AA TCPO does not perform any optimization for flows that have fragmented packets, IPv6 extension headers or unsupported or unknown TCP options, such as TCP encrypt. If such packets are received in the middle of the session, AA TCPO ceases optimization for the rest of the session duration.
Nokia recommends enabling the error-drop AQP action to avoid having error packets bypassing AA TCPO and reaching the end systems. Similarly, Nokia recommends that the operator configures the drop out-of-order fragments AQP action.
Operators are recommended to configure session-filter entries to drop unsupported IPv6 extension headers to keep the state machine of AA TCPO synchronized with the TCP stacks at the endpoints.
The unsupported extension headers are:
139, Experimental use, Host Identity Protocol [RFC 5201]
140, Level 3 Multihoming Shim Protocol for IPv6, [RFC 5533]
253, Assigning Experimental and Testing Numbers Considered Useful [RFC 3692], Experimental Values in IPv4, IPv6, ICMPv4, ICMPv6, UDP, and TCP Headers [RFC 4727]
254, Assigning Experimental and Testing Numbers Considered Useful [RFC 3692], Experimental Values in IPv4, IPv6, ICMPv4, ICMPv6, UDP, and TCP Headers [RFC 4727]
If these packets arriving in the middle of a flow are not dropped, they arrive at the far end TCP stack without going through AA TCPO. Problems arise when packets of the same session are sent without having EH, arrive at TCPO, but AA TCPO has missed the earlier packet exchanges for that session.