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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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 ...
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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 ...
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1k 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 ...
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620 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 ...
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212 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 ...
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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 ...
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3answers
519 views

Max client TCP connections through a router

I've just been thinking about what the maximum number of client connections would be out of my home LAN to a single server on the internet. My home router is also NAT'ing the connections to convert ...
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1answer
75 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 ...
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132 views

tcp recycle and retransmission

TCP recycle reduces TIME WAIT by reusing sockets. It avoids collision with older packets by storing timestamp and receives packets with greater TCP timestamp. What happens when the client retransmits ...
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237 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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2answers
131 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 ...
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1answer
627 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 ...
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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 ...
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133 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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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 ...
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4answers
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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 ...
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1answer
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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 ...
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1answer
249 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 ...
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2answers
218 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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3answers
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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 ...
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99 views

50% Throughput on direct connect XCOPY transfer

I have two Dell Servers with multiple gigabit network ports each. These run a sync process using XCOPY. To improve throughput and reduce overall network impact, I have dedicated a connection on each ...
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2answers
100 views

Special Routing and NAT requirement

I have a rather special routing and NAT issue which I hope I can fix somehow. Inside my company we run a supernet like 192.168.0.0/21 (192.168.0.1 - 192.168.7.254) All computers have this subnet mask, ...
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Best way to calculate optimal subnet masks for a range of IP addresses? [closed]

I thought I saw a tool like this once upon a time, but can't find it anymore... Anyone know a tool that would take a free range of IP addresses (as in start / end) and calculate a set of submasks ...
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130 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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Connecting to MS SQL 2012 with TCP/IP

I'm trying to enable TCP/IP connections on a SQL Express 2012 database, and it seems as though I'm missing a step somewhere. To enable it, I: Opened SQL Server Configuration Manager Selected ...
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1answer
379 views

Way to do basic WAN optimization between two Linux servers that splits single connection into multiple parallel ones? [closed]

There are utilities on Linux that allow you to work around WAN conditions which cause you to not be able to utilize your full bandwidth. They do this by performing multiple requests in parallel (for ...
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2answers
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Why tcp/ip model is being used for Developing Protocols and not OSI [closed]

why TCP/IP model is used for designing Protocols and why not OSI model,if i am not wrong OSI is the first reference model and in TCP/IP model same concept is followed but coupled with other layers. ...
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283 views

SQL Server 2008 intermitent error 40 running parallel queries

Here's our setup : We are using Red Gate SQL Multi-Script to run queries on our ~1000 databases which reside on a single SQL Server 2008. SQL Multi Script can be configured to run queries in ...
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2answers
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Why would a process be showing an outbound connection from a 169.254 address when there's no unconfigured adapter?

I have a system that has several network adapters, only one of which is enabled. That adapter has ipv4 only enabled and it has a single IP address. It was previously part of a team. The team was ...
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3answers
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No route to host after changing interface to static ip [closed]

I installed a Linux (Ubuntu) server inside my home LAN, initially it's automatically configured to use DHCP interface. I'm connecting to this server from another computer using that server's hostname. ...
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450 views

Why do we need logical addressing [duplicate]

Possible Duplicate: Why couldn’t MAC addresses be used instead of IPv4|6 for networking? If physical address or Mac address is unique why do we need logical addressing? This because ...
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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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4answers
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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 ...
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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 ...
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841 views

Where are my TIME_WAITs on Mac OS X?

No TIME_WAITs on Mac OS X Normally, when a TCP connection is closed, the socket on the side where close() is called first is left in the TIME_WAIT state. When one of the peers is a Mac OS X (Lion) ...
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1answer
139 views

Sender Information Not Cached on the Receiver During an ARP Request

I'm currently trying to get my head around more advanced networking concepts. The way I am doing this is by going on one of the servers I look after as a sysadmin and running network captures to see ...
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357 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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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 ...
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HTTP, TCP, UDP and connectionless

I am a bit confused with HTTP lately. Some facts are that TCP can operate connection orientated or connectionless, this I understand. TCP though is connection-oriented while UDP is connectionless ...
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4answers
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Just one client bound to address and port: does it make a difference broadcast versus unicast in terms of overhead?

Scenario: I am implementing failed over for a network node, so my idea is to make the master node listens on a broadcast ip address and port. If the master node fails, another failover node will ...
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1answer
91 views

Host data transfer limit calculations and network protocol headers

OK, this might be a really stupid question, but... I'm building a web app that utilises websockets. There's fairly rapid messaging going on, so I've been taking a look at the network traffic with ...
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249 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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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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1answer
292 views

IPv6 & ReservedPorts in Windows Server 2008 registry

I have HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\ReservedPorts set to 1153-1153, but sometimes IPv6 programs get assigned this port. Is this setting for IPv4 only? Is ...
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2answers
939 views

Raw TCP/IP port forwarding software

I have server which IP address is whitelisted in some external system. And also, I have a few software developers with dynamic IPs which develop software and they need to connect to external system, ...
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470 views

Can ranges overlap in ReservedPorts?

The value ReservedPorts in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters contains a list of port ranges to reserve so the system won't assign them to programs dynamically. ...
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2answers
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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 ...
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1answer
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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 ...
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1answer
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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 ...
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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 ...