VPN (Virtual Private Network) technology enables users with a computer to use a public Internet connection to get connected to a private network in a secure way. A VPN is usually required by businesses for enabling the employees access the office/private network from distant places.

How to Configure a VPN Connection on a Computer Running Windows OS ?

Inorder to configure VPN Connection on your Windows machine, it is important that you are logged in as Administrator (one who has full permissions)

The following are the steps to configure a VPN :

Step a – Ensure that the Internet connection is correctly configured on your local machine.

Step b – Go to Start >> Settings >> Hit the Network And Dial-Up Connections option

Step c – You must now double-click the icon Make New Connection.

Step d – Hit the Next button and then the Connect To A Private Network Through The Internet, again hit the Next button

Step e – You may choose to do any of the following depending on your connection

• Select Automatically Dial This Initial Connection incase you have a dial-up connection for accessing the Internet, then from the list you must choose your dial-up Internet connection.
• If you don’t have a dial-up but a dedicated connection, you must choose Do Not Dial The Initial Connection.

Step f – Choose the Next button

Step g – You would be presented with an empty box wherein you would need to enter the host name (ex. Eukhost.com) or the IP address of the computer to which you intend to connect, then hit the Next button.

Step h – Choose the option For All Users to allow everyone who access your computer, else you may choose the option Only For Myself inorder to restrict the access to yourself, then hit the Next button.

Step i – You are now required to add a distinct name for the connection and hit the Finish button.

Step j – Now again go to Start >> Settings >> Select Network And Dial-Up Connections

Step k – Then Double-click the new connection icon

Step l – Go to Properties, this will allow you to configure the options to establish a connection:

• Incase you intend to connect to a particular domain, you must click the Options tab, select the check-box against Include Windows logon domain.
• If you intend to redial incase of a line drop, you must choose the option titled Redial if line is dropped

Now, inorder to use the connection, you must follow the below procedure :

Step 1 – Go to Start >> Settings >> choose Network And Dial-Up Connections

Step 2 – You must again double-click the new connection icon

Step 3 – Once you are connected to the Internet, you would be prompted by the VPN server asking to enter the Username and the Password. Hit the Connect button once the appropriate details are entered.

Step 4 – After usage you mustn’t forget to disconnect the VPN connection. To do that, you must right-click the connections icon and choose Disconnect.

This would enable you to connect to your Web Hosting UK Server from your home computer.

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• Virtual Private Network | Part 3
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The following article will describe you how to optimize the parameters of the protocol TCP.

Basically, TCP uses a parameter, which is known as «congestion window», or CWND, in order to determine the number of packets can be sent to the destination per unit time. The larger the congestion window, the higher the bandwidth. Congestion window size is determined by algorithms TCP «slow start» and «congestion avoidance».

The maximum value of congestion window depends upon the buffer size assigned to the kernel for each socket. For each socket it has a buffer size value from the default, which you can easily edit it programmatically by using the system call from the library, before it opened this socket. As there is a parameter that specifies the maximum buffer size of the nucleus. You can simply change the size of both the sending and the receiving socket buffer.

To get the maximum amount of bandwidth, you need to use the optimal set size of the sending and the receiving socket buffer for the channel you will be using. If the buffer would be too small, the “congestion window” will never open completely. If the transmitting buffer is too large, there may be tears flow control and TCP sender can overflow the receive buffer, which causes to reduce the window of TCP. This is likely to happen faster on the sending host than on the destination host. Excessive receiver buffer – not the biggest problem, as you have the extra memory.

Optimal buffer size can be calculated as bandwidth * delay channel used.

buffer size = 2 * bandwidth * delay

To determine the delays can be used by utility ping to determine the capacity of the channel from point A to point B (if the bandwidth between the points of a variable). Since the ping utility makes time pass packets back and forth (RTT), then instead of the previous can be used formula Next:

buffer size = bandwidth * RTT

For example, if ping shows a 50 ms, and from point A to point B using channels 100 BT Ethernet and OC3 (155 Mbps), the value of the TCP buffer will be .05 sec * (100 Mbits / 8 bits) = 625 KBytes. (If you have doubts gnaw, 10 MB/sec would be a good first approximation for networks of ESnet / vBNS / Abilene-like).

There are two parameter settings TCP, which you need to know. This is the size of buffers send / receive the default and maximum size of buffer send/receive. Note that in most modern UNIX OS maximum buffer size by default, only 256 KB!

Below, we show how to change this value in most modern operating systems. You hardly want to increase the default buffer size to a value greater than 128 KB, because it may adversely affect the performance of the network. Therefore, you should use the UNIX setsockopt function call for buffers send/receive to set the optimal buffer size for the channel that you are using.

