Explain the concept of inter-networking?

- The practice in which one computer network is connected with the other networks is called inter-networking. 

- The networks are connected with the help of gateways. 

- These gateways are used since they offer a common method for routing the data packets across the networks.

- The resulting system in which a number of networks are connected is called the inter-network or more commonly as the internet. 

- The terms “inter” and “networking” combine together to form the term “internet working”.  

- Internet is the best and the most popular example of the inter networking. 

- Internet has formed as a result of many networks connected with the help of numerous technologies. 

- Many types of hardware technologies underlie the internet. 

- The internet protocol suite (IP suite) is the inter networking protocol standard responsible for unifying the diverse networks. 

- This protocol is more commonly known as the TCP/ IP. 

- Two computer local area networks (LANs) connected to one another by means of a router form the smallest internet but not the inter network. 

- Inter networking is not formed by simply connecting two LANs together via a hub or a switch. 

- This is called expansion of the original local area network. 

- Inter networking was started as a means for connecting the disparate networking technologies. 

- Eventually, it gained widespread popularity because of the development needs of connecting many local area networks together through some kind of WAN (wide area network). 

- “Catenet” was the original term that was used for the inter network. 

- Inter network includes many types of other networks such as the PAN or personal area network. 

- Gateways were the network elements that were originally used for connecting various networks in predecessor of the internet called the ARPANET. 

- Today, these connecting devices are more commonly known as the internet routers. 

- There is a type of interconnection between the various networks at the link layer of the networking model. 

- This layer is particularly known as the hardware centric layer and it lies below the TCP/ IP logical interfaces level. 

Two devices are mainly used in establishing this interconnection:

Ø  Network switches and

Ø  Network bridges

- Even now this cannot be called as inter networking rather, the system is just a single and large sub-network. 

- Further, for traversing these devices no inter networking protocol is required. 

- However, it is possible to convert a single network in to an inter network. 

- This can be done by making various segments out of the network and also making logical divisions of the segment traffic using the routers. 

- The internet protocol suite has been particularly designed for providing a packet service. 

- This packet service offered by the IPS is quite unreliable. 

- The elements that maintain a network state and are intermediate in the network are avoided by the architecture. 

- The focus of the architecture is more on the end points of the active communication session.

- For a reliable transfer of the data, a proper transport layer protocol must be used by the applications. 

- One such protocol is the TCP (transmission control protocol) and it is capable of providing a reliable stream for communication. 

- Sometimes a simpler protocol such as the UDP (user datagram protocol) might be used by the applications. 

- The applications using this protocol carry out only those tasks for which reliable data delivery is not required or for which realtime is required. 

Examples of such tasks include voice chat or watching a video online etc. Inter networking uses two architectural models namely:

1. OSI or the open system interconnection model: This model comes with 7 layer architecture that covers the hardware and the software interface.
2. TCP/ IP model: The architecture of this model is somewhat loosely defined when compared with the OSI model. 

What is optimality principle?

A network consists of nodes which require communicating with other on various grounds. This communication is established via communication channels that exist between them. The communication involves data transfers. In a network a node may or may not have a link with every other node in the network. 

Applications that require communicating over a network include:

1. Telecommunication network applications such as POTS/ PSTN, local area networks (LANs), internet, mobile phone networks and so on.

2. Distributed system applications

3. Parallel system applications

- As we mentioned above, each and every node might not be linked with every other nodes since for doing so a lot of wires and cables are required which will the whole network more complicated. 

- Therefore, we bring in the concept of the intermediate nodes. 

- The data transmitted by the source node is forwarded to the destination by these intermediate nodes. 

Now the problem that arises is which path or route will be the best to use i.e., the path with the least cost. 

- This is determined using the routing process. 

- The best path thus obtained is called the optimal route. 

- Today, we have a number of algorithms available for determining the optimal path. 

These algorithms have been classified in to two major types:

1. Non – adaptive or static algorithms
2. Adaptive or dynamic algorithms

Concept of Optimality Principle

- This is the principle followed while determining the optimal router between the two routes. 

The general statement of the principle of optimality is stated below:

“An optimal policy has the property that whatever the initial state and initial decision are, the remaining decision must constitute an optimal policy with regard to the state resulting from the first decision.”

- This means if P is an optimal state that results in another state say Q, and then the portion of the original from that state to this state i.e., from P to Q must be optimum. 

- This only means the optimality of the part of the optimal policy is preserved. - The initial state and the final state are the most important parts of the optimum. 

- Consider an example, suppose we have problem with 3 inputs and 26 states. - Here, the state is associated with the optimum and the total cost is associated with the optimum policy.

- If brute force method is used for 3 inputs and 100 stages we have the total number of computations as 3¹⁰⁰. 

- That means for solving this problem, a super computer is required.

- Therefore, the approach used for solving this problem is a parallel processing approach. 

- Here, for the each state the least step is computed and stored during the programming. 

- This reduces the number of possibilities and hence reducing the amount of computation.

- The problems become complex if the initial and the final states are undefined. - It is necessary for the problem to follow the principle of optimality in order to use the dynamic programming. 

- This implies that whatever the state may be, the decisions that follow must be optimal in regard with the state obtained from the previous decision. 

- This property is found in combinatorial problems but since they use a lot of time and memory, this method is inefficient for them. 

- These problems can be solved efficiently if some sort of best first search and pruning technique is applied.

- In regard to the routing in networks, it follows from the optimality principle if a router B lies between router A and C which lie on an optimal path, then the path between the router B and C is also an optimal path and lies on the same path. 

- Sink tree is formed as a result of all optimal routes which is the ultimate goal of all the routing algorithms.

What are the goals and properties of a routing algorithm?

Routing requires the use of routing algorithms for the construction of the routing tables.

