All About RDP

All About Remote Desktop Protocol (RDP)

Remote Desktop Protocol (RDP) is developed by Microsoft. It is a proprietary protocol which gives users a graphical interface to connect to another desktop/Laptop over a secure network connection.

Clients exist for most versions of Microsoft Windows (including Windows Mobile), Linux, UNIX, macOS, iOS, Android, and other operating systems. RDP servers are built into Windows operating systems; an RDP server for UNIX and OS X also exists. By default, the server listens on TCP port 3389[1] and UDP port 3389.

Microsoft currently refers to their official RDP client software as Remote Desktop Connection, formerly "Terminal Services Client".

The protocol is an extension of the ITU-T T.128 application sharing protocol. Microsoft makes some specifications public on their website.

Uses of RDP:-

RDP is mainly used for remote management and for the remote access to virtual computers,
Applications and for a RDP terminal server.

RDP helps network administrators in remotely diagnosing and resolving problems individual subscribers encounter.

Windows operating system supports almost every version of RDP. 
Now RDP for Apple macOS is also available in the online market.
Even the open source version is also available.

Features and functions:-

RDP can support up to 64,000 independent channels for data transmission. 
Data can be encrypted using 128-bit keys, and the bandwidth reduction feature optimizes the data transfer rate in low-speed connections.

Features:-

RDP includes the following features and capabilities:

Encryption

RDP uses RSA Security's RC4 cipher, a stream cipher designed to efficiently encrypt small amounts of data. RC4 is designed for secure communications over networks. Administrators can choose to encrypt data by using a 56- or 128-bit key.

Bandwidth reduction features

RDP supports various mechanisms to reduce the amount of data transmitted over a network connection. Mechanisms include data compression, persistent caching of bitmaps, and caching of glyphs and fragments in RAM. The persistent bitmap cache can provide a substantial improvement in performance over low-bandwidth connections, especially when running applications that make extensive use of large bitmaps.

Roaming disconnect

A user can manually disconnect from a remote desktop session without logging off. The user is automatically reconnected to their disconnected session when he or she logs back onto the system, either from the same device or a different device. When a user's session is unexpectedly terminated by a network or client failure, the user is disconnected but not logged off.

Clipboard mapping

Users can delete, copy, and paste text and graphics between applications running on the local computer and those running in a remote desktop session, and between sessions.

Print redirection

Applications running within a remote desktop session can print to a printer attached to the client device.

Virtual channels

By using RDP virtual channel architecture, existing applications can be augmented and new applications can be developed to add features that require communications between the client device and an application running in a remote desktop session.

Remote control

Computer support staff can view and control a remote desktop session. Sharing input and display graphics between two remote desktop sessions gives a support person the ability to diagnose and resolve problems remotely.

Network load balancing

RDP takes advantage of network load balancing (NLB), where available.

In addition, RDP contains the following features:

• Support for 24-bit color.
• Improved performance over low-speed dial-up connections through reduced bandwidth.
• Smart Card authentication through Remote Desktop Services.
• Keyboard hooking: The ability to direct special Windows key combinations, in full-screen mode, to the local computer or to a remote computer.
• Sound, drive, port, and network printer redirection: Sounds that occur on the remote computer can be heard on the client computer running the RDP client, and local client drives will be visible to the remote desktop session.

How the remote desktop protocol works

The RDP protocol is designed to provide remote access through port 3389. 
An RDP-enabled application or service packages the data that is to be transmitted, and the Microsoft Communications Service directs the data to an RDP channel. 
From there, the operating system encrypts the RDP data and adds it to a frame so that it can be transmitted.

The Terminal Server Device Redirector Driver handles all RDP protocol activity. 
This driver is made up of subcomponents such as the RDP driver (Wdtshare.sys), which handles user interfaces, transfers, encryption, compression and framing. 
The transport driver (Tdtcp.sys) is responsible for packaging the protocol in such a way that allows it to be sent across a TCP/IP network.

Security

The protocol has presented some security issues in the past. However, Early versions contained a vulnerability that allowed an RDP session to fall victim to a man-in-the-middle attack, through which the attacker could gain unauthorized access.

Newer versions of RDP are far more secure. 
More recent Windows operating systems contain a mechanism for specifying which users are allowed to access the system through an RDP session.

There is also an option to prevent anyone from remotely accessing the system unless they are using network-level authentication.

Microsoft provides a number of security related features you can use to increase the security of a remote desktop connection. 
You can limit the number of users able to connect, set an account lockout policy, require passwords, encrypt data transmission, change the port the client computer "listens" on and set up an IP address "White List." 

A periodic check of the Microsoft Event Viewer will provide a report containing failed login attempts and account lockouts. 
The Event Viewer is accessible from the Control Panel "System and Maintenance Administrative Tools" section.

Process

When you begin a remote desktop session, the client computer sends a signal via a standard "listening" port 3389 over the Internet to the host computer asking for permission to connect and log on. 
The host computer responds by asking for your logon credentials, which it verifies against a list of Remote Desktop Users using an internal authentication process. 

Once you log on, display data and keyboard strokes transmit from the host to the client computer, allowing you to view and work with the host computer as if you were sitting directly in front of it. 

One thing to keep in mind is that Remote Desktop allows only one connection. If someone attempts to use the host computer, your remote connection will automatically terminate.

Considerations

If you are connecting a home computer to a computer on a business network, firewall issues may require an additional step before the computers can connect and communicate. Establishing a Virtual Private Network (VPN) is one way to accomplish this. 
Another way is to use a Terminal Services Gateway server. 
Both methods require set up by either a network administrator or member of the technical support staff.