Zte ZXDSL 9210 (V3.1), Техническое руководство

Страница: 97 / 182

Chapter Erro! Estilo não definido. Erro! Estilo não definido.
5-11
5.4.6 L2 Protocol Subsystem
The L2 protocol subsystem is responsible for implementation of Layer 2 switching
protocol. The L2 switching protocol subsystem consists of the STP module,
TRUNKING module, and IGMP SNOOPING module. They are described as follows:
1. STP module
This module implements STPs. In Ethernet, a bridge is used for extension of
physical scope. The running bridge checks the MAC sublayer address, and
employs the destination and source addresses as the basis for its forwarding
direction. A common bridging mode is transparent bridging. This mode checks
MAC frames to get the address of workstations over network and saves
information as an address table in its internal memory address.
A transparent bridge does not allow the establishment of ring or round topology.
It generally adopts spanning tree algorithms to block some bridge ports to
prevent any broadcast storm resulting from loops in network logic structure.
Upon action of the STP, a bridge LAN with random topology automatically
configures each port with its forwarding status to make there only be a data
route between any two terminals. When some pieces of equipment or ports over
network become faulty or encounter broken links, the bridge LAN automatically
reconfigures network ports and forms new spanning trees to ensure the
communication between any two terminals.
Main content of STP algorithm: Configure dynamic topological structure,
release topology information, reconfigure topological structure, change port
status, and release topological change notification.
The STP protocol runs on the SCBF alone and for an uplink interface.
2. TRUNKING module
TRUNKING implements link aggregation. In networking, the most important
connections in the whole network are those between core switches, those
between a core switch and a data server, and those between a core switch and an
edge switch. These connections are called Trunk. The trunk connections require
high bandwidth and high reliability. Obviously, a single physical link does not
necessarily provide sufficient bandwidth and reliability. The aggregation
technology, however, binds multiple physical links as a logic link. This