Questions tagged [tcp]
TCP stands for Transmission Control Protocol and is one of the core protocols of the Internet Protocol Suite. TCP complements the Internet Protocol (IP), and therefore the entire suite is commonly referred to as TCP/IP.
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High TCP retransmissions from RHEL 8.6 client (BBR) to RHEL 7.9 server (Cubic) during iperf3 test [closed]
We're testing TCP performance between a client and server using iperf3 in a controlled environment. Client: RHEL 8.6 with BBR congestion control enabled Server: RHEL 7.9 using default Cubic congestion ...
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Socket Leak in Network-Intensive Application: Discrepancy in 'Closed' State Count
I'm experiencing a socket leak in a network-intensive application where the number of sockets in the 'closed' state reported by ss -s does not match the actual count from detailed commands. Here are ...
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When one node connects to more than 1000 nodes using an envoy proxy, there are some connection failures with `URX` status code. What can fix this?
I am connecting two services behind envoy proxy and each node makes 6 TCP connections to another. The nodes are designed to connect from one->many. When one node tries to connect to more than 1000 ...
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How can I limit the number of accepted sessions on a specific port in Windows server?
I have a Windows service that is limited in the number of threads it can handle at a given time, say 10. But Windows will accept many more than that simultaneous TCP connections on the listening port (...
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Unusual TCP connection issue and Windows Server 2022 strange behavior
Last night I had another unsuccessful attempt to migrate one of the machines to a newer version of Windows Server. The entire system is composed from several virtual machines running Windows Server ...
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Nginx TCP steam $ssl_preread_server_name randomly fail to extract host
I'm struggling with a puzzling behavior. I have a TCP streamer in front of: and NGINX site listening to 127.0.0.1:444 a traefik ingress endpoint (:8443) exposing all of my services and a k8s ...
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Persistent ephemeral port reuse and CLOSE_WAIT states after cold reboot
I'm running into a persistent and puzzling issue involving two Linux and one Windows guest VMs hosted on a third-party VMware ESXi server, and I'm hoping someone here can offer insight or share a ...
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From client POV, ICMP (ping) works, but any TCP connection does not
Here's a strange situation on a Windows Server 2016 Standard: (All within our AD domain) Any ping request works just fine but whenever a TCP connection is tried to be established, this does not work. ...
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Windows Server with 10Gbit NIC - Severe Performance Issues over Certain Routes
we recently upgraded our Windows server (hosted by Hetzner) to a 10Gbit/s connection. The server does reach the full 10Gbit/s capacity, and our customers are not reporting any issues. However, we're ...
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redhat + how to revert TCP BBR congestion changes
We have configured the BBR settings on all our RHEL 8.6 machines as follows: (according to Red Hat's documentation [https://access.redhat.com/solutions/3713681]). The goal is to assess whether the BBR ...
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How can 10G link be slower to WAN than 1G link, on the same machine?
I'm using the following command to test network speed to my.remote.server, from my workstation: dd if=/dev/random | pv | ssh my.remote.server "dd of=/dev/null" When I set en0 to 10Gb, ...
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Use LLD in zabbix to discover open TCP ports
We're using Zabbix 6.0 and want to monitor application ports on around 40 Debian 11 servers. There runs multiple times the same application on each server, so there are two to 11 ports to monitor. I ...
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Network stops working in one direction for 40s, then fixes itself
I'm a Java developer. Something strange happened recently and I am a bit befuddled and would like to have a list of hypothesis to start asking the right questions. The TCP connection between two Java ...
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How to Forward TCP Packets to Multiple Destinations Using nftables?
I am looking for a solution where TCP packets need to be forwarded or broadcasted to multiple destinations. Using nftables, I managed to forward packets to another machine with the following rule: nft ...
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Random Linux->Windows retransmissions with delays/timeouts
We have been notified about random application slowness and random HTTP 503 errors coming from the reverse proxy machine (Debian/Apache). HTTP requests coming from Debian/Apache machine are received ...
