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<html><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><!--Converted with jLaTeX2HTML 2002 (1.62) JA patch-1.4patched version by: Kenshi Muto, Debian Project.LaTeX2HTML 2002 (1.62),original version by: Nikos Drakos, CBLU, University of Leeds* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan* with significant contributions from: Jens Lippmann, Marek Rouchal, Martin Wilck and others --><HTML><HEAD><TITLE>10.8 Different agent objects</TITLE><META NAME="description" CONTENT="10.8 Different agent objects"><META NAME="keywords" CONTENT="everything"><META NAME="resource-type" CONTENT="document"><META NAME="distribution" CONTENT="global"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"><META NAME="Generator" CONTENT="jLaTeX2HTML v2002 JA patch-1.4"><META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css"><LINK REL="STYLESHEET" HREF="everything.css" tppabs="http://www.isi.edu/nsnam/ns/doc/everything.css"><LINK REL="next" HREF="node120.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node120.html"><LINK REL="previous" HREF="node118.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node118.html"><LINK REL="up" HREF="node99.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node99.html"><LINK REL="next" HREF="node120.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node120.html"></HEAD><BODY ><!--Navigation Panel--><A NAME="tex2html3124" HREF="node120.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node120.html"><IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="file:/usr/share/latex2html/icons/next.png"></A> <A NAME="tex2html3118" HREF="node99.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node99.html"><IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="file:/usr/share/latex2html/icons/up.png"></A> <A NAME="tex2html3112" HREF="node118.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node118.html"><IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="file:/usr/share/latex2html/icons/prev.png"></A> <A NAME="tex2html3120" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html"><IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="file:/usr/share/latex2html/icons/contents.png"></A> <A NAME="tex2html3122" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html"><IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index" SRC="file:/usr/share/latex2html/icons/index.png"></A> <BR><B> Next:</B> <A NAME="tex2html3125" HREF="node120.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node120.html">10.9 Commands at a</A><B> Up:</B> <A NAME="tex2html3119" HREF="node99.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node99.html">10. Agents</A><B> Previous:</B> <A NAME="tex2html3113" HREF="node118.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node118.html">10.7 The Agent API</A>   <B> <A NAME="tex2html3121" HREF="node1.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node1.html">Contents</A></B>   <B> <A NAME="tex2html3123" HREF="node590.html" tppabs="http://www.isi.edu/nsnam/ns/doc/node590.html">Index</A></B> <BR><BR><!--End of Navigation Panel--><H1><A NAME="SECTION03780000000000000000"></A><A NAME="sec:agentobjects"></A><BR>10.8 Different agent objects</H1>Class Agent forms the base class from which different types of objectslike Nullobject, TCP etc are derived. The methods for Agent class aredescribed in the next section. Configuration parameters for:<DL><DT><STRONG>fid_</STRONG></DT><DD>Flowid.</DD><DT><STRONG>prio_</STRONG></DT><DD>Priority. </DD><DT><STRONG>agent_addr_</STRONG></DT><DD>Address of this agent. </DD><DT><STRONG>agent_port_</STRONG></DT><DD>Port adress of this agent. </DD><DT><STRONG>dst_addr_ </STRONG></DT><DD>Destination address for the agent.</DD><DT><STRONG>dst_port_</STRONG></DT><DD>Destination port address for the agent.</DD><DT><STRONG>flags_</STRONG></DT><DD></DD><DT><STRONG>ttl_</STRONG></DT><DD>TTL defaults to 32.