nam.txt

NS的教程

User Commands                                              NAM(1)



NAME
     nam - VINT/LBL Network Animator

SYNOPSIS
     nam [ -g geometry ] [ -t graphInput ][ -i interval ] [ -P
     peerName ] [ -N appName ] [ -c cacheSize ] [ -f configfile ]
     [ -S ] tracefile

DESCRIPTION
     Nam is a Tcl/TK based animation  tool  for  viewing  network
     simulation traces and real world packet trace data.

     The first step to use nam is to produce the trace file.  The
     trace file should contain topology information, e.g., nodes,
     links, as well as packet  traces.  The  detailed  format  is
     described in the TRACE FILE section. Usually, the trace file
     is generated by ns(1). During an  ns  simulation,  user  can
     produce  topology  configurations,  layout  information, and
     packet traces using tracing events in ns. Refer to ns(1) for
     detailed information.

     When the trace file is generated, it is ready to be animated
     by  nam.  Upon startup, nam will read the trace file, create
     topology, pop up a window,  do  layout  if  necessary,  then
     pause  at  the  time  of the first packet in the trace file.
     Through its user interface, nam provides control  over  many
     aspects   of   animation.   These  functionalities  will  be
     described in detail in the USER INTERFACE section.

     This version of nam is highly experimental - there  will  be
     bugs!. Please mail [e-mail] if you
     encounter any bugs, or with suggestions  for  desired  func-
     tionality.

OPTIONS
     -g   Specify geometry of the window upon startup. The format
          is described in X(1)

     -t   [Information incomplete] Instruct nam to  use  tkgraph,
          and specify input file nam for tkgraph.

     -i   [Information for  this  option  may  not  be  accurate]
          Specify  rate  (real) milliseconds as the screen update
          rate.  The default rate is 50ms (i.e.,  20  frames  per
          second).   Note  that  the  X server may not be able to
          keep up with this rate, in  which  case  the  animation
          will  run as fast as the X server allows it to (at 100%
          cpu utilization).

     -N   Specify the application name of this nam instance. This
          application name may later be used in peer synchroniza-
          tion.



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User Commands                                              NAM(1)



     -P   Specify the application name of the peer  nam  instance
          whose execution will be synchronized with the execution
          of this nam instance. Refer to the above option (-N) as
          how to specify application names.
          General usage is: (1) starting the first  nam  instance
          (slave) by:
          nam -N <name #1> <trace file name #1>
          Then start the second nam instance (which will  be  the
          master):
          nam -N <name #2> <trace file name #2>
          Then every animation control (play, stop, backward, but
          exclude  other  inspection  and  interactive operations
          such as monitoring) will be  synchronized  between  the
          two instances.
          Please note that because this mechanism uses Tcl's send
          command,  it  requires that your X server used xauth as
          authentication. Specifically, you should add option  `-
          auth  <authorization file name>' when you starts your X
          server. Without  this  option,  X  will  use  xhost  as
          authentication,   which  is  too  weak  and  considered
          insecure. Refer to man page  of  Xsecurity,  xauth  and
          Xserver  for  details, and the available authentication
          protocols.

     -c   [Information incomplete] The maximum size of the  cache
          used to store 'active' objects when doing backward ani-
          mation.

     -f   Name of the initialization files to  be  loaded  during
          startup.  In this file, user can define functions which
          will be called in the trace file. An example  for  this
          is  the  'link-up'  and  'link-down'  events of dynamic
          links in ns. (Refer to  $ns  rtmodel  for  detail,  and
          tcl/ex/simple-dyn.tcl  in  your  ns directory for exam-
          ple). Example initialization  files  can  be  found  at
          ex/sample.nam.tcl and ex/dynamic-nam.conf.

     -S   Enable synchronous X  behavior  so  it  is  easier  for
          graphics debugging. For UNIX system running X only.

     tracefile is the name of the file containing the trace  data
     to  be  animated  (format  described  in  TRACE FILE section
     below).  If tracefile cannot be read, nam will try  to  open
     tracefile.nam.

