Description of the problem

The customer carries out network cutover, and the whole network equipment is transformed into Huawei NE40E equipment through Huawei transmission network, the web page can not be opened, while Huawei NE40E equipment through ZTE transmission network, the web page can be opened normally.

Description of network transmission.

Upper-layer servers-CE(Beijing)------(MPLS+VPN)NE40(Beijing PE)-------(hereinafter referred to as the equipment in Jilin Province)--- NE40(P)------NE40(P)----Huawei SDH-EGS4------ NE40(P)----NE40(PE)(MPLS+VPN) --- --Cisco switch (CE)-----PC terminal

Alarm messages

No abnormal alarms for transmission devices, and no abnormal alarms for NE40E devices.

Processing

1. Query the optical power of the docked Huawei NE40E equipment, which is normal, and rule out optical power problems;

2. Query the working modes of the docked optical ports, and rule out the problem of working modes;

3. query the cross-connection configuration of OSN 3500 devices, excluding cross-connection errors;

4. check the alarms of NE40E and OSN 3500 devices, and there are no abnormal alarms;

5. because the OSN 3500 client side does not involve overhead bytes for interfacing with the NE40;

6. After connecting the NE40E to ZTE's transmission equipment, the customer can access the web page normally, and all the transmission equipment through Huawei is not available, so it can be judged to be a common problem, and the only difference between Huawei equipment and ZTE equipment is that the maximum frame length of ZTE is 9600, and the default frame length of Huawei's EGS4 single board is 1522;

7. The MTU of NE40-X8 is 1500, which does not contain Layer 2 headers and MPLS labels. Since the scenario is mpls vpn via cross-domain option C. Then the size of the largest TCP message with Layer 3 IP header + Layer 2 header going out is: 1460 load + 20 tcp header + 20 ip header + two layer labels 8 mpls header + 14 ethernet header + 4 bytes of CRC = 1526. The MTU of the transmission corresponds to 1522, since the MTU value is smaller than the MTU of the router that actually carries it, so it cannot be transmitted, resulting in the service not being able to be opened.

8. Modify the maximum frame length of the EGS4 board of the transmission OSN 3500 device to 1526, and test again, the service is normal, and the web page can be opened.

Root Cause

Maximum frame length of the Ethernet port does not match that of the peer device

Solution

1. Failure of the docking optical module: abnormal optical power of the device.

2. Failure of optical fiber.

3. service interruption due to line board failure.

4. Ethernet port operating mode mismatch.

5. mismatch between the TAG attributes of the Ethernet port and the peer device; and

6. the maximum frame length of the Ethernet port does not match that of the peer device; 6. the maximum frame length of the Ethernet port does not match that of the peer device.

7. cross-binding error causing service interruption.

8. Service interruption or packet loss due to inconsistent encapsulation protocols on the Ethernet port.

9. Inconsistent parameter settings for GFP encapsulation resulting in service interruption or packet loss; and

10. Inconsistent time slot numbering strategies, there are currently two time slot numbering strategies: sequential and interpolated, Huawei equipment defaults to the sequential time slot numbering strategy.

11. mismatch between the overhead bytes of J1 and C2 of the docking device, resulting in the transmission board constantly reporting AU_AIS alarms, so the docking needs to pay attention to the consistency of the overhead byte settings.

Suggestions and Summary

1. The MTU of Huawei routers refers to the IP header and its upper-layer data portion, which is the length of the IP packet, excluding the frame header and frame tail.

2. The MTU of the transmission device port refers to the maximum frame length (MFL: Maximum Frame Length). (RFC1042 based on 802.3 definition of maximum frame length: IEEE 802.3 networks have a maximum packet size which depends on the transmission rate. For type 10BASE5 802.3 networks the maximum packet size is 1518 octets. For type 10BASE5 802.3 networks the maximum packet size is 1518 octets including all octets between the destination address and the FCS inclusive.) Referring to 802.1q, the product sets the maximum frame length of the interface as For this faulty network, when transmitting SDH-EGS4 without VLAN tag and setting the MTU of the router to 1500, the maximum frame length of the transmitting device = 1500 bytes (IP header MTU) + 8 bytes (double-layer MPLS header) + 14 (byte Ethernet header) + 4 bytes (FCS) = 1526 bytes. 1526 bytes.

3. Under the networking condition of router and transmission equipment, ping big packet can not get through, which may lead to some web pages can not be opened, and the message of some web pages may be bigger when you open the web page. It is recommended to solve the problem of ping big packet failure first, i.e. adjust the MTU of the transmission device first.

4. For the handling of equipment docking problems, first check whether there is no problem with the basic configuration of the equipment, then check whether there is any abnormal alarm of the equipment, and finally, according to the special circumstances, check the overhead configuration and MTU configuration of the equipment.

The related technical information and SDH equipment troubleshooting process in this chapter are provided by Shenzhen Optical Transmission Network Technology Company Limited (www.opticaltrans.com), please retain! Huawei SDH Optical Transmission Equipment,SDH Transmission Equipment Sales