Linux

There are big differences in between the Linux versions, but now we will be considering the common issues only. To change the settings of TCP, you need to add following lines to the file /Etc/sysctl.conf  and simply run the sysctl-p command.

As in all other operating systems, the size of buffers in Linux is precisely very small. You need to apply the following settings:

# Increase TCP max buffer size setable using setsockopt ()
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
# Increase Linux autotuning TCP buffer limits
# Min, default, and max number of bytes to use
# Set max to at least 4MB, or higher if you use very high BDP paths
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216

Also, you need to check if the following parameters are set to the default value of 1.

sysctl net.ipv4.tcp_window_scaling
sysctl net.ipv4.tcp_timestamps
sysctl net.ipv4.tcp_sack

Note: You must leave tcp_mem alone. Default values, and so beautiful.

Another thing you may want to try that may help increase the capacity of TCP, should increase the size of the queue interface. In order to do this, enter the following command.

ifconfig eth0 txqueuelen 1000

You will get good increase in speed, making this setting in the wide channels. Doing this makes sense for channels Gigabit Ethernet, but may have side effects such as uneven sharing between multiple streams.

Also, as per the rumors I have heard, it may help in increasing the bandwidth utility.

Related Posts:

• Modify / remove xorg.conf via Terminal/Command Line – Linux – Ubuntu
• Linux Part 4
• Linux Part 3
• Linux Part 2
• Linux Part 1

Zeroconf – is a protocol developed by Apple Inc. and planned to solve the following issues:

• Network address choice for the devices
• Presence of computers by hostname
• Detection of services, such as printer

Avahi – is a protocol Zeroconf implementation for Linux and BSDs.

Bonjour – also known as Rendezvous, is a proprietary protocol zeroconf implementation from Apple Inc.

For assigning IP-address of the device “zeroconf” uses RFC 3927 standard. The RFC 3927 standard explains the purpose, the so-called link-local addresses. The technology is called IPv4 Link-Local or Ipv4LL.

For resolution of names protocol is used Multicast DNS or reduced mDNS. It lets the device to choose a name in the local zone. Each computer holds a record of its area (A, MX, SRV) and he himself serves requests to them. When a machine or wants to know the entry zone, for example to determine the IP-address by name (to get an A record for a given area), it turns on multicast-address. Accordingly, the request is received to all computers on the LAN, and meets the one who keeps the area of interest to us for the name.

To search a service discovery protocol is used DNS based Service Discovery or DNS-SD.

List of programs supported by Avahi:

Rhythmbox, KDE’s KDNSSD, VideoLAN Client, Service Discovery Applet source v0.4.3, Vino Vnc server 2.13.5 or newer, Ekiga 2.0 or newer, gnome-vfs, Banshee 0.10.4 or newer, WzdFTPD, Tangerine, GShare, nss-mdns, cyphesis, Epiphany, Apache 2.0, Zope, mt-daapd, OpenLDAP, Netatalk, Beagle, PulseAudio, XMMS2, gnome-user-share, Seahorse,LAT, One Laptop Per Child’s Sugar, GGZ Gaming Zone, SuperCollider, GtkSQL, GNU Bayonne, apt-zeroconf, Nokia Canola, Gajim Jabber Client, OWFS, Thousand Parsec, KTorrent, FreeNAS – pfSense, libdmapsharing DAAP/DPAP client library, daap-sharp, WengoPhone, LM42, GLChess, Elisa Media Center, AccessGrid, Glom, Music Player Daemon (mpd), lab-audio, libvncserver, Gobby,Conduit, libdmapsharing, Vinagre, Telepathy Salut, OMISCID, FireFly Media Server, Mugshot, Liferea, oxine, Pidgin, Easy Publish and Consume Library, Mandos, Remmina.

Using Avahi:

• Browse all service types registered on the LAN using the “avahi-browse – all”.
• With the help of a daemon avahi-dnsconfd can be cloned /Etc/resolv.conf all the computers on the local network.