OBJECTS IN NAM
     nam does animation  using  the  following  building  blocks:
     node,  link, queue, packet, agent, monitor. They are defined
     below:

     node Nodes are created from 'n' trace event in  trace  file.
          It  represents  a  source/host/router,  etc.  nam  will



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User Commands                                              NAM(1)



          terminate if there are  duplicate  definition  for  the
          same  node. Node may have many shapes, (circle, square,
          and hexagon), but once created  it  cannot  change  its
          shape.  Node  may  also have many colors, it can change
          its color during animation. Refer to ns(1) for  related
          tracing events.

     link Links are created  between  nodes  to  form  a  network
          topology.  nam  links are internally simplex, but it is
          invisible to the users. The trace event 'l' creates two
          simplex  links  and  other  necessary  setups, hence it
          looks to users identical to a  duplex  link.  Link  may
          have many colors, it can change its color during anima-
          tion. Refer to ns(1) for related tracing events.

     queue
          Queue needs to be constructed in nam between two nodes.
          Unlike link, nam queue is associated to a simplex link.
          The trace event 'q' only creates a queue for a  simplex
          link. In nam, queues are visualized as stacked packets.
          Packets are stacked along a line, the angle between the
          line  and  the  horizontal line can be specified in the
          trace event 'q'.

     packet
          Packet is visualized as a  block  with  an  arrow.  The
          direction  of the arrow shows the flow direction of the
          packet. Queued packets are shown as little  squares.  A
          packet  may  be dropped from a queue or a link. Dropped
          packets are shown as rotating squares, and disappear at
          the  end of the screen. Dropped packets are not visible
          during backward animation.

     agent
          Agents are used to separate protocol states from nodes.
          They  are  always associated with nodes. An agent has a
          name, which is a unique identifier of th agent.  It  is
          shown as a square with its name inside, and a line link
          the square to its associated node.

AUTOMATIC LAYOUT
     In nam, a topology is specified by alternating node  objects
     with  edge  objects.   But  to  display  the  topology  in a
     comprehensible way, a layout mechanism is needed.  Currently
     nam provides two layout methods.

     First, user may specify edges' orientations. An edge  orien-
     tation  is  the  angle  between  the edge and the horizontal
     line, in the interval [0, 2*pi).  During  layout,  nam  will
     honor  the given edge orientations. Generally, it will first
     choose a reference node, then place other nodes  using  edge
     orientation  and  edge  length,  which is determined by link



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User Commands                                              NAM(1)



     delay. This works well  for  small  and  manually  generated
     topologies.

     Second, when we are dealing with randomly generated  topolo-
     gies,  be  it  small  or  large,  we  may  want to do layout
     automatically. An automatic graph layout algorithm ([1] [2])
     is  adapted and implemented. The basic idea of the algorithm
     is to model the graph as balls (nodes) connected by  springs
     (edges).  Balls  will repulse each other, while springs pull
     them together. This system will (hopefully)  converge  after
     some iterations. In practice, after a small number of itera-
     tions (tens or hundreds), most graphs  will  converge  to  a
     visually comprehensible structure.

     There are 3 parameters to tune the automatic layout process:

     Ca   Attractive force  constant,  which  controls  springs's
          force between balls. Default value is 0.15

     Cr   Repulsive force constant, which controls the  repulsive
          force between balls.  Default value is 0.15

     Number of iterations
          Self explained. Default value is 10.

          For small topologies with  tens  of  nodes,  using  the
          default  parameters  (perhaps with 20 to 30 more itera-
          tions) will suffice to produce a nice layout.  But  for
          larger topology, careful parameter tuning is necessary.
          Following is a empirical method to layout  a  100  node
          random  transit  stub  topology  generated  by  Georgia
          Tech's ITM internet topology modeler. First,   set  Ca
          and Cr to 0.2, do about 30 iterations, then set Cr to
          1.0, Ca to about 0.01, then do  about  10  iterations,
          then set Ca to 0.5, Cr to 1.0, do about 6 iterations.

