What is Unicast, Anycast, Multicast and Boadcast??

Depending on the packet transmission or communication process we say which kind of communication it is. Usually three main cast we say generally Unicast, Multicast and Broadcast. Rarely we use to hear term called anycast. Total we can say four types as per the packet transmission, they are.

1. Unicast
2. Anycast
3. Multicast
4. Boradcast

What is Unicast ?

Unicast is the term used when a packet communication is between a particular one source to one particular destination. It is basically One-One communication. Unicast uses IP delivery methods like TCP and UDP, which are session based protocols.

Where Unicast can be used?

Unicast will be used in our regular applications like HTTP, SMTP and TELNET, these applications uses TCP/IP protocol and they are one to one communications and they are session based also.

What is Anycast ?

Anycast is delivering or transmitting a packet to one interface of a set of receivers. It is similar to multicast but we don't send to all destination users. This will be used in IPv6, In this the packet will be transmitted to nearest network node from that it will be sending to other destinations.

Where Anycast can be used?

Anycast method will be used in applications like DNS and Cloud. When we type URL in browser it will be sending request to Slave server which is located near by, this is kind of unicast, sending a packet to nearest located server. The main advantage is whenever nearest server / nearest DNS fails it will not drop the request, if we remove the server from network it will be sending to next nearest server.

 

What is Multicast ?

Multicast is transmitting or sending a packet or information to a group of selected users. In multicast we can send same packet to more than one user, it is not like anycast. In unicast way it will be sending information to all destinations.

Where Multicast can be used?

Multicast can be used in television video streaming services, where same packet will transmitted to many users at a same time. In this security of the packet also taken into consideration.

What is Broadcast ?

Broadcast is when we transmit one packet to all the users in network. In this just sender transmit the packet and it travels through full topology and all users will be receiving the message. 

Where Broadcast can be used?

Broadcast can be used in the network when administrator want to communicate all the users in network or wanted to send same packet information to all the members of network.

** All the images were taken from "Google" and "Wikipedia".

Written By:
SANDY -- (Jarvishelp Member)

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What is a Browser? How Does it fetches Web Pages?

When we open google chrome and type www.google.com, we are able to see a web page. How is browser getting and displaying that page.  To know that, first let us know what is a browser.


What is a Browser?

1. A Browser is a software application(process) running on your computer.
2. It is used to fetch Information Resource(web pages) from Web Servers.
3. It will send a request to Web server for Information Resource and Web server will respond back with Information Resource.

How will Browser identify Information Resources to be fetched?

1. Information Resource is identified by a URI.
2. URI - Uniform Resource Identifier.
3. Eg: http://www.google.com/

How will Browser sends request to Web Server?

1. Browser will form a URI and sends request using HTTP Protocol.
2. HTTP functions as a request-response protocol.
3. HTTP client initiates a request by establishing a TCP connection to a particular port on a server(80 or 8080)
4. Web Server listening on port 80 will process the request, creates response and sends it back using same tcp connection.

What are the types of requests a Browser can trigger using HTTP?

HTTP Provides different request methods to trigger various requests to server.

GET - Requests using GET method should only retrieve data and have no other effect.
HEAD - Request using HEAD method retrieves only metadata information(like response state, response content type etc) without response content.  This is useful incase to test the meta data information of response with exact response content.
POST - A POST request is used to send data to the server, for example, customer information, file upload, etc. using HTML forms.
PUT - Replaces all current representations of the target resource with the uploaded content.
DELETE -  Deletes the resource on the server.
CONNECT - Establishes a tunnel to the server identified by the URI.
OPTIONS - It is used to find out the HTTP Methods supported by web server.
TRACE - Trace method is used to send back the contents of http request in http response. it is mainly used for debugging while development.


How will Browser Interpret the response from Web Server?

1. The response sent by the Web Server should be interpreted by the browser.
2. Before that, browser should be able to understand if the request it has sent is processed by web server properly.
3. The request status will be sent to browser by web server in the response using HTTP Status Codes.
4. Various Status codes will give information about the request status. To know more about HTTP STATUS CODES Please go to - Http Status codes.

Written By:
VENKY -- (Jarvishelp Member)
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Why WDM is required in Optical Networks?

What is Optical Networking?

Optical networking is a means of communication that uses signals encoded onto light to transmit information among various nodes of a telecommunications network. They operate from the limited range of a local-area network (LAN) or over a wide-area network (WAN).

What is WDM ??

WDM means Wavelength Division Multiplexing, this technology is widely used in optical fiber communication. By using WDM technology we can multiplex many optical carrier signals on to single optical fiber cable. This is bi-directional link.

How multiple optical carrier signals can be transmitted over a single fiber?

In Optical communication, it uses optical fiber cable as medium to communicate between two nodes. The data transmission between them is in the form of light, this light is generated by a particular type of lasers which are capable to transmit a light signal for long distance. This laser generates signal with particular wavelength, physically different wavelengths will be having different colors. In WDM each request will be transmitted with different wavelength because of this multiple requests can be transmitted over a single optical fiber. Two different wavelength signal never get mixed if they have proper band gap.

Why we have to use WDM ?

In optical networks, the medium optical fiber has bandwidth in terms of Tera Bytes, with this bandwidth we no need to go for WDM or multiplexing all the data can be transmitted over a single carrier along with this loss, distortion and cost can be reduced. But practically we can not use this, even though optical fiber has capability to transmit the data in terms of Tera Bytes per second but none of the existing electronics devices can accept this data rate, data will be lost if you transmit higher rate than it support, existing devices support in terms of Mbps. This limitation is called as "Electronic Bottle Neck", because of this reason we can not transmit all data over single carrier. If we transmit each data over separate link then cost for communication will be huge, in order to reduce the cost, to utilize the bandwidth of fiber properly Wavelength Division Multiplexing is used.

Maximum how many signals can be transmitted over a single fiber using WDM?

That completely depends on the band what user selected to transmit. Every band has limited number of channels, here channels means the number of wavelengths can be transmitted without interference. Each band is divided in to channels with a proper band gap between them.  

Written By:
SANDY -- (Jarvishelp Member)

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