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Latency across link

Posted on 2011-09-14
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Last Modified: 2012-06-21
I have a 1 gb link but FTP transfers get about 3MB per second and windows file transfers get about 2MB per second across the link.

We have sent 100MB across with an analyzer and it showed no packet loss.

Wireshark shows some errors but no warnings.

What are some ways to determine if this is a network or server issue?

Do I need to capture all the traffic on the link with wireshark?

Currently I am just capturing the traffic destined to the local machine receiving the file transfers.

There is some broadcast traffic but it does not seem to be excessive but I am not sure how to determine that.
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Question by:Dragon0x40
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FarWest earned 72 total points
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use tracert to check if routers in the middle and which one is causing the delay if any
if no letancy appears with tracert, then check if you have antivirus that monitor the packets,
and check NIC drivers in both source and distination

good luck
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by:SeeMeShakinMyHead
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are the errors you are seeing in WireShark checksum errors.  This is typically normally with today's NIC's that do checksum offloading at the NIC.  Also, try running iPerf on  both locations and send a large amount of data and see what it reports.  @fryezz - I had a similary issue with CIFS transfers where Symantec Enterprise Protection (SEP) was hindering the traffic flow.  
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by:eeRoot
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How many network devices are there between the 2 devices?  At least one of them may have QOS or some speed limiting setting.  Also, do a read/write speed test on the 2 machines to verify neither is having an issue with its hard drive(s).  If one of the machine has very slow read/write results, it may be a workstation issue, rather then a network issue
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by:giltjr
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Its' a bit unusual that FTP gets slower throughput than Windows (SAMBA) File copies.

Are you sure the full path is 1 Gbps between the client and the server?  Assuming you mean mega bytes when you say 2-3 MBps, that is 16 to 24 mega-bits per second.  Sounds almost like wireless, cable, or a fractional DS3 WAN link.
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by:rochey2009
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Hi,

What does the wireshark capture show? Have a look at TCP round trip times, retransmissions, maximum segment size, TCP window size etc.
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by:rochey2009
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TCP window scaling should allow better utilization of the bandwidth.
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by:mikebernhardt
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you haven't yet explained the topology of your network, but since your analyzer can send 100mpbs I'm assuming that this is all LAN with no WAN/wireless links in between. So make sure that:
1. The speed of the link is actually 1GB on both sides. Look at the Local Area Connection status.
2. The duplex setting on the 2 machines match the duplex setting on the switch ports. A mismatch has an enormous impact on performance. This isn't normally an issue with Gig links (should always be full duplex) but it's worth looking at.
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by:giltjr
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Actually the analyzer sent a 100MB file, he does not say how fast it sent it.  

I was assuming that it sent it at 2-3 MBps (16-24Mbps).  Which is about what I would expect from a 54Mbps wireless link with WPA encryption or some time of WAN link.
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by:Dragon0x40
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I have attached a RTT graph from Wireshark.

We did send a 100MB test signal with an analyzer across the link and did not have any packet loss.

Also looking at a routing problem that may be sending traffic through the layer 2 cloud twice.

This is going through a layer 2 cloud so how many hops in between I don't know.
RTT-graph.png
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by:Dragon0x40
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by:giltjr
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Assuming you are running Windows, from one of the computers you are testing with can you provide the output from the command:

     pathping -n x.x.x.x

where x.x.x.x is the IP address of the of the other computer you are testing with?
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by:Dragon0x40
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I think this may be a routing issue with extra hops through the layer 2 cloud. I will post when I find out.
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by:giltjr
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Can you please provide the output from pathping, or even just a ping.

The only time a "layer 2 could" should come into play is if layer 2 is bridged over a WAN.
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by:Dragon0x40
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I wil do a pathping and post the results.
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by:Dragon0x40
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C:\Users\xxxx>pathping 1.2.3.4

Tracing route to 1.2.3.4 over a maximum of 30 hops

  0  2.3.4.5
  1  7.8.9.10
  2  3.4.5.6
  3  4.5.6.7
  4  5.6.7.8
  5  6.7.8.9
  6  1.2.3.4

Computing statistics for 150 seconds...
            Source to Here   This Node/Link
Hop  RTT    Lost/Sent = Pct  Lost/Sent = Pct  Address
  0                                           2.3.4.5
                                0/ 100 =  0%   |
  1    0ms     0/ 100 =  0%     0/ 100 =  0%  7.8.9.10
                                0/ 100 =  0%   |
  2    2ms     0/ 100 =  0%     0/ 100 =  0%  3.4.5.6
                                0/ 100 =  0%   |
  3    2ms     0/ 100 =  0%     0/ 100 =  0%  4.5.6.7
                                0/ 100 =  0%   |
  4   60ms     0/ 100 =  0%     0/ 100 =  0%  5.6.7.8
                                0/ 100 =  0%   |
  5   60ms     0/ 100 =  0%     0/ 100 =  0%  6.7.8.9
                                0/ 100 =  0%   |
  6   60ms     0/ 100 =  0%     0/ 100 =  0%  1.2.3.4

Trace complete.

C:\Users\xxxx>ping 1.2.3.4

Pinging 1.2.3.4 with 32 bytes of data:
Reply from 1.2.3.4: bytes=32 time=60ms TTL=59
Reply from 1.2.3.4: bytes=32 time=60ms TTL=59
Reply from 1.2.3.4: bytes=32 time=60ms TTL=59
Reply from 1.2.3.4: bytes=32 time=60ms TTL=59

Ping statistics for 1.2.3.4:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 60ms, Maximum = 60ms, Average = 60ms
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by:giltjr
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O.K, unless you work for a real rich company or a major telco company, you do not have a 1Gbps link between the two computers in question.  Your computer may have a 1Gbps NIC and the other computer may have a 1 Gbps NIC, but there is a WAN between the two which is running MUCH slower than 1 Gbps.

So you need to find out what the WAN bandwidth is.  I am going to assume that you are not in the networking group, or you would have already known that there is a WAN between the two computers.  So you need to contact somebody in your networking group and find out what the WAN bandwidth is.

I am also assuming that you, or your company, owns/controls both computers that are involved.

Based on the 60ms RTT, my guess is that these two computers are a few thousand miles apart.  The company I work for has a location just outside Washington DC and one in London and the RTT avg. 90-100 ms.
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Author Closing Comment

by:Dragon0x40
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Was a routing issue with an incorrect next hop in the routing table. The traffic was having to go thru the mpls cloud twice instead of once.
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