NETTEST(1)NETTEST(1)NAME
nettest, nettestd - Performs client and server functions for timing data
throughput
SYNOPSIS
/etc/nettest [-c] [-C] [-d] [-f] [-F] [-h] [-b bufsize] [-S tos]
[-n conns] [-p tcp|udp|iso] [-sn] [-m] [-w] [host [count [size [port]]]]
/etc/nettest [-c] [-C] [-d] [-f] [-h] [-b bufsize] -p unix|unixd|pipe
[-n conns] [-w] [count [size [filename]]]
/etc/nettest [-c] [-C] [-d] [-f] [-h] [-b bufsize]
-p file writefile readfile [count [size]]
/etc/nettest -V
/etc/nettestd [-d] [-p tcp|udp|iso] [port]
/etc/nettestd [-d] -p unix|unixd|pipe [filename]
/etc/nettestd [-d] -p file readfile writefile
/etc/nettestd -V
DESCRIPTION
The nettest and nettestd commands invoke client and server programs that
are used for timing data throughput of various methods of interprocess
communication. For TCP and OSI connections, the nettest program
establishes a connection with the nettestd program, and then it does
count writes of size bytes, followed by count reads of size bytes. For
UDP, the nettest program performs only writes; reads are not performed.
The nettestd program, if used with UDP connections, reads the data
packets and prints a message for each data packet it receives. The
number and size of the reads and writes may not correlate with the number
and size of the actual data packets that are transferred; it depends on
the protocol that is chosen. If you append an optional k (or K) to the
size, count, or bufsize value, the number specified is multiplied by
1024.
The nettest and nettestd commands accept the following arguments:
-c To specify that the data must be checked to verify its accuracy, use
the -c flag. Because this is done by comparing one character at a
time, using the -c option can cause noticeable throughput
degradation. The data is verified by filling up the data buffer
with a 32-byte repeating pattern of all the lower case letters and
the first 6 upper case letters of the alphabet. This option is
useful for detecting data that has been corrupted. If there is a
problem with lost or duplicated data, this option may generate a
large number of error messages.
-C Similar to -c, except that the data is written out as a sequence of
sequential 64-bit numbers in network byte order. Because this is
done by comparing one word at a time, it is slightly faster than the
-c option, but it can still cause noticeable throughput degradation.
This option is useful for detecting data that has been lost or
duplicated, as it resynchronizes itself when an error is
encountered. However, if the size of the lost or duplicated data is
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not an even multiple of 8, it may not resynchronize properly.
-d For TCP, UDP, and OSI connections, the -d flag turns on the socket-
level debugging flag.
-f Indicates that a full-size read must be issued. Usually, when a
read returns a short count, both nettest and nettestd issue a read
for the remaining data for that buffer, whether or not a short count
was received. (The total number of bytes is not changed.)
-F For TCP connections, the -F flag turns on the TCP_NODELAY socket
option. The TCP code in the kernel usually tries to send only
full-sized packets over the network; this is accomplished by
delaying some writes until a full packet size accumulates. The -F
flag disables this algorithm.
-h To turn on hash marks to be printed, use the -h flag. Each time a
complete buffer is written or read, a hash mark is printed. If a
read returns a partial count and the -f flag is not specified, a
period is printed. If the -f flag is specified, a hash mark is
printed each time a read completes, regardless of the amount of data
read.
-b bufsize
This option applies only to nettest. For TCP and UDP connections,
use the -b flag to specify the amount of kernel buffering allowed.
-b This option applies only to nettestd. Run as a background daemon.
In this mode, nettestd will detach itself from its controlling
terminal, and put itself into the background. In addition, all
error messages are logged via syslog(3), instead of via perror(3).
Note that if both the -C and -v options are used in conjunction with
the -b option, any errors that are detected in the data stream will
not be reported.
-S tos
For TCP and UDP connections, the -S option can be used to specify
the Type-of-Service (TOS) value for the connection. (Not Supported)
A check for the symbolic name tos in /etc/iptos determines the
actual order. (The -t tos option is a valid synonym, for historical
compatibility.)
-n nconns
For TCP, UNIX and ISO connections, the -n option specifies the
number of simultaneous connections to be opened. For each
connection, a subprocess is created. Each subprocess, after
establishing a connection to the server and negotiating the options,
suspends itself. When all the connections have been established, a
continue signal is sent to all the subprocesses to start them
running at the same time. As each subprocess completes, it returns
its timing results, and returns that information to the main
process, which then prints out the individual timing information.
