No QoS is in use anywhere.. To the best of my ability I've eliminated Packet loss. However, I've not found a way any better than ICMP/MTR/Ping -f..etc. The reason flow control has been mentioned is to correct buffer overflow at the Microwave links. Where they physically link at GigFDX. But the radio interface is only capable of ~360Mb/s, It's possible for the sending device to overflow the buffer between the fiber/ethernet and the radio interface.I can say we've had an issue like this in the past, Which forcing 100Mb/s FDX on a licensed radio fixed the problem. Being that, The ethernet was now slower then the radio interface. However, The down fall of this is that it limits the link to 100Mb/s which isn't sufficient anymore. In terms of congestion, There is not from my point of view. Every link in questions runs =>30% utilization. Nick Olsen Network Operations (855) FLSPEED x106 ---------------------------------------- From: "Blake Dunlap" <ikiris@gmail.com> Sent: Tuesday, August 27, 2013 11:42 AM To: nick@flhsi.com Cc: nanog@thedaileyplanet.com, "nanog@nanog.org" <nanog@nanog.org> Subject: Re: TCP Performance This really sounds like you aren't testing the correct flow type in i/jperf, or you have some QoS queues for http traffic but not the perf traffic that are filled. Regardless, your problem looks like either tail drops or packet loss, which you showed originally. The task is to find out where this is occurring, and which of the two it is. If you want to confirm what is going on, there are some great bandwidth calculators on the internet which will show you what bandwidth you can get with a given ms delay and % packet loss. As far as flow control, its really outside the scope. If you ever need flow control, there is usually a specific reason like FCoE, and if not, it's generally better to just fix the backplane congestion issue if you can, than ever worry about using FC. The problem with FC isn't node to node, its when you have node to node to node with additional devices, it isn't smart enough to discriminate, and can crater your network 3 devices over when it would be much better to just lose a few packets. -Blake On Tue, Aug 27, 2013 at 9:49 AM, Nick Olsen <nick@flhsi.com> wrote: Duplex mismatch has been checked across the board. On every device. Nick Olsen Network Operations (855) FLSPEED x106 ---------------------------------------- From: "Chad Dailey" <nanog@thedaileyplanet.com> Sent: Tuesday, August 27, 2013 10:48 AM To: nick@flhsi.com Subject: Re: TCP Performance Check for duplex mismatch at the server. On Mon, Aug 26, 2013 at 2:07 PM, Nick Olsen <nick@flhsi.com> wrote: Greetings all, I've got an issue I was hoping to put a few more eyes on. Here's the scenario. Downloading a file at our Border is multiple orders of magnitude faster then a few hops out. Using the same 128MB test file, I tested at two different locations. As well as between them. Using multiple connections improves throughput, However it's the single stream issue we're looking at right now. All testing servers in question are Centos Linux. Orlando Datapath: Cogent>Orlando Border Router (Mikrotik)>HP Procurve Switch> Server Results: 2013-08-29 05:04:09 (52.6 MB/s) - `128mbfile.tgz' saved [127926272/127926272] Cocoa NOC Datapath: Cogent>Orlando Border Router (Mikrotik)>Licensed Microwave Link (300+Mb/s Capacity)>East Orange Router (Mikrotik)> Licensed Microwave Link (300+Mb/s Capacity)>Cocoa Router (Mikrotik)>Licensed Microwave Link (300+Mb/s Capacity)>Colo Router (Mikrotik)>NOC Router (Mikrotik)>HP Procurve Switch>Server Results: 2013-08-26 13:42:25 (398 KB/s) - `128mbfile.tgz' saved [127926272/127926272] Orlando-Cocoa NOC Datapath: Orlando Server>HP Procurve Switch>Orlando Border Router (Mikrotik)>Licensed Microwave Link (300+Mb/s Capacity)>East Orange Router (Mikrotik)> Licensed Microwave Link (300+Mb/s Capacity)>Cocoa Router (Mikrotik)>Licensed Microwave Link (300+Mb/s Capacity)>Colo Router (Mikrotik)>NOC Router(Mikrotik)>HP Procurve Switch>ServerResults: 2013-08-26 13:56:25 (3.31 MB/s) - `128mbfile.tgz' saved [134217728/134217728] Now, For the fun of it. I ran Iperf single TCP between our Cocoa and Orlando POP's. Just like the HTTP test above. (Server has a 100Mb/s port). It maxes out the port, Unlike the HTTP test. [root@ded01 ~]# iperf -c 208.90.219.18------------------------------------------------------------Cli ent connecting to 208.90.219.18, TCP port 5001TCP window size: 16.0 KByte (default)------------------------------------------------------------[ 3] local 206.208.56.130 port 47281 connected with 208.90.219.18 port 5001[ ID] Interval Transfer Bandwidth[ 3] 0.0-10.0 sec 114 MBytes 95.7 Mbits/sec Here's associated packet captures for each transfer. As well as full wget output and traceroutes for each test. As you can see, The tests crossing the wireless links show about 3x more TCP re-transmits/dup ACK's. But I'm not sure I'm sold this could show such a huge drop in throughput. Other then that, nothing really stands out to me as to why these transfers are so much slower. Intra-network iperf testing shows full throughput the whole way with single connection. As well as UDP testing. One thing to note is the Iperf testing has far less TCP re-transmit/dup acks then any of the HTTP testing, Crossing the same Microwave Links and routers. http://cdn.141networks.com/files/captures.zip I appreciate any insight anyone might have. Thanks! Nick Olsen Network Operations (855) FLSPEED x106