Introduction to Data Communications
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37b. Types of LLC Operation

LLC defines 2 types of operation for data communication:

Type 1: Connectionless

Connectionless service for data communications is very similar to sending mail with the postal system (hand delivered mail). The data is sent and we hope it arrives at its destination. There is no feedback from the destination to indicate whether it arrived or not.

Type 1: Connectionless Service

Type 2: Connection Oriented

Connection Oriented service for data communications is very similar to having a phone conversation. First a connection is made and established by dialing the number, waiting for it to ring, someone picking up the line and saying hello. This establishes the connection. During the conversation, confirmation that the other person is still there (hasn't fallen asleep or died) and listening is given by hearing things like: yeah, oh really, uh huh, etc.. This is the acknowledgement of receipt of data. If the destination party did not hear something correctly, they ask to have it repeated which is called automatic repeat request (ARQ).

Connection Oriented service

NOTE: These models for connectionless and connection-oriented can be used for any protocol.

Introduction to Data Communications
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