COMMENT ⊗   VALID 00006 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	Notes on the TOPS-10 implementation of IP/TCP and conversion to WAITS.
C00004 00003	Undefined globals when trying to load TOPS-10 IMP code.
C00013 00004	Analysis of the TOPS-10 code.
C00015 00005	Entry points and internal symbols.
C00026 00006	Data structures.
C00028 ENDMK
C⊗;
Notes on the TOPS-10 implementation of IP/TCP and conversion to WAITS.

Files (on [IP,SYS] at SAIL):

COMDEV.MAC	Monitor device-dependent code, symbols, and data.
F.MAC		Sets "feature" switches for TOPS-10 system.
FTPSRV.MAC	FTP server for IP/TCP.  (Comment by Provan:  Doesn't work at
		the moment because it tries to treate the IMP as a device,
		but in the new monitor, the FTPSRV connection is just a
		TTY and should be treated that way.)
IMP.MAC		IMP system symbol definitions.
IMPCOM.MAC	IMP Command handler.  (Provan: corrected for absense of ICP.
		Seems to work.)
IMPHLP.MAC	Text for HELP command in IMPCOM.
IMPSER.MAC	IMP interrupt service, input and output UUOs handlers,
		TTY routines (for telnet connections), host table handling.
IMPSUB.MAC	User subroutines for host table management, ICPs, and IMP
		error handling.
IPSER.MAC	IP service.
MACTEN.MAC	Macros and symbols for TOPS-10 style coding.
MAIL.MAC	The MAIL program.
NETCON.MAC	Network Control Program (NCP).
NETDEF.MAC	Common definitions for network code.
NETSUB.MAC	Common subroutines.
S.MAC		System parameter file for TOPS-10.
TULIP.MAC	Tulip.  (Whatever that is.  Gets searched by several files.)
TCPSER.MAC	TCP service, IMPUUO handler.

Undefined globals when trying to load TOPS-10 IMP code.

I found some of these in COMDEV.MAC (all on page 78); they are marked below.  It
is fairly obvious that most of COMDEV.MAC deals with things unrelated to Arpanet
service.  COMDEV itself won't compile, because it tries to search the file
NETPRM, which is missing.  (Perhaps, with a name like that, it contains more of
the missing symbols.)

Other comments here are from code found that references these symbols.
Reference in brackets is one of possibly several to the symbol.

