kevinamadeus wrote:
Yea I won't say the home connection is perfect in overseas routing... but is it normal to have 10 times speed difference in download and upload to a same location? Isn't the routing the same?
Not necessarily (though for my part I wish it were more often). For example, I regularly (but not 100% of the time) find myself with asymmetric routing between my home connection in New York to the Dallas data center. The path is consistently symmetric from, for example, the Newark data center. Annoyingly, in almost all cases I've tracked connectivity issues, the most likely problem point was a transit provider only existing on the return path in cases when the asymmetry was present. Makes troubleshooting tricky.
Since IP routing is (by and large) purely destination based, and provides can make choices about how long to stay internal to their own network before handing off a packet if multiple exit points are present - and depending on the network announcements and metrics involved - it's not that hard to get such scenarios. I suspect it's more prevalent nowadays than in the earlier days of the network where there were fewer connection points exchanging routes, but it's been a long time since I looked closely.
Of course, this need not be a problem if both paths are of roughly the same quality (loss, latency and bandwidth), or in the case of TCP, if the return path (opposite of primary data transfer) is at least within an order of magnitude of the forward path. In fact, the bandwidth asymmetry of most consumer broadband connections (at least in the US) depends on this fact.
But if the two paths are not of similar quality, you can absolutely get pretty significant differences in performance - think of uploading over that home asymmetric connection versus downloading.
-- David
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