Monitoring

Monitoring

Watch who all uses your internet connections and check what they are browsing through your network connectivity.
https://www.youtube.com/watch?v=U4N0Em_Pz-g

https://www.youtube.com/watch?v=JQO7v3eaSw0

Interview Tips

http://www.indiabix.com/technical/networking/

Its not a crack to pass the interview its just a study material to recognize your level of knowledge in networking.

Go through it and update your knowledge.

Your mind should always hungry to get updates.

OSI MODEL

OSI REFERENCE MODEL

OSI (Open Systems Interconnection) is reference model for how applications can communicate over a network. A reference model is a conceptual framework for understanding relationships. The purpose of the OSI reference model is to guide vendors and developers so the digital communication products and software programs they create will interoperate, and to facilitate clear comparisons among communications tools. Most vendors involved in telecommunications make an attempt to describe their products and services in relation to the OSI model. And although useful for guiding discussion and evaluation, OSI is rarely actually implemented, as few network products or standard tools keep all related functions together in well-defined layers as related to the model. The TCP/IP protocols, which define the Internet, do not map cleanly to the OSI model.

Easy Way To Remember Layers

Please Do Not Take Sales Person Advice

IP Address || Logical Address

• Private IP
• Public IP
• APIPA

NAT(network address translation)

Port Address

0-65535

well known---->     0  -1023

Registered  ----> 1024-49151

Dynamic    ---->  49152-65535

Static and Dynamic

• Static address
• Dynamic address

In IP address network portion is considered as 1's and host portion is considered as 0's.

5 classes

Class A----->  0  -126

Class B----->128-191

Class C----->192-223

Class D----->224-239

Class E----->240-255(Research Purposes)

Dynamic address

DHCP

*Provide dynamic ip address in lease.

APIPA(automatic private ip address)

169.254

DHCP works (DORA)

Address

IP ADDRESSMAC ADDRESSPORT ADDRESS

• IP ADDRESS

An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication.An IP address serves two principal functions: host or network interface identification and location addressing. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there.

The designers of the Internet Protocol defined an IP address as a 32-bit number and this system, known as Internet Protocol Version 4 (IPv4), is still in use today. However, because of the growth of the Internet and the predicted depletion of available addresses, a new version of IP (IPv6), using 128 bits for the address, was developed in 1995.IPv6 was standardized as in 1998,And its deployment has been ongoing since the mid-2000s.

• MAC ADDRESS

A media access control address (MAC address), also called physical address, is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used as a network address for most IEEE 802 network technologies, including Ethernet and WiFi. Logically, MAC addresses are used in the media access control protocol sublayer of the OSI reference model.

MAC addresses are most often assigned by the manufacturer of a network interface controller (NIC) and are stored in its hardware, such as the card's read-only memory or some other firmware mechanism. If assigned by the manufacturer, a MAC address usually encodes the manufacturer's registered identification number and may be referred to as the burned-in address (BIA). It may also be known as an Ethernet hardware address (EHA), hardware address or physical address. This can be contrasted to a programmed address, where the host device issues commands to the NIC to use an arbitrary address.

• PORT ADDRESS

In computer networking, a port is an endpoint of communication in an operating system. While the term is also used for hardware devices, in software it is a logical construct that identifies a specific process or a type of service.

A port is always associated with an IP address of a host and the protocol type of the communication, and thus completes the destination or origination address of a communications session. A port is identified for each address and protocol by a 16-bit number, commonly known as the port number.

Specific port numbers are often used to identify specific services. Of the thousands of enumerated ports, 1024 well-known port numbers are reserved by convention to identify specific service types on a host. The protocols that primarily use ports are the transport layer protocols, such as the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) of the Internet protocol suite.

In the client–server model of application architecture, the ports that network clients connect to for service initiation provide a multiplexing service. After initial communication binds to the well-known port number, this port is freed by switching each instance of service requests to a dedicated, connection-specific port number, so that additional clients can be serviced.

• https://en.wikipedia.org/wiki/IP_address
• https://en.wikipedia.org/wiki/MAC_address
• https://en.wikipedia.org/wiki/Port_(computer_networking)

From the view of a network engineer this is nothing...

There is lot of things to learn in address.

Please refer to Wiki.

Modem

A modem (modulator-demodulator) is a device that modulates one or more carrier wave signals to encode digital information for transmission and demodulates signals to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used with any means of transmitting analog signals, from light emitting diodes to radio. A common type of modem is one that turns the digital data of a computer into modulated electrical signal for transmission over telephone lines and demodulated by another modem at the receiver side to recover the digital data.

History

News wire services in the 1920s, used multiplex devices that satisfied the definition of a modem. However the modem function was incidental to the multiplexing function, so they are not commonly included in the history of modems. Modems grew out of the need to connect teleprinters over ordinary phone lines instead of the more expensive leased lines which had previously been used for current loop–based teleprinters and automated telegraphs.

Mass-produced modems in the United States began as part of the SAGE air-defense system in 1958 (the year the word modem was first used^[1]), connecting terminals at various airbases, radar sites, and command-and-control centers to the SAGE director centers scattered around the U.S. and Canada. SAGE modems were described by AT&T's Bell Labs as conforming to their newly published Bell 101 dataset standard. While they ran on dedicated telephone lines, the devices at each end were no different from commercial acoustically coupled Bell 101, 110 baud modems.

The 201A and 201B Data-Phones were synchronous modems using two-bit-per-baud phase-shift keying (PSK). The 201A operated half-duplex at 2,000 bit/s over normal phone lines, while the 201B provided full duplex 2,400 bit/s service on four-wire leased lines, the send and receive channels each running on their own set of two wires.

The famous Bell 103A dataset standard was also introduced by AT&T in 1962. It provided full-duplex service at 300 bit/s over normal phone lines. Frequency-shift keying was used, with the call originator transmitting at 1,070 or 1,270 Hz and the answering modem transmitting at 2,025 or 2,225 Hz. The readily available 103A2 gave an important boost to the use of remote low-speed terminals such as the Teletype Model 33 ASR and KSR, and the IBM 2741. AT&T reduced modem costs by introducing the originate-only 113D and the answer-only 113B/C modems.

Connection	Modulation	Bitrate [kbit/s]	Year released
110 baud Bell 101 modem	FSK	0.1	1958
300 baud (Bell 103 or V.21)	FSK	0.3	1962
1200 modem (1200 baud) (Bell 202)	FSK	1.2
1200 modem (600 baud) (Bell 212A or V.22)	QPSK	1.2	1980[9][10]
2400 modem (600 baud) (V.22bis)	QAM	2.4	1984[9]
2400 modem (1200 baud) (V.26bis)	PSK	2.4
4800 modem (1600 baud) (V.27ter)	PSK	4.8	[11]
9600 modem (2400 baud) (V.32)	QAM	9.6	1984[9]
14.4k modem (2400 baud) (V.32bis)	trellis	14.4	1991[9]
28.8k modem (3200 baud) (V.34)	trellis	28.8	1994[9]
33.6k modem (3429 baud) (V.34)	trellis	33.6	1996[12]
56k modem (8000/3429 baud) (V.90)	digital	56.0/33.6	1998[9]
56k modem (8000/8000 baud) (V.92)	digital	56.0/48.0	2000[9]
Bonding modem (two 56k modems) (V.92)[13]		112.0/96.0
Hardware compression (variable) (V.90/V.42bis)		56.0–220.0
Hardware compression (variable) (V.92/V.44)		56.0–320.0
Server-side web compression (variable) (Netscape ISP)		100.0–1,000.0