Urgent flag of TCP, computer networks

the Urgent Flag (URG) is set every time the sender Application layer wants to send some urgent data to the receiver. In this case, the Transport layer you do not expect enough data to reach the maximum segment size. Now my question is How do intermediate routers recognize that the packet needs to be forwarded urgently?(don't have the transport layer)?

TCP Sequence Number Approach based on denial of service

I installed Ubuntu 16.04 64-bit desktop O. S and configured apache2 web server but while doing Qualysis analysis I get lower vulnerability.
"Denial of service based on approximation of TCP sequence number"
Can someone help me with this

Linux: Why can't I reliably send or receive data over TCP after moving servers?

I am currently dealing with a network problem on high latency internet links (100-400 ms). I ran a Minecraft network, and recently moved it to a separate data center to get a server with a better CPU and more RAM. The users of this server are spread all over the world. Before the change, the server was in Montreal and users in Europe had a latency of ~ 100-200ms, and those in Australia had a latency of ~ 200-300ms. After the change, the server is in Germany, users in North America get a latency of ~ 100-200 ms, and users in South America and Australia get a latency of 200-400 ms. Overall, the latency is pretty similar, but who gets excellent latency and who gets tolerable latency varies (note that Minecraft isn't very latency-sensitive overall, especially compared to most video games). There is also no significant packet loss, as measured by the MTR and ping tools. Also, the software on both servers is almost identical. Both servers are running Debian 10, and I checked all the software + settings that are not in the APT repositories to send, while reinstalling the exact same packages via apt. As such, the software configuration must be essentially identical.

However, many users have connection problems. It appears to only occur around 6:00 PM (± a few hours) in the eastern United States. The connection problem specifically takes the nature of the performance of all TCP connections to be appallingly low. With an SSH + SOCKS proxy, it took minutes Loading a normal web page (Gmail), and in-game, it often takes minutes even a simple chat message to arrive if a few MB of global data is transferred. The effective latency of a TCP connection (for example, the time it takes for a chat message to pass through it) increases unreasonably massively when data is placed on that TCP connection. A normal SSH session with only one terminal is basically fine, and the game is fine overall if not much is happening, but as soon as something of significant size is sent over TCP and is during the time mentioned above then performance it breaks and the latency over TCP (but not through ping) becomes irrational, even several minutes in the worst cases. When this problem first occurred, there was a significant packet loss (~ 25%) which I thought was to blame, but that packet loss no longer occurs (according to ping etc.) but the problem persists. The packet loss, but not the troublesome symptoms, disappeared after I made a general report to the new host about the packet loss, but before I could give them more detailed data with MTR as requested in their response to that report. My impression of the host is that nothing was changed, but who really knows.

As such, at this point, I suspect that the relevant difference between servers is that the previous host (OVH) performs some kind of tweaking of their operating system images (something I know to be the case), and that the new host ( Hetnzer) no.

I suspect this setting has something to do with the size of the TCP window, but when I tried to manipulate those settings to make changes, the settings didn't seem to do what they were supposed to. Specifically, when I configure the various net.ipv4.mem or net.core.mem settings i find listed on the internet via sysctl, the size of the window that iperf select (or the maximum that is allowed to select, when using the -w option) seems to take a random value with no discernible relationship to me with the values ​​I configured via sysctl, rather than behaving the way I expected, where its maximum value is simply what I configured via sysctl. Note that iperf -s It misbehaves even before a client connects to it, so not making the same changes on the client is not a plausible explanation.

As such, I wonder 2 things:

1) How can I repair my server and allow the latency on TCP connections to be similar to the actual latency on the link, even at peak times and under moderate load (a few mbps)?

2) How can I reliably and predictably change the TCP window size of all applications? (Or equivalently, what's going on with the sysctl setting being applied in seemingly random ways? What's the pattern I'm missing?)

Networks – How does TCP get UDP over the return packets?

How does a server send packets to the client if there is only one UDP connection, when the client is behind a firewall and UDP, by definition, does not maintain a stateful connection? If I had a better mental model of this, I would be in a better position to diagnose any firewall issues that hinder the success of this openvpn connection.

The particular problem is that my coworker's openvpn setup works fine, except from your home LAN, where there is no response from the openvpn server. I'm trying to diagnose any problems with your / nat / firewall router, but it would be better if I understood how the server might even respond. The OpenVPN server is configured for UDP, which is the recommended configuration.

something causing my Windows Server 2019 TCP / IP to crash after a GSA SER runtime

something that causes my Windows Server 2019 TCP / IP to crash after a GSA SER runtime.
If I stop GSA SER, the problem on my server goes away immediately.
Also, in GSA being, I see an error: "No buffer space available" when this happens.
I only use high quality proxies.

Database system checksum to avoid network corruption not detected by TCP checksum

Since the TCP checksum is not enough to detect / prevent any corruption (https://stackoverflow.com/questions/3830206/can-a-tcp-checksum-fail-to-detect-an-error-if-yes -how-is -this is), do modern database systems (eg SQL Server, MariaDB / MySQL, Oracle, etc.) use any additional checksum of network traffic as part of their client protocol / server?

I did a little searching but couldn't find anything that made me wonder if maybe they don't and I just rolled the dice.

How to transmit JSON using HTTP instead of pure TCP

I also put this question in Quora:


Basically, if we have a long list of JSON entries, we could put them in an HTTP body like this:

HTTP/1.1 200 OK
Date: Sun, 10 Oct 2010 23:26:07 GMT
Server: Apache/2.2.8 (Ubuntu) mod_ssl/2.2.8 OpenSSL/0.9.8g
Last-Modified: Sun, 26 Sep 2010 22:04:35 GMT
ETag: "45b6-834-49130cc1182c0"
Accept-Ranges: bytes
Content-Length: (big number)
Connection: close
Content-Type: application/json


to be able to analyze the entire JSON body with something like JSON.parse ().
Or we could divide the body into new lines.

So, my question is: is there any way to write the http body continuously (line by line) and also read the http body continuously? Line by line? Or does it make no sense since the HTTP body is always protected?

php: Laravel server and TCP hosted on GoDaddy

Can someone point me in the right direction to configure a TCP server in GoDaddy to accept incoming data from a device? I have found this guide that seems fine, but I am not sure how to handle the server by automatically accepting an incoming TCP connection and automatically maintaining the TCP server / socket. In Laravel API, routes can be configured and directed to controllers / services automatically; something similar to this for TCP connections would be great.

Thank you
Any help is appreciated.

ssh: is it possible to resend tcp remotely through a free proxy?

I know you can forward the connection from a proxy server like this:

ssh -R 8080:localhost:80 public.example.com

But I'm curious to know if it's possible to forward from a free proxy like:


It seems unlikely that you will use the ssh option because you would not have access to the server. If so, what would be a practical way?

TCP / IP learning: where should you start?

I am a web developer (LEMP stack), but I am looking to change the professional course to security (which I know is an incredibly broad topic). Ideally, I would like to be a pen tester. When looking at the Offensive Security OSCP course page, one of the prerequisites is a solid understanding of TCP / IP, which I am unfortunately unaware of and therefore I feel is a suitable place to start learning.

That said, I'm not sure where or how to learn. Specifically, given my personal logistics, I cannot take a course at a local university (I don't have the finances and, more importantly, being physically disabled means that traveling is difficult). So, I'm looking for recommendations for:

Authorized books