TCP is just one communications protocol on the web. Others include: User Datagram Protocol (UDP) udp Internet Control Message Protocol (ICMP) icmp Hypertext Transfer Protocol (HTTP) http Post Office Protocol (POP3) pop3 File Transfer Protocol (FTP) ftp Internet Message Access Protocol (IMAP) imap ...
2
votes
2answers
22 views
Workarounds for probable TIME_WAIT issue preventing reestablishing broken SSH tunnels?
While not intending to cross-post, after sending this question to the OpenSSH list on SecurityFocus, I noticed that the list is rather low traffic (the previous post was approximately 5 months prior). ...
4
votes
4answers
114 views
Share one IP address with a simple router
We have just moved into a new office and have been given our 'internet connection' in the following form:
One Ethernet cable in the corner of the room
An IP address with subnet mask 255.255.255.0
...
3
votes
0answers
22 views
Different versions of iperf for windows give totally different results
Measuring TCP output from a Windows client to Solaris server:
WXP SP3 with iperf 1.7.0 --> returns an average around 90Mbit
Same client, same server but iperf 2.0.5 for windows --> returns an average ...
2
votes
1answer
40 views
Unclosed TCP connections in CLOSE_WAIT for various processes
I have cluster of several machines connected on 10GBE network (NICs are Intel 82599EB 10GBE SFI/SFP+) running under Debian 6.0 and faced with problem of hung up TCP connections in CLOSE_WAIT state. I ...
0
votes
1answer
19 views
130s timeout when accessing service exposed on HTTPS through HTTP
I have windows client application and windows service hosting a web service over HTTPS (on behind it uses standard http.sys). Everything is ok except the situation where user makes a mistake and uses ...
1
vote
1answer
46 views
No TCP connections to hosts behind VPN server (SYN, SYN-ACK, but no ACK), UDP, ICMP works
I'm probably doing something incredibly stupid, but I just can't seem to figure out what. Here's what I'm trying to accomplish: I want remote users to be able to log into our network, so I set up a ...
0
votes
3answers
39 views
TCP Port prioritizing on switch/router (QoS)
I have some HP ProCurve series Switch. There is a QoS option for prioritize traffic by TCP/UDP port. I set two ports: one with highest priority and another with lowest. Then I performed tests to ...
2
votes
2answers
41 views
HAProxy + nginx reaching max numtcpsock in about 24 hours
I'm running a relatively simple VPS (a Media Temple (ve)) with a few PHP-based websites and (eventually) a few Node servers. In order to enable WebSockets support, I'm using HAProxy on port 80, which ...
0
votes
0answers
29 views
What happens if a DNS requsted was not found in ther server? [closed]
Hello I am a newbie in networking. After trying and reading Networking and the Internets and the web I have not managed to find the right answer to this question
"Why it is required to configure a ...
24
votes
3answers
410 views
Tuning iSCSI storage
This is a Canonical Question about iSCSI we can use as a reference.
iSCSI is a protocol that puts SCSI commands as payload into TCP network packets. As such, it is subject to a different set of ...
0
votes
1answer
48 views
TCP Window Scaling. TCP scale factor not supported due to dynamic TCP Frame Size on windows 2008 server
PROBLEM
Calling an asp webservice hosted by an ISP from our WCF service hosted on Windows 2008 Server is showing timeout/no response from webservice.
DIAGNOSIS
Using windows network monitor ...
1
vote
2answers
17 views
SMTP server force outbound traffic
I'm having some trouble with setting up a SMTP server on a windows server 2003 machine, while trying to send emails using PHP through the internet, but to domain email addresses.
Common info:
...
0
votes
1answer
37 views
Waiting until TCP socket is available in bash
Helli,
I have a script that waits some time until a machine (being provisioned) comes up and then it connects to ssh and executes something. I use "sleep" for that.
I would like change my script to ...
0
votes
0answers
17 views
OpenSTA performance testing
I try to run some performance tests through OpenSTA. Here is the setup:
Windows 7 (4 core, 8GB RAM) running Apache Web Server; Windows XP SP2 virtual machine running on the same physical computer, it ...
0
votes
0answers
43 views
Wireshark capture stops showing packets…even though my server is definitely receiving client traffic
I'm looking into a potential network issue. On a dev box I've been noticing mysteriously FIN/ACK and RST/ACKs that are breaking comm between my client and server. However, before I can start to ...
