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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.

TCP is just one communications protocol on the web. Others include:

  • User Datagram Protocol (UDP)
  • Internet Control Message Protocol (ICMP)
  • Hypertext Transfer Protocol (HTTP)
  • Post Office Protocol (POP3)
  • File Transfer Protocol (FTP)
  • Internet Message Access Protocol (IMAP)

TCP on Wikipedia

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How does linux / netfilter / iptables "know" if a packet is meant for itself for to be forwarded

I have setup an ubuntu box as a router manually , using iptables + NAT. But I was wondering, how does the "middle-router" know if the packet is meant for it or to be forwarded? I tested this scenario: SYN …
poiasd
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TCP packets being lost

I have some TCP packets being lost. I have monitored the interface with tcpdump pcap file - https://www.dropbox.com/s/7m3hr1b7065tenx/tcp.pcap?dl=0 I noticed that when I lose packets I only get 5 frames whereas I usually see 9. Example lost…
Ruby dev
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How can I inspect everything that happens before a TCP handshake

On my local machine when I connect to a remote linux machine with netcat I can only see 3 related packets(the tcp handshake) in Wireshark. I'm pretty sure there's more that happens before that(router --> ISP --> remote network) but I can't figure…
voyager19
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TCP port forwarding/tunneling by file sharing

I have a Linux server and a windows client. A folder is shared between these machines with read and write access for both of them. I want to access a production database from my development machine, normally I do that using ssh port forwarding but…
HamedH
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proxy a Ssh server that is on my home over a vps

I want to proxy my home SSH-server over a VPS from Dedipath, but I don't know how it works. because I already tried it with many tcp proxies and they didn't work. My VPS has Debian 10 and my home server too.
fynntheking675
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Debugging why the packets get dropped

I've started on stackoverflow, then after some investigation asked on superuser, because it looks like network or kernel (mis)configuration, but probably I need some seasoned network engineer to help:) I'm mangling packets with help of NFQUEUE,…
aikipooh
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Difference between TCP Segment Data and Data on a Wireshark capture

I am trying to replicate some TCP communication that is sent from MongoDB and I have been able to replicate it byte by byte and it is still not being recognized. The only difference I could find when analyzing the packets on Wireshark was that my…
kolrie
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Running out of TCP ports in linux(Red hat) while doing load test

I'm doing load test for 30000TPS(transaction per second) using gatling, I facing the following error i.n.c.u.Errors$NativeIoException: newSocketStream(..) failed: 99128 (99.43%) Too many open files > j.n.ConnectException: connect(..) failed:…
Debugger
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How to list all the TCP_alloc on a server?

I run a node_exporter on my server and node_exporter shows that there are over 5K TCP_alloc on the server. After rebooting the server, the count of TCP_alloc is still over 5K. There are only a few lines when I run the command netstat -anltup. Is it…
Hank Chow
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Server 2019: slow upload

I have both Windows 10 Pro and Server 2019 VMs set up on the same host. From the Server 2019 instance, using iperf and the same NIC/driver as the Windows 10 guest, I get ~3Mbps on a theoretically 100Mbps link. The Windows 10 guest gets me ~40Mbps…
Harv
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Why we get TCP retransmissions through IPSec Site-by-Site Tunnel

We use two pfsense firewalls at two locations and have connected the locations using IPsec site-by-site. That had worked well for a long time, now we had installed the 2.6.0 update at both locations and suddenly the speed dropped massively. I've…
kockiren
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TCP communication on port not responding on different Availability Zone or Subnet

I'm a little curious and confused about this situation. We setup a monitoring instance scraping an exposed endpoint on 2 different instances. Both on same VPC, same security group, same route table and ACL. Also, both instances uses the same AMI.…
forgondolin
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UFW route not responding

Hi i tried to make a server where every software running on it is in a vm. i tried using ufw to route the requests and it worked ... locally. when i tried to connect to one of my vm using a vpn i saw this in tcpdump(ran outside a vm dump where we…
Marc BARBIER
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The packet goes through the other router

I want to connect two hosts in parallel with two different models of virtual routers. These are made redundant by VRRP. Originally, packets are sent through only one of the routers. However, when the packet is sent, it goes through two routers. This…
rei
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Having Trouble Identifying TCP Congestion Control Provider option: Default

I am running a Windows 10 (Version 1909) OS and when I am entering the following command in CMD ... netsh interface tcp show global ...I am able to see add-on congestion control provider set to "Default" I would like to know what do you mean by…
DeathS7roke
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