elvey
Spamassassin
join:2001-02-17
San Francisco, CA
 ·Pacific Bell - SBC
 ·Comcast
·SONIC.NET
 ·Cogent Communicati..
| [Info] Impact of duplex change on COGENTco.com connection HUGE!!
I just sped up a client's Internet access from around
9000 kbps down/700 kbps up to about
30000 kbps down/30000 kbps up!
Now, they are paying $800 or so for this, and are on a MAN in an office building, but I was very surprised HOW MUCH this helped.
Initial setup, 'net-wise: Fiber comes in, and goes to a fiber to Ethernet converter, and from there to a Gb switch, and from there to a Cisco PIX, and from there to the LAN.
I.e.:
fiber from basement--media converter-Gb switch--PIX--LAN Gb switch
I'm there to reconfigure the PIX for various reasons and move some devices behind the firewall. Also, they're complaining about network slowness (LAN and WAN).
So, I go about doing the reconfiguration, and mention that we could remove the Gb switch, as it just had 2 cables connected to it. Before doing so, I notice that it indicates 100Mbps connections on both cables, and half duplex on one of them. I swap the cables, noting that the lights indicate the ports are set to auto-negotiate; the media converter is still connecting at half duplex. I try to connect directy to the media converter. It works. Speeds are as before. I configure the Cisco WAN port from auto to full duplex and try to connect directy to the media converter. Success, and the speed test results skyrocket.
Yeah, I know auto-negotiation is troublesome with interoperability being a weak point, what surprised me was that the improvement was huge, consistently and with various test tools and locations. (speakeasy (various locations), megapath, sbc, etc.)
I didn't realize how aggressively today's TCP algorithms are at backing away in the face of packet loss.
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