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Clustered Website Hosting

Clustered website hosting is a type of hosting which involves multiple servers for the same task, and is generally seen as a more reliable type of hosting over standard shared website hosting. With clustered web hosting, all website services are ‘load balanced’ across multiple servers to ensure that the best redundancy possible is achieved; security resources and other standard features are also spread across multiple servers. No human interaction is required for the clustered hosting system to work; this is because most clustered hosting platforms are data driven in some way or another. Most clustered hosting services suffer no downtime because if one server within the cluster fails, there is multiple servers to take over its role; if downtime is ever experienced with clustered website hosting, the reason is normally because there has been a major problem with either the power or the network at the data centre in which the clustered setup – although both instances of fault are very rare. Most clustered setups are normally continually monitored, so if a server does happen to malfunction or face an error of sorts, an on-site network team or support team from the web host will be quickly dispatched to ensure that the problem is fixed quickly and effectively; there are also normally automated systems in place to ensure that the cluster isn’t affected if it is missing a server or two, but in most cases the end-users will not see any problems. Clustered hosting is seen as a solution for businesses and large corporations who require an update percentage which is near to or equals to 100%; this is because although clustered hosting does come at a cost, it is one that is cheaper than a dedicated server – one other thing to note is that the reliability of dedicated servers is not as good as clustered hosting, although some individuals think the opposite.

Virtualization

Clustered hosting could also be seen as a type of virtual website hosting; this is because the actual system is in a sense ‘virtualized’ because of the number of servers that are clustered together. To ensure reliability, and to allow clustered website hosting to achieve its job, websites and services related to the hosted websites are always spread across multiple servers; the systems are ‘load balanced’ to ensure that websites are always available since load balancing makes the use of the server which is being used at the given time of the request for any service – it goes one step further from redundancy since normal redundancy just makes the use of several servers, but does not spread the information out to ensure the maximum reliability is achieved. An example of load balancing would be an end user requesting a page on a website which is hosted on a clustered hosting service; all the web servers within the cluster are too busy serving other websites, so the user is served the web page from a server which is currently free and not serving too many visitors, it also has a low CPU usage at this point because it is not being utilized much. Some web hosts allow you to purchase power for your website; what is meant by power is ‘CPU’ or ‘RAM’, this is because a clustered server pool is a more or less infinite source of resources, and is perfect if you are unable to afford a dedicated server which can match the specifications and reliability of clustered website hosting.

Security

With standard shared website hosting, the security which is provided on both the hosting node and the network is pretty poor when compared to that of a standard clustered website hosting network. In most cases, a standard shared hosting network incorporates a basic hardware firewall as the main line of security to keep a number of server secure; after that layer of security it is then down to security software installed on the servers to fight back any attack or to stop any intruder from accessing the server and compromising any information that it hosts. With a clustered hosting network, the security is normally much more stronger as a series of hardware firewalls as well as redundant proxy, routing and switching technology to ensure that the network is both fast and secure; intelligent routing can help load balance information across multiple servers, along with the use of VPNs and proxies the intelligent routing is also able to bind more than one server to just one IP address to ensure that if one server on one IP does go down, there is a number of other servers to take over its role. This type of network architecture can benefit both the servers and their users / websites that they host during a DDos attack; this is because the attack is being dispersed amongst a large pool of servers in which it is having no effect, when the attack is aimed at one piece of equipment, that piece autmatically stops serving traffic because it is unable to take the strain.

High Availability Cluster

A high availability cluster is one that makes use of several physical hosting nodes with a goal of achieving a reliable network for a certain service which it has been built to host. High availability clusters are normally deployed for things such as file sharing, business class enterprises, customer services (specifically e-commerce websites) and mission-critical databases; all these types of business related IT activities are of the utmost importance for some companies and it is important that the information for them can be accessed when needed, this is the reason for deploying a high availability cluster to host them – albeit at a high cost. The automation processes involved are fairly complicated; nodes have the ability to start services on each other if the service concerned has gone down on another node – they can also carry out the appropriate processes automatically in order to start a service if needed, such as the importing and mounting of file systems. However ‘good’ this high availability may seem, the automation processes involved in it can easily cause problems; for example if the private ‘heart beat’ connection between the nodes goes down, then each node could think that every other node is down when in fact they aren’t and lead to an instance of a service being started although that service is the responsibility of another node – this could lead to data corruption, or even worse: data loss. Implementations of high availability clusters are sometimes put in to increase the reliability of a regular cluster; via the use of things such as storage area networks (SANs) and the erradication of single points of failure; multiple network connections are also used to ensure that there is always at least one connection route available, even if one does fail. Most nodes take advantage of a number of technologies to ensure that they can provide the utmost best reliability. Hard disk wise, they take advantage of disk mirroring meaning that if one internal disk does fail, another internal disk which is a mirror of the main one can take over to ensure that the server carries on running – the technical term for this is RAID (‘Redudant Arrays of Inexpensive Disks’). Redundant network connections are also utilized to ensure that if one switch or network interface card fails, there will be another one network switch or network interface card available to ensure that the node stays connected to both the network and the internet. Most of the storage on a clustered network is taken care of by networked storage devices; multiple connections to the storage area network are also used to ensure that files can always be accessed. Multiple power connections are also available for servers via the use of UPS and diesel generators which can be used in the event of a power outage of sorts. The use of multiple connections and other devices ensures that even in the event of connections going because of a fault, the cluster will still be able to operate.

