;
; LNI header format
;

..OFST = 0
	WORD	LN.DMH			;DPNM (high word)
	WORD	LN.DML			;DPNM (low word)
	BYTE	LN.PR			;Protocol (in DPN)
	BYTE	LN.SNT			;Sub-net
	BYTE	LN.RSD			;Reserved
	BYTE	LN.HST			;Host
	WORD	LN.OPH			;OPN (high word)
	WORD	LN.OPL			;OPN (low word)
	WORD	LN.ML			;Packet length
LN.LEN	= ..OFST

;
; Define the ARPANET header equates
;

..OFST=0
	BYTE	AH.FMT			;MESSAGE FORMAT FLAGS
	BYTE	AH.NET			;DESTINATION NET (NOT USED)
	BYTE	AH.FLG			;LEADER FLAGS
	BYTE	AH.TYP			;MESSAGE TYPE
	BYTE	AH.HND			;MESSAGE HANDLING TYPE
	BYTE	AH.HST			;SOURCE HOST ID
	WORD	AH.IMP			;SOURCE IMP ID
	BYTE	AH.LNK			;MESSAGE ID (LINK) FIELD
	BYTE	AH.SBL			; SUB-LINK FIELD
	WORD	AH.ML			;MESSAGE LENGTH
AH.LEN	=..OFST				;LENGTH OF ARPA LEADER

PKTLEN	=	1020.			;MAX ARPANET PACKET LENGTH


;
; DEFINE EQUATES FOR THE INTERNETWORK ADDRESSING HEADER.  THE TWO FORMATS
; SUPPORTED ARE FOR THE OLD TCP 2.5 ADDRESSING HEADER AND THE NEW
; INET HEADER VERSION 4.  THE DESTINATION ADDRESS FROM THIS HEADER IS USED 
; TO DECIDE ON WHICH HOST PORT THE MESSAGE SHOULD BE SENT.  A DISTINCTION
; BETWEEN HEADERS IS MADE AT RUNTIME BASED OF THE CONTENTS OF THE FIRST 
; FIELD:  IN THE OLD HEADER THIS IS THE DESTINATION NET ID; IN THE NEW
; HEADER THIS IS THE VERSION & HEADER LENGTH.  IF THIS FIRST BYTE OF THE
; HEADER CONTAINS A VALUE LESS THAN 105 IT IS ASSUMED TO BE THE OLD FORMAT.
;

;
; OLD TCP V2.5 ADDRESSING HEADER
;

..OFST=0
	BYTE	OH.DN			;DESTINATION NET
	BYTE	OH.DTH			;DESTINATION TCP, HIGH BYTE
	WORD	OH.DT			;DESTINATION TCP
	BYTE	OH.SN			;SOURCE NET
	BYTE	OH.STH			;SOURCE TCP, HIGH BYTE
	WORD	OH.ST			;SOURCE TCP
	WORD
	WORD
OH.LEN	=	..OFST			;OLD INET HEADER LENGTH

;
; NEW INET V4 HEADER
;

..OFST=0
	BYTE	IH.IHL			;VERSION # AND HEADER LENGTH
IH.VAL	=	105			;VER #4 & LENGTH OF 5 DOUBLEWORDS
	BYTE	IH.TOS			;TYPE-OF-SERVICE FIELD
	WORD	IH.LEN			;TOTAL FRAGMENT LENGTH
	WORD	IH.ID			;FRAGMENT ID
	WORD	IH.FRG			;FRAGMENTATION FLAGS & OFFSET
	BYTE	IH.TTL			;TIME-TO-LIVE
	BYTE	IH.PRO			;PROTOCOL NUMBER
	WORD	IH.CHK			;INET HEADER CHECKSUM
	BYTE	IH.SN			;SOURCE NET ID
	BYTE	IH.STH			;SOURCE TCP HI
	WORD	IH.ST			;SOURCE TCP
	BYTE	IH.DN			;DESTINATION NET
	BYTE	IH.DTH			;DESTINATION TCP HI
	WORD	IH.DT			;DESTINATION TCP
IH.HDL	=	..OFST


;
; DEFINE THE EQUATES FOR A "CONNECTION BLOCK."  AN ENTRY IS MADE IN A 
; CONNECTION BLOCK FOR EACH MESSAGE SENT INTO THE ARPANET.  WHEN THE RFNM
; (OR INCOMPLETE TRANSMISSION) MESSAGE IS RECEIVED, THE COUNT OF THE NUMBER 
; OF MESSAGES OUTSTANDING IS DECREMENTED.  THIS DATA STRUCTURE IS USED TO
; ENSURE THAT NO MORE THAN 8 MESSAGES ARE EVER OUTSTANDING TO A SINGLE 
; DESTINATION.  THIS IS TO PREVENT THE IMP FROM BLOCKING OUR INTERFACE.
; THE CCB TEST IS MORE STRICT THAN THE IMP'S, SINCE THE IMPMUX WILL ONLY
; ALLOW 8 MESSAGES PER DESTINATION AND THE IMP WILL ALLOW 8 PER DESTINATION 
; PER LINK PER HANDLING TYPE.
;

