COMMENT ⊗   VALID 00008 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	Notes on the TOPS-10 implementation of IP/TCP and conversion to WAITS.
C00004 00003	TOPS-10 notes.
C00006 00004	Undefined globals when trying to load TOPS-10 IMP code.
C00017 00005	Analysis of the TOPS-10 code.
C00019 00006	Entry points and internal symbols.
C00031 00007	Data structures.
C00035 00008	Potential problems.
C00038 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.

TOPS-10 notes.

The MONGEN program is apparently used to create several parameter files to
construct a TOPS-10 system.  MONGEN asks you questions, and based on the answers
it inserts symbol definitions into the files

	HDWCNF.MAC to define hardware configuration
	TTYCNF.MAC to define terminal configuration
	NETCNF.MAC to define network configuration
	F.MAC to define software features

These are then read by other files.  Amazingly enough, MONGEN compiles and runs
on WAITS.  The file MONGEN.LOG is the result of trying this, producing output
on HDWCNF.WTS, TTYCNF.WTS, NETCNF.WTS, and F.WTS.  It didn't seem completely
successful (especially in the case of F) but it did locate some of the undefined
symbols.

The file NETPRM is SEARCHed by some of the code; we still don't have it in
either [IP,SYS] or [T10,SYS].
Undefined globals when trying to load TOPS-10 IMP code.

The symbols on this page were undefined as a result of:

	LOAD/link netdef,impser,ipser,tcpser,netsub

A location in parentheses after a symbol indicates where it is defined.  A
location in brackets is a reference to one of these symbols; there may also be
others.  Page numbers may often be off by 1, as a result of E directories and
the files on [IP,SYS] being different from the listings printed on 19-Dec-82.

