Protocols

Reverse ARP

RARP: The Reverse Address Resolution Protocol

Out-dated technology can still be interesting. Even though the Reverse Address Resolution Protocol was introduced in 1984, and considered obsolete the following year due to the Bootstrap Protocol, it continued to be used long after. The RARP has not completely disappeared from network technology even today. As the Reverse ARP, this protocol is a counterpart to the Address Resolution Protocol. But...

DNSSEC: internet standards for authenticated name resolution

DNSSEC: internet standards for authenticated name resolution

Without the Domain Name System, users of the World Wide Web would have serious problems when trying to load websites and other online presences. It’s only thanks to this system that internet addresses appear in their trusted text format: they’re actually nothing more than combinations of numbers. The communication between browser and name server responsible for this isn’t actually as secure as you...

Error 405 Method Not Allowed: Explanation and solutions

HTTP Error “405 Method Not Allowed”: How to solve the problem

HTTP is indispensable as a mediator between the browser and web server: Both communicate with each other using the transmission protocol on the application layer by sending various types of messages. With an HTTP request, for example, the browser can request a resource or return its own data to the server. If one of these HTTP methods doesn’t work, error 405 (Method Not Allowed) occurs. But what...

550 requested action not taken: possible solutions

SMTP error 550: how to fix “Requested action not taken: mailbox unavailable” and other SMTP 550 error messages

If you want to send a message with your e-mail client and the sending fails, you’ll receive a corresponding error message from the server, including an SMTP status code. For example, the message “550 Requested action not taken: mailbox unavailable” means that the targeted address couldn’t be reached. Since this problem can have various causes, even more possible solutions exist, some of which you...

SQL injection: Fundamentals and safeguards

SQL Injection: Protect your database system

There are daily reports on how security gaps in applications are exploited – because hardly a day goes by without a new gap being discovered or a known gap being closed. One attack method, which has always been based on exploiting such weak points, is called SQL injection. But what is actually hidden behind the malicious database exploitation and how can you protect your database system from it?

HTTP 400 Bad Request | finding the causes

HTTP 400: Bad Request explained

Internet users are often confronted with error messages. HTTP status codes can be especially annoying, and even more so if you don’t understand what they mean. The message 'HTTP 400 – Bad Request' is a mystery for many internet users, but luckily it can be solved in most cases. We explain what the error message means and how to fix the error.

HTTP 408: How to fix the “Request Timeout” error

HTTP 408: how to fix the timeout error

Permanent availability is one of the most important things when it comes to a website. However, even the best technical conditions do not offer a 100% guarantee that a website will constantly run smoothly. Connection errors like HTTP error 408 regularly present websites with minor and major difficulties, especially since the causes are often found on the client side. Our guide looks at the causes...

504 Gateway Timeout: How to fix it

HTTP 504 (Gateway Timeout): How to fix an error 504

If the error message ‘HTTP 504 Gateway Timeout’ appears when you attempt to open a website, it means that the allowed time for responding to browser queries has been exceeded. A lot of the time the culprit is not the web server itself, but instead some other component of the server, i.e. a gateway, which is integral to the path of communication. What does 504 gateway timeout mean? How can you fix...

What does ‘502 bad gateway’ mean?: Explanation and solution

Error 502 Bad Gateway: Where’s the problem?

HTTP status codes emerge when something isn’t running properly on the internet. In this respect, the 502 Bad Gateway error is no exception. But this familiar error message can be particularly tricky: It’s not actually clear where the source of the problem lies. In the chain of gateways along which internet requests run, the error could occur at a number of different points. This article explains...

HTTP error 500: Internal Server Error

HTTP error 500: Where does the problem lie and how to fix it?

Error messages when surfing the net are a nuisance for everyone involved, but especially for those who have to find out what the problem is. The search for a solution can be particularly tedious if the status code message barely provides any information on the source of the error. The HTTP error 500 (“Internal Server Error”) is a collective status code. We give you tips on where errors could have...


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