NBF supports both unreliable connectionless and reliable connection-oriented data transfer. Unreliable connectionless data transfer is also called datagram, or Type 1, operation.
Unreliable connectionless communication is similar to sending a letter in the mail. No response is generated by the receiver of the letter to tell the sender that the letter made it to its destination.
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Connectionless communications can be either unreliable or reliable. NBF provides only unreliable connectionless communications. Reliable connectionless communications is like a registered letter whose sender is notified that the letter arrived.
In unreliable connectionless communicaton, the transport protocol driver transmits the message once or a specified number of times, ensuring only that the message was properly transmitted to the network medium. The message can only be a single frame. Acknowledgment from the destination computer is not required.
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If reliable connectionless communication is required, NBF can be configured for certain communication commands to send a number of frames that will allow time for the destination computer to respond to the message. The number is based on retry Registry value entries, such as NameQueryRetries. The time between sending each frame is determined by timeout Registry entries, such as NameQueryTimeout.
Reliable connection-oriented communication is also called session, or Type 2, operation. Reliable connection-oriented communication provides reliable communications between two computers in a way that is analogous to a phone call where two callers connect, a conversation occurs, and then the connection is dropped when the conversation ends. A reliable connection requires more overhead than connectionless communications do.
In reliable connection – oriented communications, the transport protocol driver assumes responsibility for transferring the entire message from source to destination, and within an acceptable time period. Sequencing is provided; a message that is larger than the maximum transmit frame size can be broken down into multiple frames, sent across the network, and properly reassembled at the receiving computer.