As attached network top
metro 1 and metro 2 connect each other with 3 E1s(EPL services) to offer a services for DSLAM internet service and DSLAM management.
the DSLAM management go though
DSLAM------------- metro 1 ET1D------E1 -----metro 2 ET1D------switch
ping switch from DSLAM with 82 byte,no problem
ping switch from DSLAM with 83 byte, can't ping.
end user connect to DSLAM can ping any IP with small packets,but can't browse.
no alarm on any device and 82 byte packet works well.
1.connect PC with DSLAM uplink port, ping DSLAM with size 1500 byte,no problem.DSLAM problem out.
2.check with other sites connect to the same Switch, all ok.
3.ping DSLAM from switch with size 700 and time out 10ms and 10ms send the next packet.
open RMON on metro 2 ET1D,the statistics for packet with size 512 to 1023 is 36 packets per 5 seconds.
open RMON on the metro 1 ET1D, the statistics for packet with size 512 to 1023 is 0 packet packet per 5 seconds
4.confirm that it is Transmission that who drop the big packet.
5.try to exclude one E1 from the 3 E1s and test again.
6. Problem solved.
1.DSLAM uplink board E4GFA have some problem
2.switch S5352 has some problem
3.Tx metro drop some packect
when can't pass packet with special size limitation. Try to check transmission resource.
The encapsulation protocol of ET1D is ML_PPP, it encapsulates service to E1 sequentially, so if one E1 is faulty, may the small package can be transmitted, but big
package can not.