Hosts

There are three types of hosts in the internetwork: hosts initiating a bulk transfer, hosts receiving a bulk transfer, and hosts generating traffic connections.

The hosts engaged in bulk transfers are at the supercomputer sites. Below, host h1n40 is at the SDSC and will initiate a transfer; host h1n42 is at the PSC and will receive the data sent by host h1n40.

    set ip = ip, ip vnet, vnet eth arp, arp eth, eth ethd, ethd sim;
    set tcpMegS = vtcp;
    set tcpMegR = btcp;
    set buf1 = 400;
    set len1 = 1024;
    set tcpTrace1 = -tcpTrace=350000:5;
    set thresh1 = 200;
    set ed = 0;
    set delay1 = 10s;
    set megTime1 = 12s;
    set db = db/junk -tcpTimerAuto ;
    set dbStr1 = -dbStr=rbufs:$rbufs;
    set dbStr2 = -dbStr=group:$group;
    set dbStr3 = -dbStr=qmin:$qmin;
    set dbStr4 = -dbStr=qmax:$qmax;

    host h1n40;
      protocols = megtest $tcpMegS, $tcpMegS $ip;
      args = -c192.0.42.1 -buf=$buf1 -len=$len1 $tcpTrace1 -thresh=$thresh1 
             -megTime=$megTime1 -delay=$delay1 -dbStr=delay:$delay1
             -db=$db -timeInc=10000 -ethdTraceOut -ethdTraceIn $dbStr1 $dbStr2 
             $dbStr3 $dbStr4;
 
    host h1n42;
      protocols = megtest $tcpMegR, $tcpMegR $ip;
      args = -s -len=$len1 -buf=$buf1 -timeInc=10000 -ethdTraceIn 
             -ethdTraceOut;

The protocol stacks for both hosts are straightforward; note, however, that h1n40 will use TCP Vegas as its transport protocol, while h1n42 will run Big Window TCP.

Let's look at the more significant arguments for the hosts in detail. For explanations of arguments not discussed, see Section 3.5.

• The -c192.0.42.1 parameter indicates that h1n40 will initiate the bulk transfer to the specified address. If you look at the entry for network 192.0.42.0, you will see that this is the address of h1n42, which is given the -s argument.

• -buf sets the maximum size of the TCP send buffer to 400KB for both hosts.

• -len specifies that 1024KB of data should be transferred.

• -thresh sets the initial threshold for TCP Slow Start at 200KB.

• -delay specifies that the host should wait 10 seconds before starting the transfer, and megTime says that the transfer should be cut off at 12 seconds. Thus, the transfer is given 2 seconds to run.

• -ethdTraceOut and -ethdTraceIn trace the average number of bytes sent and received, respectively, by the host.

• -tcpTrace will trace significant TCP events, such as the transmission of a segment, the size of the send window, and the firing of a timeout.

The other kind of host on our internetwork generates traffic connections. Each of these hosts is both a client and a server.

    set ip = ip, ip vnet, vnet eth arp, arp eth, eth ethd, ethd sim;
    set tcpTraff = btcp;
    set begcit = 25;
    set begdur = 7 -begint=2;
    set cit2 = 90;
    set db = db/junk -tcpTimerAuto ;
    set ed = 0;
    set time = 15;
    set ethdTrace = ;
    set dbStr1 = -dbStr=rbufs:$rbufs;
    set dbStr2 = -dbStr=group:$group;
    set dbStr3 = -dbStr=qmin:$qmin;

    host h1n1;
      protocols = traffic $tcpTraff, $tcpTraff $ip;
      args = -hosts=3 192.0.5.1 192.0.9.1 192.0.13.1 -s1 -begcit=$begcit 
             -begdur=$begdur -begkeep=200 -cit=$cit2 -db=$db -trafficTime=$time 
             -ethdDelay=$ed $ethdTrace $dbStr1 $dbStr2 $dbStr3 -reset=10;

There is nothing surprising about the protocol stack on this host. Big Window TCP is used as the transport protocol. Again, let's examine the arguments.

• The -hosts=3 192.0.5.1 192.0.9.1 192.0.13.1 argument specifies that this traffic host will act as a client, and open traffic connections with the three hosts specified. Note that host 192.0.5.1 is near San Francisco, 192.0.9.1 is near Chicago, and 192.0.13.1 is near Cleveland; thus, packets sent to these hosts will have to traverse the point-to-point links between routers. The

  -s1 parameter tells the host to accept connections initiated by other hosts.

• The -begcit, -begdur, -begint, and -cit arguments all have to do with how often tcplib opens connections during the simulation. See section 3.5 for details.

• -trafficTime specifies to stop the traffic host after it has run for 15 seconds.

• -reset says to reset the trace information after 10 seconds. The bulk transfers start running then, and that's when the traces will get interesting.