200Mbps seems a bit slow for a Gen3.. but it is getting old, and the actual setup of the NAT matters. As well as any degradation of the ethernet which tends to be one of the first things affected on Gen 3.
Actually, I can buy new one, if I were sure it solves the problem.
No it won't fix it.. as I said the new Gen5 TC is worse due to using a slower processor.. and Apple have not turned on hardware NAT. The same chipset used in say Asus achieves much higher results by using a built in speed up in the chip. Apple do not use the broadcom drivers because they use NETBSD firmware whereas everybody else uses Linux.
And in bridge mode I have full speed, in specs there say: "One Gigabit Ethernet WAN port for connecting a DSL or cable modem"
The fact that it has gigabit WAN is what is allowing you to get 200Mbps and not 90Mbps which is about the limit of 100mbit ethernet. But that is irrelevant to the speed reduction you get.. which is caused by the slowness of NAT processing. A router needs a very powerful processor to handle 1GB connection. Like a build your own PC with at least 3ghz i5 and maybe i7 running PFSense or similar router OS.
See http://www.pfsense.org/index.php@option=com_content&task=view&id=52&Itemid=47.ht ml
To simply get over 500Mbps throughput you need 3ghz processor. The TC is not even in the ballpark.
Without hardware speedup, the processor has to inspect every packet for NAT connection information at the very least.. if there is anything else happening in the router, QoS, Firewall etc they all make higher demands of the processor.. Apple routers of course don't have any of those things.. but you are still forced to handle the outgoing stream which might be half the speed of the incoming. Albeit much smaller packets.
See the WAN to LAN tables here.
http://www.smallnetbuilder.com/lanwan/router-charts/bar/74-wan-to-lan
You can see the tests for Airport Extreme which are the same as the TC. The Gen 4 is equal to the Gen5 AE.. and it achieved 430Mbps..The Gen4 AE which is equivalent to your Gen3 TC achieved 420, so, slightly less. The new AC version has a slower processor only managed 325Mbps.
The speed with the TC in bridge is fine.. it is then a switch... no router load at all.