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Traefik TCP Router for RDP, using TLS SNI for routing
Here's my setup: I have several namespaces, and some of these contain pods that expose RDP ports. Port 3389 is block by a firewall, so I have to use another port that maps to port 3389 on the pod. ...
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Custom HTTP server with Godot 4.3 can't handle over 5 SSE connections
Since Godot does not have a built in HTTP server, but only a TCP server, I managed to write proper responses manually. Javascript, css and html load and work properly, you might say seamlessly. ...
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Nethogs (cumulative) printing a weird IP address
I'm currently stumbling on Nethogs' output because (when using the cumulative view, with m, or launched via nethogs -v 1) I see a line like this: PID USER PROGRAM DEV ...
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HAProxy connection limit per backend server is limited to port_range
I am running a HAProxy load balancer for a WebSocket server. If I put one backend servers backend pieproxy option http-keep-alive timeout tunnel 0ms balance leastconn server s1 IP:3001 ...
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Websockets with websocat: How to find out what resource is running out?
I'm in a situation where I've got a TCP server and a websocket client, and I'm using websocat as a bridge between them. Everything works great until I get to about 60 concurrent connections, and then ...
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Slow upload speeds from Windows on single TCP connection, likely due to packet reordering of Intel 82599ES (ixgbe) 10 Gbit/s NIC cards
Between servers windows-in-Finland <-> linux-in-Germany I am experiencing 100x slower upload than download (windows -> linux is 100x slower than windows <- linux). Details and existing ...
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PF Redirect rule does not validate on Darwin
I'm running pf on OSX 13.6.1, and I wanted to create a rule so that all TCP packets outbound towards 146.59.110.108:1337 (example) will have to be redirected to 127.0.0.1:1337, except if it comes ...
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Data Size difference Between Client-Proxy and Proxy-Server Connections with CONNECT Proxy
I have a small setup which I have a wss server running on port 4433. I also have a client trying to access the wss server via a CONNECT proxy. My understand of CONNECT proxy is that proxy will create ...
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TCP SEQ or ACK do not increment despite non-zero LEN
My TCP downloads (git fetch, Chrome browser downloads, flatpak downloads) often fail to complete. When I look into the packets with Wireshark, I find that the connection ends in RST from the client. ...
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GCP Cloud run: Connection Reset by peer
We are running a web service with the structure of Client (Web, App) <-> AWS API Gateway <-> GCP Cloud Run Server (called by public URL) The following error occurs when proxying a ...
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Understand lsof outputs for remote port forwarding SSH connections
Given ServerB and ServerA, I run the following command on ServerB to setup Remote Port Forwarding, so that requests arriving on port 4000 on serverA are forwarding to ServerB:22. ssh -R 4000:localhost:...
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LWIP protocol stack, send interface blocking
Using the LWIP protocol stack for TCP communication, the device ran as a TCP server for a period of time and found itself stuck in the send interface: send (socket_num, (const void *) msg, len, 0), In ...
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What is the difference between "packet drops" from "ip -s link" and "socket drops" from "ss -tm"?
ss -tm shows detailed memory information about each TCP session. I found that some of the tcp sessions show sock_drop, here is one: ESTAB ***** some irrelevant info here **** ...
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Behaviour of TCP setting ForceWS (Windows)
I'm in the process of setting up a new Windows Server 2022 to replace a very old (2012 R2) one. When looking through the settings I can see that the new and the old server have different settings for ...
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REST API POST Only Fails When the Client Object is Reused & Only on Production Server in the Clients Network
For over a month, we had been creating a new HTTP client object for every POST request without encountering any issues. This, however, led to many open TCP connections, and the documentation suggests ...
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Testing mail-server with mxtoolbox -- SMTP connection time over 5 seconds?
We're having intermittent problems receiving e-mails from one company, and their side are pointing out, that our server takes just over 5 seconds to respond to incoming SMTP connections, whereas their ...
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TCP fast retransmit is not working
We have a cluster of 3 hosts (actually an Apache Doris cluster, with the servers transmitting data via a third-party library brpc). When transmitting data between servers via TCP, we often encounter ...
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Do TCP sequence numbers increase by the Ethernet frame size, or tcp payload size?
