S Layer 2 Managed Switch User Manual
陈泽科技有限公司
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In this way, when switch calculate the bandwidth, will add new 4 byte in it, so, when switch calculate the inflow port
bandwith, and the 802.1Q function is on, now if the inflow data without VLAN TAG, this time inflow data rate bandwidth
control rate is small than setting rate. For example, if bangwidth control the without VLAN TAG data bandwidth is 64Kbytes,
in fact the bandwidth control will be about 62Kbytes.
4.2.6 port broadcast storm
Swtich port received three type broadcast: normal broadcast ,mutlicast,unicast package with Destination Lookup Fail(DLF
package /UL package),every port can chose which storm they want to control and package transmit ratio.
Following is concept description of three data package broadcast storm control,following fig is basical format of ethernet.
Broadcast package
broadcast package is ethernet package with destination MAC address FF FF FF FF FF FF.
multicast package
multicast package is the first character of destination MAC with 1.
DLF package
DLF package or UL package is the ethernet frame that MAC address can not lookup form address table(FDB) of the switch, and will
broadcast in the VLAN area. About the detail description of Mac address should be consult the charter “FDB Table(arl table)” of this
user guide.
When storm break out ,switch control broadcast transmit ratio which has four type: 3%,5%,10%,20%. Transmit ratio is relative to
linear speed,that is to say, relatived transmited ratio is 3%*100M
、
5%*100M,10%*100M,20%*100M, above this limit will be
discard by broadcast package.
Note:
Basical conception of broadcast storm please refer to 4.1.2
4.3 Network configuration
DA
SA
Tag
Type
Data CRC
0X8100 Priority CFI VLAN ID
DA SA Type Data CRC
