ravi namboori modem presentation
DESCRIPTION
Ravi Namboori, a Cisco evangelist and an IT entrepreneur, is based out of Bay Area, California. Ravi Namboori holds nine Cisco certifications, in addition to one each from Microsoft and Novell in networking. Ravi Namboori earned his MBA from The F.W. Olin Graduate School of Business at Babson College. A router (including a wireless router) is a specialized networking device connected to two or more networks running software that allows the router to move data from one network to another. Router functions in an Internet protocol based network operate at the network layer (OSI Model's layer 3). The primary function of a router is to connect networks together and keep certain kinds of broadcast traffic under control. There are several companies that make routers: Cisco, Linksys, Juniper, Netgear, Nortel (Bay Networks), Redback, Lucent, 3Com, HP, Dlink and Belkin just to name a few. Several networking exams (CCNA, CCNP, JNCIA, JNCIE) will test your ability to identify different types of network equipment. This network certification tutorial on routers focuses on identifying network routers, and explaining the functions of routers provide. This tutorial is not specific to any vendor's technology. How Do Routers Work? Let's use a home wireless router connected to a cable provider's internet network in a very simplified example. The router powers on and loads it's OS from flash The router loads the configuration file last saved to NVRAM and sets up the network interfaces and routing protocols it will run. The router adds the network address and subnet for each interface to it's routing table along with the name of the interface itself. The router has a simple static default route to send all non-local data out the network port connected to the cable company. When the router receives a web page request from your computer, it checks the destination IP address against its routing table. The bits forming the destination IP address in the IP packet are used as a hash key to point to the correct route, which in turn points to the correct network interface that the packet should be forwarded out of. The router transmits the packet out the correct interface, to the next router, which repeats the process until the packet reaches the destination. The process is mostly the same for any router. CAVEAT: A small complication here. For home cable and wifi routers, the router is also acting as a "proxy" so the router does one thing that is NOT normal for a router out on the Internet somwehere: it changes the source IP address in the IP packet to it's own address.TRANSCRIPT
ModemPresented by
Ravi Namboori
Index
Introduction to modem
Types of modem
Modem Functions
Modem purpose
Modem security
Introduction
A modem is an electronic device that transforms computer's digital information into analog carrier signals and vice versa. Computers use modems to interconnect with each other over a network. The word modem is derived from "modulator-demodulator" that defines the functions it performs. Modulation is the process of changing the form of the signal carrying the information. The demodulation process does the task of extracting information from the signals that are modulated.
Modems are generally classified by the amount of data they can send in a given unit of time, usually expressed in bits per second (bit/s or bps), or bytes per second (B/s). Modems can also be classified by their symbol rate, measured in baud. The baud unit denotes symbols per second, or the number of times per second the modem sends a new signal.
The following characteristics distinguish one modem from another:
Bps : How fast the modem can transmit and receive data. At slow rates, modems are measured in terms of baud rates. The slowest rate is 300 baud (about 25 cps). At higher speeds, modems are measured in terms of bits per second (bps). The fastest modems run at 57,600 bps, although they can achieve even higher rates by compressing the data. Obviously, the faster the transmission rate, the faster you can send and receive data.
Voice/data: Many modems support a switch to change between voice and data modes. In data mode, the modem acts like a regular modem. In voice mode, the modem acts like a regular telephone. Modems that support a voice/data switch have a built-in loudspeaker and microphone for voice communication.
Auto-answer: An auto-answer modem enables your computer to receive calls in your absence. This is only necessary if you are offering some type of computer service that people can call in to use.
Data compression: Some modems perform data compression, which enables them to send data at faster rates. However, the modem at the receiving end must be able to decompress the data using the same compression technique.
Flash memory : Some modems come with flash memory rather than conventional ROM, which means that the protocols can be easily updated if necessary.
Fax capability: Most modern modems are fax modems, which means that they can send and receive faxes.
Different types of Modem are as follows:
Types of modem
Internal Modem
External Modem
PC Card Modem
It is the device installed in the desktop or laptop computer to communicate over a network with other connected computers. These are cheaper than external modems as they do not require a power supply or a chassis. There are two types of internal modems: dial-up and Wi-Fi (wireless). Dial up works on the telephone cables and requires a network access phone number and log on credentials to make a connection and Wi-Fi modem comments to the network without filling these credentials.
Internal Modem:
A modem that resides in a self-contained box outside the computer system. Contrast with an internal modem, which resides on a printed circuit board inserted into the computer. External modems are the simplest type of the modem to install this kind of modem you didn’t open the computer. The telephone line plugs into a socket on the rear panel of the modem. As external modems have their own power supply you can turn off the modem quickly to break the connection. The examples of these modems are the DSL modems which are used in the broadband connections. External modems tend to be slightly more expensive than internal modems.
External Modem:
These modems, designed for portable computers, are the size of a credit card and fit into the PC Card slot on notebook and handheld computers. These modems are removed when the modem is not needed. Except for their size, PC Card modems are like a combination of external and internal modems. These devices are plugged directly into an external slot in the portable computer. So no cable is required other than the telephone line connection. The cards are powered by the computer, which is fine unless the computer is battery-operated. Running a PC Card modem while the portable computer is operating on battery power drastically decreases the life of your batteries.
PC Card Modem:
Functions of Modem Error correction
Flow control
Compressing the data
Thank You