	.C0PC	401675			;job's PC [IMPSER/61P]
	.CPCPN	401174			;some CPU number [IMPSER/46P]
*	.CPJOB	406252
	.CPSK0	401626
*	ADRERR	406173			;	[TCPSER/47P]
	ADVBFE	401522			;advance buffer [IMPSER/58P]
	ADVBFF	401444			;advance buffers [IMPSER/56P]
*	ASSASG	406627	(UUOCON/180P)	;assign a device [TCPSER/66P]
	CCTYO9	402555			;	[IMPSER/82P]
	CLRACT	406335	(UUOCON/209P)	;clear IOACT and return [IMPSER/62P]
	CPOPJ	407574	(COMMON)	;return
	CPOPJ1	407637	(COMMON)	;skip return
	CPOPJ2	401744	(COMMON)	;skip 2 return
	DDBLDB	406356	(SCNSER/23P)	;ptr to TTY LDB in TTY DDB [TCPSER/56P]
	DEVSRG	406611	(UUOCON/189P)	;search for a device [TCPSER/66P]
	DEYCPF	401173	(COMMON)	;ptr to CPU number somewhere [IMPSER/46P]
*	DIE	407570			;see S.MAC/109P
	FPOPJ	402560	(COMMON)	;POP P,F and return	(F=4)
	GET4WD	407527	(CORE1/17P)	;gets a 4-word FS block [NETSUB/23P]
*	GETWD1	406527			;gets a word from a user buffer [TCPSER/52P]
*	GETWDU	406645			;gets a word from a user buffer [TCPSER/50P]
	GIV4WD	407620	(CORE1/18P)	;release 4-word FS block [NETSUB/25P]
	HDSITE	0	(COMDEV/78P)
	HNGSTP	401545			;type user message and stop [IMPSER/59P]
	IADRCK	406216	(UUOCON/174P)	;address check [TCPSER/43P]
	IMPBFE	407332	(COMDEV/78P)
	IMPBFN	401260	(COMDEV/78P)
	IMPBFS	407352	(COMDEV/78P)
	IMPBFT	407347	(COMDEV/78P)
	IMPBUF	407353	(COMDEV/78P)
	IMPCHK	401050			;check IMP hardware (skip 2 if OK, etc.) [IMPSER/14P]
	IMPDWN	401243			;turn IMP off [IMPSER/49P]
	IMPIOF	400052			;turn off input [IMPSER/12P]
	IMPION	401142			;turn on input (?) [IMPSER/12P]
	IMPM36	407260	(COMDEV/78P)
	IMPN	407622	(HDWCNF)	;number of connections to the Arpanet [COMDEV/78P]
	IMPOUT	400503
	IMPRQF	402203	(COMDEV/78P)
	IOSNEC	402704			;	[IMPSER/80P]
	ITIMPL	406574	(COMDEV/78P)
	ITMCNT	401465			;get byte count [IMPSER/54P]
*	ITYFST	406575			;offset from ITY # to line # [IMPSER/93P]
	ITYN	0	(HDWCNF)	;number of IMP-crosspatched TTYs [COMDEV/78P]
	ITYOFS	406310	(COMDEV/78P)
	ITYTAB	403132			;pseudo teletype 'ITY' linkage tale
	JBTLCL	401652			;	[IMPSER/59P]
	JIFSEC	405521			;	[NETSUB/23P]
	JOBPD1	401636			;	[IMPSER/61P]
	LDBDCH	403112			;TTY characteristics [IMPSER/64P]
	LDBDDB	403127			;TTY DDB pointer [IMPSER/80P]
	LDBIMP	406311	(SCNSER/12P)	;pointer from LDB to IMP DDB [IMPSER/65P]
	LDLLCP	402703			;flag bit for local copy line [IMPSER/80P]
	LDPLNO	406321	(SCNSER/20P)	;ptr to hardware line number [IMPSER/65P]
	LDPQTB	406353	(SCNSER/22P)	;table of pointers [TCPSER/56P]
	LDPRTC	402407			;ptr to RTCOMP bit [IMPSER/78P]
	LDRIMP	402454			;flag bit for IMP line [IMPSER/80P]
	LDROSU	403111			;	[IMPSER/66P]
	LINTAB	406303	(COMDEV/20P)	;	[IMPSER/93P]
	LOKSCI	407467	(COMMON/200P)	;see S.MAC/126P
	LOKSPI	407526	(COMMON/200P)	;see S.MAC/103P
	MIMBS1	400115	(COMDEV/78P)
	MIMBS2	400044	(COMDEV/78P)
	MITYN	403117	(COMDEV/78P)
*	MNQUPT	406360			;# of quote ptrs for TTY control [TCPSER/56P]
	MYSITE	403245	(COMDEV/78P)
	ONPOPJ	407530			;turns PIs on and returns [TCPSER/30P]
	OUT	401270
	PBUFSZ	401655	(COMMON)	;ptr to some buffer size [IMPSER/61P]
	PDVTIM	406326	(COMMON)	;set timeout in DDB
	PJOBN	407461	(COMMON)	;ptr to job number [NETSUB/20P]
	PRVBIT	406057
	PRVJ	406457
	PSIIOD	401665			;signal input done [IMPSER/17P]
*	PUTWD1	406602			;puts a word in a user buffer [TCPSER/50P]
*	PUTWDU	406653			;puts a word in a user buffer [TCPSER/48P]
*	PUTWRD	406172			;	[TCPSER/47P]
	QUOCHK	406351	(SCNSER/193P)	;check a quote/escape character [TCPSER/56P]
	RECIMP	402650			;	[IMPSER/71P]
	REGSIZ	401275			;	[IMPSER/53P]
	RELEA6	407513	(UUOCON/164P)	;releases a device [NETSUB/22P]
	SAVE1	407564	(COMMON)	;saves register P1 (14)
	SAVE2	407621	(COMMON)	;saves registers P1-P2 (14-15)
	SAVE3	403442	(COMMON)	;saves registers P1-P3 (14-16)
	SAVE4	406035	(COMMON)	;saves registers P1-P4 (14-17)
	SAVT	407603	(COMMON)	;saves registers T1-T4 (6-11)
*	SCNPIF	0			;see S.MAC/126P
*	SCNPIN	0			;see S.MAC/126P
	SETACT	406330	(UUOCON/209P)	;set IOACT [IMPSER/60P]
	SETBYT	401460			;set byte size [IMPSER/54P]
	SETDVL	406651	(UUOCON/184P)	;store job # and add to logical table [IMPSER/65P]
	SETECH	402720			;enable user TELNET echoing [IMPSER/80P]
	SETNEC	402712			;disable user TELNET echoing [IMPSER/80P]
	SONPJ1	406230	(SCNSER)	;SCNSER interrupts on and skip return
	SONPPJ	406033	(SCNSER)	;SCNSER interrupts on and return
	STIIOD	401711
	SYSUPT	405533			;current system uptime [IMPSER/32P]
	T2POJ1	407167	(COMMON)	;POP P,T2 then CPOPJ1	(T2=7)
	T2POPJ	407255	(COMMON)	;POP P,T2 and return	(T2=7)
	THSITE	0	(COMDEV/78P)
	TICSEC	407561			;number of ticks per second [NETSUB/10P]
	TIME	407251	(COMMON/100P)	;time in ticks since midnight [NETSUB/10P]
	TOTAKE	402305			;	[IMPSER/74P]
	TPOPJ	407403	(COMMON)	;POP P,T1 and return	(T1=6)
	TPOPJ1	407563	(COMMON)	;POP P,T1 then CPOPJ1
	TSETBI	404725	(SCNSER/104P)	;clears corresponding input buffer
	TSETBO	404726	(SCNSER/104P)	;clears some output buffer [TCPSER/12P]
	TTFCXF	0	(SCNSER/156P)	;name of FTP server [TCPSER/13P]
	TTFCXG	0	(SCNSER/156P)	;name of finger server [TCPSER/13P]
	TTFCXH	0	(SCNSER/156P)	;name of Telnet server [TCPSER/13P]
	TTFORC	404733	(SCNSER/69P)	;forces a TTY command [TCPSER/12P]
	TTPLEN	406301			;# of TTY lines? [TCPSER/52P]
	TTYFLT	0			;	[IMPSER/61P]
	TTYIMP	401751			;give SCNSER the IMP DDB [IMPSER/65P]
	TTYOFF	403153			;signal disconnect [IMPSER/94P]
	TTYTAB	406355	(COMMON/75P)	;same as WAITS
	TTYTTI	402017	(SCNSER)	;get a character [IMPSER/66P]
	TTYXMT	402113
	UNLSCI	407507	(COMMON/200P)
	UNLSPI	407531	(COMMON/200P)
	UNLSPT	0	(COMMON/200P)
	UPOPJ	403134	(COMMON)	;POP P,U and return	(U=5)
*	WSYNC	406333	(CLOCK1)	;wait [IMPSER/60P]
	XMTCHR	402310			;get a char to send [IMPSER/74P]
	XMTIMP	402274			;code in SCNSER to simulate interrupt [IMPSER/74P]
	ZRNGE	401660			;some kind of range check [IMPSER/61P]

