Description of the problem

OSN7500 equipment station A-B use EGS4 single board, open broadcast service, station A: PORT1-vctrunk1, 7×VC4, PORT2-vctrunk2, 3×VC4, station B: use 2 VBs to hook up respectively. vctrunk1, PORT1, PORT2, vctrunk2, PORT3, PORT4, and the service is used normally. When the vctrunk2 channel capacity is expanded to 7×VC4, packet loss occurs on PORT1 at station B.

Processing

1. VB's broadcast restriction:

The chip multicast/broadcast forwarding capability is limited. Utilizing the multicast/broadcast method of forwarding messages, each multicast/broadcast port can not send more than 9/(number of port) Mpps , where number of port is the number of ports hooked up on the multicast/broadcast domain (note: even the source port to which the multicast/broadcast service should not be forwarded should be involved in the bandwidth allocation). The sending rate of each port cannot exceed 9/(number of ports)*8*(packet length)Mbps, where, packet length is the message length. The actual test results may have a little deviation from the theoretical calculation of the formula.

2, from the Ethernet port and VCG port into the single board, the single board will be divided into a fixed length of the message piece. The theoretical bandwidth rate of the single board to deal with these fragments is about 2.9G~5.8Gbps in both directions, and up to 2.5Gbps in one direction. therefore, when the length of the message is different, the bandwidth is also different, in the actual network, the length of the message will not be concentrated only in the region of the lowest efficiency of the chip processing the length of that section of the message, generally will not be too much impact, the bandwidth can reach more than 2G.

In short, PORT1 and PORT2 of station A will not be able to enter 900M broadcast message at the same time, and the total bandwidth of PORT1, PORT2, PORT3 and PORT4 of station B will reach 3.6G.

Root Cause

Limited multicast/broadcast forwarding capability of the chip

Solution

1. Expand the EGS4 single board;

2. Reduce the channel capacity.

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