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April 12, 2019 0 Comment

1. There are 7 layers in OSI network model and they are integral aspects of network as it gives us concepts and/or protocols on what they each layer does and becomes essential part of network trouble shooting.
Layer 7 (Application Layer) basically network specific applications (browsers, file transfer, mail and others)
Layer 6 (Presentation Layer) provides context or the communication. So compression of the data or encryption or decryption of the data happens here in this layer. It prepares the data from application layer for lower layers
Layer 5 (Session Layer) it is also known as handshaking layer as it creates dialog between computers. /it controls duplexing, termination and restarts.
Layers 7, 6 and 5 are also known as upper layer data. Layers 6 and layer 5 are considered to be a part of application layer. So the 7 layers of OSI model is considered somewhat obsolete but still in existence.
Layer 4 (Transport Layer) is also known as flow control as it provides protocol to transfer data such as TCP(reliable connections, when data needs to arrive securely/timely manner) and UDP (non-reliable connections, latency is issue and can be seen in VOIP). Data is called segments.
Layer 3 (Network Layer) is where routers are operated (so routing of packets happen in this layer) it provides connections to different networks through protocols such as IPv4 and IPv6. Data is called packets at this layer.
Layer 2 (Data Link Layer) is provides connection within same network. It should provide error-free and reliable transmission of data. Data is called frames at this layer
Layer 1 (Physical Layer) is where all the physical equipment (like hubs, cables, and others) are located. It transmits data through hardware, electrical and mechanical interfaces. Data is called bits at this layer.
Data flows through flow one end down through layer 7->6->5->4->3->2->1 and across physical layer and upward on the other end from 1->2->3->4->5->6->7.
Each layers have several protocols that it follows based on the need of communications. All Programmers Seems To Need Data Processing (Application, Presentation, Session, Transport, Network, Data Link, Physical layer) easy to remember pneumonic.
2. Internet Engineering Task Force (IETF) RFC (request for comments): 8147 (Next-Generation Pan-European eCall). Status of this RFC is already proposed Standard since May 2017. What is interesting about this is to look at the time line and see how many steps are involved and how many changes gets made to the standards before they are accepted for proposals or updated the outdated standards.
Next-Generation Pan-European eCall is basically setup of protocols that would support eCall (a standard and mandatory system for emergency calls made through vehocals) through IP based emergency services in the next generation of Pan-European vehicles and provides real-time data and communications.
It shows initiation in November 2013 from initial draft to multiple drafts and then submission to IETF in July 2014 and then several internal edits and changes (27 to be exact) and finally open for RFC on May 2017. Its fascinating and horrifying at the same time how long it takes to get something like this that’s is for safety protocols and making next-generation cars.

3. A 2-tier architecture is presentation layer than runs on client and data layer is stored on a server. Best Example of this is Bank ATM machines. (The interface where you can withdraw or deposit money is client and that information is getting stored and updated on the bank server and then getting response in terms of bank receipt is confirmation that the task was performed correctly. There are few real world applications as real world applications fast changing rules are not suitable for this and also limited number of users that can be connected at the same time to this architecture. It is great for users as it is accurate and offers best performance.
4.
A 3-tier architecture is basically distributing processing across three computers (Client (presentation), Application server and database server). The best example of this is shopping on Amazon.com. You start by accessing amazon.com and looking over items to purchase (presentation layer). Once you find an item (application server) , it is confirming against amazon database for the price, availability and estimated shipping time (database server) and you get all that information presented to you in the cart, ready to order/purchase (presentation layer). This happens with every query of an item. It is great for performance, scalability and availability. It is secured as client do not interact with server directly. The problem with this layer is if the application layer is crashes or having issues you can no longer be able to access database.

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A N-tier architecture is 3 or more number of computers distributing processing powers. The information flow is linear (communication only takes place if they are on adjacent tiers). It can run powerful application; accessible by hundreds of users. It balances traffic better than any other architecture and it is always scalable. The bad part is it always has heavy traffic and really difficult to maintain and program. It is also complicated to design and also expensive

5. Cloud Computing (software application, data storage Architecture is cheaper and simpler than traditional client-server architecture. It is different because part or all of the infrastructure can be outsourced. It is distinguished in 3 models.
First, Software as a Service (SaaS) allows users to run existing software/applications over the internet. (Gmail, SalesForce, Microsoft Office 365 and others). Applications are either free or subscription based. Great for collaboration.
Second, Platform as a Service (PaaS) allows users to build and change their own cloud applications using vendor tools. It helps by renting infrastructure and then creating custom applications on those server like Microsoft Azure and some even allow those applications to run and hosted for free (google app enginge and force.com).
Third, Infrastructure as a Service (IaaS) allows users to run any software/applications on cloud hardware including storage and network servers. Using this type of infrastructure is low-cost, great for scalability and can be temporary or long-term, based on individual or business needs.
All 3 cloud models have different user accessibility and control, however it has changed how people interact online through those applications or through renting those services.

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