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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Windows XP/7: custom routing for VPN connection

We are dealing with a badly configured VPN connection from a vendor, which set up the default gateway but doesn't route traffic anywhere beyond their VPN zone. I managed to do some ad-hoc routing to ...
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“Address already in use” error from socket bind, when ports are not being used [closed]

I can not bind (using C or python sockets) to any port in the range: 59969-60000 Using lsof, netstat and fuser I do not see any processes using these ports. Other ports such as 59900-59968 and ...
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TCP RST Reset Every 5 Minutes on Windows 2003 sp2

Recently I had a web developer come to me and ask why he was receiving connection errors in his app that was accessing a sql database. So, I went through my normal trouble shooting steps to isolate ...
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use of tcp_delack_min on redhat linux (kernel 2.6.18)

we're moving from Solaris to Redhat Linux, and trying to duplicate our low-latency setup, that, on solaris, includes the ndd settings related to TCP NO DELAY, and NAGLE ALGORITHM. I got the impression ...
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How can I make WinXP bind to ports other than 1025-5000 for outgoing TCP connections?

(I originally posted a similar question on StackOverflow but readers recommended I post here instead) When you create outgoing TCP connections, most applications let the operating system choose which ...
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Linux IPTables / routing issue

EDIT 1/3/10 22:00 GMT - rewrote some of it after further investigation It has been a while since I looked at IPtables and I seem to be worse than before as I can not seem to get my webserver online. ...
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807 views

Solaris TCP/IP performance tuning

I am trying to tune a high message traffic system running on Solaris. The architecture is a large number (600) of clients which connect via TCP to a big Solaris server and then send/receive relatively ...
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3answers
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how do i change outgoing ip address for server centos

I need to make sure my clients outgoing ip address uses the dedicated ip they are assigned. For example, site123.com has an ip of 123.123.123.2(eth0:1) (resolves fine when incoming) but it is using ...
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Accepting a connection on a socket on Windows 7 takes more than a second

Here's what I've done: I wrote a minimal web server (using Qt, but I don't think it's relevant here). I'm running it on a legal Windows 7 32-bit. The problem: If I make a request with Firefox, ...
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4answers
449 views

Prevent a download to saturate all bandwidth on Linux

In Linux, a single download can use all available bandwidth, so that any other connection can't be started. (e.g. if I am downloading updates, I can't surf the web at the same time) Is there a way to ...
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674 views

Sonicwall VPN site unable to communicate with Windows PDC

(First question, please be patient) We have a SonicWall NSA-2400 appliance as our firewall within our primary location. (SonicOS Enhanced 5.1.0.8-17o) Remotely we have 2 sites with Cisco 2800 ...
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320 views

Wrong DNS for just one site on development machine

www.superyoink.de is my clients' website. I can access it from any machine except my development one. If I ping it on my development machine, I get 80.67.28.107 - this is wrong. My laptop, next to ...
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An already acknowledged data sequence number is coming back as null byte repeatedly

There is a transaction processing server (TP-Server) to which my application (Client) connects to. We are seeing a strange packet sequence where in the TP-Server is sending a PUSH packet with a null ...
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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 ...
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2answers
186 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, ...
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319 views

switch OFF syn cookies

We have several servers they have public IP's, but work together (one is with Load Balancer, orther with Apache Web server, other with MySQL and so on. Most of the ports are fire-walled, so only ...
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675 views

NIC Teaming , Multi-Homed, Active/Passive

I'm fairly new to NIC Teaming.. So I apologize if I’m not making any sense while describing this. I’ve, of course, set up plenty of simple Active/Active NIC teams for our servers without any issues ...
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880 views

Multiple Homed Windows 2008 Server / Windows 7 Client

I have a small Windows 2008 network, with some Windows 7 clients. The clients are both laptops with docking stations and I would like them to communicate with the Windows 2008 server (for filesharing) ...
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416 views

Why won't sql server express 2008 service restart after I enable TCP/IP Protocol?

Whenever I enable TCP/IP connections on my SQL Server Express 2008 database server running on Windows XP SP3, I cannot restart the service, it simply states "The request failed or did respond in a ...
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671 views

Changing TCP/IP IPID sequence generation algorithm on Windows Server

a recent security review on a customers webserver yielded the following results: "[...] The system under test is using incremental ip ids. This means that every outgoing ip packet has an ...
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423 views

Can't connect using TCP though UDP/ICMP works

My office changed IP addresses yesterday and since then we can't access any site hosted by mediatemple.net plus a couple of other sites. The office connection is ADSL (PPPoA). Both MT and my ISP ...
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492 views

Moxa serial-to-ethernet connection problem

We have a Windows 2003 Server (32-bit) running in VMWare and connecting to 2 Moxa NPort 5450 serial-to-ethernet devices. We are experiencing a sporadic "disconnect" with the serial devices attached ...
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775 views

Network Transfer Rate on SMB/FTP

We're trying to optimise our network transfer rate from the client PCs to the file server, but having no luck. If I run an iperf test between a client PC (Windows XP) and our server (Linux) with a ...
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274 views

Validity of my basic Performance Testing Results on a LAN

Networking is not my main job and i am hoping you guys can comment on my test procedure so far to identify PCs best to host a few voip softphones. Our 100Mb LAN comprises of 40 Win XP/2000 PCs and a ...
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how to make standard ssh port a stealth port?

