10.2 Configuration of remote hosts

This dialog box allows to configure the remote hosts that can be used to run calculation jobs. In this way, it's possible to use the power of other systems connected trough TCP/IP protocol (e.g. PCs, workstations, HPC systems), reducing the computational time.


10.2.1 The calculation host concept

The calculation host is a logical unit used by VEGA ZZ to perform a calculation. There is no difference if the unit is placed in a local or in a remote machine, because the software layer selects automatically the more appropriate communication protocol. The advantage of this implementation is the totally transparency at the user side, allowing to run local or remote jobs in the same easy way.
The most common scenario in computational chemistry research laboratories, is the installation of a reduced number of high performance calculation systems (HPC) and a large number of middle-low performance PCs. These PCs can dramatically increase their computational power submitting the calculations to HPC systems in transparent and interactive way. The first implementation of this technology is available for AMMP: a molecular mechanics software integrated in the VEGA ZZ enviroment.
VEGA ZZ is able to manage three host types: local host, master host and child host. The local host is automatically configured when the software starts and it can be used to perform local calculations. In this case the computational power depends on the hardware running VEGA ZZ.


Local host communication


VEGA ZZ uses the pipe protocol to communicate with AMMP which is the application example managed by the host. The piping process is implemented in the operating system and it consists to put the output of a program as input of another one and vice versa. It is much faster then the TCP/IP connection used for the remote hosts (see below).
Each physical remote host is called master host from which is generated one or more child host. It is a virtual host corresponding to each manageable thread, one for each physical CPU installed in the remote system. As an example, if a master host has installed two CPUs, it can manage two calculation threads at the same time and so it are generated two child hosts capable to run two single-threaded application at the same time.
The communication with the remote hosts is implemented by TCP/IP and it's based on the telnet protocol. For this reason, the remote host must have a full configured telnet service.


Remote unix host


In the Windows hosts, it's strongly recommended to use the WarpTel service instead of the Microsoft's telnet service for security reasons (see below).


Remote Windows host


The telnet protocol is insecure because all TCP/IP packets are sent in clear form. For this reason, it's strongly recommended to use the encrypted connection, available in the WarpTel service:


Protected connection


The TCP/IP packets are sent on the net using a 256 bit encryption and are encoded/decoded on-the fly by VEGA ZZ and the WarpTel service.
The telnet daemons available in the Unix systems don't have the capability to encode/decode the packets and so you must use the WarpGate service to create a secure encrypted connection.


 Protected connection


The telnet daemon must be protected by a firewall, otherwise the system could undergo to malicious attacks. To install the WarpTel and the WarpGate services, consult their documentation.


10.2.2 Host configuration

The dialog is accessible selecting Tools Host configuration in the main menu.


Host configuration


In the right corner is located the master host list. The child hosts aren't not visualized in this window because they have the same configuration parameters of their master host. The child hosts are shown in the calculation dialogs such as in the AMMP's one.
The first three hosts in the list are called local hosts and they can't the changed with this window, because they are automatically configured when VEGA ZZ. They can be used to perform calculation using the local hardware (default condition) and in this case the faster pipe communication is used instead of the TCP/IP protocol. Selecting Localhost in the application control panel (e.g. AMMP calculation window), the calculation is immediately executed in interactive mode (if you close VEGA ZZ, the job is stopped); selecting Localhost background, the calculation is started in background and it can't be controlled by VEGA ZZ (if you close VEGA ZZ, the job continues without stopping itself); selecting Localhost save file, the calculation is not started and the input file is created to run the job later.
Add and Remove buttons, respectively, creates a new host and removes the selected host. In the right box, it's possible to change the host Name, the Description and the Type (Unknown, Unix, Linux, Windows 9x, Windows NT). Please pay attention selecting the host type, because a wrong selection make the connection unusable: use Unknown if you don't know the remote host operating system, Unix or Linux for *nix operating systems, Windows 9x for the old Windows operating systems (Windows 95, 98 and ME) with the WarpTel standard version, Windows NT for Windows NT, 2000, XP and Vista with the WarpTel standard or service version.
The number of the childs for each master host is controlled by the Threads filed, which values must be in the 1 to 65535 range. It correspond to the number of the installed CPUs or CPU cores: dual core CPUs are as two physically separated CPUs and each one is equivalent to two normal CPUs (e.g. 2 x dual core CPUs = 4 threads). The CPUs with the Hyperthreading technology (e.g. Pentium 4) are equivalent to two standard CPUs (e.g. 1 x Hyperthreaded CPU = 2 threads).
Address and Port defines the parameters for the TCP/IP connection: the first one is the IP (e.g. XXX.XXX.XXX where XXX is a number in 0 to 255 range) or the nameserver entry (e.g. myserver.mydomain) of the remote host, and the second one is the telnet service listening port that must be in the 1 to 65535 range (default 23). For security reasons, it's recommended to change the default listening port from 23 to anyone different (e.g. 7000), because the default port is the first one attacked by the hackers. This change must done in the remote host telnet service and in the VEGA ZZ host configuration panel at the same time: the two port numbers must be the same.
User name and Password are optional arguments: they are the credentials to login to the remote host. In the Confirm field, you must repeat the password in order to validate it.
Checking Encryption, it will be used the super-secure encrypted connection and the encryption key (WarpKey) is required: it must be 64 characters long and it must contain hexadecimal digits only (e.g. 0123456789ABCDEF). The WarpKey must be the same used by the remote host connection services (WarpGate or WarpTel). Clients and hosts with different keys can't communicate each other. If you need to create a new encryption key, you could click the Gen. Key button or the external utility called WarpKeyGen.
All host changes will be effective clicking Apply button. If you change the host without clicking Apply, all changes will be lost. If a wrong parameter is found, its field is highlighted and the error message is shown in the bottom window bar.
The host list is saved clicking Save button and if you close the window after a change without saving it, a warning message is shown.