SDNP Bangladesh Tech. Info

The Pilot Phase Project of SDNP Bangladesh

Technical Setup

The Pilot Phase (PP) of the project is planned by keeping the 'Daughter nodes' of the SDN (with a "Mother Node" at BIDS). In the later stage, the PP will be moved to a nodal point and the setup will be duplicated there.

The Servers

In the PP, there will be two servers. They will act as primary and secondary servers. Their details are provided below.

The Primary server

This server will perform as the database server. Since the 'Daughter nodes' will only mirror the database from the 'Central server', the database server is not going to be a single server by itself. The same server will act as the authentication server for the users, electronic mail (e-mail) server and primary Domain Name System (DNS) server as well. In addition, it will be configured for World Wide Web server and newsgroup server (which will be served by the secondary server) so that in case of a failure of the secondary server, it can resume those services to the users.

The Secondary server

The Secondary server will provide World Wide Web service, File Transfer Protocol (FTP) service, News group service and also act as the secondary DNS server. But this server will have a duplicate setup of the main server, so that in case of a failure of the primary server, this will act as the primary server until the primary server restores its operation for uninterrupted services. This server will also be connected to the data backup device.

Other Major Hardware

The other major hardware are the Terminal server, the Modem pool and the Local Area Network (LAN) Switch. The details are provided below.

Terminal server

A Terminal server acts as an answering machine for the users connecting over phone lines using modems. Since most of the users will be connecting over phone lines, a Terminal server is required. All the ports of the Terminal server will be configured for dial-in. The users will get connected to the Terminal server from outside the BIDS by dial-up method and the Terminal server will connect them to the whole network. Until further modification of the central node's setup, the PP is going to be connected to the Internet through one of the ports of the Terminal server by dial-up to the ISP.

The Modem pool

The Modem pool is nothing but a group of modems in a single box or chassis for better management. The Modems in the pool will be connected to the Terminal server. The dial-in phone lines will be connected to each of the modems in the pool.

Local Area Network Switch

For a UTP cable based Ethernet network, a LAN Hub or a Switch is required. It's opted to use a Switch because it provides much better bandwidth utilization over a Hub by reducing collision and caching the hardware addresses of the network adapters in the servers.

Software

The Operating System (OS) and the various server software used for the project has to be highly reliable and stable as well as well performed. That is why Linux has been selected as the Operating System. All other various server software that are required are available under Linux, a Unix platform. The added advantage of Linux is that it is completely free of cost. The other SDN projects are also using Linux for their servers all around the world. Using Linux will give the flexibility of configuring the system better suited to the SDNP targets.

Network Protocol

The Network protocol is going to be the Transmission Control Protocol/Internet Protocol (TCP/IP). TCP/IP is the standard protocol for the Internet. It is also the native network protocol for the selected OS, Linux. Using TCP/P will give the PP the option of connecting to the Internet and exchanging information without any major modification to the setup.

Servers setup details

The servers (Primary, Secondary server and the Terminal Server) will be connected to the Switch, thus forming the server LAN. The Hub of the Local Area Network consisting the workstations will be connected to a port of the Switch.

Software setup details

Both the primary and the secondary servers will run under Linux. To make the setup robust, both servers will be configured to run all common services.

Database server

The Primary server will run as the database server. At the PP stage not much have been done regarding the database and they are not been finalized yet. Rather at the primary stage, it will be acting as a dummy database server by offering accessibility through any web browser.

Authentication server

When someone will try to log in over phone lines, the Terminal server will have to verify that the person is indeed a valid user with appropriate access. The Terminal server does this by contacting the authentication server. The primary server will hold all the user accounts and passwords. Therefore, the authentication service will be running on the primary server. The authentication service for dial-in will be the standard Remote Authentication Dial In User Service (RADIUS). The primary server will run the RADIUS service. The secondary server will keep a duplicated copy of the user database in case it has to serve as the Authentication server.

Electronic Mail server

The email server software is going to be sendmail, the Internet standard Mail Transport Agent (MTA). All Linux distribution comes with the sendmail software. However, sendmail only acts as the transport agent, in other words, a different service is required for the user to download their mails. The standard protocol for that is POP3. Both of these services will be running on the primary server, since the user accounts are going to be on that. The secondary server will also have these services configured.

Domain Name System server

In the network world based on TCP/IP, each computer (either a user or a server) is identified by a numeric address. This numeric address is known as the IP Address. But for human usability, all the machines are given a name as well. The name to IP address mapping is known as the Domain Name System (DNS). Both the primary and the secondary server will run the DNS service. The DNS server software going to be used is Berkeley internet Name Domain (BIND). BIND itself has the feature of running in primary and secondary mode, which is going to be deployed in the standard way in the servers.

World Wide Web server

The protocol used for the World Wide Web is Hyper Text Transfer Protocol (HTTP). The WWW or HTTP server we are going to use is Apache, the most used http server on the Internet. The Secondary server will run this service, but the primary server will be configured for it as well.

File Transfer Protocol server

A File Transfer Protocol (FTP) server acts as a server that has many files (could be information, could be programs) which the user can transfer (known as download) to his or her computer. The Secondary server will provide this service. That means, all the downloadable files will also reside on the Secondary server. The primary server will also have this service configured.

Newsgroup server

A Newsgroup is a discussion group, where any user can post an article or respond to an article posted by someone else. The Newsgroup server going to be used is InterNetNews (INN). INN is the most used Newsgroup server software on the Internet and comes with Linux as well.

The PP in Operation

When a user needs some information and accesses the servers over the phone line, this is what happens:

A user wants to access some information
He/She dials the PP dial-in number using his/her computer
The modems get connected
The Terminal server asks for the users credentials (i.e. login and password)
The Terminal server consults the Authentication server to verify that the credentials provided by the user is valid
If they are invalid, access is denied and the user is disconnected. If they are valid, connection to the Terminal server is allowed to establish, which makes the user connected to the whole Local Area Network.
The user starts the appropriate application software (a web browser or email software) to access his required information
The application package connects to the server and fetches the information
The user disconnects. The phone line is freed.

If the user is on a local workstation on the LAN, the process is different. Since the user is already on a connected computer (the workstation), it is assumed that he or she is an authenticated user. Therefore, no additional authentication is required, except in case of the service he wants to access requires it (for example, checking e-mail requires authentication in all cases).

Maintenance and Backup Schedule

During the normal operation of the servers, the major maintenance job is to take backup of the servers on a regular basis. We have selected to use DLT4000 tape drives, which can hold up to 2OGB of uncompressed (40GB compressed) data. Backup will be taken every other day to a new tape. The tapes will be received after 30 days, which means there are going to be 15 tapes, each holding the backup of the servers for the past 30 days at an interval of 2 days.

The backup device will be connected to the secondary server. The Primary server will be backed up over the network and the secondary server will be backed up directly.