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Ahmed shamim hassan
Software Engineer. Polyglot programmer. Avid learner. Average person.

I was once asked in an interview, I immediately figured that Pub-Sub means ‘Publisher-Subscriber’ and i then vividly recalled from the book “Head first Design Pattern”:

- I thought.

I replied with a winning smile, .

But the interviewer smiled back like he got me and said, And i was like-

So, what did i miss? How did it went wrong?After came back home I decided to find the answer by googling. This post is about the excerpt I learned from that query.

Before delving into the difference, let’s first talk about the ‘Observer’ and ‘Pub-Sub’ pattern a bit.

Observer DesignPattern:

I think a lot of people will agree with me that ‘Observer’ Design Pattern is one of the easiest design pattern of them all. I mean, unlike most of the other design patterns, you can at least ‘Feel’ what is the main concept of Observer design pattern by first read.

See, even the Wikipedia definition is not that hard, right? If you are still struggling, let’s explain it in layman’s term.

Let’s assume that you are searching for job as a software engineer and very interested in a company named ‘Banana Inc.’. So, you contacted with their Hiring Manager and gave him your contact number. He ensured you that if there is any vacancy they will let you know. And there are several other candidate interested too, like you. They will let all of the candidates know about the vacancy and maybe if you response then they will conduct interview. So, how is this scenario related to ‘Observer’ design pattern? Here, the company ‘Banana Inc.’ is the Subject which is maintaining a list of all the Observers (candidates like you) and will notify the observers for a certain event ‘vacancy’. Ain’t it easy, mate?

So, if you ever need to implement this scenario in some software or application you can follow this process and can say that you have implemented ‘Observer Design Pattern’. (I’m not bloating my article by showing any code example, because there are tons of example available at the mighty Internet)

Pub-Sub(Publisher-Subscriber) DesignPattern:

Yes, the Subject in the Observer Pattern is like a Publisher and the Observer can totally be related to a Subscriber and Yes, the Subject notify the Observers like how a Publisher generally notify his subscribers. That’s why most of the Design Pattern books or articles use ‘Publisher-Subscriber’ notion to explain Observer Design Pattern. But there is another popular Pattern called ‘Publisher-Subscriber’ and it is conceptually very similar to the Observer pattern. The major difference between the (real) ‘Publisher-Subscriber’ pattern and ‘Observer’ pattern is this:

Oops! sorry not that one. This one:

This means that the publisher and subscriber don’t know about the existence of one another. There is a third component, called broker or message broker or event bus , which is known by both the publisher and subscriber, which filters all incoming messages and distributes them accordingly. In other words, pub-sub is a pattern used to communicate messages between different system components without these components knowing anything about each other’s identity. how does the broker filter all the messages? Actually there are several processes for message filtering. Most popular methods are: and . Well, not going to further on that road, if you are interested, Wildflower Printed Slip Dress in Black size L also in MSXS Free People Pick A Best Cheap Online Shopping Online Free Shipping Explore Cheap Sale Shop Offer XSAJuMQ

So, in a nutshell the major difference between these two patterns can be shown as this:

Makes sense?

Let’s list out the differences as a quick Summary:

Despite of the differences between these patterns, some might say that Publisher-Subscriber pattern is a variation of Observer pattern because of the conceptual similarity between them. And it won’t be wrong at all. Don’t need to take the differences religiously. They are similar, aren’t they?

Well, that’s all for now. Hope you get the idea. Thanks for reading the article. Please let me know if there is any mistake or any modification needed. Thanks in advance.

observer pattern

Using a technique called traffic amplification and reflection, the attacker can reflect his traffic from one or more third-party machines toward the intended target. In this type of assault, the attacker sends a message to a third party, while spoofing the Internet address of the victim. When the third party replies to the message, the reply is sent to the victim — and the reply is much larger than the original message, thereby amplifying the size of the attack.

BCP38 is designed to filter such spoofed traffic, so that it never even traverses the network of an ISP that’s adopted the anti-spoofing measures. However, there are non-trivial economic reasons that many ISPs fail to adopt this best practice. This blog post from the Internet Society does a good job of explaining why many ISPs ultimately decide not to implement BCP38.

Fortunately, there are efforts afoot to gather information about which networks and ISPs have neglected to filter out spoofed traffic leaving their networks. The idea is that by “naming and shaming” the providers who aren’t doing said filtering, the Internet community might pressure some of these actors into doing the right thing (or perhaps even offer preferential treatment to those providers who do conduct this basic network hygiene).

A research experiment by the Center for Applied Internet Data Analysis (CAIDA) called the “ With Paypal Online Shop tied neckline blouse Red Marni Footlocker Finishline For Sale crvrDO
” is slowly collecting this data, but it relies on users voluntarily running CAIDA’s software client to gather that intel.Unfortunately, a huge percentage of the networks that allow spoofing are hosting providers that offer extremely low-cost, virtual private servers (VPS). And these companies will never voluntarily run CAIDA’s spoof-testing tools.

Center for Applied Internet Data Analysis

CAIDA’s Spoofer Project page.

As a result, the biggest offenders will continue to fly under the radar of public attention unless and until more pressure is applied by hardware and software makers, as well as ISPs that are doing the right thing.

How might we gain a more complete picture of which network providers aren’t blocking spoofed traffic — without relying solely on voluntary reporting? That would likely require a concerted effort by a coalition of major hardware makers, operating system manufacturers and cloud providers, including Amazon , Apple , Google , Microsoft and entities which maintain the major Web server products ( Apache , Nginx , e.g.), as well as the major Linux and Unix operating systems.

Amazon Microsoft Apache

The coalition could decide that they will unilaterally build such instrumentation into their products. At that point, it would become difficult for hosting providers or their myriad resellers to hide the fact that they’re allowing systems on their networks to be leveraged in large-scale DDoS attacks.

The STOA Drug Life oversized Tshirt Black Amiri Fashion Style Outlet Pay With Visa Discount Pre Order EnjXylTY
found that, on average,EU performance in education is weak, and the percentage of low-performing students is high, especially in comparison with some Asian countries, such as Japan and South Korea. Dirk Van Damme from OECD will speak about the effect of technology on educational performance. Could educational technology contribute to maintaining or even increasing the productivity level of an ageing workforce, thus increasing the competitiveness of the EU workers in a global and fast evolving economic environment? And what are the possible options for European policy makers to ensure that the education sector, but also all citizens, will keep up withtechnological developments and remain successful in the digital economy?

The STOA study concluded that it is not technology itself that matters the most; rather, it is how teachers, students, families, and schools use the technology. What are the long-term impacts of such technology-based innovative learning and teaching environment on society? Despite stakeholders’ best intentions,could technology actually foster socio-economic disparities? Could the use of cloud-based technologies at schools pose risks for the protection of personal data?

The workshop is an opportunity to discuss possible answers to these concrete, relevant and complex questions. STOA counts on your contribution to power a lively, productive and enriching debate.

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