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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1answer
46 views

Any tool for forking/teeing/sharing a TCP connection to the remote server?

Here's my problem. I'm building an automation program that talks to a remote server (think of it as a chat server or MUD game server) through TCP. While my automation program is doing its thing, I ...
0
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0answers
7 views

What is the default value for TCP accept queue length on Linux?

I have read this article but it doesn't mention where the default accept queue length can be found (it does mention tcp_max_syn_backlog though, but it's different). I'm working on a Java 8 project ...
0
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0answers
19 views

Large payload - connection get's Hung with CLOSE_WAIT or LAST_ACK state

We have a webservice client which posts data to a 3rd party Webservice. We are having an issue when the payload is a bit large (Around 600KB) xml. Once we pay the process hangs forever. The Netstat ...
0
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2answers
31 views

Wireshark Packet Capture Data Data ACK Confusion

I understand how acks work and windowing works. What I am not getting is why am I seeing the following behavior in packet captures Client Server data1-----> data2-----> <--------ack ...
0
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1answer
39 views

How to setup linux to retransmit TCP packets by reducing the packet size like OS X

On OS X I noticed that for packets which are not ACKed, the system retransmits them with reduced packet size. This can be seen in the image below. Is it possible to enable the same behavior in ...
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1answer
12 views

Time until a TCP socket closes if the connection is lost

How long will a TCP socket remain open if there's a loss of a network connection between the source and the destination?
0
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0answers
22 views

Why sar ETCP shows TCP retransmission but wireshark tcp.analysis.retransmission doesn't

I am trying to investigate the cause of TCP retransmission. When I use sadc and sar, it shows there are tcp retransmission; but when I use wireshark on all of the server's interfaces, it doesn't show ...
0
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1answer
16 views

What's the default TCP window size of iperf3?

Does anyone know what's the default TCP window size for iperf3? It is not mentioned in the manual and I also can't find it in the output, when running a test.
0
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0answers
18 views

Can't transmit from multiple virtual vlan id interfaces on same interface

I'm creating virtual interfaces of vlan id on same interface, i.e: eth0 - the main interface with ip 0.0.0.0 . eth0.1 - tagged interface under eth0 with ip 10.0.0.1 . eth0.2 - tagged interface ...
-1
votes
2answers
65 views

How does TCP offload NIC cause the TCP checksum to be invalid?

A tcpdump pcap exported and being investigated on another machine with wireshark is showing a lot of invalid TCP checksum messages. This is a known and documented phenomenon when using TCP offload ...
0
votes
1answer
34 views

Linux server failing to send SYN/ACK after receiving SYN remotely, works locally

Problem: A server process can be accessed by a device on the LAN or by the server itself, but it cannot be accessed outside the LAN (port forwarding is configured correctly as the server does receive ...
1
vote
1answer
36 views

How to set the maximum TCP receive window size in Linux?

I want to limit the rate of every TCP connection. Can I set the maximum TCP receive window size in Linux? With iptables + tc can only limit IP source. The parameters net.core.rmem_max and ...
-1
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0answers
15 views

Wifi, remote connection, mysql

I am having this really strange error on my connection to my mysql server from a remote host. It basically hangs out large queries with blob or throws the following Warning: Empty row packet body; I ...
0
votes
2answers
27 views

Count number of incoming connection on a port - Linux

We have a server which listens on port X. The server has a large number of clients, from time to time the process gets hung, I am seeing SYN flooding messages in the log. I have been trying to tune ...
0
votes
1answer
22 views

TCP connection RST after FIN, ACK

I have a situation that would like to clarify with the experts here. I am no network expert so maybe it's normal, but i rather ask. We are trying to diagnose a problem between two servers, both are ...
3
votes
3answers
67 views

Do clients typically implement failover/load-balancing on multiple A records?

Typically, load balancers like Amazon's Elastic Load Balancers use a DNS record set with multiple A records to provide multiple load balancer instances which can handle traffic to requesting ...
0
votes
0answers
35 views

multiplexing a TCP connection through a dumb shell connection?

