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Asymetric routing can affect TCP session. Just imagine that inbound and outbound traffic is taking different paths, so different MTU can be used, different ACLs will be used on different interfaces, different QoS/policy can be applied....and lot of other things.
Of most of the items you mention, it's unclear how an asymmetrical path would be especially different. As you've described, you have inbound and outbound which can have different ACLs and QoS but that can also be true even on a symmetrical path.
Mention of MTU is interesting, as different paths, forward and reverse, might have different MTUs. The TCP handshake, I believe, negotiates the lowest common MSS based on MTUs. Unsure the MTU being used would be minimum path MTU rather than host MTU. I.e. if not, it wouldn't change the TCP handshake.
So it's unclear, to me, how asymmetrical routing, alone, would directly impact the TCP handshake vs. symmetrical routing. Blau could you provide any clarification or an example issue?
