Tagged Questions

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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12 views

NTttcp shows slower throughput on loopback (127.0.0.1) than on network

I am using NTttcp to find a baseline for what throughput I can expect between a client and server on windows. When I ran the client and server on two different machines on our LAN I got the following ...
-1
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0answers
15 views

apache 2.2 vs 2.4 TIME_WAIT issue

I'm using apache + tomcat through mod_prody_ajp on windows server - simplest configuration without any tunings. Apache 2.2 could reuse TCP connections when forwarding request to tomcat. Apache 2.4 ...
0
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1answer
29 views

TCP Load balancing

I need to implement an architecture that can serve 3 million GPS Devices sending Location Updates/Alerts (every 10 secs) to our system for processing. Features: 1) TCP communication. 1) Long lived ...
4
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2answers
714 views

TCP Dump, cannot understand these 4 lines?

I need support understanding these 4 lines. looks like tcp dump but im actully not understanding what exactly is happening here. 13:13:22.407445 IP 192.168.246.128.54955 > 192.168.246.13.80: S ...
0
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1answer
57 views

How does an IP address goes down from an Application Layer to IP Layer? [closed]

Using the classical TCP/IP layers model, I am thinking about an application (for example a browser) acting as a client wanting to talk with a server (e.g. a web server). Of course it has to use the ...
2
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1answer
63 views

TCP piggybacking introduced by a man-in-the-middle network node beween the client and server?

When wireshark trace taken on the client side it appears to be: ---SYN---> <-SYN-ACK- ---ACK---> -HTTPGET-> But when wireshark trace taken for the same traffic on the server side it ...
1
vote
1answer
66 views

Is there a netstat -s equivalent for windows?

I know that netstat -s exists on Windows, but it displays way less informations than on Linux/OS X. It only gives 8 counters about TCP, while on Linux it's more than 50. I'm looking for any ...
3
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0answers
54 views

TCP Window Scaling Problem over MPLS

After extensive troubleshooting why the TCP speed over an MPLS circuit is slow in one direction, I figured out that by adjusting the TCP window size the situation improved a lot. Maybe you can tell me ...
2
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0answers
36 views

TCP congestion collapse

I am experiencing suboptimal performance on an EC2 instance connecting to an RDS instance. This particular instance was built before VPC's existed, so all the traffic is flowing through a single ...
0
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2answers
43 views

Proxying TCP by hostname

I've got multiple game servers TCP ports on my single host machine. The goal is to have users be able to connect to server1.domain.net and have their directed based on that subdomain. My first ...
0
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0answers
44 views

TCP ignores some packets for no reason

I have a weird problem which I can't understand. The actual network configuration is quite complex, because I am using Openstack and Docker to build a virtual network. However, the problem is not ...
3
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0answers
49 views

TCP connection stuck in SYN_RECV state despite ACK received

My client and server are both internal machines. tcpdump on both client and server show all three parts of handshake are communicated, however netstat on server shows SYN_RECV, and on client shows ...
32
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1answer
867 views

Random TCP RST's on certain websites, what's going on?

Short version: One Windows Server 2012 machine on my network is getting persistent but intermittent TCP RSTs when connecting to certain websites. Dunno where they're coming from. Check out the ...
0
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2answers
62 views

Recommended TCP keepalive settings for a busy server

We are having some network timeout issues on a Debian server that is quite busy, and maintains multiple connections to a number of other servers on the network. Here are our current TCP keepalive ...
0
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0answers
18 views

Clients phone provider claiming high latency over UDP, how do I test?

A client of our uses a hosted phone solution for his 50 agent call centre. They use a hosted dialer who make the out going calls, once the connection is made the call is passed to my clients user ...
0
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0answers
29 views

Windows Server 2008 consuming a lot of bandwidth

My Windows Server 2008 has been consuming A LOT of bandwidth in the last days (990 GB). This is a development server so it should not consume more than 100mb aprox. We noticed this after the server ...
0
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0answers
9 views

How does a web server return an HTTP request? [migrated]

I'm sorry if this is a really stupid question; my networking knowledge is pretty sparse. So, a user makes a HTTP request to some address. That request comes from an address on a local subnet, but the ...
0
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2answers
49 views

