Server Fault Stack Exchange
Server Fault Stack Exchange

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

1656 questions
17
votes
7 answers

Why is it good practice to compare checksums when downloading a file?

Websites which supply ISO files for download will often give the md5 checksums of those files, which we can use to confirm that the file has downloaded correctly, and has not been corrupted. Why is this necessary? Surely the error correcting…
Aditya K
  • 923
17
votes
4 answers

What does LAST_ACK mean, as a State value in netstat?

If a Windows server has several thousand ports open in LAST_ACK state (as shown by netstat), what could this mean? Is it because one endpoint is waiting for the other to respond?
Nick Bolton
  • 5,146
16
votes
5 answers

How does server-side `TIME_WAIT` really work?

I know there are quite a few SE questions on this, and I believe I read as many of them as it matters before coming to this point. By "server-side TIME_WAIT" I mean the state of a server-side socket pair that had its close() initiated on the server…
Pawel Veselov
  • 846
6
votes
3 answers

Can excessive latency affect throughput?

I don't know if this question is on-topic here, so please redirect me if not. Trying to understand how TCP works, I had simulated a single point to point link using ns-3 simulator. On setting the bandwidth of the link to 5 Mbps, a suitable error…
pulsejet
  • 163
6
votes
3 answers

TCP sequence number

I would like to know if two segments of same sequence number arrive at the destination, which segment will get accepted ? For eg: A clients sends a packet to a server and wait for an acknowledgement . But it didnt received the ack(due to some…
Satheesh
  • 69
6
votes
4 answers

How do I "Close Connection" like TCPView does, using the command line?

I'd like to do what TCPView does from the command line, for example, closing a connection used by a particular process (without ending the process). Is there a way to do this?
Jon
  • 491
5
votes
1 answer

Server sends ACK in response to SYN causing a reset in TCP request from the client

We are getting 7% reset messages for our TCP layer messages. We have two sets of logs. The first of Wireshark logs shows a good request and response Here the client was replied with sync acknowledgement such as [syn, ack] seq=0 ack=1 [syn, ack]…
Sandy
  • 71
5
votes
1 answer

How to capture retransmitted packet info with tcpdump?

TCP retransmission rate on a host are often a good indicator of network problems. How do I find out the source and destination IPs for the packets that are being retransmitted? For context, on hosts that have sar installed, one can see the…
Aleksandr Levchuk
  • 2,495
5
votes
3 answers

How can I monitor the TCP traffic to a port for a given IP?

What I need to see is the TCP messages sent to a port for a given IP. So for example 127.0.0.1:11000 How can I see all the TCP messages being sent to that port? This has to work with Windows, either Windows 2003 or XP I have tried WireShark, but I…
David Basarab
  • 1,177
4
votes
2 answers

What characteristic of networking/TCP causes linear relation between TCP activity and latency?

The core of this problem is that our application uses websockets for real-time interfaces. We are testing our app in a new environment but strangely we're noticing an increasing delay in TCP websocket packets associated with an increase in websocket…
crockpotveggies
  • 336
4
votes
1 answer

TCP Connection Keep-Alive direction

When a connection have not received packets for a certain period of time (default 2 hours), it should send KEEP-ALIVE packets. My question is, who will start sending KEEP-Alive packets, the client, server or both?
Dog eat cat world
  • 216
3
votes
1 answer

What happens when a Server sends a data packet to the Client when the later (Client) is on TCP FIN-WAIT-1 state?

According to TCP/IP Guide, when a TCP session is closed by the Client, it will send a packet with FIN set to the Server and transition to FIN-WAIT-1, however it says: In this state the client can still receive data from the server but will no…
ligregni
  • 33
  • 4
3
votes
1 answer

How to enable/disable TCP DELAYED ACK parameter on SUSE linux?

I want to disable TCP DELAYED ACK parameter on SUSE Linux Enterprise Server for some performance tuning operations. I have used sysctl command but it does not list this parameter. also in SUSE Knowledge Base Docs it is mentioned that "SET TCP…
aashoo
  • 141
3
votes
2 answers

Deactivate SYN flooding mechanism

I am running a server that is running a service on port 59380. There are more than 1000 machines out there connecting to that service. Once I need to restart the service all those machines are connecting at the same time. That made some trouble as I…
mlaug
  • 202
3
votes
1 answer

In ip_conntrack, established but "stuck" TCP connections with huge time to live

I'm trying to understand the reason for/what do do about some weird entries I'm seeing in /proc/net/ip_conntrack on my (virtual) server. There appear to be a number of connections like this to/from my web server, in the ESTABLISHED state but with…
Neil Coffey
  • 171
1
2 3 4