A number of routing algorithms are today available with us such as:

1.   Distance vector algorithm (bellman ford algorithm)

2.   Link state algorithm

3.   Optimized link state routing algorithm (OLSR)

- In a number of web applications, there are a number of nodes which require communicating with each other via communication channels. 

- Few examples of such applications are telecommunication networks (such as POTS/ PSTN, internet, mobile phone networks, and local area networks), distributed applications, multiprocessor computers etc. 

- All nodes cannot be connected to each other since doing so will require many high powered transceivers, wires and cables. 

- Therefore, the implementation is such that the transmissions of nodes are forwarded by the other nodes till the data or info reaches its correct destination. 

- Thus, routing is the process of determining where the packets have to be forwarded and doing so.

Properties of Routing Algorithm
- The packets must reach their destination if there are no factors preventing this such as congestion.

- The transmission of data should be quick.

- There should be high efficiency in the data transfer.

- All the computations involved must not be long. They should be as easy and quick as possible.

- The routing algorithm must be capable of adapting to the two factors i.e., changing load and changes in topology (this includes the channels that are new and the deleted ones.)

- All the different users must be treated fairly by the routing algorithm.

The second and the third properties can be achieved using fastest or the shortest route algorithms. 

- Graphical representation of the network is a crucial part of the routing process.

- Each network node is represented by a vertex in the graph whereas an edge represents a connection or a link between the two nodes. 

- The cost of each link is represented as the weight of the edge in the graph. 

- There are 3 typical weight functions as mentioned below:

1.   Minimum hops: The weight of all the edges in the graph is same.

2.  Shortest path: The weight of all the edges is a constant non – negative value.

3.   Minimum delay: The weight of every edge depends up on the traffic on its link and is a non – negative value.

However in real networks, the weights are always positive.

Goals of Routing Algorithms

- The goal of these routing algorithms is to find the shortest path based up on some specified relationships that if used will result in the maximum routing efficiency. 

- Another point is to use as minimum information as possible.

- Goal of the routing algorithm is also to keep the routing tables update with all alternative paths so that if one fails, the other one can be used.

- The channel or the path that fails is removed from the table. 

- The routing algorithms need to be stable in order to provide meaningful results but at the same time is quite difficult to detect the stable state of an algorithm. 

- Choosing a routing algorithm is like choosing different horses for different courses. 

- The frequency of the changes in the network is one thing to be considered. 

- Other things to be considered include the cost function that is needed to be minimized and the calculation of the routing tables in a centralized fashion.

- For static networks the routing tables are fixed and therefore they require only simple routing algorithms for calculation. 

- On the other hand, the networks that are dynamic nature require distributed routing algorithms which are of course complex.

How is test driven development and documentation linked?

As we all know that the test driven development or TDD is another process in the list of the most of the popular software development processes. The topic of the test driven development is in the league of this article. 

About Test Driven Development

- The test driven development took its root from the idea of the repetition of a very short development cycles. 

- The first of all a failing automated test case is written or created by the software developer or tester which is meant to serve the purpose of defining a new function or a desired improvement. 

- Secondly a code to pass the above created test is also written by the developer. 

- This newly written code is then subjected to refactoring in order to make it meet the acceptable standards. 

- The test driven development has always been looked up as an encouragement for the simple designs and also as an inspiration for boosting up the confidence levels.

- The test driven development has always been known to be related to the concepts of the extreme programming or XP. 

- But, eventually it came to be known as a standalone process having its own ways and rights.

- The concepts of the test driven development are used by the programmers and developers as a measure for debugging the legacy code and improving it further. 

- The test driven development is usually driven by a series of automated unit tests that are written by the developer to provide definition for the requirements of the code and then the code is automatically produced. 

- These tests are constituted of the assertions of their own.

- If a test is successfully passed, the developer is confirmed of the correctness of the code and that it can be further evolved and refactored. 

The documentation forms a very important part of any development or testing and so does of the test driven development. This article has taken up the question: “how is test driven development and documentation linked?”. 

About Importance of Documentation In TDD

Now coming to the importance of documentation in the test driven development, it includes the following documents:

1. Feasibility report
2. Technical documentation
3. Operational documentation
4. Log book and so on.

- The documentation in test driven development is another source of support to the developers as well as the users.

- It provides all the crucial information required to set up a uniform environment in which the software system or application is to be operated. 

- In case of a break down when the person in charge is not available, the users experience down time and most of their resources are wasted. In such situations, there is only one thing that can save one’s precious time and efforts and that thing is nothing but the documentation. 

- It provides all the information and guidelines that are required to fix an issue. 

- The format of the documentation does not matter much as much as it content matters.

- Documentation is vital to any software development process and not particularly to the test driven development.

- Documentation is an effective mean for streamlining the test driven development process. 

- Apart from all this, documentation has got an important role to play in the business.

- Document is needed in the test driven development since it helps in codifying the procedure for the development of the software system or application. 

- The documentation provides effective protection during the audits to the test driven development.

- It is important that the documentation is developed alongside the development of software system or application. 

- Documentation will be effective if it is considered to be a part of the work and not a hindrance to it. 

What are key elements of Search Engine Optimization Part 2?

Apart from keyword analysis, other important elements of search engine optimization are:

- Page uses HTML links. These HTML links needs to be optimized and is an important element of search engine optimization. The HTML code should consists of search items which tells the search engine what is the page about. The following things should be optimized like page title, page headings, image text and link anchor text.
A good page title will not only be keyword targeted but also will entice a person to click on it in the search results.

- For good search engine optimization, good page content is also important. The content should be of high quality and unique. It should not be copied from other sites. A god content enhances the search.

- The code enhancement process determines your page rank on search engines. It understands the structure or pages of the website.

- Link building becomes very important for search engine optimization. It improves the ranking of the web page or web site.