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S12700 V200R011C10 Configuration Guide - Network Management and Monitoring

This document provides the configurations of network management and monitoring features supported by the product, including SNMP, RMON and RMON2, LLDP, Performance Management, iPCA, NQA, Service Diagnosis, Mirroring, Packet Capture, Traffic Distribution, NetStream, sFlow, and TWAMP Light.
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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Overview of Traffic Distribution

Overview of Traffic Distribution

A backbone network often has high bandwidth, overwhelming a single host. A traffic distribution device allocates traffic to different hosts according to the processing capabilities of the hosts. Figure 10-1 shows how traffic distribution is implemented.

Figure 10-1  Implementation of traffic distribution

On the network shown in Figure 10-1, SwitchB sends traffic to SwitchC through a third-party network probe. The network probe forwards a copy of traffic to SwitchA. SwitchA splits traffic into four parts and distributes the traffic to Server1, Server2, Server3, and Server4 for processing.

A traffic distribution device must support the following functions:

  • Unidirectional single-fiber communication

    After unidirectional single-fiber communication is enabled on the interfaces between the traffic distribution device and packet analysis servers, the packet analysis servers only receive packets but do not send packets. All the optical interface cards of Huawei S12700 support the single-fiber communication function.

  • Flow pair distribution to the same server

    In order to fully analyze traffic information, a packet analysis server needs to analyze not only the unidirectional traffic of two communication parties, but also the bidirectional traffic between the two parties. When analyzing the bidirectional traffic, the traffic distribution device must be able to distribute all the packets between the two communication parties to the same packet analysis server. Therefore, the flow pair sent over the same connection must be sent out through the same outbound interface of the traffic distribution server.

  • Data integrity

    In Layer 3 forwarding, packet attributes may be modified in any of the following situations:

    1. Before forwarding: The traffic distribution device replaces the destination MAC address for the received packets.


      In general forwarding process, a device compares the destination MAC address of a packet against its own system MAC address. If they are the same, the device forwards the packet at Layer 3. Otherwise, the device discards the packet. Obviously, the destination MAC addresses of service packets are different from the system MAC address of the traffic distribution device, so the device changes the destination MAC addresses of the packets, avoiding packet discarding.

    2. During forwarding: The device replaces the source MAC address of an IP packet with its own system MAC address and replaces the destination MAC address of the packet with the system MAC address of the next-hop device.
    3. After forwarding: The Time-to-live (TTL) value of each packet must be reduced by at least 1. Network devices determine whether to discard an IP packet according to the TTL value contained in the packet. If the TTL value of a packet is reduced to 0, the network device discards the packet.

    However, the traffic distribution device is not allowed to perform these modifications when forwarding packets to the packet analysis servers. This ensures the integrity of the data packets and the accuracy of the traffic analysis.

    To avoid modification on packets, the traffic distribution feature prevents an S12700 from:
    • Checking MAC addresses of packets.
    • Replacing the source or destination MAC addresses of packets.
    • Changing the TTL values of packets.
  • Querying outbound interfaces

    If you want to know the server to which a specified packet is distributed, you must know to which outbound interface this packet is distributed. The S12700 allows you to query the outbound interfaces of packets by entering five packet attributes (source IP address, destination IP address, source port, destination port, and protocol type).

Updated: 2019-10-21

Document ID: EDOC1000178113

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