5.  Performance

      Throughput, of course, is primarily dependent on transmission speed. The table below shows the real throughput of characters on communication links of different speeds. These numbers represent actual data transferred; they do not include bytes used by the line protocol for data validation such as checksums and messages. At the higher speeds, contention for the processors on both ends prevents the network from driving the line full speed. The range of speeds represents the difference between light and heavy loads on the two systems. If desired, operating system modifications can be installed that permit full use of even very fast links.

		 Nominal speed	 Characters/sec.
		    300 baud		  27
		   1200 baud	     100-110
		   9600 baud	     200-850
In addition to the transfer time, there is some overhead for making the connection and logging in ranging from 15 seconds to 1 minute. Even at 300 baud, however, a typical 5,000 byte source program can be transferred in four minutes instead of the 2 days that might be required to mail a tape.

      Traffic between systems is variable. Between two closely related systems, we observed 20 files moved and 5 remote commands executed in a typical day. A more normal traffic out of a single system would be around a dozen files per day.

      The total number of sites at present in the main network is 82, which includes most of the Bell Laboratories full-size machines which run the UNIXoperating system. Geographically, the machines range from Andover, Massachusetts to Denver, Colorado.

      Uucp has also been used to set up another network which connects a group of systems in operational sites with the home site. The two networks touch at one Bell Labs computer.