Can't block spammy IP

I'm being attacked by 37.59.4.76. It's sending me a great amount of data, which is destroying my dataplan. I've added the iptables Chain num pkts bytes target prot opt in out ...
-1
votes
2answers
42 views

TCP/UDP Small Package Size optimization [closed]

I currently have the problem, that when a LOT of RTP streams (>800) go to one server the max. speed is onlynabout 70-80 Mbit (on a Gigabit LAN - all Hardware components are Gigabit components) 130 ...
5
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0answers
76 views

POST of MTU + ~798 bytes gets lost

I have a very weird issue with certain packets not arriving on the destination host. It happens when we transmit a POST that is somewhat larger than the MTU. We can reproduce it with this script: ...
2
votes
1answer
37 views

Relationship between tcp state TIME_WAIT & HTTP keep-alive

What is the relationship between keep-alive on a HTTP request and a tcp socket in TIME_WAIT - should they be correlated? Furthermore, should system and web server settings be aligned e.g. ...
0
votes
0answers
9 views

Source ip based Anycast-BGP?

I'm just getting interested in networking so don't be too harsh on me :) Ideal: 2 servers with shared ip; ip X Client 1 pings ip X > always server A Client 2 pings ip X > always server B ...
-1
votes
1answer
25 views

Geo distributed ip [duplicate]

When i ping 8.8.8.8 from my home computer (europe) i get around 26 ms latency. When i ping 8.8.8.8 from a server(US) i get around 1 ms latency. When i ping my (US) server from home (europe) i have 130 ...
0
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0answers
28 views

HAProxy RTMP (TCP) load balancing

I am using HAProxy as load balancer for the RTMP protocol. For now it's working very very good but I have one small problem. I want to send the client's IP on the RTMP request after the load balancer. ...
0
votes
1answer
80 views

How to trace dropped TCP connections?

Trying to help someone with a situation where TCP connections get mysteriously dropped after a few minutes for no apparent reason (this happens even with non idle connections). Both client and server ...
-2
votes
0answers
31 views

Many output tcp connections in SYN_SENT status showed up [duplicate]

I manage some Linux servers, I find a strange phenomenon since last month. When I'm running netstat command, it shows me too many tcp connections point to specific ports like 22 or 80 of different ...
0
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0answers
23 views

apache bench handshake failure server sending TCP FIN

I am trying to verify handshake performance by sending number of requests with out setting concurrency with below command. ab -k -n 18750 -c 1 -Z AES128-SHA -f TLS1.3 ...
0
votes
4answers
110 views

Cannot work out what is using port 8080

In Windows Server 2003 R2 64 Bit SP2 I have an app which will only use port 8080 but something is already using it. I would be happy to just kill whatever is using it but I can't work out what it is. ...
0
votes
1answer
46 views

Existing TCP Relay Solutions [closed]

I have a scenario which requires the use of a TCP Relay. Before I set out to write something custom, I wanted to see if anyone knows of existing software that can do this for me. I have 2 devices on ...
-2
votes
1answer
36 views

TCP ports duplication [closed]

I need to communicate server1 to server2. Server1 should have to fetch some records from Server2 when we execute program.exe will make server1 to fetch server2 When I gave netstat -an | find ...
0
votes
2answers
51 views

Wireshark “length” column - what does it include?

Can anyone tell me what the "Length" column in WireShark refers to? I'm pretty sure it's the "size" of the entire frame on the wire. I did some calculations, but I didn't get the number that ...
1
vote
1answer
79 views

HTTP not finishing over LAN. Hardware cause?

On a customer server running Apache 2.2 on Windows server 2012 we're noticing that from time to time, some requests to the server never finish. Using wireshark I've found a bunch of duplicate ACKs get ...
0
votes
0answers
38 views

Cannot connect to TCP service from remote host

I have two servers running RHEL 5.8. SRV1 (10.58.192.36) has a service running on port 9002 and I need to connect to this service from SRV2 (10.58.192.42). [root@SRV1 ~]# netstat -anp | grep 9002 tcp ...
0
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0answers
58 views

