A Measurement Study of Diskless Workstation
                   Traffic on an Ethernet


                      Riccardo Gusella

          International Computer Science Institute
               1947 Center Street, Suite 600
                 Berkeley, California 94704


                          ABSTRACT


          We analyze the traffic on a 10-Mb/s  Ethernet
     local-area network that connects diskless worksta-
     tions to file servers in a university environment.
     The traffic is substantially heavier than has been
     recorded in previous  studies;  measured  over  1s
     intervals,  it  frequently exceeds 30% of the net-
     work bandwidth.

          We display and interpret the distribution  of
     packet  lengths  and packet interarrival times for
     the  three  protocols   that   carry   significant
     traffic:  the Transmission Control Protocol (char-
     acter traffic), the Network Disk protocol  (paging
     traffic),  and  the  Network  File System protocol
     (remote file access traffic).  The two latter pro-
     tocols  account  for 68% of the packets and 94% of
     the data bytes on the network.  File access  to  a
     remote  file  server  generates  bursts of traffic
     that  can  last   several   seconds   and   demand
     bandwidths  on the order of 120 kbytes/s, or about
     10% of the Ethernet bandwidth.

          It appears that network bandwidth  may  be  a
     scarce   resource  in  applications  that  involve
     high-performance virtual-memory diskless machines.
     A key prerequisite for the success of future disk-
     less workstations  will  be  the  design  of  fast
     interactive  communication protocols that function
     effectively under high network load.

(This paper was published in IEEE Transactions on Communica-
tions, Vol. 38, No. 9, pp. 1557-1568, September 1990.)