Questions tagged [tcpip]

TCP and IP are two important protocols used in networking today. Due to their importance, the Internet Protocol Suite is also commonly known as "TCP/IP"

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How does the HTTP GET method work in relation to DNS protocol?

I am trying to understand application layer protocols in TCP/IP stack. I know that both HTTP and DNS protocol stay at the top layer (Application Layer). So, when a browser wants to access a resource, ...
Giancarlo Perlo's user avatar
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359 views

Early tear down of communication

I have an application which performs an LDAP search which works in one domain but not in the other, when analyzing the packets sent between the application server and the domain controller being ...
user3129787's user avatar
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1 answer
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External DNS takes a long time to resolve for AD computers

On our AD domain, end users desktops take a long time to resolve DNS from outside our company. Internally everything works fine. The desktops are pointing pointing to 192.168.2.4 and .6. Those are ...
Keltari's user avatar
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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 ...
user3474444's user avatar
21 votes
2 answers
134k views

What is [PSH, ACK] doing during my connection to a global catalog server?

A linux server of mine is trying to establish a LDAPS connection to a global catalog server and the connection is getting dropped (presumably by the GC side). For the purpose of discussion, let's ...
Mike B's user avatar
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Port forward remote desktop without a gateway over 3G modem router [closed]

I'm trying to connect from a laptop, through a VPN, and a 3G modem/router, to a remote PC / computer. PC (192.168.1.33) | 3G Modem (192.168.1.22) | [3G internet, connecting to VPN] | ...
Rhett's user avatar
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1 vote
2 answers
2k views

Incoming TCP SYNs possibilities

This might be a general TCP question. Can I receive TCP SYN packet on an ESTABLISHED connection OR a connection in TIME-WAIT state? Is this possible?
hari's user avatar
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3 votes
2 answers
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When a server IP changes, do exising TCP (e.g. http/mysql) connections remain running

We have some PHP-FPM servers and when they need a database connection, they connect to an HAProxy server which selects them a database server to use and the connection opens. When we then want to ...
Luke Cousins's user avatar
2 votes
1 answer
139 views

How to compare 2 TCP/IP stacks or implementations? [closed]

I have to recycle an old machine into a networking node for managing TCP/IP connections and PPP protocols ( basically a DSL connection ); I'm not asking for something more than this, all the tasks ...
user2485710's user avatar
2 votes
1 answer
945 views

Host doesn't send ACK-SYN packets for transparent proxy

I am setting up a transparent proxy using haproxy, the setup works without the 'source 0.0.0.0 usesrc client' line. When I add that line in, the endpoint is called from the original client's ip ...
CamW's user avatar
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-5 votes
1 answer
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What is the incentive to operate a TCP/IP node? [closed]

I mean, why does anybody relay messages to other nodes? Why are these eleven good people below helping me send my bytes to their destination? traceroute to stackoverflow.com (198.252.206.140), ...
pinhead's user avatar
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4 votes
3 answers
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Can you use WMI to determine if a connection gets its DNS servers from DHCP?

The DNS server search order for a network interface can be read from Win32_NetworkAdapterConfiguration like this in Powershell, or programmatically using .Net ManagementObjects: > $NICs = Get-...
Derrick's user avatar
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1 vote
0 answers
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Printer lpd daemon refuses print job if a command's new-line sent separately -- bug?

I'm encountering some printer LPD daemons which work fine if the new-line is sent in the same packet as the command, but break if the new-line is sent in a separate packet. Is that a bug in these ...
Wayne Conrad's user avatar
0 votes
1 answer
593 views

TCP client and server work for X times but hang after that

I'm a software engineer, but I think my problem needs a network engineer... For the software side of things, have a look at my Stack Overflow question: https://stackoverflow.com/questions/21641219/...
Michael Balloni's user avatar
-2 votes
2 answers
10k views

List of TCP & UDP ports known to be used by malware, etc [closed]

Where can I find a regularly updated, downloadable list of TCP & UDP ports that are known to be commonly used by malware, trojans, etc.? This is for import into an IT asset management system to ...
Zek's user avatar
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Could the IPG parameter in Robocopy cause TCP/IP packet problems if it is too high?

I need to throttle a robocopy transfer to limit bandwidth usage. It is already set to 1500 (/IPG:1500). I would like to increase this IPG to around 2000 (or more) in order to lower even more the ...
Idriss's user avatar
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5 votes
2 answers
1k views

once in a while windows / .net application ignores the tcp fin flag

i've run into a network problem which i cannot solve. on a few computers running windows 8.1 and communicating with linux http server tcp connections dangle on the windows side instead of being ...
pQd's user avatar
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3 votes
1 answer
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What else does "netsh int ip reset" do?

