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"

learn more… | top users | synonyms

4
votes
6answers
844 views

What causes a delay of 100 ms in initiating an HTTP connection?

Settings: this is a quad CPU machine, plenty strong, not loaded at all (neither CPU nor network), the client is a Windows Server 2008 64bit, the server is a linux box. I have four threads that are ...
4
votes
5answers
55k views

How to fix “TCP/IP has reached the security limit…” event message

I get the following warning as a System event: "TCP/IP has reached the security limit imposed on the number of concurrent TCP connect attempts." on o box running Win XP SP3. How can I fix this issue? ...
4
votes
3answers
2k views

Backups take so long that the firewall closes the connection

A bit of a mashup of systems here, so bear with me. Essentially, I'm having some trouble using the Backup Exec agent for Oracle, while trying to backup a remote Linux server. The BE agent appears to ...
4
votes
1answer
125 views

Can a TIME_WAIT connection be restored?

Is it possible to restore a connection that is in state TIME_WAIT? If not, I use raw packets (forgering the source), is it possible? (Please understand that I do not intend to do bad things, it's ...
4
votes
1answer
4k views

Why ARP request is unicast?

I have a wireshark capture that indicating a unicast ARP request from source to destination. As per my understanding ARP requests (including gratutious ARP) use broadcast. In what case the ...
4
votes
2answers
764 views

How do I fake dropped packets (or actually make them fail)?

Background One of our clients suffers from an intermittant problem with their internet where it will drop packets when a user downloads a large file (their IT is looking into the problem). I have ...
4
votes
2answers
7k views

Why does the TCP Chimney Offload feature on some ethernet cards fail to pass some network packets to the OS?

In http://support.microsoft.com/kb/942861 Microsoft reports that in some situations Microsoft SQL Server experiences network issues due to the network card having a TCP Chimney Offload turned on. I ...
4
votes
4answers
4k views

How is the MTU is 65535 in UDP but ethernet does not allow frame size more than 1500 bytes

I am using a fast ethernet of 100 Mbps, whose frame size is less than 1500 bytes (1472 bytes for payload as per my textbook). In that, I was able to send and receive a UDP packet of message size 65507 ...
4
votes
6answers
656 views

Networking security and TCP/IP internals books/sites

I am searching for good books and articles about TCP/IP, mainly the security aspects of TCP/IP protocols. I have TCP/IP Illustrated and the TCP Guide, but they kinda lack on description of 'classic' ...
4
votes
4answers
13k views

Where did TCP/IP Filtering go in Windows Server 2008?

I'm configuring our new Windows Server 2008 machine. In Windows Server 2003 we would enable TCP/IP Filtering on our network cards to only allow traffic on specific ports to get through. This was ...
4
votes
2answers
7k views

How Can I Harden the TCP/IP Stack in Windows Server 2008? [duplicate]

I would like to make sure that my Windows 2008 servers are hardened against DDOS attacks. There is a Microsoft Technet article on Hardening the TCP/IP stack, but it was last revised in January 2006. ...
4
votes
2answers
1k views

How do I apply multiple subnets to a server with one NIC?

I am trying to route multiple IPs through one physical NIC on my dedicated server for use with Proxmox KVM VMs. I have a dedicated server which is currently running Debian 4.4.5-8 with 3 available ip ...
4
votes
2answers
12k views

UNC Path fails by IP “no network provider accepted the given network path”, but works using hostname

I have an unusual problem with a Windows Server 2003 (Standard x86) box. It appears the machine will not accept connections to its shares (locally and from other domain member servers) by using its ...
4
votes
2answers
811 views

Rapidly changing public IP addresses on certain networks?

I run/develop an online game where many of our users are in southeast asia. I recently went to southeast asia and made an alarming discovery. Anywhere I got internet access, whether it was via 3G, a ...
4
votes
1answer
543 views

Behaviour of solaris tcp stack with relatively high RTT and bursty traffic

I have an application that is distributing data from New York to Tokyo over TCP running Solaris 10. Mean throughput is < 1Mbps, peak throughput can reach 20-30Mbps for seconds at a time though ...
4
votes
1answer
132 views

How does Windows 2008 specifically select ephemeral ports (does it test to avoid conflicts)?

I have a server application which uses permanently connected incoming ports within the range that W2k8 now uses in the IANA recommended range of ~49000-65000. (For legacy reasons it's extremely ...
4
votes
1answer
126 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 ...
4
votes
1answer
3k views

TCP Windows Size vs Socket Buffer Size on Windows

I am new to Windows networking. When people talk about TCP tuning on Windows platform, they always mention about TCP Window Size. I am wondering whether Windows uses the concept of "Socket Buffer ...
3
votes
6answers
1k views

TCP Sessions and IP Changes

What happens to a TCP session when the IP of a client changes? I did a simple test of having netcat listen on a port, and connecting to that port from a client machine. I then changed the IP of ...
3
votes
2answers
3k views

IP address used by nslookup and ping is different

I have a web server hosted in the network. It has a domain name registered. However, I also host a DNS server for the LAN. So, when someone wants to access the web server, it would check the DNS ...
3
votes
1answer
293 views

Which route when there are two physical connections?