	CLRACT	406335		;clear IOACT and return [IMPSER/62P]
	TTFCXH	0
	OUT	401270
	IMPBFN	401260	(COMDEV)
	GETWD1	406527
	LOKSCI	407467
	GET4WD	407527		;gets a 4-word FS block [NETSUB/23P]
	LDLLCP	402703		;flag bit for local copy line [IMPSER/80P]
	MITYN	403117	(COMDEV)
	.C0PC	401675		;job's PC [IMPSER/61P]
	IMPBFT	407347	(COMDEV)
	IMPBFS	407352	(COMDEV)
	SONPJ1	406230		;SCNSER interrupts on and skip return
	ITIMPL	406574	(COMDEV)
	SETDVL	406651		;store job # and add to logical table [IMPSER/65P]
	PDVTIM	406326		;set timeout in DDB
	SETNEC	402712		;disable user TELNET echoing [IMPSER/80P]
	MYSITE	403245	(COMDEV)
	.CPSK0	401626
	ONPOPJ	407530		;turns PIs on and returns [TCPSER/30P]
	MIMBS2	400044	(COMDEV)
	TPOPJ	407403		;POP P,T1 and return	(T1=6)
	CCTYO9	402555		;	[IMPSER/82P]
	.CPJOB	406252
	XMTIMP	402274		;code in SCNSER to simulate interrupt [IMPSER/74P]
	SAVE4	406035		;saves registers P1-P4 (14-17)
	LDPQTB	406353
	ITMCNT	401465		;get byte count [IMPSER/54P]
	UPOPJ	403134		;POP P,U and return	(U=5)
	ITYOFS	406310	(COMDEV)
	IMPBUF	407353	(COMDEV)
	ZRNGE	401660		;some kind of range check [IMPSER/61P]
	TTYXMT	402113
	TTYTAB	406355
	PSIIOD	401665		;signal input done [IMPSER/17P]
	JOBPD1	401636		;	[IMPSER/61P]
	REGSIZ	401275		;	[IMPSER/53P]
	PUTWD1	406602
	GETWDU	406645
	DDBLDB	406356
	TTPLEN	406301
	IOSNEC	402704		;	[IMPSER/80P]
	ITYFST	406575		;offset from ITY # to line # [IMPSER/93P]
	SETACT	406330		;set IOACT [IMPSER/60P]
	T2POPJ	407255		;POP P,T2 and return	(T2=7)
	TTFCXG	0
	TTFCXF	0
	SAVT	407603		;saves registers T1-T4 (6-11)
	MIMBS1	400115	(COMDEV)
	TPOPJ1	407563		;POP P,T1 then CPOPJ1
	PRVBIT	406057
	.CPCPN	401174		;some CPU number [IMPSER/46P]
	IMPRQF	402203	(COMDEV)
	JBTLCL	401652		;	[IMPSER/59P]
	SAVE1	407564		;saves register P1 (14)
	ITYTAB	403132		;pseudo teletype 'ITY' linkage tale
	RELEA6	407513		;deassigns a device? [NETSUB/22P]
	SCNPIF	0
	TICSEC	407561		;number of ticks per second [NETSUB/10P]
	IMPOUT	400503
	DIE	407570
	SCNPIN	0
	JIFSEC	405521		;	[NETSUB/23P]
	ADVBFE	401522		;advance buffer [IMPSER/58P]
	PUTWDU	406653
	TTYOFF	403153		;signal disconnect [IMPSER/94P]
	MNQUPT	406360
	PJOBN	407461		;ptr to job number [NETSUB/20P]
	SYSUPT	405533		;current system uptime [IMPSER/32P]
	ADVBFF	401444		;advance buffers [IMPSER/56P]
	IADRCK	406216
	LDBIMP	406311		;pointer from LDB to IMP DDB [IMPSER/65P]
	FPOPJ	402560		;POP P,F and return	(F=4)
	THSITE	0	(COMDEV)
	TIME	407251		;time in ticks since midnight [NETSUB/10P]
	TTYIMP	401751		;give SCNSER the IMP DDB [IMPSER/65P]
	T2POJ1	407167		;POP P,T2 then CPOPJ1	(T2=7)
	LDBDDB	403127		;TTY DDB pointer [IMPSER/80P]
	LDPRTC	402407		;ptr to RTCOMP bit [IMPSER/78P]
	LDRIMP	402454		;flag bit for IMP line [IMPSER/80P]
	LOKSPI	407526
	IMPDWN	401243		;turn IMP off [IMPSER/49P]
	LDPLNO	406321		;ptr to line number [IMPSER/65P]
	RECIMP	402650		;	[IMPSER/71P]
	IMPION	401142		;turn on input (?) [IMPSER/12P]
	UNLSPT	0
	WSYNC	406333		;wait [IMPSER/60P]
	IMPIOF	400052		;turn off input [IMPSER/12P]
	CPOPJ1	407637		;skip return
	CPOPJ2	401744		;skip 2 return
	GIV4WD	407620		;release 4-word FS block [NETSUB/25P]
	LDBDCH	403112		;TTY characteristics [IMPSER/64P]
	SAVE2	407621		;saves registers P1-P2 (14-15)
	PRVJ	406457
	CPOPJ	407574		;return
	PUTWRD	406172
	ITYN	0		;number of IMP ports? [COMDEV/78P]
	PBUFSZ	401655		;ptr to some buffer size [IMPSER/61P]
	SETECH	402720		;enable user TELNET echoing [IMPSER/80P]
	TOTAKE	402305		;	[IMPSER/74P]
	TTYFLT	0		;	[IMPSER/61P]
	TTFORC	404733		;forces a TTY command [TCPSER/12P]
	TSETBO	404726		;clears some output buffer [TCPSER/12P]
	TSETBI	404725		;clears corresponding input buffer
	UNLSPI	407531
	LINTAB	406303		;	[IMPSER/93P]
	SONPPJ	406033		;SCNSER interrupts on and return
	IMPCHK	401050		;check IMP hardware (skip 2 if OK, etc.) [IMPSER/14P]
	SAVE3	403442		;saves registers P1-P3 (14-16)
	HDSITE	0	(COMDEV)
	IMPBFE	407332	(COMDEV)
	LDROSU	403111		;	[IMPSER/66P]
	QUOCHK	406351
	IMPN	407622		;number of IMP DDBs [COMDEV/78P]
	SETBYT	401460		;set byte size [IMPSER/54P]
	STIIOD	401711
	IMPM36	407260	(COMDEV)
	XMTCHR	402310		;get a char to send [IMPSER/74P]
	ASSASG	406627
	TTYTTI	402017		;get a character [IMPSER/66P]
	DEYCPF	401173		;ptr to CPU number somewhere [IMPSER/46P]
	UNLSCI	407507
	ADRERR	406173
	HNGSTP	401545		;type user message and stop [IMPSER/59P]
	DEVSRG	406611
Analysis of the TOPS-10 code.

