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NE40E-M2 V800R010C10SPC500 Configuration Guide - WAN Access 01

This is NE40E-M2 V800R010C10SPC500 Configuration Guide - WAN Access
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As a bit-oriented link layer protocol, HDLC transparently transmits bit flows of any type without specifying data as a set of characters.

As a typical bit-oriented synchronous data control protocol, HDLC has the following characteristics:
  • HDLC works in full-duplex mode and can transmit data continuously without waiting for acknowledgement. Therefore, HDLC features high data link transmission efficiency.

  • HDLC uses cyclic redundancy check (CRC) for all frames and numbers them. This helps you know which frames are dropped and which frames are repeatedly transmitted. HDLC ensures high transmission reliability.

  • HDLC separates the transmission control function from the processing function and features high flexibility and perfect control capabilities.

  • HDLC is independent of any character encoding set and transparently transmits data.

  • Zero-bit insertion, which is used for transparent data transmission, is easy to implement on hardware.

HDLC is especially used to logically transmit data that is segmented into physical blocks or packages. These blocks or packages are called frames, each of which is identified by a start flag and an end flag. In HDLC, all bit-oriented data link control protocols use a unified frame format, and both data and control information are transmitted in frames. Each frame begins at and ends with a frame delimiter, which is a unique sequence of bits of 01111110. The frame delimiter marks the start or end of a frame or marks for synchronization. The frame delimiter is invisible inside a frame to avoid confusion.

A trunk can aggregate many interfaces into an aggregation group to implement load balancing on member interfaces. Therefore, link connectivity is of higher reliability. Trunk interfaces are classified as Eth-Trunk interfaces and IP-Trunk interfaces. An IP-Trunk can only be composed of POS links. It has the following characteristics:
  • Increased bandwidth: An IP-Trunk obtains the sum of bandwidths of all member interfaces.

  • Improved reliability: When a link fails, traffic is automatically switched to other links, which improves connection reliability.

Updated: 2019-01-02

Document ID: EDOC1100058399

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