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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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 ...
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4answers
182 views

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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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 ...
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1answer
1k views

“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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2answers
246 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
137 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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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 ...
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2answers
974 views

How to optimize TCP / IP stack in Linux? [closed]

Currently I noticed there are about 15K open connections to localhost. It is mainly connecting to Memcached. I am clueless where I should start to optimize TCP/IP stack. Memcached support UDP, but ...
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1answer
134 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
1k 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 ...
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1answer
259 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
222 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, ...
2
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3answers
4k 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 ...
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0answers
101 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
101 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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1answer
1k views

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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1answer
132 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 ...
3
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1answer
597 views

Is Winpcap able to capture all packets going through a Gigabit NIC without missing any packets?

I want to use Winpcap to capture all network packets going through a Gigabit NIC of a server. Assuming that I am able to utilize the network link up to 100%, the maximum network speed is 1000Mbps. If ...
0
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1answer
395 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
382 views

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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2answers
3k views

Windows Server 2008R2 - can't change or remove the default gateway

We've installed VMWare Server 2.0 on Windows 2008R2. After some time playing with it (actually only removing host-only and nat networks, and binding adapters to the specified vmnets) we've noticed a ...
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1answer
291 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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5answers
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Huge amount of TIME_WAIT connections says netstat

Okay, this is creeping me out - I see about 1500-2500 of these: root@wherever:# netstat Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 ...
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2answers
73 views

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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1answer
862 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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8answers
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How to find the gateway IP address in Linux

What command can you use to find the Gateway IP Address (ie. home router address) for eth0 in Linux? I need to get the IP address from a command line app to use in a shell script.
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3answers
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Too Many ESTABLISHED connection from a single IP address in Apache

netstat -ntp |grep 80 shows too many ESTABLISHED connection from single IP address. Around 300 of them and it is not an attack and user is using a 2G connection to access Apache. This is the case ...
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3answers
253 views

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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votes
2answers
482 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 ...
2
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1answer
299 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
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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 ...
3
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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 ...
5
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1answer
143 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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0answers
363 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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3answers
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TCP/IP communication between Hyper-V host and guests

This may be a simple one. :) I have a simple Hyper-V setup with a few guest os running. The host has 1 physical network adapter with a static IP assigned to it. The guests have network adapters ...
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4answers
118 views

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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7answers
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Latency in TCP/IP-over-Ethernet networks

What resources (books, Web pages etc) would you recommend that: explain the causes of latency in TCP/IP-over-Ethernet networks; mention tools for looking out for things that cause latency (e.g. ...
2
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1answer
94 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 ...
1
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1answer
928 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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2answers
531 views

monitoring TCP/IP performance on Solaris

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 ...
0
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1answer
264 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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0answers
841 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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2answers
956 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, ...
0
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1answer
486 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. ...
3
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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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4answers
4k views

Error Connection to SQL Server using [HOSTNAME]\instance or [FQDN]\Instance, [IP]\instance working

This one's kind of weird, at least to me. I've got MSSQL server 2k5 (STD) installed on Server 2k3 R2 SP2 (on account of some legacy software that doesn't yet support x64 or Server 2008), using ...
18
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9answers
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What is the OSI model and how does it apply to todays networks?

As a system administrator what should I know about the OSI model? (Rec X.200) Briefly, what are the layers and what do they do? How much do I need to know about in my day-to-day work? How does this ...
2
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1answer
182 views

Disabling Operating System TCP Management

Is there a way to disable TCP state management of OS, for example on a specific port, or on another ip or if not, disabling the whole tcp management and managing it in an application with root access? ...