I'm running a personal ssh server on a nonstandard port. If someone tries to log into my ssh server thru the standard port 22, it seems that the server sends "Connection refused" message. $ ssh ...
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How can I add more than 255 machines to a single Class C network? [duplicate]

Possible Duplicate: How does Subnetting Work? I'm mainly a programmer. I have no idea beyond some basic theory when it comes to Networking/Administrating. My university feels that we ...
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What ports are least likely to be probed on the internet?

Suppose you've got a server that runs insecure software and you have to make it publicly accessible, what ports are "safest" for providing that service on the internet. By "safest" I mean least likely ...
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116 views

TCP/UDP Connection States documentation

Does anyone know where to find documentation for TCP/UDP connection states? Preferably non-Microsoft with unix backing. Basically, I'm looking for more information about TCP established, TCP ...
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345 views

Help me understand Public/Private IP space and NAT

I just started working at a small-medium sized business after graduating school. So much of my knowledge is high level concepts without a lot of hands on. My understanding that according to rfc1918 ...
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3answers
155 views

What is TCPIPv3

I have been reading at quite a few places about TCPIP v3 being out ... I wanted to know what is this TCPIPv3 and what are differences between 2 and 3. I tried to google out the answer but could not ...
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7answers
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How to capture postscript output via TCP/IP? (for testing purposes)

We have a propriety system that talks to various printers across multiple sites via TCP/IP. The system only outputs Postscript, which obviously sends via TCP/IP. I'm really wondering is there any kind ...
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Is there any difference between prisoner.iana.org, blackhole-1.iana.org, and blackhole-2.iana.org?

Probably not the most useful question, but I'm curious: I understand (in theory) that if a reverse lookup for a private IP makes it makes it past your own DNS servers you should get back ...
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428 views

DHCP IP address with a client specified DNS server? Is this against spec?

I have some embedded network devices that allow me to specify whether or not they use DHCP. Unfortunately, we have some clients that have less than stellar DNS servers in their networks and have ...
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Why am I getting long TCP connect latency on connect in a LAN (over a cross!)?

I am measuring a time of about 100-150 milliseconds from sending TCP SYN to getting SYN/ACK, between two linux computers connected to the same Cisco switch. Consider: The machines are very powerful, ...
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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 ...
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326 views

What is a RP Paket in a tcpdump log?

I have a tcpdump log with the following entry: 14:53:31.428570 IP 10.4.65.65.16666 > 192.168.201.10.80: RP 587:687(100) ack 48545454154 win 0 My Problem is that i have never seen an RP paket ...
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Design for wire between server and access point and RF to endpoint device

We're about to design an inhouse industry network consisting basically of the following: 1 server connected via wire to up to 100 proprietary RF access points (basically embedded devices), which each ...
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3answers
750 views

Network device to change IP address within packets

I have an appliance with a class C IP address, for example 192.168.0.10. I can't or don't want to change this IP address. However when I connect this appliance to my network I want it to appear to ...
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389 views

I'm looking at sharing a printer over the internet, what are the implications?

Is it safe to NAT to the TCP/IP printer on the appropriate port in the router? Will I get unwanted documents from hackers or is this not a huge problem?
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TCP/IP packet loss network testing (in context of PingPlotter)

My question may be pretty basic TCP/IP / router based, but I need to couch it in terms of a Winpcap application pingplotter that I have used. One of the features I did use in my last place of work ...
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184 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 ...
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125 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 ...
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2answers
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Problems with MDNS flooding on port 5353 UDP

I am running into a big issue at a small network i manage. This network is an Apple network, with airport extremes, expresses, mac book pro's, imac's, ipads, iphones etc... I went to add something to ...
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222 views

multicast streaming, too much network traffic?

I am thinking of switching our streaming servers to use multicasting instead of registering multiple clients and duplicating the streams manually on the server. It seems to work very well. However, I ...
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1answer
248 views

How to do MAC based one to one NAT on Linux?

I have a linux machine running ubuntu server with 2NICS (WAN and LAN). I want the LAN side machines to use the linux box as a gateway to get on the internet (WAN side). The only problem is that the ...
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806 views

Slow and fluctuating server network speeds in a new data center

We have a server running Windows storage server 2003 with: - an FTP server and - VMware Server running a VDS with apache (vds runs windows web 2003) This is in a data center and we just switched to a ...
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Is asymmetric latency common in practice?

This is a follow-on to a question posted on stack overflow about whether it is possible to determine the one-way latency of a point to point connection without using externally synchronized clocks - ...
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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 ...
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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 ...
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Linux kernel 3 TCP IP tuning

I found several resources about tuning linux TCP/IP stack parameters in /etc/sysctl.conf for high bandwidth connections, but all refer to kernel 2.6. Does anyone have suggestions about how to tune ...