Wireshark mailing list archives
Re: TCP Dup Ack Issues with Comcast vs. Cablevision
From: Alan Emery <ademery () us ibm com>
Date: Fri, 26 Feb 2010 10:35:55 -0600
This may be more related to a setting on the wireless access point. If the wireless AP is not set to a fixed mode such as "g" or "n", and it "hears" the presence of a "b" device associated or not, it will go into a compatibility mode and effectively run at the lower "b" rate. In my SOHO environment, I fix my wireless mode to "g" as that is compatible with all the devices I want to have connected, but if a guest brings in a "b" mode device, they cannot connect, but they don't downgrade the throughput of my existing network. Your 6-9 Mbps throughput is more typical of what I would expect in a "b" environment. If you can isolate the wireless AP to a switch that will allow you to connect a local target device, or to switch ports on the AP if available, you can look at throughput just going through the AP to a local target device to see if the issue lies with the AP or not. Alan Emery IBM Global Solution Center 1177 S Beltline Road, Coppell, TX 75019 From: William Howard <wghoward () optonline net> To: wireshark-users () wireshark org Date: 02/26/2010 09:32 AM Subject: [Wireshark-users] TCP Dup Ack Issues with Comcast vs. Cablevision Sent by: wireshark-users-bounces () wireshark org We have been investigating what seems to be an obscure issue with regards to Comcast speeds wired vs. wireless "G" speeds on a 30/5 circuit. Here are the symptoms: Wired (directly to modem): Speeds are what one would expect - 25-30 Mbps down and 4-5 Mbps up. Wireless: Speeds are in the 6-9 Mbps. We have tried a variety of consumer and higher end APs/Wireless routers. All with the same basic results - the speeds are significantly slower. The wireless NIC was connected with a "good" signal at 54 Mbps. I verified that wireless interference was not an issue. I tried several different laptops to make sure that the particular wireless NIC was an issue. The AP/Router were the only items on the circuit. Time of day did not matter as I tried going back and forth between wired and wireless - both produced consistent speeds each time. What we did discover is that when testing the same equipment on a cablevision/optimum online 30/5 circuit, the problems virtually disappear. Wired speeds are equivalent to Comcast but wireless speeds were in the 15-19 Mbps range. In order to dig deeper, I captured wireshark traces for both wired/wireless on Comcast and Optimum Online circuits. The biggest difference I could find is that on the Comcast circuit both wired and wireless, there were many: TCP Dup ACK packets (see below for an example) TCP [TCP Dup ACK 17802#55] http > apc-3052 [ACK] Seq=8154484 Ack=307815 Win=206848 Len=0 SLE=370595 SRE=447975 SLE=331175 SRE=335555 I have seen the "tcp optimizers" and they have produced good results and have improved the Comcast speeds to 12-16 Mbps but it seems very odd that only Comcast seems to suffer from packets arriving out of order (or whatever is causing this) but Cablevision does not. I don't like the idea of having to change a client device when it seems like this problem lies within the Comcast network. Has anyone seen this before? Is there a solution without changing the client laptop? We would like to have a solution that is hardware based (router or firmware) rather than telling users they must all make registry changes which makes us nervous (liability) and end-users irritated that "it works on other networks without a problem" Any insight on this would be greatly appreciated. Will Howard ___________________________________________________________________________ Sent via: Wireshark-users mailing list <wireshark-users () wireshark org> Archives: http://www.wireshark.org/lists/wireshark-users Unsubscribe: https://wireshark.org/mailman/options/wireshark-users mailto:wireshark-users-request () wireshark org?subject=unsubscribe
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Current thread:
- TCP Dup Ack Issues with Comcast vs. Cablevision William Howard (Feb 26)
- Re: TCP Dup Ack Issues with Comcast vs. Cablevision Alan Emery (Feb 26)
- Re: TCP Dup Ack Issues with Comcast vs.Cablevision William Howard (Feb 26)
- Re: TCP Dup Ack Issues with Comcast vs. Cablevision Alan Emery (Feb 26)