One of the important Networking Services being provided by NIC is its Electronic Mail Service. This Story attempts to throw light on the various aspects of the E-mail services over NICNET. Electronic Mail (better known as E-Mail), "the means to exchange messages electronically", is the most commonly used Network Service. NIC provides different kinds of E-mail services to its users, over NICNET, NIC's satellite based communication network. The different types of e-mail services being provided include SMTP, UUCP and X.400. The NICNET e-mail service is distributed over many mail servers located at different NIC centres. These are inter-linked with each other such that mails can be exchanged amongst all types of services. The E-mail service is also integrated with a X.500 directory which makes it possible to search for and locate e-mail addresses very easily. It is also possible to send fax messages through E-mail since a gateway is provided for conversion of messages for fax recipients.
The Pre-requisites. To be able to send or receive E-mail, a user requires the following: A Computer: any computer can access the NICNET e-mail service irrespective of its platform. A mail user agent software: either running on the user-end machine or on the mail server. Connectivity to NICNET: either over dial-up or a dedicated link. An e-mail account: on one of the NICNET mail servers.
Mail User Agents. User Agents are the interface software which help a user in accessing the mail service effectively. These may be: Remote Mail User Agent: The most common mode of accessing a mail server is using a Windows based client machine through IP based connectivity, over dial-up or dedicated link. These Mail User Agents are an integral part of the Windows software (no additional software is required) although other mail client software may also be used. These are configured to make a connection and valid login to the mail server and automatically send or receive messages. Composition, reading and filing of messages are all taken care of, at the user's end. Thus minimum connect time is used on the mail server. For Windows95 and above, the POP/IMAP client software is supported in mail user agents such as Microsoft Exchange client, Netscape mail agent, Eudora etc. Similarly, Enterprise mail software etc. use the P7 protocol at the client end. For a DOS-based client machine, the PCBOX User Agent is available to access the mail server.
Local Mail User Agent: Here the client logs onto the mail server and accesses the Local Mail User Agent (e.g. Pine, mailx etc.) running on the mail server. This may be accessed using a terminal emulation software through a dial-up or a dedicated link. To facilitate the usage, local Mail User Agents such as Pine support Z-modem protocol for file-transfer. At the client end, higher versions of terminal emulation software such as PCPLUS, PROCOMM etc. for DOS, and NIC's Zetlink and Radix for Unix/XENIX support this protocol. This enables the transfer of files onto the server for attaching into a mail to be composed. Pine also provides a search facility, to look for and obtain a particular recipient's e-mail address in the X.500 based NIC directory. These users occupy valuable disk space at the server since all mails lie on the server and may also be using a long duration of connect time if they compose their mails while being logged onto the server.
Connectivity to NICNET. Users can access the NICNET using the following types of connectivity: Dial-up connectivity to the nearest NICNET node. The user accesses the network by connecting to either of the following: a router or terminal server using SLIP/PPP protocol to avail the IP connectivity. Such users can use the mail service through remote mail user agents such as the Microsoft Exchange, Eudora etc. the NICNET node's X.25 PAD. Such users are usually provided with a mail service through the use of the local mail user agents such as pine, mailx etc. A dedicated link to the nearest NICNET node through: a leased line connection, a RF-link, a VSAT connection.
Mail Servers. The NICNET mail servers are systems that run specific software to provide E-Mail service. There are various standards that define how messages are exchanged between two mail servers. Mail servers may have the capability to support one or more of these standards. The different mail servers based on their standards are: Simple Mail Transfer Protocol (SMTP): These servers use the standard TCP/IP protocol. SMTP mail supports the transport of textual as well as MIME-formatted messages. The SMTP mail server generally has a dedicated IP based connection to NICNET. The System running as a SMTP server is configured on the DOMAIN NAME SERVER (DNS), which may either be the primary DNS or a secondary DNS. UUCP/UUPC mail servers: These are Unix/DOS machines using the configuration of Unix-to-Unix Copy Protocol (UUCP) on two communicating machines. Users with accounts on one such system access e-mail service through it, which in turn relays all the spooled user mails to the other mail server in the background mode at specified intervals of time. UUCP is the protocol used in Unix systems and the corresponding protocol for DOS systems is UUPC. X.400 Mail based NICMAIL400 service: This service is conformant to the X.400 ITU-T recommendations. It provides the facility to handle data, voice, image and fax. A gateway is provided to transport messages between a SMTP/UUCP server and the X.400-based NICMAIL400 server in a seamless manner. The NICNET mail servers are distributed at the various NITPU and State Centres, besides the Headquarters. This enhances the balance of E-mail load on the network. The User also experiences a good response since the network delay is minimal. These servers are interconnected to be able to exchange mails through very high speed links. The servers are in turn connected to other mail servers to further disseminate the E-mail load and take care of a larger user base. These servers also exchange mails with international servers through high-speed links.
Aides to an Effective E-mail Service. To facilitate the usage of e-mail, certain value-addition has been made to the NICNET e-mail service. Some such features are: Directory Service: Since the mail service is distributed over many servers and it is not possible to remember so many e-mail addresses, the NICNET directory service is provided on a centralized machine accessible from any node on the network. This X.500 based directory service provides help in locating any e-mail address. This directory has a search facility to look for addresses based on the search for names or for addresses grouped as per their organizations. The directory is accessible through any commonly used browser such as Netscape, Internet Explorer etc. A mail can be directly sent to the retrieved address after a search has been completed. Mail user agents such as Pine have been customized to provide similar directory access facility. Other mail agents such as Microsoft Exchange Client and Netscape mail client can be configured to retrieve the addresses.
A 'Global Distribution List' facility is also provided. These lists are maintained by the System Administrator at the mail server and used by any User of any mail server to send mails to a common group of recipients. Fax Gateway: A fax gateway allows an e-mail user to send faxes to recipients with only a fax facility. The fax is sent as a mail message and is received at the destination server, which in turn dials the number of the recipient's fax machine and delivers the fax. Such gateways are available most mail servers located in the Headquarters as well as the NITPU centres.
Relevant Security Issues. The aspect of security assumes prime importance in this age of e-mails. Some relevant security tools are: Authentication using XTACACS: In addition to authentication of the user at the mail server, authentication is also done while accessing NICNET using XTACACS (eXtended Terminal Access Controller Access System), a protocol supported by most routers. It provides authentication, authorization and logs by creating shell accounts on the network server (where XTACACS is running) for each individual. To provide a better solution, XTACACS has been integrated with a X.500 directory server. To authenticate the user name and password, XTACACS connects to the X.500 server, which contains the list of all the valid users along with their passwords (in encrypted form) and their access permissions. Handling SPAM mails: SPAM is a term adopted by the Internet community to signify the mindless mass-posting of messages through e-mail, flooding one's mailbox. In addition to being an irritant, the major problem that these mails cause is the theft of resources. This is because an increasing number of spammers relay most or all of their mails through innocent intermediate systems. This fills the intermediate systems and its disks with unwanted SPAM messages resulting in system crashes or any other similar consequence. To take care of this problem special software has been installed in the mail servers on NICNET which detect spam-mails and reject them. An Anti-Spamming site has also been set up to help identify if a server has been targeted by a spammer and safeguard it against such attacks.
For further information, please contact: Communication Software Group NIC Headquarters, A-Block, CGO Complex, Lodhi Road, N.Delhi -110003. Ph: 91-11-4364951 E-mail: csg@hub.nic.in www: http://hub.nic.in