Triangular routing

<p>Triangular routing is a method for transmitting packets of data in communications networks. It uses a form of <a href="/facts/Routing/Ml6MVCaC">routing</a> that sends a packet to a proxy system before transmission to the intended destination. Triangular routing is a problem in <a href="/facts/Mobile_IP/55FC9Exv">mobile IP</a>; however, it finds applications in other networking situations, for instance to avoid problems associated with <a href="/facts/Network_address_translation/nFweFNfN">network address translation</a> (NAT), implemented for example by <a href="/facts/Skype/qdKbuh23">Skype</a>.
</p>
               2) Datagram is intercepted   3) Datagram is
                  by home agent and            detunneled and
                  is tunneled to the           delivered to the
                  care-of address.             mobile node.

+-----+          +-------+         +------+
                     |home | =======> |foreign| ------> |mobile|
                     |agent|          | agent | <------ | node |
                     +-----+          +-------+         +------+
    1) Datagram to    /|\         /
       mobile node     |        /   4) For datagrams sent by the
       arrives on      |      /        mobile node, standard IP
       home network    |    /          routing delivers each to its
       via standard    |  |_           destination. In this figure,
       IP routing.   +----+            the foreign agent is the
                     |host|            mobile node's default router.
                     +----+

Figure 1:  Operation of Mobile IPv4

From RFC 5944.

Triangular routing open-in-new

Triangular routing