icmp man page on BSDOS

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icmp(n)			Tnm Tcl Extension		  icmp(n)

_________________________________________________________________

NAME
       icmp - Send ICMP messages to hosts on the Internet.
_________________________________________________________________

DESCRIPTION
       The  icmp command allows to send Internet Control Messages
       (ICMP) (RFC 792, RFC 1122) to  a	 list  of  hosts  on  the
       Internet. ICMP messages can be used to check whether hosts
       are reachable. The icmp command can also be used to  trace
       routes  to  Internet  hosts  by	sending	 UDP datagrams to
       unused UDP ports and interpreting the ICMP responses  (Van
       Jacobsen and Steve Deering algorithm).

ICMP COMMAND
       The  icmp  command  always accepts a list of target hosts.
       ICMP messages are send to the  targets  in  a  round-robin
       fashion	which allows to check entire IP address ranges or
       a list of core routers efficiently. The user of	the  icmp
       command should be careful not to flood a network with ICMP
       requests.

       icmp [options]
	      Invoking the icmp command with options but  without
	      any command arguments allows to retrieve and change
	      the default values. See  the  description	 of  sup-
	      ported options below. Default values are bound to a
	      Tcl interpreter which allows to have  multiple  Tcl
	      interpreter with different defaults.

       icmp [options] echo hosts
	      The  icmp	 echo  command	can  be	 used to test the
	      reachability of IP devices  by  sending  ICMP  echo
	      requests	to the hosts.  The command returns a list
	      of host / round trip time	 pairs.	 The  round  trip
	      time  is returned in milliseconds. A negative round
	      trip time indicates that a host did not respond  in
	      the timeout interval.

       icmp [options] mask hosts
	      The  icmp mask command sends ICMP mask requests and
	      returns a list of host / netmask	pairs.	The  mask
	      will  be	set to 0.0.0.0 if a host does not respond
	      to ICMP mask requests.

       icmp [options] timestamp hosts
	      The icmp	timestamp  command  retrieves  timestamps
	      using  the  ICMP	timestamp  request.  This command
	      returns an estimate of the time difference  between
	      local  time  and	the  time  on  the hosts given in
	      hosts. The command returns a list of  host  /  time

Tnm								1

icmp(n)			Tnm Tcl Extension		  icmp(n)

	      offset  pairs.  The time offset is returned in mil-
	      liseconds. An empty time offset  indicates  that	a
	      host did not respond in the timeout interval.

       icmp [options] ttl num hosts
	      The icmp ttl command, which may not be supported on
	      every operating system, sends a UDP  packet  to  an
	      unused  port  number with the time to live field of
	      the IP header set to num. This  command  returns	a
	      list  of	host  /	 round trip time pairs, where the
	      host is the IP device  being  num	 hops  away.  The
	      round trip time is returned in milliseconds. A neg-
	      ative round trip time indicates that a host did not
	      respond in the timeout interval.

       icmp [options] trace num hosts
	      The  icmp	 trace	command works similar to the icmp
	      ttl command but it always returns	 the  destination
	      address  even  when  the	responding  host  chooses
	      another interface with a different  IP  address  to
	      send  the	 reply. This can be used to trace a route
	      to a host since the command returns the  host  that
	      discards the packet if it does not reach the desti-
	      nation.

ICMP OPTIONS
       The following options control how ICMP requests	are  send
       and how the icmp command deals with lost ICMP packets.

       -timeout time
	      The  -timeout option defines the time the icmp com-
	      mand will wait for a response. The time is  defined
	      in seconds with a default of 5 seconds.

       -retries number
	      The  -retries  option  defines  how  many	 times	a
	      request is retransmitted during the timeout  inter-
	      val. The default number of retries is 2.

       -delay time
	      The -delay option defines the minimum delay between
	      two  outgoing  ICMP  packets.  The  delay	 time  is
	      defined  in  milliseconds with a default delay of 0
	      milliseconds. Delays are useful to reduce the  load
	      on intermediate devices like gateways or bridges.

       -size number
	      The -size option allows to control the size of ICMP
	      packets. The number defines the size of ICMP  pack-
	      ets in bytes with a default size of 64 bytes. Sizes
	      smaller than 64 bytes are silently  rounded  to  64
	      bytes.

Tnm								2

icmp(n)			Tnm Tcl Extension		  icmp(n)

BUGS
       The   icmp   command  requires  the  setuid  root  program
       ntping(8) because sending icmp packets requires access  to
       raw sockets on most operating systems.

SEE ALSO
       scotty(1), ntping(8), Tnm(n), Tcl(n)

AUTHORS
       Juergen Schoenwaelder <schoenw@cs.utwente.nl>

Tnm								3

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