Most effort has been made to locate those symbols referenced from IPSER and TCPSER.
Some of those not yet identified are called from routines in IMPSER that we may not
use anyway.

Of those globals referenced in IPSER and TCPSER, the ones marked with a * above
have not had their definitions located yet.
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 ACKs when necessary.  The main work
     is finding the DDB for the connection and linking the data to the
     input stream for this DDB.  If this connection in hooked up to an ITY
     (an IMP-crosspatched TTY), then the appropriate TTY service routines
     are called (some code in IMPSER).

B. At UUO level.

  1. [IMPSER, p. 53-55] Transfers data from IMP buffers to user input buffers.
     Calls several TCPSER routines to update information.


** IMP output

 (not looked at yet)

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:

*	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.

More from NETSUB:

D	IMPGTT
D	IMPDAT
D	MESTYP
D	EPLCNT
D	INCCNT
D	BADIMP
D	BDMLNK
D	BDMMES
D	BDMRFM
D	NODRFM
D	SIZERR
D	IMPOOB
D	IMPIME
D	BUFERR
D	BUFNUM
D	BUFAVG
D	SIZHST
D	IPELED
D	IPEPRT
D	IPEVER
D	IPECHK
D	IPEUOP
D	IPOPT
D	IPFRAG
D	IPFDUN
D	ICMNLD
D	ICMDER
D	ICMCHK
D	ICMUNT
D	ICMTYP
D	TCELED
D	TCEMES
D	TCECHK
D	TCEPRT
D	TCEDDB
D	TCEITY
D	TCEUOP
D	TCPOPT
D	TCENIT
D	TCPPRT
D	TCPFTS
D	TCPFTU
D	TCPMNW
D	TCPWFT
D	TCPWET
D	TCPITY
D	TCPOTY
Data structures.

