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NE40E V800R010C00 Feature Description - NAT and IPv6 Transition 01

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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).
PCP Connection

PCP Connection

PCP Connection Establishment

Figure 5-1 shows the process of establishing a PCP connection.
Figure 5-1  Process of establishing a PCP connection
  1. Customer premises equipment (CPE) sends a Carrier Grade NAT (CGN) device a PCP request for a public IP address and a public port number for user access.
    NOTE:

    Both the CPE and CGN device must support PCP.

    PCP request packets are classified into the following types:
    • MAP requests: supported only by full-cone NAT (3-tuple) mode.
    • PEER requests: supported only by symmetric NAT (5-tuple) mode.
    Select a proper translation mode in a service instance on a CGN device based on the PCP request type sent by a CPE. Full cone NAT is recommended because most CPEs send MAP request packets.
  2. Upon receipt, a CGN device selects a public IP address from the public address pool and generates a NAT entry containing the mapping between the private IP address and port number and the public IP address and port number. The CGN device then sends a PCP response packet carrying the public IP address and port number to the CPE.

PCP Connection Teardown

A CGN device tears down a PCP connection to reclaim public network resources in the following situations:
  • A PC triggers a teardown.
    1. A PC uses P2P software to send a UPnP teardown request to a CPE.
    2. The CPE constructs a PCP request packet for a connection teardown to the CGN device. The packet carries a PCP connection lifetime of 0.
    3. Upon receipt, the CGN device tears down the PCP connection, deletes the NAT mapping entry for the PC, and reclaims the public network resources.
  • The CPE triggers a teardown.
    1. If the CPE detects no traffic destined for the PC on the listening port after the listening timeout period elapses, the CPE constructs a PCP request packet for a connection teardown and sends it to the CGN device. The packet carries a PCP connection lifetime of 0.
    2. Upon receipt, the CGN device tears down the PCP connection, deletes the NAT mapping entry for the PC, and reclaims the public network resources.
  • The CGN device triggers a teardown.
    • After the PCP connection lifetime elapses on the CGN device, the CGN device does not receive a PCP connection teardown request with a PCP connection lifetime of 0 from the CPE. Upon receipt, the CGN device tears down the PCP connection, deletes the NAT mapping entry for the PC, and reclaims the public network resources.

PCP Connection Lifetime

If a user on a piece of CPE maliciously establishes a large number of PCP connections to a CGN device, public network resources are wasted. To prevent this problem, the CGN device must be able to tear down the PCP connections to reclaim resources after the specific PCP connection lifetime elapses.

The CPE also sends a PCP request packet carrying a PCP connection lifetime to the CGN device. The lifetime value on the CGN device takes effect according to the following rules:
  • If the received lifetime is greater than or equal to the minimum lifetime and less than or equal to the maximum lifetime, the received lifetime takes effect.
  • If the received lifetime is less than the minimum lifetime, the minimum lifetime takes effect.
  • If the received lifetime is greater than the maximum lifetime, the maximum lifetime takes effect.
You can set the minimum and maximum lifetime values based on the network traffic volume and the number of allowable PCP connections and public network resources on the CGN device.
  • This rule helps prevent a PCP connection from being frequently torn down and reestablished due to a small lifetime.

  • This rule helps prevent a PCP connection from retaining and being unable to release service resources due to a large lifetime.

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Updated: 2018-07-04

Document ID: EDOC1100027155

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