Have Googled this but it's difficult to word this without getting irrelevant results. The TCP sequence number increases by "how many bytes were sent". Does this mean literally the entire ...
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Intermittent TCP connection drops and timeouts over wireguard
I have three servers, fully connected via wireguard. They run Ubuntu Server 22.04 and postgresql repmr cluster with streaming replication. All computers have a public address, but PostgreSQL instances,...
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Can TCP Packets Be Spoofed? How to handle fake SYN requests / identify who is responsible for these packets?
Long story short, my server's system load is off the charts, but nothing is taxing the CPU script or program wise. It appears that it is under a TCP Syn flood attack, but I cannot figure out how to ...
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DNS re-resolution and failover of TCP connections
I manage some stateless services that work over TCP, and we are working to ensure reliability and recoverability in case of a regional outage. I find that I lack enough understanding about the ...
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Linux automatically timeouts incoming connections just after accepting
We have a dedicated server that works fine and accepts incoming connections fine. it receives and sends data fine as well. Works great for some hours, but after that all accepted connections ...
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Apisix kubernetes Discovery not work
I am using official helm chart to install the APISIX in my Kubernetes. I only override the following values from the official helm chart: useDaemonSet-> true serviceAccount -> set create to ...
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Why would a server not send ACK in response to PSH, ACK?
We have a client/server implementation, where the client continuously, periodically sends data at 800Hz over ethernet. The packets are small so we're significantly under the network bandwidth limit. ...
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The TCP connection is always reset while transmitting a 6M file
I have a web server, which allows user to upload or download files through HTTP requests. Internet Internet loopback interface LAN ...
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5 answers
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TCP source port sharing
My understanding of TCP connection is that a source PORT remains exclusive to one connection, no matter the destination is, so the number of connections from local port 12345 for example can never ...
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Linux Kernel keeps retransmitting data already ACKed by peer
I have the strange issue that a session without obvious cause hangs and timeouts. The session is a syslog stream with rather high volume, and traffic only flows from client to server. In capture files ...
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TCP stream ends with retransmission of last FIN,ACK packet
The TCP network connection between an Haproxy server in TCP mode (.94) and Postfix (.137) randomly ends with the retransmission of last FIN,ACK packet from the Postfix server: It only happens for ...
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TCP CWND and RWND Mismatch
currently I am doing some Measurements (using iperf3, TCP-Tracepoints (for monitoring the Congestion-Window (CWND)) and tcpdump). While altering the TCP-Window (RWND) Field (using a nf-hook kernel ...
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Can I make TCP_NODELAY a default setting for all connections on a GNU/Linux system?
This article: It’s always TCP_NODELAY. Every damn time. suggests, as a bottom line, to set TCP_NODELAY by default, always. Can I do that on a (recent) GNU/Linux system... As root, for all sockets ...
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Exposing Kubernetes pods with TCP and UDP traffic
I'm writing a Kubernetes operator to deploy individual, dedicated game servers, inside the same cluster. What would be the best method for exposing these servers outside of the cluster? Requirements ...
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What factors determine the TCP window size?
We have a network throughput issue, but cannot find a bottleneck. We have spent four weeks looking at router logs, FW logs, and monitoring and we are now looking into the TCP window size on client. ...
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Local WireGuard responing to a SSH TCP SYN to a wrong interface
I have a local WireGuard gateway that I am trying to manage using Ansible. I found an issue when connecting over SSH. That connection was getting timed out. After looking into the problem, I realized ...
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Do I need to do anything to manage many outgoing connections to an outside service from a kubernetes cluster?
In my kubernetes cluster I'm running many small pods per node (about 30) and each pod creates a few TCP connections to a single service on the internet to send HTTP requests to. So each node on the ...
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TCP & Wireshark - Server not re-transmitting segments?
I am new to TCP-in-depth-analysis which I need for a current problem. Connections: Client = Host PC, Ubuntu 22.04.4 LTS (IP: ...60) Switch (TL-SG1016D by tp-link, Gbit) Server = Proprietary embedded ...
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