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Voices Services Are Interrupted Because of UMG Problem

Publication Date:  2012-07-27 Views:  41 Downloads:  0
Issue Description

Networking:

        AG
          |                |
 S3528G-1----S3528G-1
       |                      |
  NE40-1-------NE40-2
            |              |
            UMG8900
The AG (UA5200) is connected to the S3528G. The S3528G enables VRRP as the gateway of the AG. The UMG8900 is connected to the upstream NE40. The NE40 enables two VRRPs as the signaling gateway and media gateway of the UMG8900.
The primary link is used from AG to S3528G-1, UMG to NE40-1, and S3528G-1 to NE40-1. Others are backup links.
Fault phenomenon:

The voice services of the AG are interrupted frequently, and packets are discarded when the AG pings the UMG. 

      
Alarm Information

Null

Handling Process

1. Check the CPU of all devices, and they are normal.

2. Ping the AG from NE40-1, and the delay is about 2-3 ms and there is no packet loss.
3. Ping the UMG from NE40-1, and the delay is instable and there is packet loss. You need locate the fault between the UMG and the NE40.
Perform the following tests.
4. Switch the service on the UMG to the slave link. Ping the UMG from NE40-2, and there is packet loss.
To further locate the loss, do as follows:
Perform port mirroring on the connected interface of the NE40 and UMG and capture packets.
5. When the NE40 pings the UMG and packet loss occurs, the NE40 sends a request packet. The NE40, however, does not receive a reply packet of the UMG.
6. When the UMG pings the NE40, the NE40 receives a request packet of the UMG and sends a reply packet to the UMG, but packet loss occurs on the UMG. Packets may be discarded by the UMG.
7. Change the UMG to the S3928 (use the optical module of the UMG), assign the network segment address of the UMG, and simulate the UMG.
8. Ping the S3928 from the NE40, and the delay is about 3-4 ms and there is no packet loss. The UMG discards packets.

9. Change slots 14 and 15 of the UMG to slots 12 and 13 and perform the test. Voice services are not interrupted for a long time. The R&D confirms that the hardware in slots 14 and 15 fails. 

Root Cause

According to the phenomenon, voice services are interrupted because of packet loss. The network is an NGN bearer network and only voice services are carried. The network attacks and link traffic flows can be removed.

Possible causes are as follows:
1. The CPU of the device is high.
2. Packets are discarded from the AG to S3528G, including negotiation failures among devices, cables, and transmission.
3. Packets are discarded from the UMG to the NE40, including negotiation failures among devices, cables, and transmission.
4. Packets are discarded on the bearer network, including negotiation failures among devices, cables, and transmission.

5. Other causes. 

      
Suggestions

At present, the NGN is widely applied and has high requirements on the bearer network. The problem is related to many network elements and products, so locating the problem is difficult. You need perform the test step by step.

END