** IMP input

A. At interrupt level.

  1. [IMPSER, p. 12-16]  Message is transferred into one or more buffers
     (allocated as needed).  Non-data messages are handled appropriately,
     otherwise, if the link number indicates an IP packet, IPIN is called.
     Non-IP data messages are ignored.

  2. [IPSER, p. 7-9]  Message is checksummed, etc.  IP options are handled
     and message fragments put together.  Then the appropriate routine is
     called depending on the protocol (ICMPIN or TCPIN).

  3. [TCPSER, p. 9-  ]  Checksums TCP message, handles options.  Then
     processes messages in the "future queue" which have already come in
     and can now be processed.  Sends ACK when necessary.
Entry points and internal symbols.

[* = code, D = data]


IPSER:

*	IPIN - handle an incoming IP message.
D	IPADDR - our site number.
*	IPMAKE - get a fresh buffer and put an IP leader (in 32 bit format) into
	  it.  then link the buffer to the beginning of the current output
	  stream.  then send this message down to 1822 level (IMPSER) to get it
	  fired off.
*	IPSEC - once a second code for IP.  it checks for time outs in the
	  fragmentation reassembly chain.
*	SNDNSP - send a message to the sender of the current message saying
	  "no such port".


TCPSER:

*	FLSFMB - routine to delete an FMB chain.
*	IMPUUO - provides ability for the user to initiate IMP connections
	  under program control.
*	SETURG - set up TCP data to send an URG message next time out.
*	TCPCHK - subroutine to do various once a second checks to an IMP DDB.
*	TCPICK - check a connection to see if it is in a state where input is legal.
*	TCPIFN - check to see if this input stream has received a legitimate
	  FIN.  called after data is exhausted to see if there's any more data
	  coming or if this is EOF.  if we have received a FIN for this
	  connection, close it now.
*	TCPIN - process incoming TCP message.
*	TCPMAK - put TCP leader (in 32 bit format) into fixed TCP output leader
	  buffer.  then link the buffer to the beginning of the current output
	  stream.  then send the message down to the next level of protocol for
	  further processing.
*	TCPOCK - check a connection to see if it is in a state where output
	  is legal.
*	TCPWUP - update a window if the user has read some of the data waiting.


IMPSER:

