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+.. _srv6_ad_plugin_doc:
+
+SRv6 dynamic proxy
+==================
+
+SRv6 endpoint to SR-unaware appliance via dynamic proxy (End.AD)
+----------------------------------------------------------------
+
+Overview
+~~~~~~~~
+
+The dynamic proxy is an improvement over the static proxy (@ref
+srv6_as_plugin_doc) that dynamically learns the SR information before
+removing it from the incoming traffic. The same information can then be
+re-attached to the traffic returning from the SF. As opposed to the
+static SR proxy, no CACHE information needs to be configured. Instead,
+the dynamic SR proxy relies on a local caching mechanism on the node
+instantiating this segment. Therefore, a dynamic proxy segment cannot be
+the last segment in an SR SC policy. A different SR behavior should thus
+be used if the SF is meant to be the final destination of an SR SC
+policy.
+
+Upon receiving a packet whose active segment matches a dynamic SR proxy
+function, the proxy node pops the top MPLS label or applies the SRv6 End
+behavior, then compares the updated SR information with the cache entry
+for the current segment. If the cache is empty or different, it is
+updated with the new SR information. The SR information is then removed
+and the inner packet is sent towards the SF.
+
+The cache entry is not mapped to any particular packet, but instead to
+an SR SC policy identified by the receiving interface (IFACE-IN). Any
+non-link-local IP packet or non-local Ethernet frame received on that
+interface will be re-encapsulated with the cached headers as described
+in @ref srv6_as_plugin_doc. The SF may thus drop, modify or generate new
+packets without affecting the proxy.
+
+For more information, please see
+`draft-xuclad-spring-sr-service-chaining <https://datatracker.ietf.org/doc/draft-xuclad-spring-sr-service-chaining/>`__.
+
+CLI configuration
+~~~~~~~~~~~~~~~~~
+
+The following command instantiates a new End.AD segment that sends the
+inner packets on interface ``IFACE-OUT`` towards an appliance at address
+``S-ADDR`` and restores the encapsulation headers of the packets coming
+back on interface ``IFACE-IN``.
+
+::
+
+   sr localsid address SID behavior end.ad nh S-ADDR oif IFACE-OUT iif IFACE-IN
+
+For example, the below command configures the SID ``1::A1`` with an
+End.AD function for sending traffic on interface
+``GigabitEthernet0/8/0`` to the appliance at address ``A1::``, and
+receiving it back on interface ``GigabitEthernet0/9/0``.
+
+::
+
+   sr localsid address 1::A1 behavior end.ad nh A1:: oif GigabitEthernet0/8/0 iif GigabitEthernet0/9/0
+
+Pseudocode
+~~~~~~~~~~
+
+The dynamic proxy SRv6 pseudocode is obtained by inserting the following
+instructions between lines 1 and 2 of the static proxy SRv6 pseudocode.
+
+::
+
+   IF NH=SRH & SL > 0 THEN
+       Decrement SL and update the IPv6 DA with SRH[SL]
+       IF C(IFACE-IN) different from IPv6 encaps THEN              ;; Ref1
+           Copy the IPv6 encaps into C(IFACE-IN)                   ;; Ref2
+   ELSE
+       Drop the packet
+
+**Ref1:** “IPv6 encaps” represents the IPv6 header and any attached
+extension header.
+
+**Ref2:** C(IFACE-IN) represents the cache entry associated to the
+dynamic SR proxy segment. It is identified with IFACE-IN in order to
+efficiently retrieve the right SR information when a packet arrives on
+this interface.
+
+In addition, the inbound policy should check that C(IFACE-IN) has been
+defined before attempting to restore the IPv6 encapsulation, and drop
+the packet otherwise.