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SIG1000 monitor vlan links flows loss

Publication Date:  2012-09-24 Views:  60 Downloads:  0
Issue Description
SIG1000 monitor link really flow is 250m,but in SIG1000 statistical flow,its less than 200m,loss 20% flow 
Alarm Information
none
Handling Process
First, we investigate for sig 1000 performance,cpu be used less than 40%,exclude the reason of performance deficiency
Then,check statistical data of sig1000 network,display as follows
sbeth_rmonshow 1
R_MAC_RMON_TX_BYTES = 0x0
R_MAC_RMON_COLLISIONS = 0x0
R_MAC_RMON_LATE_COL = 0x0
R_MAC_RMON_EX_COL = 0x0
R_MAC_RMON_FCS_ERROR = 0x0
R_MAC_RMON_TX_ABORT = 0x0
R_MAC_RMON_TX_BAD = 0x0
R_MAC_RMON_TX_GOOD = 0x0
R_MAC_RMON_TX_RUNT = 0x0
R_MAC_RMON_TX_OVERSIZE = 0x0
R_MAC_RMON_RX_BYTES = 0x40f12e91a96
R_MAC_RMON_RX_MCAST = 0x12021
R_MAC_RMON_RX_BCAST = 0xac3a
R_MAC_RMON_RX_BAD = 0xa9d8516  //SIG1000 network card drop packages
R_MAC_RMON_RX_GOOD = 0xaeaed6e8  // disposed packages by SIG1000 network card
R_MAC_RMON_RX_RUNT = 0x1291
R_MAC_RMON_RX_OVERSIZE = 0xa9d6955  //SIG1000 network card loss packages for big package
R_MAC_RMON_RX_FCS_ERROR = 0xa9d6d31 // SIG1000 network card loss packages for check value mistake
R_MAC_RMON_RX_LENGTH_ERROR = 0x1d
R_MAC_RMON_RX_CODE_ERROR = 0x19db
R_MAC_RMON_RX_ALIGN_ERROR = 0x0
value = 32 = 0x20 = ' '
Analyze from these data we can know,lots of packages are drop by sig1000 network card because of big package。Sig1000 network card support biggest package is 1518 bytes,this network appear 1518 bytes data certainly
Log on users switch,inquire these information
1 this link is Ethernet link(mac layer 14 bytes)
2  MTU are 1500bytes
3 this links configured vlan(need for 4 byte)
Mac layer 14 + IP layer 1500 + VLAN 4 + FCS 4 = 1522 bytes
So,we can know,sig1000 loss package is caused by this link add a layer of vlan tag,and result in the biggest data package is bigger than 1518 byte
although sig support analyze vlan tag data,but if it have vlan tag,MTU is 1500byte all the same,this link will appear big package drop by network card result in flows loss, there are 2 solutions:
1 sig monitor links has no vlan tag
2 links with valn tag change MTU to 1496 
Root Cause
Loss flow caused by these reasons
1 sig performance deficiency results loss
2 sig network card drop these data
Suggestions
none

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