rfc2151.txt

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Kessler &  Shepard           Informational                      [Page 6]

RFC 2151          Internet & TCP/IP Tools & Utilities          June 1997


   In the second example, the user pings the host smcvax.smcvt.edu,
   requesting that 10 messages be sent in quite mode (-q). In this case,
   a summary is printed at the conclusion of the test and individual
   responses are not listed.

   TECHNICAL NOTE: Older versions of the Ping command, which are still
   available on some systems, had the following general format:

      ping [-s] {IP_address|host_name} [PacketSize] [Count]

   In this form, the optional "-s" string tells the system to
   continually send an ICMP Echo message every second; the optional
   PacketSize parameter specifies the number of bytes in the Echo
   message (the message will contain PacketSize-8 bytes of data; the
   default is 56 bytes of data and a 64 byte message); and the optional
   Count parameter indicates the number of Echo messages to send before
   concluding the test (the default is to run the test continuously
   until interrupted).

  ====================================================================
**syrup:/home$ ping -c 6 -s 64 thumper.bellcore.com
  PING thumper.bellcore.com (128.96.41.1): 64 data bytes
  72 bytes from 128.96.41.1: icmp_seq=0 ttl=240 time=641.8 ms
  72 bytes from 128.96.41.1: icmp_seq=2 ttl=240 time=1072.7 ms
  72 bytes from 128.96.41.1: icmp_seq=3 ttl=240 time=1447.4 ms
  72 bytes from 128.96.41.1: icmp_seq=4 ttl=240 time=758.5 ms
  72 bytes from 128.96.41.1: icmp_seq=5 ttl=240 time=482.1 ms

  --- thumper.bellcore.com ping statistics ---
  6 packets transmitted, 5 packets received, 16% packet loss
  round-trip min/avg/max = 482.1/880.5/1447.4 ms

**syrup:/home$ ping -q -c 10 smcvax.smcvt.edu
  PING smcvax.smcvt.edu (192.80.64.1): 56 data bytes

  --- smcvax.smcvt.edu ping statistics ---

  10 packets transmitted, 8 packets received, 20% packet loss
  round-trip min/avg/max = 217.8/246.4/301.5 ms
  ====================================================================











Kessler &  Shepard           Informational                      [Page 7]

RFC 2151          Internet & TCP/IP Tools & Utilities          June 1997


3.3. Finger

   The Finger program may be used to find out who is logged in on
   another system or to find out detailed information about a specific
   user. This command has also introduced a brand new verb; fingering
   someone on the Internet is not necessarily a rude thing to do!  The
   Finger User Information Protocol is described in RFC 1288 [32]. The
   most general format of the Finger command is:

      finger [username]@host_name

   The first example below shows the result of fingering an individual
   user at a remote system. The first line of the response shows the
   username, the user's real name, their process identifier,
   application, and terminal port number. Additional information may be
   supplied at the option of the user in "plan" and/or "project" files
   that they supply; these files are often named PLAN.TXT or
   PROJECT.TXT, respectively, and reside in a user's root directory (or
   somewhere in an appropriate search path).

   The second example shows the result of fingering a remote system.
   This lists all of the processes currently running at the fingered
   system or other information, depending upon how the remote system's
   administrator set up the system to respond to the Finger command.

  ====================================================================
**C:> finger [e-mail]
  [smcvax.smcvt.edu]
  KUMQUAT  Gary Kessler            KUMQUAT not logged in
  Last login Fri 16-Sep-1996 3:47PM-EDT

  Plan:

  ===================================================================
  Gary C. Kessler
  Adjunct Faculty Member, Graduate College

  INTERNET:  [e-mail]

  ===================================================================

**C:> finger @smcvax.smcvt.edu
  [smcvax.smcvt.edu]
  Tuesday, September 17, 1996 10:12AM-EDT   Up 30 09:40:18
  5+1 Jobs on SMCVAX  Load ave  0.16 0.19 0.21






Kessler &  Shepard           Informational                      [Page 8]