TCP [RST,ACK] ignored

I have a Windows 2008 server and an application that connects over Internet to it. From time to time I see that I receive a TCP [RST, ACK] that is ignored by my application. Using TCPViewer I still ...
2
votes
1answer
66 views

iptables: match only the first packet of established TCP-connection

In my Apache-logfiles I find a lot of entries that contain "GET /w00tw00t.at.ISC.SANS.DFind:) HTTP/1.1" 400 or similar crap. They come from non-RFC2616-connections (HTTP/1.1 without hostname). I ...
0
votes
0answers
36 views

Networking issue in IBM x3650 after install Ubuntu 14.04

I have a problem making TCP connections after a fresh Ubuntu 14.04 installation. First of all, after booting the interface is always off. In my case the interface is manually configured and named em2. ...
0
votes
1answer
36 views

High number of TCP RST packets

Whilst looking into some transient network issues, I have noticed what seems to be a high number of RST packets received: Tcp: 40091950 active connections openings 44754733 passive connection ...
10
votes
1answer
236 views

Under what circumstances is TCP-over-TCP performing significantly worse than TCP alone (2014)?

Many admins keep perpetuating - on ServerFault and elsewhere - how bad of an idea TCP-over-TCP is, e.g. in VPNs. That even the slightest packet loss will make one suffer from at least severe ...
0
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0answers
20 views

Duplicated TCP SYN Messages: second one is ACKed, but the connection is finally FINed

While wring a TCP server program, I found a very interesting symptoms. clients sends a first SYN packet. (server does not show any reactions.) clients sends another SYN packet after one second. ...
-1
votes
1answer
26 views

Application protocol-based port forwarding/redirection [closed]

I need to split traffic on port 80 between HTTP and non-HTTP, and internally forward HTTP traffic to a port nginx will listen to, and non-HTTP traffic to port 22. Does anyone know of a piece of ...
1
vote
2answers
120 views

Send Text String to a Socket In Windows

I have a server that has an open socket that listens for a particular text string on it in order to perform an action. Our linux machines send this data via: echo "text_string" | nc -w 2 ...
-1
votes
1answer
46 views

FTP upload slows down when devices are connected via hub [closed]

I have a setup with a network hub and three Ethernet devices. One of them is a PC (running windows XP), two others are hardware components that need to communicate with each other over the network. ...
1
vote
0answers
29 views

Why do some outgoing IP traffic not contain UID information?

I am doing egress logging on my server using IPTABLES with the following line which is supposed to provide UID information on all traffic that is logged: -A OUTPUT -j LOG --log-prefix "IPTABLES(O): " ...
0
votes
2answers
63 views

tcp ack delay almost 600ms, is this all right?

As far as I konw, tcp delay ack always 200ms, but now in my production environment it delay almost 600ms, my environment is below: ubuntu 11.04 48G memory 16 core, load not heavy; I catch packet in ...
1
vote
0answers
57 views

Why do I get connection timeouts to private services in Azure?

I seem to be seeing this with both my SQL Server, and my MongoDB replica set. I only get a handful a day, but it still concerns me. I am getting a timeout when trying to open a new connection to the ...
1
vote
0answers
51 views

TCP Window Size Allocation, TCP Window Zero Errors and Network Latency

My mind is about to explode as everyone is always blaming the network guys for disconnections and slowness in the networks, but Solarwinds Reports that all utilization in the network devices and links ...
1
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2answers
563 views

What does TCP: too many orphaned sockets mean?

When I use dmesg to look at linux kernel messages, I see a flood of.... TCP: too many orphaned sockets messages. My guess is this is sockets that are hanging around in TIME_WAIT after being closed ...
0
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0answers
77 views

Connection Timeout Issues - Solaris 11 SPARC

We're currently running some performance tests using Solaris 11 (SPARC) on some large hardware. The tests, which consist of sending SOAP requests (50kb per request), are running well up until we get ...
2
votes
2answers
182 views

TCP under OpenVPN is very slow (tsg attached)

I have a very weird problem with OpenVPN. Most VPNs work fine, except this one. Here I get very low performance from TCP connections, but the CPU load is low (so, not a CPU issue). OpenVPN is ...
0
votes
0answers
40 views

Single TCP-CLOSE_WAIT connection brings down application till restart

Recently found a behaviour where my application had a connection in TCP Close_wait state till the app was restarted (after about 5 hours). But during this period the SUnreclaim space was also ...