I'm a developer, not an admin, so apologies in advance. In a small office I have two Windows Server 2008 boxes connected to a 100mbps router, which is fine for day to day running. I'm looking to ...
3
votes
2answers
9k 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 ...
3
votes
4answers
1k views

Determining cause of TCP/IP connect issue without traceroute

I'm trying to connect from a company network to a host (via HTTPS), but my attempts fail with timeout. I can resolve the host. I know the host is up. I know there is a firewall filtering by incoming ...
3
votes
3answers
1k 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 ...
3
votes
4answers
7k views

Ethernet Loopback plug - running a ping

For a project at work, I need to be able to test various Ethernet NICs by connecting them to a "loopback adapter plug", like this one on various embedded Linux boxen that come off a production ...
3
votes
5answers
250 views

List of IPs that are not in DNS

What's the easiest way to get a list of windows desktops that are on a subnet but do not have names listed in the dns server?
3
votes
2answers
657 views

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 ...
3
votes
1answer
238 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 ...
3
votes
3answers
10k views

wireshark http POST

I would like to have a http POST request method CAPTURE filter. I know it is easy to do it by display filter http.request.method==POST but I need tcpdump compatible. I wrote tcp dst port 80 and ...
3
votes
2answers
2k views

custom route not working on windows

My windows laptop is directly connected to 192.168.1.0/24 (wireless lan). I access 10.21.0.0/16 though a router that is connected to both networks. The routing works fine with this configuration. I ...
3
votes
2answers
4k views

IIS7 hundreds of connections in CLOSE_WAIT

I have a .Net application on my IIS7 server it was working fine until I had to move it to another server. I moved the exact same code to the new server and I noticed that after some hours the ...
3
votes
5answers
765 views

Is it possible to configure Nginx to send TCP keepalive?

On TCP connections held by NGinx, can it be configured to send TCP Keepalive (Not HTTP KeepAlive!)
3
votes
4answers
7k views

What are good and bad jitter times for a LAN

Ive just ran jperf (frontend to iperf) on our network between 2 workstations, its recorded jitter between 0.033ms and 0.048ms. Is this good or bad? Are there more variables that i would need to ...
3
votes
1answer
306 views

Iproute2 tools vs conntrack tools

I have a linux box which is setup as firewall/gateway for the network. Was just wondering why ss and other iproute2 tools show much less than iptables conntrack. Is it because the router function is ...
3
votes
2answers
2k views

How to get a service to listen on port 80 on Windows Server 2003

I've coded a custom windows service that listens on TCP port 80 but when I try to install it on a Windows Server 2003 machine it fails to start because some other service is already listening on that ...
3
votes
2answers
4k views

Using IP alias and route to visit a site through assigned IP address

I want to visit a site through assigned IP address. I run the following commands: ifconfig eth0:1 [ip address] route add -host [the target host ip] dev eth0:1 gw [gateway] This works fine on ...
3
votes
2answers
2k views

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 = ...
3
votes
2answers
329 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 ...
3
votes
1answer
210 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 ...
3
votes
1answer
305 views

Restricting ssh tunnel port access by group

My understanding is when creating an ssh tunnel to a remote machine, the ports become open on that machine for anyone to use and connect back to my local box (not just the user who opened the tunnel). ...
3
votes
1answer
81 views

Machine cannot communicate on local network any more

I have a machine that has a problem I've never seen and cannot understand. The machine is a Dell laptop with Windows 7 Ultimate. The user tried to do something fancy with this machine (bridging the ...
3
votes
1answer
844 views

Solaris TCP stack tuning

We have a large web project (about 2-3k requests per second), using haproxy (http://haproxy.1wt.eu/) as a frontend and load balancer between the java application servers. The frontend (haproxy) is ...
3
votes
3answers
10k views

How to increase MTU size on Linux 2.6?

How to increase MTU size on Linux 2.6? Is such a thing possible? If yes, which files (in /etc or elsewhere) must one edit?
3
votes
4answers
3k views

Windows 7 DHCP Default Gateway not Overridden by manual Default Gateway

We have recently installed Windows 7 for student computers. All student computers must be routed through our content filter which is located at 192.168.0.63. This was done in WinXP by adding a Default ...
3
votes
1answer
2k views

LVS Configuration issue (Using piranha Tool)

I have configured LVS on cent os using piranha tool .I am using vip of internal n/w as gateway for real server we have two NIC one having exteranl Ip and other for internal n/w which is on ...
3
votes
1answer
263 views

different ACK behaviors (slowing down throughput?)

I'm running netio (http://freshmeat.net/projects/netio/) on one machine (opensolaris) and contacting two different Linux machines (both on 2.6.18-128.el5 ), machine A and machine B. Machine A has a ...
3
votes
3answers
85 views

If I make a request to my server's IP address, will it be the same as using 127.0.0.1, or slower?

I have application servers with memcached running on them. What will happen if I make a request to memcached on 10.243.98.5, which just happens to be the originating server? Will it use the same ...
3
votes
2answers
2k views

Sporatic Connection issues connecting to SQL 2005 - Named Pipes vs TCP/IP issue?

We have a production website that is experiencing periodic connection errors to our SQL 2005 server, several times a day during peak usage: An error has occurred while establishing a connection ...
3
votes
1answer
9k views

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\ ...
3
votes
1answer
7k views

Maximum number of TCP clients in Windows 7?

I am running client load testing software for my server from a Windows 7 Enterprise box. The client box is able to get up to 16346 TCP connections out, and then it starts giving the error “An ...