GENWiki

Network Working Group Edward Taft (PARC-MAXC) Request for Comments: 618 Feb 1974 NIC #21989

              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 typescript.

  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 various hosts.

  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.

1. 1-

  The strategy used by the Harvard NCP is to assign a "desired level
  of allocation" figure to each socket (typically quite small for
  Telnet connections and large for FTP data connections; it is a
  user program settable parameter). When the actual allocation for
  the socket falls below 50% of this level, enough additional
  allocation is sent to bring it up to the full "desired level".

  The effect of this strategy is to significantly reduce the number
  of allocates returned for a given number of small messages
  received. This reduces both network traffic and control message
  overhead at the other end. The strategy has no effect on FTP data
  messages, since each message is usually large enough to reduce
  outstanding allocation by at least half at a single blow.

Finally, I should remark on the appallingly large number of NOPs received (typically 25% of all control messages). Most of these seem to be piggy-backed onto other control messages, so the situation is not as awful as the figures would indicate. Nevertheless, I am forced to wonder why anyone would want to send so many.

TELNET typescript file started at THU 31 JAN 74 428:05

#harv-10 (settings loaded) is complete.#

Harvard 5.06A-18 7:28:38 Type "HELP" if you need it.

.login 62,# JOB 2 Harvard 5.06A-18 TTY25 Your name please (last name first): Taft You are logged in as 62,404000 0728 31-Jan-74 Thur SCHEDULED PM ON THURSDAYS, 0830-1200 EOT

.imp error

NCP version 1573.1604 operating statistics

07:29:02 31-JAN-74

NCP (link 0) message errors: Socket not found: 2184

1. 2-

Improper state: 323 Illegal message type: 2 Last discarded allocation from PARC-MAXC (XEROX) link 12 Timed-out exec ICPs: 3

NCP messages: Type Received Sent NOP 81850 0 RTS 3688 2507 STR 2388 3562 CLS 6055 6059 ALL 183050 101442 GVB 772 0 RET 0 772 INS 109 0 ECO 7472 15426 ERP 15065 7472 ERR 2 0 RST 2782 226 RRP 162 2782

Received NCP error messages: Type Count 4 2

Most recent error: type 4 from UCLA-CCN Data (octal) 4 74 0 10 0 0 74 254 0 200 (decimal) 4 60 0 8 0 0 60 172 0 128

IMP data message faults: Hardware fault: 2 Link not found: 8 Discarded RFNMs: 10 Simulated (timed out) RFNMs: 10

Received IMP messages: Regular 590812 Err w/o id 3 NOP 4 RFNM 490095 Dest dead 366 Inc trans 52 IMP reset 2

Histogram of received data message sizes Bits Count <1 3 <16 146834 <32 39751

1. 3-

<64 7044 <128 196983 <256 46099 <512 147609 <1024 534 <2048 1820 <4096 1152 <8192 2979

72 free buffers 7% average buffer utilization

.kjob/k Job 2, User [62,404000] Logged off TTY25 0729 31-Jan-74 Runtime 0 Min, 03.29 Sec

1. 4-