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VPS Hosting

VPS stands for ‘virtual private server’ and is a type of hosting that can be categorized under both shared and dedicated hosting. VPS hosting works by splitting the resources of a physical hosting node amongst VPS; the number of VPS which you can fit on a node is dependent on the node’s resources. The result of the resource splitting is several VPS which have their own dedicated environment; all VPS have a guaranteed amount of RAM, disk space and bandwidth, but the CPU is shared amongst the VPS on the node. VPS are seen as the fill in for the gap between standard shared hosting, and dedicated servers; this is book you are given your own dedicated environment as you are with a dedicated server, but the CPU is shared with other users who are on the same node as you. Also, VPS packages tend to be a bit more expensive than a standard shared hosting package, but less than a dedicated server. With most VPS servers, you are able to choose any operating system that you want to use; in some cases you are also able to choose the size of the data pipe that you want to use, but options such as the amount of RAM and disk space assigned to you cannot be changed meaning that if you want more, your only choice it to upgrade to the next package. If you are on a shared hosting package, but your needs point more towards a dedicated server, but don’t have the funds then a VPS might be what you need; VPS are currently available mainly on Linux and Windows platforms.

Operating System Choices

With a VPS, you are limited to your choice of OS by the OS that the node is running; for example, if you have a VPS on a node which is running Windows Server 2003, you can only have Windows Server 2003 as your operating system, and if you have a VPS on a node which is running Linux then you can only have a Linux distribution as your OS. Most hosts allow you to install what OS you want, since you are normally provided with a control panel which you can use to reload your VPS to any operating system template which is in the host’s system; however, most hosts do not allow the reloading of Windows servers since it must be done manually by the host themselves. The use for your VPS should always be reflected in the choice of OS; for example if you want to host an ASP.NET web application, you should choose a Windows VPS, and if you want to host a PHP/MySQL based web application, you should go for a Linux based VPS. Your choice of operating system might also be affected by the specs of your VPS; for example if you have a VPS which is meant to be Windows based that only has 64mb RAM, then you won’t be able to run Windows since the minimum RAM requirement for Windows Server 2003 is 128mb.

Resources

All VPS are allocated a certain amount of RAM, disk space and bandwidth. RAM comes in two different types within VPS – guaranteed and burst; guaranteed RAM is the RAM which is uniquely assigned to your VPS and cannot be used by anyone else and is always there for you, burst RAM is RAM that is shared amongst all the VPS on a node and is utilized by a VPS when it runs out of guaranteed RAM. VPS which hog the guaranteed RAM or who carry on using it for a long time at the expense of other users may be shut down by the VPS software, or might just crash themselves. Disk space which is assigned to a VPS is exclusive and can only be used by the VPS to which it has been assigned. Bandwidth that is assigned to a VPS is again, exclusive meaning that it can’t be used by any other VPS hosted on the same node; most hosts allow you to purchase extra bandwidth, but it is quite expensive since it is a treasured resource. The CPU on a host node is not split amongst VPS like other resources; it is instead left how it is so that the VPS can use as much of it or as little of it as they want – VPS which use too much of it will be shut down automatically by the VPS daemon.

Uses

Due to the fact that VPS are somewhat ‘isolated’ environments on the physical node, they are commonly used for testing (sometimes known as sandboxes) for applications, so that if any problems are found they don’t harm the main node. Due to the fact that you have your own dedicated environment, you are able to install most programs of your choice, however this may be dependent on the resource specifications of your VPS; some software such as firewalls and anti-virus clients don’t run well within a virtual environment. Unsurprising, the virtualization software itself doesn’t run well within a virtual environment itself; for example, some people have tried without success to create VPS within a VPS – the main let down being that the performance decreases as you go through virtualization layers. VPS servers are sometimes referred to honeypots – the term that is given to the action of running a piece of software with known security flaws; these are run within VPS environments since if there are any problems with the software, then the host node is unlikely to be damaged.

VPS Software

All VPS need virtualization software to run them – this software can either come at a very high price or cost nothing at all. The main pieces of virtualization software that are run by web hosts are Virtuozzo by SWSoft which can run on both Linux and Windows, but comes at a high price tag, and OpenVZ which is an open source alternative to Virtuozzo for Linux, and costs nothing. Another solution which is used by large corporations as well as home users is VMWare, which is available for Linux, Mac and Windows and allows you to create multiple virtual environments from your desktop.

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