1
vote
0answers
60 views
Disable kernel processing of TCP packets for raw socket
I'm working on a TCP/IP implementation, for an embedded device, that I want to test from a Linux user space process using raw sockets.
raw(7) says that
Raw sockets may tap all IP protocols in ...
5
votes
2answers
159 views
Clarification about Linux TCP window size and delays
I have delays when sending data through a TCP channel I am not able to understand. The link is a 1Gb link with a end to end latency of roughly 40ms. In my current setup, latency (the time from one ...
1
vote
0answers
111 views
ksoftirqd process overloads CPU with high-bandwidth and multiple network connections
I got a 10GBit Server with proxmox 2.1
installed. There's an OpenVZ container running with Ubuntu
10.04 64bit.
I can get 200-300MB/sec with wget from data-center internal servers (-O
/dev/null) which ...
1
vote
3answers
111 views
How to formulate IP forwarding rule using iptables
I have two Systems A and B. A is a TCP Client and sends a message to TCP Server on B.
------------------ --------------------------
System A System B
...
1
vote
0answers
55 views
haproxy tcp transparent mode on the same box as service
I'd like to set up transparent HA Proxy for TCP protocol.
It works flawlessly when HA Proxy is in front of the boxes that are running the service.
But when I try to set up HA Proxy in transparent mode ...
1
vote
1answer
65 views
Windows Server 2008 Low Throughput on Internet Latency Connections
We have some windows servers (2008 R2) and we are experiencing a strange network issue on them. The best way that I can describe it is that we are experiencing low throughput (but high bandwidth) ...
0
votes
0answers
61 views
Packets dropped at endpoint NIC — Windows 2003
I have a virtualized Windows 2003 server that hosts one of my pieces of server software. The problem is that the port listener of this server doesn't get the client traffic sometimes. With Wireshark ...
0
votes
3answers
47 views
TCP firewall allows connection to external server but blocks response packets?
Consider this basic network setup:
Client -> Router -> "Internet" -> Router -> Server
Problem: the client can open a connection to the server and send data ("request"), but the server data packets ...
1
vote
1answer
75 views
netstat reports ESTABLISHED connection even after I've pulled the cord
I'm experimenting with lost connections between my java application and my mysql server.
The application and the server are on two different machines and I'm pulling the physical cord between the ...
-1
votes
1answer
46 views
Determining TCP Congestion
How do I detect if I have TCP Congestion from looking at TCPDump data from a Linux box running a 2.6.x kernel ?
2
votes
1answer
58 views
How to debug dropped SYN-ACK packets
I have 2 load balancers in front of 4 other server machines doing roughly a combined 5-6000 requests per second. I've noticed that every few minutes, one the load balancers gets a connection timeout ...
2
votes
0answers
154 views
TCP Window Size going to 0 / Wget stops downloading?
I have a somewhat complex setup that doesn't work, and I'm struggeling quite a bit to track down the root cause.
First of all the big picture:
Node backend is a medium size windows azure worker role ...
3
votes
2answers
161 views
syn/ack sequence number confusion
I was looking at some random traffic in wireshark and came across this (using relative seq/ack numbers):
1. myIP -> 74.125.227.96 [SYN] seq=0
2. 74.125.227.96 -> myIP ...
0
votes
1answer
73 views
TCP sender and receiver window issues
I just want to clarify some things. Lets say the receiver advertises a window of 2000 bytes. The sender sends a 1500 bytes and receives an ack from receiver with window size 100. The ack does not ...
-2
votes
1answer
81 views
Windows7 attack Port: 1080, What can be? [closed]
I have a computer running Windows 7 64bit,
I'm realizing that in recent days, I'm being attack on port 1080/TCP that my firewall is blocking.
What can be?
I would be very grateful for the help.
4
votes
2answers
188 views
How do I optimize TCP stack for HTTP server?
I have a HTTP server that serves only two kinds of page: about 10 KB and about 16 KB (both compressed, other files are from CDN). As the latency is quite high (ping takes more than 300 ms), I want to ...
1
vote
0answers
70 views
Connection to mysql server in SYN_SENT
We are facing a strange problem from last few days between our application server and database server(Mysql): connection to database server from application server hangs in SYN_SENT state and after ...
3
votes
1answer
72 views
redirect all youtube video requests to a specific one
I'm on an IT team in my company and I would like to block youtube to users. I don't want to just deny access to the whole youtube domain, but only to replace the .flv/.mp4 request with the one that I ...
