RSA is an Internet encryption and authentication system that uses an algorithm developed in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman. The RSA algorithm is the most commonly used encryption and authentication algorithm and is included as part of the Webbrowsers from Microsoft and Netscape. It's also part of Lotus Notes, Intuit's Quicken, and many other products. The encryption system is owned by RSA Security. The company licenses the algorithm technologies and also sells development kits. The technologies are part of existing or proposed Web, Internet, and computing standards

How the RSA System Works

 The mathematical details of the algorithm used in obtaining the public and private keys are available at the RSA Web site. Briefly, the algorithm involves multiplying
two large prime numbers (a prime number is a number divisible only by that number and 1) and through additional operations deriving a set of two numbers that constitutes the public key and another set that is the private key. Once the keys have been developed, the original prime numbers are no longer important and can be discarded. Both the public and the private keys are needed for encryption /decryption but only the owner of a private key ever needs to know it. Using the RSA system, the private key never needs to be sent across the Internet.
The private key is used to decrypt text that has been encrypted with the public key. Thus, if I send you a message, I can find out your public key (but not your private key) from a central administrator and encrypt a message to you using your public key. When you receive it, you decrypt it with your private key. In addition to encrypting messages (which ensures privacy), you can authenticate yourself to me (so I know that it is really you who sent the message) by using your private key to encrypt a digital certificate. When I receive it, I can use your public key to decrypt it. A table might help us remember this.

 

 

 

Touch will just create an empty file but has all the same attributes as an actual file. You can see this by using “ls –l.”
Commands : 

• touch test file
• mkdir workfolder

chmod – adds and removes permissions

chmod +x testfile – this would allow me to execute
chmod –wx testfile – this would take out write and executable permissions

You’ll notice that this only changes the permissions for the owner of the file, in this case roman 
chmod o+w testfile
chmod o-rwx workfolder
Lastly you can change it for everyone: “u” for users, “g” for group, & “o” for others; uog or a (for all)

chmod ugo+rwx workfolder – will give read, write, execute to everyone
chmod a=r workfolder – will give only read perission for everyone 

chgrp – changing groups of files & directories

Another useful option is to change file permission to the group owning the file. Perhaps you create the files, but people on the db2 team can write/execute as well. We use chgrp for this purpose.

You can see above that testfile and the work folder belong to the users group
By issuing the command – chgrp “name of the group” “name of the file” – you can change this

chgrp sales testfile
chgrp sales workfolder 

This give sales control of the file & then I can take away permissions for everyone else
  
Note: The group must exit before you try to assign groups to files and directories

chown – changing ownership

Another helpful command is changing ownerships of files and directories. The command is “chwon” along with “name of new owner” & “name of file.”

The files belonged to roman. To give ownership to tom, issue the command:

chown tom testfile
chown tom workfolder 

We can also combine the group and ownership command by 
chown -R tom:sales /home/roman/ts files
 

Permission in numeric mode

The above way of changing permissions will work fine but you may also need to know how to change permissions in numeric mode. chmod is used in much the same way, but instead of r, w, or x you will use numbers instead

What are the numbers? 

0 = No Permission 

1 = Execute 

2 = Write 

4 = Read 

Examples:

chmod 777 workfolder

Will give read, write, and execute permissions for everyone

chmod 700 workfolder

Will give read, write, and execute permission for the user, but nothing to everyone else.

chmod 327 workfolder

Will give write and execute (3) permission for the user, w (2) for the group, and read, write, and execute for other users

Permission numbers
0 = —
1 = –x
2 = -w-
3 = -wx
4 = r—      
5 = r-x
6 = rw-
7 = rwx  

PORT NUMBERS

Overview

                  PC-over-IP (PCoIP)  is a display protocol that allows complete compression of a desktop which is then displayed through a zero client device over a standard IP network. While there are several display protocols that exist in desktop virtualization such as RDP, ICA and RGS, PCoIP has become the most prevalent protocol for display back of a virtual desktop.

Does PC-over-IP sound vaguely familiar? It might remind you of Voice-over-IP (VoIP) and there are definitely similarities. While Voice-over-IP delivers voice over a standard IP network, that is where it ends. PCoIP not only delivers full audio it also delivers USB and the full user display. How is it different from RDP (Remote Desktop Protocol) or ICA (Independent Computing Architecture)? That's a great question, because PCoIP is not the only display protocol.  Let's take a look at some of the other display protocols and how they compare to PCoIP.