RFC 2151          Internet & TCP/IP Tools & Utilities          June 1997


   User    Personal Name     Subsys       Terminal  Console Location
  GOODWIN  Dave Goodwin      LYNX           6.NTY2  waldo.smcvt.edu
  JAT      John Tronoan      TELNET         1.TXA5
  HELPDESK System Manager    EDT         2:08.NTY4  [199.93.35.182]
  SMITH    Lorraine Smith    PINE            .NTY3  [199.93.34.139]
  SYSTEM   System Manager    MAIL          23.OPA0  The VAX Console
                              *DCL*     SMCVX1$OPA0  The VAX Console
  ====================================================================

3.4. Traceroute

   Traceroute is another common TCP/IP tool, this one allowing users to
   learn about the route that packets take from their local host to a
   remote host. Although used often by network and system managers as a
   simple, yet powerful, debugging tool, traceroute can be used by end
   users to learn something about the ever-changing structure of the
   Internet.

   The classic Traceroute command has the following general format
   (where "#" represents a positive integer value associated with the
   qualifier):

     traceroute [-m #] [-q #] [-w #] [-p #] {IP_address|host_name}

         where
            -m   is the maximum allowable TTL value, measured as
            the number of hops allowed before the program terminates
            (default = 30)
            -q   is the number of UDP packets that will be sent with
            each time-to-live setting (default = 3)
            -w   is the amount of time, in seconds, to wait for
            an answer from a particular router before giving up
            (default= 5)
            -p   is the invalid port address at the remote host
            (default = 33434)

   The Traceroute example below shows the route between a host at St.
   Michael's College (domain smcvt.edu) and a host at Hill Associates
   (www.hill.com), both located in Colchester, VT but served by
   different Internet service providers (ISP).











Kessler &  Shepard           Informational                      [Page 9]

RFC 2151          Internet & TCP/IP Tools & Utilities          June 1997


      1 St. Michael's College is connected to the Internet via BBN
      Planet; since the mid-1980s, BBN operated the NSF's regional ISP,
      called the New England Academic and Research Network (NEARNET),
      which was renamed in 1994. The first hop, then, goes to St. Mike's
      BBN Planet gateway router (smc.bbnplanet.net). The next hop goes
      to another BBN Planet router (denoted here only by IP address
      since a name was not assigned to the device), until the packet
      reaches the BBN Planet T3 backbone.

      2 The packet takes two hops through routers at BBN Planet's
      Cambridge (MA) facility and is then forwarded to BBN Planet in New
      York City, where the packet takes four more hops. The packet is
      then forwarded to BBN Planet in College Park (MD).

      3 The packet is sent to BBN Planet's router at MAE-East, MFS
      Datanet's Network Access Point (NAP) in Washington, D.C. MAE
      stands for Metropolitan Area Exchange, and is a Fiber Distributed
      Data Interface (FDDI) ring interconnecting routers from
      subscribing ISPs. The packet is then forwarded to NETCOM, Hill
      Associates' ISP.

      4 The packet now travels through NETCOM's T3 backbone, following
      links from Washington, D.C. to Chicago to Santa Clara (CA), to San
      Jose (CA).

      5 The packet is now sent to Hill Associates router (again, a
      system designated only by an IP address since the NETCOM side of
      the router was not named) and then passed to the target system.
      Note that the host's real name is not www.hill.com, but
      syrup.hill.com.

   TECHNICAL NOTE: The original version of Traceroute works by sending a
   sequence of User Datagram Protocol (UDP) datagrams to an invalid port
   address at the remote host. Using the default settings, three
   datagrams are sent, each with a Time-To-Live (TTL) field value set to
   one. The TTL value of 1 causes the datagram to "timeout" as soon as
   it hits the first router in the path; this router will then respond
   with an ICMP Time Exceeded Message (TEM) indicating that the datagram
   has expired. Another three UDP messages are now sent, each with the
   TTL value set to 2, which causes the second router to return ICMP











Kessler &  Shepard           Informational                     [Page 10]

RFC 2151          Internet & TCP/IP Tools & Utilities          June 1997


   TEMs. This process continues until the packets actually reach the
   other destination. Since these datagrams are trying to access an
   invalid port at the destination host, ICMP Destination Unreachable
   Messages are returned indicating an unreachable port; this event
   signals the Traceroute program that it is finished!  The Traceroute
   program displays the round-trip delay associated with each of the
   attempts. (Note that some current implementations of Traceroute use
   the Record-Route option in IP rather than the method described
   above.)

