An Adaptive Reliable Multipath Centralized RWA Algorithm for All-Optical WDM Networks

 The abstract of this paper is :

Balancing the load among multiple paths leads to the degradation in the all-optical WDM network. It is always desirable to deliver the entire load on a single optimal path depending upon the current network-wide load status. For this case, multiple light paths need to be maintained to provide the choice of selecting the best light path, based on the changing traffic load conditions, This paper presents the design and analysis of an adaptive reliable multipath centralized routing algorithm (ARMCR) with two central management systems (CMS-1 and CMS-2) which considers load heuristic for selecting the optimal and backup paths. Initially in this algorithm when a request comes to a source it sends the information to CMS-1 for allocating the optimal primary and backup paths for the received request, depending on the number of available free wavelengths. With the assigned primary path, source starts clearing the request meanwhile CMS-2 keeps track of the changes in the available free wavelengths and failure of all the paths. In the assigned primary path if the available free wavelength number comes below the threshold number ‗N‘ and at the same time if any other path is available with more number of free wavelengths, then CMS-2 assigns this path as primary path and very next more number available free wavelengths path is assigned as backup path. The advantage of this algorithm is that it reduces the set up time by using two CMS which share the work and also if one fails the other will take over the entire process. As opposed to the reactive protocols, our proposed protocol is proactive in the sense that it avoids the chances of blocking. Furthermore, the approach is self-regulating, it automatically adapts to the traffic load variation across the network. By simulation results, we showed that our proposed protocol has low set up time and blocking.

Full paper you can read and download from the following link, 

http://www.ciitresearch.org/dl/index.php/nce/article/view/NCE042011008

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IP Address Classes

The communication between two devices over a particular medium wired/wireless is called networking. To communicate in a wired network every system must and should have a valid IP address. IP address in an identification tag or key for a system. IP address looks like 192.168.10.21. Based on these IP address, they can be classified into five types; Class A, Class B,Class C, Class D and Class E. 

Each IP address can be divided into four octettes, IP address can be written as Octet1.Octet2.Octet3.Octet4. Here Octet 1 represents network class type. 

 Class A Network:

Class-A address are used for networks with very higher number of systems. Range for Octet-1 value of Class-A network is 1-126. Default subnet mask for Class-A type is 255.0.0.0. Number of possible network ID's are 126.

127 is excluded from Class-A, Ranges 127.X.X.X are reserved for the loopback or localhost, example 127.0.0.1 is the common local host address. 

 Class B Network:

Class-B addresses are used for medium-sized to large-sized networks. Range for Octet-1 value of Class-B network is 128-191. Default subnet mask for Class-B type is 255.255.0.0. Number of possible network ID's are 16,384.

 Class C Network:

Class-C address are used for smaller networks, like university campus. Range for Octet-1 value of Class-C network is 192-223. Default subnet mask for Class-A type is 255.255.255.0. Number of possible network ID's are 20,97,152.

 Class D Network:

Class-D network addresses are reserved for multicast purpose. Range for Octet-1 value of Class-D network is 224-239.

 Class E Network:

Class-E network addresses are reserved for Future purpose. Range for Octet-1 value of Class-E network is 240-255.

Range 255.255.255.255 broadcasts to all hosts on the local network.

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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".

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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.

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Why RWA is a challenge in all-optical WDM networks?

How the data requests will be served in Optical - WDM Networks ?

In Optical WDM Networks, when ever a data request arrives at a Node, first it validates the request, during this process all the headers in the request will be validated, after validating request it identifies the source node and destination node addresses. Once it get the Source-Destination pair it will assign a route and wavelength to transmit. This assignment is valid till all the data is transmitted. 

What is RWA?

RWA -- "Routing and Wavelength Assignment", As described above once a node identifies source and destination pair the process of assigning a route and wavelength is called as RWA Protocol. There are many RWA protocols exists and depends on the requirement and network type the protocol will be choose or implemented.

What are the main network types in WDM Networks?

 

 Mainly there two types of Network architecture but these days hybrid implementation also being used so we can say three types. They are Distributed Networks, Centralized Networks and Hybrid or Global Networks.

In Distributed Networks each and every node in network will have the information of entire network structure, in future if there is any new node added or removed that information need to be updated at all the nodes in network. Along with this each node maintain a minimum information of paths between source and destination pair. It also keep track of wavelengths assigned.

In  Centralized Networks all the network information will be stored at Central Management System and every request will be processed or served by CMS. In this case if there is any modification in network then it is enough if we update only at CMS. But major dis advantage is when there is failure in CMS the entire network will be down. In order to avoid this in the design people will maintain the backup CMS also. 

In hybrid or Global Networks, they will use the combination of both Distributed and Centralized Network types, means small small groups will in Centralized manner and all these CMS will be a part or act as nodes of a Distribute Network. The major advantage of this is if there is any failure in network a particular group or very few number of devices will be affected.

Why RWA is challenge?