According to this KB article when you run the "netsh int ip reset" command, all it does is to reset the content of two registry keys: SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\ SYSTEM\...
Chris's user avatar
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5 votes
1 answer
19k views

ping -a sometimes returns host name and sometimes returns FQDN. Why? Does this mean DNS is corrupt somehow?

I have a Windows machine called abcd for example and it uses DHCP to receive an IP address (172.28.45.5 for example) When I perform ping -a 172.28.45.5 sometimes I receive abcd as the hostname. ...
Blue Tongue's user avatar
10 votes
1 answer
47k views

Diagnosing packet loss / high latency in Ubuntu

We have a Linux box (Ubuntu 12.04) running Nginx (1.5.2), which acts as a reverse proxy/load balancer to some Tornado and Apache hosts. The upstream servers are physically and logically close (same DC,...
Sam Gammon's user avatar
1 vote
1 answer
2k views

Server with two default gateways won't listen on the second gateway

I am testing a redundant internet connection setup that works like this - I have a network segment, 192.168.80.X It has two gateways - 192.168.80.1 - a FW connected to a frame relay line 192.168.80....
V. Romanov's user avatar
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6 votes
3 answers
53k views

ESXi network setup for isolated internal virtual machines

Using ESXi v5.1 and vSphere, my networking is setup like so: One standard Switch: vSwitch0 vSwitch0 has one uplink physical adapter (Internet connected) vSwitch0 VM Network has 3 virtual machines (...
Inator's user avatar
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0 votes
1 answer
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Where to find WINS IP address in registry?

I have been writting a powershell script to remotely dump the TCPIP information from the registry of machines in my Windows Domain. I was able to dump the default gateway, subnet mask, DHCP server ...
Blue Tongue's user avatar
-1 votes
1 answer
271 views

Need help routing Cisco network- IP routing [closed]

In the above network, can you help me configure routes so the computers on the left can see the computers on the right, and vice versa? I know the syntax of the command is ip route {network address} {...
Dave's user avatar
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1 vote
1 answer
2k views

Do keepalives to socket connections exist?

Pre briefing: Although my question is broad on purpose, I am dealing with nginx connecting to php-fpm (fcgi), which is served via a local socket (/tmp/somesocket.socket). Nginx has a setting to ...
anonymous-one's user avatar
0 votes
1 answer
1k views

is it possible to use ms loop back adapter to setup local vlan

Is it possible to use Microsoft Loop back adapter to set up Lan connection between two computer which is logically isolated from the main network? 1st computer: has a regular ip stack 192.168.1.x 255....
zman's user avatar
  • 633
3 votes
2 answers
6k views

How to globally limit total number of TCP connections with iptables?

I'm having quite a difficult time figuring out how to REJECT both inbound and outbound connections from a machine with iptables once the total number of TCP connections hits a global maximum without ...
Gordon Morehouse's user avatar
-1 votes
1 answer
619 views

Is their an official tool to tweak Windows 2008 server TCP configurations?

We are running scripts that initiates numerous TCP connections and disconnects right away. It's just to test if the remote report is opened and responsive. But we are having random strange issues ...
Muhammad Gelbana's user avatar
2 votes
1 answer
458 views

Enabling TCP/IPv4 through Windows PE

From RDP, i've disabled the TCP/IPv4 protocol by mistake and now, obviously, i can't use rdp anymore to re-enable it. Is there a way to enable it again from Windows PE?(OVH rescue pro)
user188237's user avatar
2 votes
2 answers
141 views

Random three minute delay for database server connect

we use InterBase on a Windows 2003 server, and in random intervals the client connection to the server takes 180 seconds (three minute) longer than usual. The application does not "hang" with the ...
mjn's user avatar
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2 votes
2 answers
3k views

Frequent interruptions of SSH connection to VPS

My SSH sessions die at what seem like random times - response will stop, and then a few seconds later PuTTY will pop up a message with, "Server unexpectedly closed network connection." It seems to ...
OsakaWebbie's user avatar
-3 votes
2 answers
657 views

what is meant by application layer protocols being encapsulated into transport layer protocols? [closed]

I am reading this wikipedia article: http://en.wikipedia.org/wiki/TCP/IP_model#Application_layer It talks about how TCP and UDP are transport layer protocols which are designed to connect one host ...
JohnMerlino's user avatar
0 votes
2 answers
9k views

Slow data transfer between Server 2012 and Windows XP/7 Clients

I've installed a new Dell PowerEdge R720 server at a small company which eight workstations. It is running Windows Server 2012 Standard. I've then installed Hyper-V (role) onto the server and created ...
David Mackey's user avatar
4 votes
1 answer
143 views

TCP works for a while, then fails, why?