I am connecting to a VPN whose gateway is sufficiently misconfigured that basically the only useful thing I can do with it is to ssh to a specific Linux host set up for my usage inside the VPN, and ...
0
votes
0answers
16 views

stunnel keeps stopping with WSAECONNREFUSED given

Right so bit of background to start with I've got 2 stunnel installs on 2 different servers and basically using ensemble and stunnel to bounce a message around with ssl cert. Here is the flow. Where ...
0
votes
0answers
32 views

TCP Balancer active/standby active/passive

I have two Servers, Server A,ServerB. running as TCP socket server. I want to a active/standby or /active/passive failover. that means: 1:Server A and Server B Running, route ALL connection to ...
1
vote
0answers
40 views

Nginx log to syslog on TCP port

I need to redirect Nginx access and error logs to a remote syslog server. From http://nginx.org/en/docs/syslog.html I saw that I can do: error_log syslog:server=192.168.1.1; However I need to ...
1
vote
1answer
36 views

TcpTimedWaitDelay is missing in Windows Server 2012

Suddenly my server log shows: An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full And I googled and found these links as ...
0
votes
1answer
31 views

PCI Scan failing at TCP Source Port Pass Firewall testing

I'm trying to get PCI scan PASS for my website, Scan failing at this step. The host responded 4 times to 4 TCP SYN probes sent to destination port 20 using source port 80. However, it did not ...
1
vote
1answer
24 views

utility of using ALL in --tcp-flags in iptables rule

I m wondering what is the difference between the following 2 --tcp-flags rules: 1) -p tcp --tcp-flags SYN,FIN,RST SYN,FIN,RST 2) -p tcp --tcp-flags ALL SYN,FIN,RST
0
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0answers
7 views

Windows/IIS7.5 half-closing connections resulting in sockets in TIME_WAIT

I'm seeing scenarios where the client side initiates the TCP close but the webserver (IIS 7.5) simply responds with an ACK and the connection ends up in TIME_WAIT. Why would it do that? Typical HTTP ...
0
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0answers
25 views

lower tcp throughput than expected

I've conducted some tests which measured tcp throughput via wireless and wired connection. (a) was wired link between my desktop and my home router. (b) was wireless link between my desktop and my ...
-1
votes
1answer
34 views

Manually sent ICMP redirect packets [closed]

I'm trying to sent a ICMP redirect to my router to add a new route, as I can not configure it from the portal, and have no access to it though telnet/ssh. The scenario is the next. LAN network ...
0
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0answers
9 views

What filter in Wireshark, can return the ACKs packets employed to complete TCP three-way handshakes instigated by a particular party?

What filter in Wireshark, can return the ACKs packets employed to complete TCP three-way handshakes instigated by a particular party? For instance if machine A requests for a TCP connection to be ...
0
votes
1answer
35 views

Is it normal to have HTTP 499 errors in 1 out of 4000 requests?

I made a website, behind CloudFlare, and sometimes I get an early terminated (nginx 499) request, which is really hard to work around in the codebase. This happens in about 1 out of 4000 requests. ...
1
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0answers
13 views

TCP tuning for DPM on Windows 2012

I've got a pair of servers on opposite ends of a fast (1-10Gb depending on the server) but higher latency (40-60ms) link. Various network tuning options have been set resulting in iperf3 yielding ...
0
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0answers
316 views

Weird CLOSE_WAIT statuses at standard PHP application

I am asking for help regarding tcp problems on a webserver serving a web application built in PHP. The client is a standard html/js page viewed in the web browser. This client sends Ajax requests ...
0
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0answers
15 views

How to debug lost connections

I'm having a problem between a computer running Filemaker Server and their clients: clients loose the connection often (3-4 times per day), even when the user is using it (so no disconnect on idle). ...
1
vote
1answer
52 views

Cannot ping through one of the network interfaces

Setup ubuntu linux VM ( virtual-box) is configured with two interfaces, eth0 and eth1. eth0 is on a bridged network and directly connected to external network. eth1 is on "nat network", which is ...
0
votes
2answers
24 views

How should a long-lived connection behave when there is a DNS change?