There are many routing and wavelength assignment techniques are available and depends on the technique the cost, delay, resource utilization and QoS are effected. If we use standard technique like shortest path algorithm then there is more chance of congestion in the network, If use the Wavelength Continuity Constraint WCC algorithm then cost of request can be reduced but the number of calls or requests served will be limited. If we choose a path based on blocking of calls then there is a chance of choosing a long path though which latency increases. Like this many other techniques are available for RWA so based on our requirement we need to select which algorithm is suitable like shortest path, Less blocking path. Wavelength also need to be choosed based on requirement like least used, most used, WCC or some other. So ultimately RWA plays an important role in network Quality of Service. The major contributors are the number of nodes on path, number of wavelength conversions required and number of wavelengths are utilized on links.

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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.  

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HTML Status codes & Response Error details

In our daily life, when ever we click on web page most of the time we see some content on our browser but some times it tries to load for a long time and finally throws an error saying some XXX error, because of this it couldn't load your content. Status codes represent whether your request is accepted or rejected or some other state.

Basically these status codes and error codes can be differentiated as 5 types, based on their start of status. Like 1,2,3,4,5...

HTTP Status Code Information:

• 1XX : Informational
• 2XX : Success
• 3XX : Redirection
• 4XX : Client Error
• 5XX : Server Error

Starts with 1:

Status starts with 1 means your request received and it is under process.

100: Continuing your process
101: User requested to change protocol and server saying Okay.
102: Server says that it received request and so far there is no response, this prevents client from timeout.

Starts with 2:

Status starts with 2 represents a success acknowledgement, user request accepted and processed successfully.

200: Get request response OK
201: New resource Created
202: User request Accepted
203: User request processed successfully and user will receive requested information from some other non authorized source.
204: Request processed successfully but there is no content available.
205: Request processed successfully but not returning any content, user need to reset.
206: Partial Content response usually used in downloads.
207: Multiple Status Responses.The body consist of XML.
208: Response for this request is  already reported.

Starts with 3:

Status starts with 3 represents a redirection of your request. It can be request re-direction or URL re-direction.

300: More than 1 selection options available for this request.
301: This request moved permanently all the future requests will be redirected.
302: Your request re-directed temporarily. Few web applications deny the temporary redirections because of security reasons.
303: When request response available with other URL, the POST request need to have separate GET and this need to be added.
304: No modification in content no need to re-transmit.
305: The requested resource is only available through a proxy.
306: Subsequent requests should use the specified proxy, User needs to switch to proxy.
307: Redirect URL and similar to 302.
308: Permanent redirect similar to 301, but do not allow HTTP method to change.

Starts with 4:

Status starts with 4 represents a error message, this can be temporary error also.

400: Bad request, format of the request is not expected
401: Unauthorized request.
402: This will be used by few websites to know the multiple requests from same IP, like Gmail enter wrong password for few times from same IP and it will ask you to enter captcha to confirm that you are not a robot.
403: The request was a valid request, but the server is refusing to respond to it.
404: FAMOUS ERROR::: URL NOT FOUND, some issue with URL, that page may deleted.
405: This particular request method is not allowed.
406: This particular request is not acceptable.
407: Client must authenticate with proxy.
408: Request Timed out.
409: Some conflict in request.
410: The resource request is no longer available, like 404 only.
411: Length of your request should be part your request.
412: Precondition failed.
413: Request is too large to process.
414: Request URL is too long.
415: This particular media type is not supported by HTTP protocol.
416: Some issue with the requested range.
417: Not met the expected request header.
418: I am a tea pot.
419: Authentication Timeout.
420: Method Failure.
420: Enhance Your Calm.
421: Misdirected Request.
422: Un processable Entity.
423: Access Locked .
424: Failed Dependency.
426: Upgradation Required.
428: Precondition Required .
429: Too Many Requests.
431: Request Header Fields Too Large.
440: Login Timeout (Microsoft)
444: No Response (Nginx).
449: Retry With (Microsoft)
450: Blocked by Windows Parental Controls (Microsoft)
451: Unavailable because of court rules or legal issues.
494: Request Header Too Large (Nginx).
495: Cert Error (Nginx).

Starts with 5:

Status starts with 5 represents a server error message.

500: Internal Server Error

502: Bad Gateway.

503: Service Unavailable

504: Gateway Timeout

505: HTTP Version Not Supported

506: Variant Also Negotiates

507: Insufficient Storage

508: Loop Detected

509: Bandwidth Limit Exceeded

511: Network Authentication Required

598: Network read timeout error

599: Network connect timeout error

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First Post - www.jarvishelp.in

We are happy to launch our official website, http://www.jarvishelp.in . This web site mainly for Computer Science and Electronics & Communication Engineering Students, Both B.Tech and M.Tech. We help engineering students in their graduation projects. The projects available on website are completely free. There is no login or payment credentials are required. If you are having some issues in your current working projects and related stuff is not mentioned in website still you are welcome to write a mail to us, mail@jarvishelp.in . We have free-lancers who are expertize in their fields you can take guidance from them.

Thanks & Regards,
JarvisHelp Team,
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