Remote Desktop Protocol (RDP)

                 With Remoted Desktop Protocol (RDP) you have a terminal server on the opposite end that acts as a controller to the client's screen. The client is basically getting a drawn representation of the hosts desktop display. RDP reaches back to the terminal server which sends a refresh on 10 second intervals so long as there is activity at the client. Every 10 seconds is a pretty hard rate to stick to if you aren't constantly typing away or moving the mouse.  When the client end has no activity for 10 seconds the terminal server decides to cut the refresh rate in half in order to ensure bandwidth is not being wasted between terminal server and client on the network.  As an administrator, you can attest to this issue when having multiple RDP sessions open but they keep timing out and the window closes.  You must then re-establish the session when it times out, and it can become a tedious chore.

Independent Computing Architecture (ICA)

                   Independent Computing Architecture (ICA) is another display protocol that is used by several vendors, most prominently used and promoted by Citrix. It was specifically created to deliver graphical displays and keyboard/mouse input over a standard IP network. When using ICA, you are connecting to a Citrix server via an ICA client on your desktop. ICA clients are UNIX based and they allow you to connect to Windows clients on a Citrix server. Both RDP and ICA are good display protocols for desktops over an IP network. However, PCoIP has been widely adopted and seems to be the leader in remote display protocols.

Why PCoIP?

           Now that we know what the other protocols are, why would we choose PCoIP? The most compelling reason to go with PCoIP is that it uses the UDP protocol which is much better suited for streaming media and display back situations. UDP (User Datagram Protocol) is not concerned with how the data ends up on the receiving end, it's only concerned with speed, this is why streaming media is sometimes not good quality. RDP uses TCP as it's protocol, which is widely used across the Internet.

          The difference being, TCP is concerned with how the data is being received. TCP will actually ask the receiving client if it's received all of the packets sent successfully.  If the client isn't receiving what they should, they can reply back to stop sending or they can narrow the amount that they are receiving as to process it better. UDP just keeps sending and is much speedier simply because there is no acknowledgement from the receiver.

             Along with UDP being the protocol, PCoIP leverages host rendering.  The image is rendered on the host to provide the framework in which the host can transmit only the pixels across the network without being concerned about the applications or responses from the client. In best case scenarios, zero clients are used to receive the pixels and decode them essentially eliminating display latency.

               PCoIP also has settings that you can configure to manage your bandwidth use. Bandwidth is the culprit in most if not all display related issues in virtual desktop infrastructures.  With PCoIP's image quality settings, you can avoid any lapse in display due to bandwidth issues.  What's really cool about these settings is, when faced with a congested network, PCoIP's adaptive encoders kick in and provide the best image quality with the available bandwidth. Then, when congestion dies and the network resumes it's normal traffic load, it returns to maximum image quality.

Who is Behind PCoIP?

PCoIP was created by a company named Teradici which is located in Burnaby, BC.  Teradici was founded on the idea that there were major problems with the desktop PC.  Every user in every oraganization across the globe essentially utilized a desktop PC.  The problem Teradici saw was "how do we centrally  manage and secure these desktops?"  Security threats were increasing and there was a need for desktop consolidation.

The fix was simple, consolidate all of the desktops and place them in the datacenter. The only issue with that was, how to connect the users to their desktops in the datacenter. That was essentially how the PCoIP display protocol was created.

Teradici utilizes a PCI-e card that is installed on the server in the datacenter. Your monitor and all peripherals (USB) are plugged into a thin or zero client at the desktop which reaches out to the image held on the server in the datacenter. Thanks to host rendering, all the host has to do is transmit the pixels via the IP network to the zero client which receives the pixels and decodes them to display your desktop image.  Magic!  Here's a nice video from Teradici in which CTO Randy Groves explains the three essential features of PCoIP and Teradici.

Conclusion 

           PCoIP is a great display protocol for a virtual desktop environment. The technology behind it is reliable, fast and will ensure your desktop display experience is that of a physical box. The only thing left to do is test different thin or zero clients, and there are many built specifically with PCoIP in mind.

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