BPDU

the root determines values for configuration messages, in the bpdus, and then sets the timers for the other bridges.

这个根桥接器在BPDU决定了设定的讯息，然后为其它的桥接器设定计时器。

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A tree is created and maintained by the switch for every VLAN according to the mark affiliated in BPDU. It can cut down the delay from the block state to transmitting state obviously and improve the real-time characteristic in the Ethernet.

在BPDU中加入标示性能的标志，交换机根据这个标志为每个VLAN生成、维护一个稳定的树结构，使交换机端口由阻止状态到转发状态的延迟明显缩短，提高了网络的实时特性。

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BPDU and network management messages are processed.

BPDU和网络管理消息仍将被处理。

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bpdu. it consists of the following fields

它由下面的域组成

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In the same condition, testing shows that this self-adaptive-interval sending BPDU data-package algorithm spends network bandwidth more reasonably and reduces the convergent-time more effectively.

测试表明在其他条件相同的情况下，该自适应时间间隔发送BP-DU数据包算法比定时发送BPDU数据包更合理地利用了网络带宽，更有效地减小了收敛时间。

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However, according to the standard of 802.1D, it is impossible to forward BPDU segment with VLAN TAG.

然而，按照802.1D标准BPDU不带VLAN tag，而且要求所有网桥不能转发BPDU；

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