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A20B-2100-0690

型  号:
A20B-2100-0690
价  格:
2100
订货量:
(块):>=1
发货地点:
福建省 厦门
产品类别:
PLC
更新时间:
2019/4/16 9:12:32
  • 供应商信息
公 司 名:厦门航拓电气有限公司
联 系 人:小戴
电话:086-0592-5072089
传真:086-0592-5072083
Email:565167042@qq.com
QQ:565167042
所在地区:福建省 厦门

A20B-2100-0690
A20B-2100-0740
A20B-2100-0741


报价单位:厦门航拓电气有限公司
联系人:戴先生
手机:18006003561(微信同号)
座机:0592-5072089
QQ:565167042


二层交换机,三层交换机及四层交换机的区别
二层交换
二层交换技术的发展比较成熟,二层交换机属数据链路层设备,可以识别数据包中的MAC地址信息,根据MAC地址进行转发,并将这些MAC地址与对应的端口记录在自己内部的一个地址表中。
具体的工作流程如下:
1) 当交换机从某个端口收到一个数据包,它先读取包头中的源MAC地址,这样它就知道源MAC地址的机器是连在哪个端口上的;
2) 再去读取包头中的目的MAC地址,并在地址表中查找相应的端口;
3) 如表中有与这目的MAC地址对应的端口,把数据包直接复制到这端口上;
4) 如表中找不到相应的端口则把数据包广播到所有端口上,当目的机器对源机器回应时,交换机又可以记录这一目的MAC地址与哪个端口对应,在下次传送数据时就不再需要对所有端口进行广播了。不断的循环这个过程,对于全网的MAC地址信息都可以学习到,二层交换机就是这样建立和维护它自己的地址表。
从二层交换机的工作原理可以推知以下三点:
1) 由于交换机对多数端口的数据进行同时交换,这就要求具有很宽的交换总线带宽,如果二层交换机有N个端口,每个端口的带宽是M,交换机总线带宽!过N×M,那么这交换机就可以实现线速交换
2) 学习端口连接的机器的MAC地址,写入地址表,地址表的大小(一般两种表示方式:一为BEFFER RAM,一为MAC表项数值),地址表大小影响交换机的接入容量
3) 还有一个就是二层交换机一般都含有专门用于处理数据包转发的ASIC(Application specific Integrated Circuit,专用集成电路)芯片,因此转发速度可以做到非常快。由于各个厂家采用ASIC不同,直接影响产品性能。
以上三点也是评判二、三层交换机性能优劣的主要技术参数,这一点请大家在考虑设备选型时注意比较。



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Kalrez AS-568A Oring,K#372,Compound 4079,8-3/4 X 9-1/8 X 3/16 IN,414834

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