This comes from an implementation of OpenStack, and we have a fix, but I don't understand why we need this fix. My machine has an ip of 192.168.20.45 My default gateway (pfsense) has an ip of 192....
boatcoder's user avatar
  • 548
1 vote
1 answer
7k views

Determing MSS value on Windows Server

In this Technet article about the MSS limitations of Windows Server 2008, it mentions: After analyzing the network trace collected on the source Windows 2008 Server, we found out that the remote ...
Rob Nicholson's user avatar
3 votes
1 answer
2k views

How to debug why WAN TCP/IP throughput is lower than expected?

I'm trying to figure out why tcp/ip throughput between two hosts I control is much lower than expected. Host A: internet connectivity provided by Comcast (Residential) in Boston Metro -- can ...
lilinjn's user avatar
  • 133
3 votes
1 answer
525 views

TCP Congestion Window on Windows Server 2003

After reading this blog post by Ben Strong, I started looking on the internet for information on how the Initial Window size could be manipulated on Microsoft Windows Server 2003 (R2, 64bit in case it ...
DRCRON's user avatar
  • 171
1 vote
1 answer
4k views

TCP/IP connection to SQL Express works on HALF of the clients in a WORKGROUP

So far I have learned the following facts about Microsoft SQL Server Express, including version 2012, and earlier versions like 2008R2, and 2008, and for the most part all the way back to SQL Server ...
Warren P's user avatar
  • 1,195
1 vote
2 answers
2k views

RPC SERVER is unavailable

windows 2003 is getting this error. restart the machine or just the network connection fix the problem. date and time is the same one. tcp/ip is started and running remote registry is running the ...
Y.G.J's user avatar
  • 317
1 vote
2 answers
586 views

How does VPN software 'hijack' packets for tunneling?

My current mental model An application interacts with the operating system to produce an OSI model stack-based packet process - subsequent layers of encapsulation Somewhere along the line before the ...
gal's user avatar
  • 113
0 votes
2 answers
410 views

Thousands of port 25 connections

Tonight a few IP addresses made almost 2500 connections on port 25 of a mail server. 2500 is the max limit, and 50 or less simultaneous connections is normal. They did nothing once they made the ...
xpda's user avatar
  • 151
0 votes
1 answer
1k views

Long TCP/IP Connect time (20-40s) with Apache 2.4, mod_proxy_ajp, Tomcat 7.0.39 running on Windows Server 2008 R2

The initial connection to an Apache HTTP Server is taking a very long time (20-40s), but the subsequent connection is very fast (<50ms). I use Apache HTTP Server as a load balancer using ...
Yusuf S's user avatar
  • 41
1 vote
2 answers
3k views

Linux server resend SYN ACK

I am troubleshooting a connection timeout problem between two Linux boxes, where it seems the ACK to SYN-ACK was lost on the server's stack. The tcpdump is done on the server side. The client got ...
wilsonh's user avatar
  • 11
0 votes
1 answer
152 views

Multi-IP server: how do programs know which IP to use?

I recently tried adding second IP address to our server for various reasons and found that now when I check netstat -anob there are many programs/services listening and establishing connections to ...
Kev's user avatar
  • 984
5 votes
3 answers
4k views

Practical Anycast

I've read How can I send visitors to the closest server using DNS? post, but there's still some thing, on a practical level that I don't understand. Say I have two servers. One in NY another in Paris....
Daniel's user avatar
  • 157
3 votes
4 answers
19k views

Smaller network packets vs bigger packets - confused

Some are saying that bigger packets are better to send then smaller. But in this app: http://media.pearsoncmg.com/aw/aw_kurose_network_2/applets/message/messagesegmentation.html The lower the packet ...
exeq's user avatar
  • 33
4 votes
1 answer
10k views

How to setup an TCP/IP proxy with traffic interception, for MS SQL traffic in this case

I would like to setup an MS SQL proxy server. It should forward all requests 1:1 and make it possible to log them, and modify some of the requests or answers according to some replacement rules I ...
mit's user avatar
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3 votes
1 answer
665 views

Given a 100mbit connection, what is your max downstream speed?

I'm a (very) junior sysadmin and was asked this question on an interview. The answer was 96mbit/s. I know this is related to network overhead but I cannot find any good information on why this ...
Scruff McGruff's user avatar
1 vote
2 answers
268 views

How to implement firewall in LAN(out of users' os) like EC2 have done?

In aws ec2, users can set up security groups which works like a firewall, usually, firewall work behind a gateway/nat server, however, I found that firewall in EC2 works in the LAN, too. For example, ...
ley's user avatar
  • 13
2 votes
3 answers
15k views

Squid TPROXY connection fails on specific sites?

When squid setup as TPROXY, returns ERR_CONNECT_FAIL on some sites . The server which squid runs on it is able to open those sites by lynx, wget, curl etc . Even if we manually set proxy in browser ...
Omid Kosari's user avatar

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