Network Working Group Edward Taft (PARC-MAXC)
Request for Comments: 618
A Few Observations on NCP Statistics
The NCP in use at HARV-10, CMU-10A, and CMU-10B collects a number of
operating and error statistics, which may be typed out on demand by
any user by means of the 'IMP ERROR' command, as shown on the sample
The figures shown cover the period since the system was last
restarted. They are not logged or recorded in any more permanent
form due to extremely limited on-line storage at HARV-10. where
the software was implemented. However, due to the small size of
the system and infrequent monitor development work, HARV-10 tends
to stay up for periods approaching the interval between hardware
maintenance, which is one week. The attached output was obtained
after 168 hours system uptime.
There are a few things I would like to point out that may be of
interest to NCP implementers.
First, note that the number of discarded (unexpected) RFNMs is equal
to the number of simulated (timed out) RFNMs. This has been the case
almost every time I have looked at these statistics. It suggests
that the RFNMs are not being lost but are rather delayed beyond the
NCP timeout interval, which I believe is 30 seconds.
I have heard talk among a few people in the Network community
about "lost RFNMs", and would like to suggest this as a possible
alternative explanation. Perhaps longer timeouts are in order.
Second, the observed ratio of received allocates to transmitted
allocates (on the order of two to one) is also fairly typical. I
believe this reflects differences in allocation strategies among
Many hosts appear to send out an allocate for every data message
received. While this is reasonable for connections such as FTP
data transfer connections, it imposes considerable extra traffic
in the case of the single character messages that seem to be the
most common on the network.
72 free buffers
7% average buffer utilization
Job 2, User [62,404000] Logged off TTY25 0729 31-Jan-74
Runtime 0 Min, 03.29 Sec