Các mặt hàng được yêu cầu nhiều nhất đã được cho một dịch vụ dựa trên web và không thể hiện về chủ đề của cuốn sách và công nghệ liên quan. Đáp lại, chúng tôi"BCRAN là về trao quyền cho công nghệ. Cuốn sách này sẽ giúp bạn phát triển về mặt kỹ thuật, | Configuring Asynchronous Remote Access Connections Chapter 2 37 MNP 4 This class of MNP works with either synchronous or asynchronous communications with data placed into packets to reduce errors. The packetization also increases transmission speeds. The packet size is variable as the modem monitors the line conditions. A smaller packet is used on noisy lines and a larger packet can be used on a clean line. MNP 4 also streamlines some information in packet headers and increases data transmission overall by approximately 22 percent. MNP 4 also provides automatic error correction. MNP 5 MNP 5 uses the same type of error correction and packetizing as MNP 4 but with a different twist. MNP 5 can alter data to reduce its size. This compression encodes data so that repeating or redundant data is eliminated and therefore is represented by fewer bits. The receiving modem decodes the data before transmitting it to the host s serial port. The effective throughput can be almost twice as much as a modem that s not using MNP 5. Keep in mind that if the data is already compressed such as into a ZIP or TAR file it might actually take longer for the data to be transmitted with MNP 5. This increase in time is caused by the modem examining the data for compressibility. MNP 6 7 9 and 10 MNP levels 6 7 and 9 feature enhancements in data compression and error correction. MNP Level 10 is used by a cellular modem developed by Microcom. No MNP level 8 exists. Link Access Procedure for Modems LAPM Link Access Procedure for Modems LAPM is a protocol that provides error control. LAPM is part of the specification. When a modem establishes a connection with another modem it tries to establish LAPM as the error-correction protocol. If LAPM is not negotiated MNP is tried. In the event that MNP is not available or not negotiated a normal connection with no error correction or control is established. In a normal connection error correction is typically implemented in software or the
