When you open ADSL Router configuration page, you are bombarded with various alien terms what are impossible to understand for common people. Here is a discourse on these networking terms in easy to understand language.
ATM
Asynchronous Transfer Mode (ATM) is a network protocol designed to facilitate the simultaneous handling of various types of traffic streams (voice, data, and video) at very high speeds over the same physical connection. By always using 53-byte cells, ATM simplifies the design of hardware, enabling it to quickly determine the destination address of each cell. This allows simple switching of network traffic at much higher speeds than are easily accomplished using protocols with variable sizes of transfer units, such as Frame Relay and Transmission Control Protocol/Internet Protocol (TCP/IP).
VPI
This is Virtual Path Identifier, used by ATM. Use value 0 for MTNL Triband.
VCI
This is Virtual Circuit Identifier, used by ATM. Use value 32 for MTNL Triband.
PPP
In computer networking, Point-to-Point Protocol (PPP) is a data link layer (layer 2) communications protocol used to establish a direct connection between two nodes. It connects two routers directly without any host or any other networking device in between. It can provide connection authentication, transmission encryption, and compression.
PPPoE
The Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol for encapsulating PPP frames inside Ethernet frames. It appeared in 1999, in the context of the boom of DSL as the solution for tunneling packets over the DSL connection to the ISP's IP network, and from there to the rest of the Internet.
PPPoA
In computer networking, the Point-to-Point Protocol over ATM (PPPoA) is a layer 2 data-link protocol typically used to connect domestic broadband modems to ISPs via phone lines.
NAT
Network address translation (NAT) is a method of remapping one IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic routing device. The technique was originally used as a shortcut to avoid the need to readdress every host when a network was moved. It has become a popular and essential tool in conserving global address space in the face of IPv4 address exhaustion. One Internet-routable IP address of a NAT gateway can be used for an entire private network.
MTU
The Maximum Transmission Unit (MTU) feature of your router is an advanced configuration that allows you to determine the largest data size permitted on your connection. Generally, if your MTU is too large for the connection, your computer will experience packet loss or dropping internet connection.
Use 1400 bytes for MTNL Triband
MRU
Maximum Receive Unit (MRU) is the largest packet size that an interface can receive, so it's an ingress interface parameter. In most of the cases MRU equals MTU but it's not a requirement. You can configure different values for both MTU and MRU to achieve some benefits.
Use 1492 bytes for MTNL Triband
Default Route
Set Enabled for MTNL Triband
NAT
Set enabled.
Firewall
Set Disabled for MTNL Triband
DNS Servers
Open DNS : 208.67.222.222/208.67.220.220
Google DNS : 8.8.8.8/8.8.4.4