3 seconds to make the roundtrip. From the first
example to the second example, latency increased by a factor of 31! A data link that goes from
working normally to slowing down by a factor of 31 is a clear sign that link utilization should be
investigated.
For a more accurate measure of data throughput, you can use a tool such as ttcp. To test your connection
with ttcp you must have installed the ttcp package on machines inside and outside of your
network. (The ttcp package is available with Fedora and other Linux systems.) If you are not sure
whether the package is installed, simply type ttcp at a command prompt. You should see something
like the following:
# ttcp
Usage: ttcp -t [-options] host [ < in ]
ttcp -r [-options > out]
Common options:
-l ## length of bufs read from or written to network (default 8192)
-u use UDP instead of TCP
-p ## port number to send to or listen at (default 5001)
230
Running the Show Part II
-s -t: source a pattern to network
-r: sink (discard) all data from network
-A align the start of buffers to this modulus (default 16384)
-O start buffers at this offset from the modulus (default 0)
-v verbose: print more statistics
-d set SO_DEBUG socket option
-b ## set socket buffer size (if supported)
-f X format for rate: k,K = kilo{bit,byte}; m,M = mega; g,G = giga
Options specific to -t:
-n## number of source bufs written to network (default 2048)
-D don??™t buffer TCP writes (sets TCP_NODELAY socket option)
-w ## number of microseconds to wait between each write
Options specific to -r:
-B for -s, only output full blocks as specified by -l (for TAR)
-T ???touch???: access each byte as it??™s read
-I if Specify the network interface (e.
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