   As an aside, Traceroute did not begin life as a general-purpose
   utility, but as a quick-and-dirty debugging aid used to find a
   routing problem.  The code (complete with comments!) is available by
   anonymous FTP in the file traceroute.tar.Z from the host
   ftp.ee.lbl.gov. (See Section 4.2 for a discussion of anonymous FTP.)

  ====================================================================
**SMCVAX$ traceroute www.hill.com
  traceroute to syrup.hill.com (199.182.20.3), 30 hops max, 38 byte
  packets
   1  smc.bbnplanet.net (192.80.64.5)  10 ms  0 ms  0 ms
   2  131.192.48.105 (131.192.48.105)  0 ms  10 ms  10 ms
   3  cambridge1-cr4.bbnplanet.net (199.94.204.77)  40 ms  40 ms  50 ms
   4  cambridge1-br1.bbnplanet.net (4.0.1.205)  30 ms  50 ms  50 ms
   5  nyc1-br2.bbnplanet.net (4.0.1.121)  60 ms  60 ms  40 ms
   6  nyc2-br2.bbnplanet.net (4.0.1.154)  60 ms  50 ms  60 ms
   7  nyc2-br2.bbnplanet.net (4.0.1.154)  60 ms  40 ms  50 ms
   8  nyc2-br1.bbnplanet.net (4.0.1.54)  70 ms  60 ms  30 ms
   9  collegepk-br2.bbnplanet.net (4.0.1.21)  50 ms  50 ms  40 ms
  10  maeeast.bbnplanet.net (4.0.1.18)  200 ms  170 ms  210 ms
  11  fddi.mae-east.netcom.net (192.41.177.210)  60 ms  50 ms  70 ms
  12  t3-2.was-dc-gw1.netcom.net (163.179.220.181)  70 ms  60 ms  50 ms
  13  t3-2.chw-il-gw1.netcom.net (163.179.220.186)  70 ms  80 ms  80 ms
  14  t3-2.scl-ca-gw1.netcom.net (163.179.220.190)  140 ms  110 ms  160
  ms
  15  t3-1.sjx-ca-gw1.netcom.net (163.179.220.193)  120 ms  130 ms  120
  ms
  16  198.211.141.8 (198.211.141.8)  220 ms  260 ms  240 ms
  17  syrup.hill.com (199.182.20.3)  220 ms  240 ms  219 ms
  SMCVAX$
  ====================================================================










Kessler &  Shepard           Informational                     [Page 11]

RFC 2151          Internet & TCP/IP Tools & Utilities          June 1997


4. The Two Fundamental Tools

   The two most basic tools for Internet applications are TELNET and the
   File Transfer Protocol (FTP). TELNET allows a user to login to a
   remote host over a TCP/IP network, while FTP, as the name implies,
   allows a user to move files between two TCP/IP hosts. These two
   utilities date back to the very early days of the ARPANET.

4.1. TELNET

   TELNET [27] is TCP/IP's virtual terminal protocol. Using TELNET, a
   user connected to one host can login to another host, appearing like
   a directly-attached terminal at the remote system; this is TCP/IP's
   definition of a virtual terminal. The general form of the TELNET
   command is:

      telnet [IP_address|host_name] [port]

   As shown, a TELNET connection is initiated when the user enters the
   telnet command and supplies either a host_name or IP_address; if
   neither are given, TELNET will ask for one once the application
   begins.

   In the example below, a user of a PC uses TELNET to attach to the
   remote host smcvax.smcvt.edu. Once logged in via TELNET, the user can
   do anything on the remote host that would be possible if connected
   via a directly-attached terminal or via modem. The commands that are
   subsequently used are those available on the remote system to which
   the user is attached. In the sample dialogue below, the user attached
   to SMCVAX will use basic VAX/VMS commands:

      o The dir command lists the files having a "COM" file extension.
      o The mail command enters the VMS MAIL subsystem; the dir command
      here lists waiting mail.
      o Ping checks the status of another host.

   When finished, the logout command logs the user off the remote host;
   TELNET automatically closes the connection to the remote host and
   returns control to the local system.

   It is important to note that TELNET is a very powerful tool, one that
   may provide users with access to many Internet utilities and services
   that might not be otherwise available. Many of these features are
   accessed by specifying a port number with the TELNET command, in