NETDEF, NETSUB:

      IMP buffers - hold various data, mostly the actual text of IMP
	communications.  Each is =37 words long.  The number of these is =12
	times the number of IMP connections, but any buffer may be used for any
	connection.  I don't know when they are allocated, but it appears that
	this is done once when the system is loaded; then the routines BUFGET
	and BUFREL (in NETSUB) manipulate a bit table to assign and release
	buffers.  RELBUF releases a chain of IMP buffers.
      BIB - Buffer information block: used to keep track of where and why a
	buffer stream exists.  Four words long.  MAKBIB (in NETSUB) allocates
	a BIB by calling GET4WD which gets 4 words from FS, and also places
	information about the current output buffer in the BIB and places it
	on the retransmission queue.  Released by RELBIB.
      IMP DDB - information about an IMP connection.  114 words long.  Contains
	data about the IP level, TCP level (including the data described in RFC
	793 as the Transmission Control Block - TCB), Telnet level, and TTY
	crosspatch information.

IPSER:

      FDB - fragmentation data block:  block containing data to allow a
	fragmented message to be reassembled.  The length of the block,
	according to the description, depends on the maximum message size that
	is accepted, but the definition itself seems to allocate two words to
	the bit mask, thus making =72 octets (=576 bytes) the maximum size.

	Contains a pointer to the first IMP buffer with data in this packet.

	FDBs are allocated by ALLFDB, which calls BUFGET (in NETSUB), which
	gets one of the IMP buffers.  [I think it would be better to allocate
	free storage. - JJW]  They are released by FLSFDB.

TCPSER:

      FMB - future message block:  block of information about a message whose
	sequence number we are not ready to handle yet.  Eight words long.

	FMBs are allocated by GETFMB, which calls GET4WD with an argument of
	2 to get two 4-words blocks [presumably consecutive!].  They are
	released by RELFMB which calls GIV4WD to give back the core.

Potential problems.

The problems on this page all arise from places where the TOPS-10 code
defines a symbol that is already used in WAITS.

1. TOPS-10 has a DPOPJ which is

    DPOPJ:: MOVEM   S,DEVIOS(F)     ;DEPOSIT I/O STATUS WORD IN DDB
    CPOPJ:: POPJ    P,

   WAITS's DPOPJ (DSKSER/24P) is a lot more complicated.  What to do?

Also, TOPS-10 has:

    TPOPJ1::AOSA    -1(P)           ;RESTORE T1 THEN SKIP RETURN
    TTPOPJ::POP     P,T2
    TPOPJ:: POP     P,T1            ;RESTORE T1
	    POPJ    P,              ;AND RETURN

which conflicts with WAITS's routines of the same name.  (Note that TOPS-10
saves a few words by combining things like this.)

2. NETSUB has a routine called FNDDDB, which WAITS also has (COMCSS/56P).
   They are fairly different, so I would suggest renaming one of them.

3. The DEVCHR word in TOPS-10 DDBs stores different information for timeouts.
   As explained in S.MAC/17P,

    ;BITS 7-9 ARE A CODE FOR HUNG DEVICE
    ; TIMEOUT. 0 MEANS DEVICE CANNOT BE HUNG
    ; 1-7 MEANS HUNG TIME IS 2**N-1 SECONDS
    ; POINTER = PDVTIM
    ;BITS 10-16 ARE THE COUNTDOWN TIMER
    ; FOR HUNG DEVICE. POINTER = PDVCNT
    ; TRANSITION TO ZERO MEANS DEVICE HUNG

   Other information in DDBs is probably also different.

4. IMPDDB in WAITS (CACDAT/72P) points to a different data structure than IMPDDB
   in TOPS-10 (IMPSER.MAC/5P).  Since WAITS's is tied to the PUP DDB according
   to comments in the code, perhaps the best thing to do is change what the
   TOPS-10 code does.  In fact, changing all of the code that references DDBs
   would eliminate problem (3) as well.