Scenario: Connector.com connects to server.net, which resolves to 20.30.40.50 Connector.com and 20.30.40.50 keep the connection open DNS is updated so that server.net now resolves to 7.8.9.10 ...
1
vote
1answer
75 views

Nginx TCP stream routing based on source IP

I have configured nginx as a reverse proxy for a TCP (non-http) stream. I'd like to apply different routing for a particular source IP address - can this be done, and how? I'm aware of recomendations ...
8
votes
2answers
1k views

How to configure iptables so an unwanted port is not reported as filtered

I'd like to stop others from seeing my ports as filtered in the nmap standard scan (unprivileged). Let's say that I have the following ports open: 22, 3306, 995 and a firewall configured like this: ...
0
votes
1answer
78 views

Nginx TLS Performance Optimization

I switched a busy site to TLS-everywhere and HTTP/2 last week. Performance hasn't improved as much as hoped. In fact, depending on how you measure it, you can argue it has degraded. There is plenty ...
1
vote
1answer
51 views

Ephemeral port reuse for TCP connections to different IP addresses

I know that a web server running a website on TCP port 80 can receive TCP connections from many different IP addresses sourced from many different ephemeral ports. Can a client initiate multiple ...
0
votes
1answer
82 views

Sonicwall: cannot send email (outlook) and drops connection (google drive)

I will start by saying Im a web developer and my networking knowledge is very limited, please be patient =) . We dont have network/sysad in our company. We are having problem with our connection. We ...
2
votes
1answer
43 views

Can I trust a TCP segment with a payload of 255 bytes will be delivered in a single Ethernet frame?

I'm writing some server software that upgrades the firmware on an electronic device. It's a tricky task, because currently these devices don't have enough memory to hold a full firmware before ...
1
vote
1answer
41 views

Long lived TCP connection to DNS servers

Typically the TCP connections to DNS servers are expected to be short lived, ie: the client connects, sends the query and disconnects on getting the response. If a client wants to keep a long lived ...
-4
votes
1answer
29 views

How to open entire subnet with iptables [closed]

I want to enable the entire subnet 192.168.1.0/24 which is connected to eth0 in input. I'm very unfamiliar with iptables. If I add the rule: # iptables -A INPUT -s 192.168.1.0/24 -p tcp -m tcp ...
-1
votes
1answer
43 views

What is a TCP Relay and when is it used? [closed]

Tcprelay is a TCP connection forwarder with load balancing capabilities. If compiled with TLS support, it may be used as SSL encryption wrapper. What are some practical applications of TCP relay?
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votes
1answer
25 views

Is it possible for SYN/ACK to not be immediately proceeded by a SYN in a network trace

I'm writing a simple program to calculate initial RTTs from a network capture I took using Wireshark. To do this I wan't to calculate the difference in time between the SYN and the SYN/ACK. I don't ...
0
votes
0answers
35 views

What happens when connecting to port in TIME_WAIT state?

I'm trying to understand the effect of TIME_WAIT on subsequent TCP connections. I understand how TIME_WAIT behaves when net.ipv4.tcp_tw_reuse = 1, as explained by this answer. But what happens when ...
2
votes
0answers
32 views

TCP Handshake fails when ICMP Redirects are enabled

So it seems that due to ICMP redirects it's not possible to connect to a server behind a VPN connection. It immediately responds with a TCP RST (with manifests itself in SSH as ...
6
votes
4answers
651 views

ran out of tcp udp ports [closed]

How to resolve a Windows or Linux system that runs out of the tcp/udp ports on a single server? I have over around 65000 tcp/udp ports being used on a single server as a result of SQL connections, ...
0
votes
0answers
21 views

tcp receive buffer size min value seems not work

I tried to increase tcp min receive buffer size to 87380, so in my test it would OOM quickly with a little connections. net.ipv4.tcp_rmem = 87380 87380 6291456 net.ipv4.tcp_wmem = 87380 87380 ...
5
votes
3answers
294 views

How to fine tune TCP performance on Linux with a 10Gb fiber connection

We have 2 Red Hat servers that are dedicated for customer speedtest. They both use 10Gb fiber connections and sit on 10Gb links. All network gear in between these servers fully support 10Gb/s. Using ...
1
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0answers
18 views

Measure goodput before sending a response

My idea is to make it possible for web applications working on slower connections to fallback on alternative smaller asset versions(like images, videos, etc.). HTTP Live Streaming has similar behavior ...
2
votes
1answer
85 views

TCP connection; ACK not received

I am having trouble sending mail from Linux to Exchange server. When I telnet from Linux to Windows on port 25, I am not receiving any message from Exchange. The connection is automatically terminated ...