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has received frames zero through six. In other words, all frame numbers lower than the one acknowledged are assumed to have been safely delivered.
The advantage of this process is that it reduces overhead by limiting the number of acknowledgment frames sent onto the network. In the previous example, only a single ack frame was sent instead of the seven that would have been required if each outstanding frame were acknowledged individually. Network tip of the month A workstation running the LLC2 protocol has the option to send a receive not ready or RNR frame back to the transmitter if it is too busy to accept any more data. While several RNR frames can be considered a normal part of LLC2 operation, if these frames are seen often the station may be overloaded Virtually all Local Area Networks incorporate some type of sequencing for data delivery between devices. The most common type of sequencing is found in LLC2 or Logical Link Control Version #2 operations. Even in those networks that do not use LLC2 for data transfer, a similar type of generic sequencing is required. Hot Tip: The LLC2 protocol is used extensively within SNA networks. Much of the information presented in this column can be used to troubleshoot failing SNA sessions. Proper sequencing ensures that data packets will be delivered to the recipient intact and in proper order. The importance of this can best be illustrated by the following example. Imagine a critical document is created in a word processing package...