</DD></DL>There are no state variables specific to the generic agent class. Otherobjects derived from Agent are given below:<P><DL><DT><STRONG>Null Objects</STRONG></DT><DD>Null objects are a subclass of agent objects that implement a trafficsink. They inherit all of the generic agent object functionality. Thereare no methods specific to this object. The state variables are:<UL><LI>sport_</LI><LI>dport_</LI></UL><P></DD><DT><STRONG>LossMonitor Objects</STRONG></DT><DD>LossMonitor objects are a subclass of agent objects that implement atraffic sink which also maintains some statistics about the received datae.g., number of bytes received, number of packets lost etc. They inheritall of the generic agent object functionality. <P><TT>$lossmonitor clear</TT><BR>Resets the expected sequence number to -1. <P>State Variables are:<DL><DT><STRONG>nlost_</STRONG></DT><DD>Number of packets lost. <P></DD><DT><STRONG>npkts_</STRONG></DT><DD>Number of packets received. <P></DD><DT><STRONG>bytes_</STRONG></DT><DD>Number of bytes received. <P></DD><DT><STRONG>lastPktTime_</STRONG></DT><DD>Time at which the last packet was received. <P></DD><DT><STRONG>expected_</STRONG></DT><DD>The expected sequence number of the next packet. </DD></DL><P></DD><DT><STRONG>TCP objects</STRONG></DT><DD>TCP objects are a subclass of agent objects that implement the BSD TahoeTCP transport protocol as described in paper: "Fall, K., and Floyd, S.Comparisons of Tahoe, Reno, and Sack TCP. December 1995." URL ftp://ftp.ee.lbl.gov/papers/sacks.ps.Z. They inheritall of the generic agent functionality. Configuration Parameters are:<DL><DT><STRONG>window_</STRONG></DT><DD>The upper bound on the advertised window for the TCPconnection. <P></DD><DT><STRONG>maxcwnd_</STRONG></DT><DD>The upper bound on the congestion window for the TCP connection. Set tozero to ignore. (This is the default.) <P></DD><DT><STRONG>windowInit_</STRONG></DT><DD>The initial size of the congestion window on slow-start. <P></DD><DT><STRONG>windowOption_</STRONG></DT><DD>The algorithm to use for managing the congestion window. <P></DD><DT><STRONG>windowThresh_</STRONG></DT><DD>Gain constant to exponential averaging filter used to compute awnd (seebelow). For investigations of different window-increase algorithms. <P></DD><DT><STRONG>overhead_</STRONG></DT><DD>The range of a uniform random variable used to delay each output packet.The idea is to insert random delays at the source in order to avoid phaseeffects, when desired [see Floyd, S., and Jacobson, V. On Traffic PhaseEffects in Packet-Switched Gateways. Internetworking: Research andExperience, V.3 N.3, September 1992. pp. 115-156 ]. This has only beenimplemented for the Tahoe ("tcp") version of tcp, not for tcp-reno. Thisis not intended to be a realistic model of CPU processing overhead. <P></DD><DT><STRONG>ecn_</STRONG></DT><DD>Set to true to use explicit congestion notification inaddition to packet drops to signal congestion. This allows a FastRetransmit after a quench() due to an ECN (explicit congestionnotification) bit. <P></DD><DT><STRONG>packetSize_</STRONG></DT><DD>The size in bytes to use for all packets from this source. <P></DD><DT><STRONG>tcpTick_</STRONG></DT><DD>The TCP clock granularity for measuring roundtrip times. Note that it isset by default to the non-standard value of 100ms. <P></DD><DT><STRONG>bugFix_</STRONG></DT><DD>Set to true to remove a bug when multiple fast retransmits are allowed forpackets dropped in a single window of data. <P></DD><DT><STRONG>maxburst_</STRONG></DT><DD>Set to zero to ignore. Otherwise, the maximum number of packets that thesource can send in response to a single incoming ACK. <P></DD><DT><STRONG>slow_start_restart_</STRONG></DT><DD>Set to 1 to slow-start after the connection goes idle. On by default. </DD></DL><P>Defined Constants are:<DL><DT><STRONG>MWS</STRONG></DT><DD>The Maximum Window Size in packets for a TCP connection. MWSdetermines the size of an array in tcp-sink.cc. The default for MWS is1024 packets. For Tahoe TCP, the "window" parameter, representing thereceiver's advertised window, should be less than MWS-1. For Reno TCP, the"window" parameter should be less than (MWS-1)/2. </DD></DL>⌨️ 快捷键说明
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