7.6 Dealing with symmetric NATs

Whereas cone NATs are used in small and domestic private networks, in most of the corporative LANs the NATs are symmetric. When a peer P is behind a symmetric NAT, only can receive blocks from a public node if P has sent at least a block to it. Another drawback of using symmetric NATs is that each different “connection” Using UDP the concept of connection does not make sense. However, we can use this name to reefer to the tuple ((public IP address, public port), (private IP address, private port)), where the public endpoint points to a public peer and the private endpoint points to the private peer. has a different public endpoint. Besides this problem, some networks administrator refuses UDP traffic because it can congest their networks easier than using TCP traffic.


Figure 5: A solution to cross symmetric NATs. A public peer P serves a stream to the private team T2.

One way of solving this problem is creating a different team for the private network, in a similar way as was explained in Section 7.5, but using a peer located in the public network (see Figure 5). Notice that in this configuration, only a TCP connection need to be established through the NAT.



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P2PSP (Peer-to-Peer Straightforward Protocol) by Cristobal Medina-López, J. A. M. Naranjo, L. G. Casado and Vicente González-Ruiz

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