0
votes
1answer
25 views
Windows XP TCP halts after burst on ZMQ channel
I have a ZMQ application the sends a high rate of data over a TCP connection upon start up. The application runs fine on Windows 7 and Server 2003, but on XP it halts shortly after connection. The app ...
3
votes
1answer
115 views
What happens to tcp packets when they are unable to finish the 3 way handshake?
Firewall for a virtual dedicated server.
I was looking into how to prevent a FIN scan and it got me thinking about the consequences.
A lot of people are using this rule:
-p tcp --tcp-flags ...
1
vote
2answers
186 views
Speed up rsync by running multiple instances at once?
I have to transfer a big directory to another server.
My problem is that i cannot use the full bandwidth that would be available, because one concurrent tcp stream does not get as fast.
Basically ...
4
votes
2answers
123 views
tcp flags in iptables: What's the difference between RST SYN and RST and SYN RST ? When to use ALL?
I'm working on a firewall for a virtual dedicated server and one of the things I'm looking into is port scanners. TCP flags are used for protection. I have 2 questions.
The rule:
-p tcp ...
1
vote
2answers
124 views
Clients can make maximum only 15 connections to ubuntu custom server
I have a custom server in C# being run on Ubuntu 9 under mono. I can make up to 15 silverlight clients connect to the server. When I make the 16th, it just waits. And if I close one of the established ...
1
vote
1answer
82 views
Block all incoming DNS requests EXCEPT from IPs x,y,
I want to block all incoming requests on my two DNS servers APART FROM certain IP addresses e.g. IP of 1.2.3.4 will be allowed to make requests but NOBODY else will.
How do you do this with iptables?
...
0
votes
0answers
51 views
tcp syn not reaching server, connects after multiple retries
I am facing this issue related to syn without ack back from the server and client keep on sending the syn, connects after three-four retries, i am using java tcp server and cpp client.
I cross ...
1
vote
0answers
110 views
mysql error : "cant connect to local mysql server through socket
Taps Server Error: Mysql::Error: Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)
I get this error whenever I try to push my local mysql to heroku postgres. It ...
2
votes
1answer
84 views
TCP buffer size analysis
Is it possible to query the current size (or some kind of graph of the buffer-size over time for that matter) of the TCP buffer of a connection?
Each endpoint of a TCP connection will have a ...
0
votes
2answers
74 views
Best network tuning variables for a Linux proxy
What are the best settings to tune so that Linux can handle a very large amount of TCP connections such as would be seen by a proxy server or a webserver?
I'm using Centos6 and squid and am seeing a ...
0
votes
1answer
70 views
Very strange localhost connections on linux workstation. Need help identifiying the source
The following is the output of netstat on a Ubuntu machine. Can someone help decrypt the output? I am especially curious what the ::1:43213 connection is.
Also, why are there so many connections ...
0
votes
1answer
142 views
How to utilise netstat information
We have an application named "Seamer" installed on 2008R2 machine named "R2DUO" which has IP address set as 192.61.247.37 in host file and 172.26.127.40 is IP address of Ethernet card .We have two ...
1
vote
1answer
114 views
Slow performance over network (Ubuntu)
i did setup this NodeJs TCP Server and tested it with a message flooder. Just to see how the performance of the server is.
While the message throughput is great if i run the server and the message ...
0
votes
1answer
54 views
fast opening and closing connection with a specific port
We have a Main application named "Trevor" installed in 2008R2 machine named "TEAMER12" which is slow now. One more application named "TVS" also running in and found there were many connections per ...
0
votes
2answers
60 views
Why does Nexenta seem to ignore my /etc/system settings?
I am trying to tune my NFS performance, but for some reason nexenta is ignoring whatever I specify in /etc/system. In the following screen shot it becomes apparent that my manual settings are not ...
0
votes
1answer
44 views
Windows 2008 Server ignoring LDAP request
I'm using Windows Server 2008 R2 and Windows NIC teaming.
This is an HP server. Firewall disabled.
I have 1 application which authenticates via LDAP to AD (TCP 389). (App is located in same VLAN)
...
0
votes
0answers
66 views
TCP HAProxy disconnects immediately and doesn't reach backend
My TCP HAProxy (used for SMTP traffic in this case) drops the connection immediately
and doesn't reach the backend.
Example:
% telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape ...