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After all the subprocesses have completed, aggregate timing results
given. The aggregate timings are based on the total amount of data
transferred by all the subprocesses, the start time of the first
subprocess to begin writing its data to its server, and end time of
the last subprocess to complete reading its data from its server.
The synchronization information shows when each subprocess began
running, the duration of the data transfer for each subprocess, and
ending time of each subprocess. These times are relative to the
start time of the first subprocess to began running.
-p protocol
Specifies the protocol in use. The valid values for protocol are
tcp, udp, iso, unix, unixd, pipe, and file.
If the -p option is not specified, tcp is the default.
The unix protocol uses UNIX domain stream sockets; filename can be
specified to override the default file name nt_socket.
The unixd protocol uses UNIX domain datagram sockets; filename can
be specified to override the default file name nt_dsocket.
For pipe protocol connections, two named pipes are created when you
specify filename, one for reading and one for writing. The nettest
program creates the names of these files by appending R and W to
filename. The default names are nt_pipeR and nt_pipeW.
For file protocols, writefile is the name of the special file to
which information is written; readfile is the name of the special
file that is read. The order of writefile and readfile is reversed
between nettest and nettestd. This allows the same file names to be
specified in the same order for both nettest and nettestd, because
the file to which nettest writes is the file from which nettestd
reads, and vice versa. The intent of this option is to allow
nettest to be run across arbitrary devices that have a character-
device interface that can be accessed just by opening up a special
character file for reading or writing. It is not intended for
reading or writing to a regular file.
-sn Increases the maximum TCP window by a factor of 2^n; 1 < n < 14.
-m Indicates that for datagram connections (-p udp and -p unixd) that
nettest should use the sendmsg system call insted of the sendto
system call (see send(2)), and that nettestd should use the recvmsg
system call insted of the recvfrom system call (see recv(2)), For
other protocols this option is ignored.
-w Use the MSG_WAITALL flag when calling recv(2). This allows the
kernel to accumulate incoming data so that the read buffer is filled
before returning control to the application. The use of this option
negates the need for the -f option.
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NETTEST(1)NETTEST(1)-V Print out information about the version of the program.
host For TCP, UDP, and OSI connections, host is the name of the machine
on which the server is running. If this is omitted or specified as
-, the name that gethostname(2) returns is used.
count
Specifies the number of read or write operations. A value of -
indicates that the default value must be used. The default value is
100.
size Specifies the number of bytes to be read or written. A value of -
indicates that the default value must be used. The default value is
4096.
port For TCP and UDP connections, specify port to select an alternate
port number. The port must be a decimal number.
The output from nettest is timing information and a histogram of the
various sizes that the read operations returned. System load affects the
results because all throughput times are calculated from wall-clock
times. The percentages listed for system and user times are percentages
of wall-clock time.
The write time is measured from the time at which the application starts
its first write until the time it completes its last write. The read
time begins when the last write is complete and ends when the last read
is complete. Because the kernel may buffer outgoing data, if everything
on the network is working correctly, it is normal for the write times to
be slightly faster than the read times. This difference in throughput
represents the amount of buffering in the kernel and the network round-
trip time. The read and write time is measured from the time the first
write is started to the time the last read is completed; thus, if the
speed of the network is the same in both directions and both machines
have the same processing power and load, the read and write times are the
most accurate.
The histogram output shows the sizes that the read system calls return.
These may not have any correlation to the size and number of packets that
are actually sent and received over the network. This is especially true
for TCP connections.
FILES
/etc/iptos IP (TOS) database (TOS is not supported)
nt_socket and nt_dsocket Default name for stream and datagram UNIX
domain sockets
nt_pipeW, nt_pipeR Default names for named pipes
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NETTEST(1)NETTEST(1)BUGS
The -p pipe, -p unix and -p unixd options create named pipes and UNIX
domain sockets, respectively, that remain after the programs exit.
If -p pipe filename is specified and filename is either a relative or
absolute path name, neither nettest nor nettestd insert the W and R
before the final component of the path name; they are always prepended to
the entire file name.
SEE ALSOgethostname(2), recv(2), and send(2)
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