*	ALCNEW - subroutine to handle wake up after allocation has increased.
D	DEVxxx - fields in IMPDDB (xxx one of:  NAM, CHR, IOS, SER, MOD, LOG,
	  BUF, IAD, OAD, STS, STA, XTR, EVM, PSI, ESE, HCW, CPU, JOB, CTR)
*	FIXRTQ - routine to take the host in T1 and make all entries in the
	  retransmission queue use that host.
*	GO1822 - subroutine to check to see that a host is good and, if so,
	  send the message.
D	IBFHLT - -1 if buffer still needed
*	IMPAIO - routine called at clock level to continue processing
	  non-blocking IMP output.
*	IMPATT - routine to set the job number into the right IMP DDB when
	  initiating a job from an IMP TTY or when an IMP TTY attaches to an
	  existing job.
D	IMPDDB - prototype IMP DDB
*	IMPDEV - subroutine to determine if a DDB is that of an IMP and whether
	  or not it is controlling a job through an ITY.
*	IMPDSP - dispatch table
*	IMPEIM - here at interrupt level upon receipt of the end of a message.
*	IMPEOM - here at interrupt level when end-of-message has been sent.
*	IMPIN - here at interrupt level on first input interrupt
*	IMPIND - here on blki runout at interrupt level.
*	IMPISR - table of interrupt service routines
*	IMPMAK - prepare a message for output to the IMP by converting it to 36
	  bit buffers from 32 bit buffers and adding the 1822 leader to it.
	  after it's all ready, we put it in the queues for transmission and
	  retransmission if necessary.
*	IMPNEW -  subroutine to tell the input code about new data.
*	IMPOND - here on blko runout at interrupt level.
*	IMPRES - routine to clean up all IMP DDBs (clear IOS flags, etc.)
	  assigned to this job.
*	IMPSEC - here every second to check things
*	IMPTIK - routine called by CLOCK1 on any clock tick during which IMPRQF
	  is set, to perform requested IMP processing.
*	IMPTTY - subroutine to set up a crosspatch between an IMP DDB and a local
	  teletype.
*	IMPUP - -1 if want the IMP system up
*	IMPW60, IMPWAT - routine to wait for interrupt activity.
*	IMPWAK - routine to wake the job at interrupt level
*	IMPWK1 - routine to clear all wait flags and reset the timeout counter
	  to infinity
*	INBYTE - get the next byte from the given DDB's input byte stream.
*	INON - here from NETSUB when a buffer is again free.
*	ITYGET - subroutine to allocate a line number for IMPs connecting
	  to a local process.
*	ITYREL - subroutine to release an ITY.
*	ITYSTO - here from clock tick level to start processing queued output
	  to ITY's.
*	MICIMP - see if crosspatched line can take more
*	OKFLAG - -1 if IMP is useable
*	OUTGO1 - subroutine to start up output
*	RQIITI, RQIITO, RQTIIO, RQTOIO - routines to request IMP processing
	  at clock level.
*	SNDMSG - subroutine to queue a TCP message for output from interrupt level.
D	STOPFL - -1 if IMP going down
D	TELTAB - this is the mapping table from TTY chars to telnet commands,
	  used by NETQUO in SCNSER.
*	TTIDET - routine to detach a crosspatched TTY from its controlled IMP DDB.
*	TTYTST - subroutine to test for a teletype connection.
*	TTYURG - subroutine to appropriately tweak everybody when an URG comes in
	  through TCP.
*	XMTQIT - routine called by SCNSER transmit interrupt code for an IMP line
	  when there are no more characters to transmit (i.e. the line becomes
	  'idle').


NETSUB (lots of data word internals not shown here):

*	BIBCHK - BIB consistency check
*	BUFGET - subroutine to allocate a buffer.
*	BUFREL - subroutine to release a buffer.
*	CLRIMP - subroutine to wipe a DDB.
*	CSMBYT - deal with a single byte for checksumming purposes.
*	CSMHWD - deal with a 16 bit byte for checksumming purposes.
*	CSMWDS - deal with 32 bit words for checksumming purposes.
*	CSMWRD - deal with a 32 bit word for checksumming purposes.
*	DDBDEA - subroutine to release a DDB.
*	DDBFLS - flush all data from a DDB.
*	DDBGET - finds a DDB for this job.
*	DDBREL - subroutine to release a DDB.
*	FLSBIB - flush a stream of BIBs link through their retransmission
	  queue links.
*	FNDDDB - scan through all the IMP DDBs to find one that matches
	  the given values.
*	GETLED - copies a leader into a preassigned storage location.
*	GETMES - pull in a message stream from IMP input, tacking it on to the
	  end of a possibly nonexistent stream.
*	MAKBIB - make a buffer information block for the current output buffer.
*	MILTIM - return milliseconds since midnight
*	NXTBYT - subroutine to read the next byte from a data stream.
*	NXTFLS - skip over bytes in the data stream described by P1, P2, and P3.
*	NXTWRD - read in a full 32-bit word from the data stream described by
	  P1, P2, and P3.
*	OPTFLS - flush an option (IP or TCP, for example) from the data stream
	  described by P1, P2, and P3.
*	RELBIB, ARLBIB - flush a BIB and everything that has anything to do with it.
*	RELBUF - subroutine to release all buffers in a stream
*	RPLWRD - replace the next full 32-bit word from the data stream described
	  by P1, P2, and P3 by the value passed in in T1.
*	SKPBYT - find the location of the Nth byte in a buffer stream.
Data structures.


IPSER:
	FDB - fragmentation data block:  block containing data to allow a
	  fragmented message to be reassembled.