Single plane networking is adopted for the G9 bearer network between two cities. Each city has one NE40. The two cities are directly connected by three E1 cables to which MP-GROUP is bound. According to the traffic statistics collected before the cutover, three E1 cables are enough to carry all voice and signaling traffic on the G9 bearer network. However, the services of the entire network were interrupted that evening after the cutover.
Add one E1 cable to transmit traffic and limit the transmission rate to 1.6 Mbit/s per E1 cable at the UMG side.
The UMG limits the traffic rate to 2 Mbit/s per E1 cable. However, for the voice traffic in small packets, each E1 cable connecting the NE40 can only transmit the traffic at a rate of about 1.6 Mbit/s. Therefore, when the traffic running into the bearer network exceeds the total bandwidth of 4.8 Mbit/s, lots of packets are lost, hence the interruption of services on the entire network.
Currently, no NE40s of VRP5 and of versions earlier than VRP3.1 2358 support E1 rate limiting. The maximum rate that each E1 cable can support is 1.6 Mbit/s, which calls for special attention during network planning and bandwidth designing for the cutover scheme.