THE USER INTERFACE
     The top of the nam nam window is a menu  bar.  Two  pulldown
     menus  are  on  the  left  of  the menu bar. The 'File' menu
     currently only contains a 'Quit' button. It has a  'Open...'
     button  as well, but that is not implemented yet. The 'View'
     menu has 4 buttons:

     -    New view button: Creates a new view of the same  anima-
          tion.  User  can  scroll  and zoom on the new view. All
          views will be animated synchronously.

     -    Show monitors checkbox: If checked, will show a pane at
          the  lower  half  of  window,  where  monitors  will be
          displayed.

     -    Show autolayout checkbox: If checked, will show a  pane



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User Commands                                              NAM(1)



          at the lower half of window, which contains input boxes
          and a button for automatic layout  adjusts.   This  box
          may  not  always  be enabled. When a trace file has its
          own layout specifications, this box will  be  disabled.
          If  and  only  if the trace file does not have complete
          layout specification (i.e., each link  has  orientation
          specified in the traces), will this box be enabled.

     -    Show annotation checkbox: If checked, will show a list-
          box  at the lower half of window, which will be used to
          list annotations in the ascending order of time.

          The 'Help' menu is on the right side of the  menu  bar.
          It has two buttons. Clicking the 'Help' button will pop
          up a new  window  showing  information  on  nam  usage.
          Clicking  the  'About'  button will pop up a new window
          showing history and status of nam.

     Acceleration Keys
          ALT+'f' will pull down the 'File'  menu.  ALT+'v'  will
          pull  down  the  'Open...'  menu. ESC will abort a menu
          selection in progress.

          Below the menu bar, there is a control bar containing 6
          buttons,  a  label, and a small scrollbar (scale). They
          can be clicked in any order. We will explain them  from
          left to right.

     Button 1 (<<)
          Rewind. When clicked, animation time will  go  back  at
          the rate of 25 times the current screen update rate.

     Button 2 (<)
          Backward play. When clicked, animation will  be  played
          backward in time.

     Button 3 (square)
          Stop. When clicked, animation will pause.

     Button 4 (>)
          Forward play. When clicked, animation will be played in
          time ascending order.

     Button 5 (>>)
          Fast Forward. When clicked, animation time will go for-
          ward  at the rate of 25 times the current screen update
          rate.

     Button 6 (Chevron logo)
          Quit.

     Time label



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User Commands                                              NAM(1)



          Show the current animation time (i.e., simulation  time
          as in the trace file).

     Rate slider
          Controls the screen update  rate  (animation  granular-
          ity).  The current rate is displayed in the label above
          the slider.

     Below the first control bar, there is  Main  Display,  which
     contains  a  tool  bar and a main view pane with two panning
     scroll bars. All new views created by menu button  'File/new
     view' will have these three components.
     The tool bar contains two zoom buttons. The button  with  an
     up  arrow zooms in, the button with a down arrrow zooms out.
     The two scroll bars are used to pan the main animation view.
     Clicking the left button on any of the objects in  the  main
     view  pane  will pop up a information window at the clicking
     point. For packet and agent objects, there  is  a  'monitor'
     button  in the popup window. Clicking that button will bring
     out the monitor pane (if it is not there), and add a monitor
     to the object. For link object, there will be a 'Graph' but-
     ton. Clink that button will bring out another popup  window,
     where user can select drawing bandwidth utilization graph or
     link loss graph of one of  the  two  simplex  links  of  the
     duplex  link  clicked  on.  These  functionalities  are also
     available in the views created  by  'File/new  view'.  NOTE:
     These  functionalities  are HIGHLY EXPERIMENTAL AND UNSTABLE