybrid Routing protocol 

Combine both distance Vector and link state

4. Path Vector Protocols

Used in large scale network like internet.

Primary Multipltiplexing equipment

1) Terminal MUX

It shall have one 2048 kbps port each for trans and receive side and shall be used as end multiplexer.

2) Primary drop/ insert mux -

This shall have two 2048 kbps ports ( P1 and P2) each for send and receive side.

3) Drop/ insert mux with Conference facility-

Similar to drop insert MUX above with additional facility of at least 3 party conference between any combination of time slots of either P1 port or P2 port and voice interface.

Port number -

Port number is a address used to identify Specific TCP/IP application.

Multiplexing-

Multiplexing is a method by which multiple analog or digital signals are combined into one signal over a shared medium. 

It is of two types 

Analog and Digital 

FDM is Analog while TDM is digital multiplexing. 

Two types of mediums

Wired medium ( Guided Medium)

Wireless medium ( EM waves)

Wired Medium 

Three types.

Twisted pair - Slow (electrical Signal)

Coaxial cable- Fast (electrical Signal)

Fibre optic- Very fast ( light signal)

Eathernet not a network protocol