NTttcp errors & retransmit threshold

45 pts.
Tags:
Network connectivity
Network monitoring
Network testing
Networking
Hello All, We trying to do some network quality  assessment in our organization , for that we choose NTttcp tool that comes from Microsoft , and started to do some test. looking at results of some test we done each test for 1 min approx  i can see few erros and retransmit , my question is how to interpret that data what should be consider amount of Errors & Retransmit threshold for amount X time test or should not pear at all?. Please advice Thanks Thread Realtime(s) Throughput(KB/s) Throughput(Mbit/s) Avg Bytes per Completion ====== =========== ================ ================== ========================      0    3600.553       28964.028            231.712                65535.753 Total Bytes(MEG) Realtime(s) Average Frame Size Total Throughput(Mbit/s) ================ =========== ================== ========================    104286.519296    3600.553           1333.465                  231.712 Total Buffers Throughput(Buffers/s) Pkts(sent/intr) Intr(count/s) Cycles/Byte ============= ===================== =============== ============= ===========   1591286.000               441.956               4       4628.24        90.9 Packets Sent Packets Received Total Retransmits Total Errors Avg. CPU % ============ ================ ================= ============ ==========     78207179         39135363                 2            4      43.86                 SUPPORT99         Thread Realtime(s) Throughput(KB/s) Throughput(Mbit/s) Avg Bytes per Completion ====== =========== ================ ================== ========================      0    3600.005       28968.474            231.748                58126.747 Total Bytes(MEG) Realtime(s) Average Frame Size Total Throughput(Mbit/s) ================ =========== ================== ========================    104286.650164    3600.005           1333.205                  231.748 Total Buffers Throughput(Buffers/s) Pkts(recv/intr) Intr(count/s) Cycles/Byte ============= ===================== =============== ============= ===========   1591287.997               442.024               1      13422.33        48.4 Packets Sent Packets Received Total Retransmits Total Errors Avg. CPU % ============ ================ ================= ============ ==========     39131229         78222514               281            1      15.06

Software/Hardware used:
windows 2003,windows xp, 1Gbit ,Cisco Catalyst 2960 ,3com 2948 sfp -plus
ASKED: October 24, 2009  11:52 AM
UPDATED: November 4, 2009  12:48 PM

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These retransmit rates are extremely low. They are less than 0.1% Packet retransmits can become a concern when approaching 1% or higher. You could use the pathping utility to diagnose where packets might be being lost in the transmission path if the packets have to cross routed networks. pathping is an excellent troubleshooting utility to look at latency & packet loss along a path.

Usage: pathping [-g host-list] [-h maximum_hops] [-i address] [-n]
[-p period] [-q num_queries] [-w timeout] [-P] [-R] [-T]
[-4] [-6] target_name

Options:
-g host-list Loose source route along host-list.
-h maximum_hops Maximum number of hops to search for target.
-i address Use the specified source address.
-n Do not resolve addresses to hostnames.
-p period Wait period milliseconds between pings.
-q num_queries Number of queries per hop.
-w timeout Wait timeout milliseconds for each reply.
-P Test for RSVP PATH connectivity.
-R Test if each hop is RSVP aware.
-T Test connectivity to each hop with Layer-2 priority tags.
-4 Force using IPv4.
-6 Force using IPv6.

It’s not a gui but it does give very valuable information within a single utility about the path between a source & destination.

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  • Tbaror
    Hello Troy, Thanks for your answer, you meant for calculating the retransmitted % i should use following Retransmits / (Packets Sent + Packets Received) = Percent Retransmits ? if so is errors could be treated/calculated the same as Retransmits? As for the actual test its been taken on flat LAN with no routing , Thanks
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  • Tbaror
    It would be hard to say if the retransmits were on the sending or receiving side. So, the calculation might be better retransmits / packets sent = %retransmits sending retransmits / packets rec'd = %retransmits received The only way you would know which direction the retransmits are happening is to use a packet sniffer between the source and destination devices and compare the packets. Low retransmit percentage on a local lan could be due to an overloaded host. Higher retransmits could be due to speed/duplex mismatches, overloaded LAN, overloaded switch or routing device.
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