Routers

There are four routers shown in Figure 6. Below is the entry that defines the router at San Francisco:

    set rbufs = 60;

    router FCFS SF;
      rtable = 192.0.5.0 192.0.5.0, 192.0.6.0 192.0.6.0, 192.0.7.0 192.0.7.0, 
               192.0.8.0 192.0.8.0, 192.0.1.0 192.0.50.1, 192.0.2.0 192.0.50.1, 
               192.0.3.0 192.0.50.1, 192.0.4.0 192.0.50.1, 192.0.40.0 192.0.50.1, 
               0.0.0.0 192.0.51.2;
      args = buf=$rbufs, timeInc=10000, shortTrace=20000:4,
             traceQueue=192.0.50.2, traceInOut=192.0.50.2, traceOut=192.0.50.2, 
             traceQueueLen=192.0.50.2, traceQueue=192.0.51.1, traceInOut=192.0.51.1,
             traceOut=192.0.51.1, traceQueueLen=192.0.51.1;

The routing table given on the rtable line is large but simple. It specifies that

• Packets destined for hosts on networks 192.0.5.0, 192.0.6.0, 192.0.7.0, and 192.0.8.0 are sent to the appropriate host. The router is directly connected to these networks.

• Packets destined for networks 192.0.1.0, 192.0.2.0, 192.0.3.0, and 192.0.4.0 are sent out on network 192.0.50.0 to address 192.0.50.1 (this is the L.A. router).

• All other packets are sent out on network 192.0.51.0 to address 192.0.51.2 (this is the Chicago router).

The first arguments listed configure the router with 60 buffers; the qmin and qmax arguments have no effect at the present time, but will be included in a future release. The rest of the arguments are trace options. They specify that the router should trace activity on the network interfaces with addresses 192.0.50.2 and 192.0.51.1; packets sent out on these interfaces are destined for the routers in L.A. and Chicago. Information that will be traced for each interface includes the minimum, maximum, and average send queue size in packets and bytes; the average number of bytes/second forwarded to the interface; and the average number of bytes/second sent out on the interface. Also, between seconds 5 and 8 of the simulation, trace information for each packet sent on interface 192.0.51.1 will be saved.

All of the other routers resemble this one. All routers trace queue size and average bytes/second for the interfaces connected to the point-to-point links; the packets sent on these interfaces are destined for another router. However, only the SF router uses the pktTrace option to trace individual packets.