..OFST=0
	WORD	CB.LNK			;LINK TO NEXT CB
	WORD	CB.IMP			;DESTINATION IMP NUMBER
	BYTE	CB.HST			;DESTINATION HOST NUMBER
	BYTE
	BYTE	CB.CNT			;NUMBER OF MESSAGES OUTSTANDING
	BYTE	CB.IDL			;CONNECTION BLOCK IDLE COUNTER
	DWORD	CB.BLK			;LINKED LIST OF BLOCKED IORBS
CB.LEN	=..OFST				;LENGTH OF CONNECTION BLOCK


;
; DEFINE THE EQUATES FOR THE "MESSAGE BLOCK."  THIS DATA STRUCTURE IS USED
; TO DIRECT INCOMING ARPANET DATA MESSAGES TO A SPECIFIC OUTPUT PORT.
; THE LIST OF MESSAGE BLOCKS ARE SCANNED UNTIL A MATCH IS FOUND.  THE PACKET
; IS THEN TRANSMITTED ON THE PORT INDICATED IN THE MESSAGE BLOCK ENTRY. 
; A PACKET "MATCHES" IF, AFTER BIT-CLEARING THE INTERNET NET/TCP DESTINATION
; ID FIELD WITH THE MB.MSK VALUE, THE MB.CMP VALUE COMPARES EQUAL TO THE
; INTERNET NET/TCP DESTINATION ID.
;

..OFST=0
	DWORD	MB.MSK			;2 WORD BIT-CLEAR MASK
	DWORD	MB.CMP			;2 WORD NET/TCPID COMPARE VALUE
	WORD	MB.PRT			;PORT ID
MB.LEN	=..OFST				;LENGTH OF MATCH BLOCK
	


;
; DEFINE THE EQUATES FOR THE "PORT BLOCK."  THERE IS A PORT BLOCK FOR
; EACH 1822 INTERFACE.  IF THE PORT IS AN "IMP" PORT THEN THE IMPMUX ACTS 
; AS A REGULAR HOST OVER THIS PORT, I.E. IT SENDS 4 NOP MESSAGES AFTER THE 
; PORT COMES UP.  IF THE PORT IS A HOST PORT, THEN THE IMPMUX ACTS AS AN IMP
; TO THE ATTACHED HOSTS, I.E. WHEN THE INTERFACES COMES UP, 3 NOP MESSAGES 
; FOLLOWED BY A TYPE 10 MSG (INTERFACE RESET) ARE SENT TO THE ATTACHED HOST.
;

..OFST=0
	WORD	PT.IN			;INPUT DEVICE NUMBER
	WORD	PT.OUT			;OUTPUT DEVICE NUMBER
	WORD	PT.ID			;PORT NUMBER
	BUFFER	PT.NAM,6		;6 CHAR ASCII PORT NAME
	WORD	PT.INI			;ADDR OF INITIALIZATION HANDLER
					;  IMP.UP - IMP INITIALIZATION
					;  HST.UP - HOST INITIALIZATION
	WORD	PT.NRY			;ADDR OF ERROR HANDLER
					;  IMP.DN - IMP DOWN HANDLER
					;  HST.DN - HOST DOWN HANDLER
	WORD	PT.RCV			;ADDR OF RECEIVE COMPLETION HANDLER
					;  IMP.IN - HANDLE INPUT FROM AN IMP
					;  HST.IN - HANDLE INPUT FROM A HOST
	WORD	PT.TYP			;TYPE OF PORT
					;  0 => 1822
					; ~0 => LNI
	WORD	PT.FLG			;PORT CONTROL FLAGS
PT.OFL	=	1			;  PORT IS OFF-LINE
PT.DWN	=	2			;  PORT DOWN FLAG
PT.WD	=	4			;  PORT WAS DOWN IN NEAR PAST
PT.ERR	=	10			;  LAST I/O REQUEST WAS IN ERROR
PT.BLK	=	20			;  PORT IS BLOCKED ON RECEIVE
	WORD	PT.UPC			;PORT UP COUNTER
					;PERFORMANCE STATISTICS COUNTERS
	WORD	PT.UP			;INTERFACE UP COUNTER
	WORD	PT.DN			;INTERFACE DOWN COUNTER
	WORD	PT.BC			;INTERFACE BLOCKED COUNTER
	WORD	PT.PKI			;PACKETS WAITING RFNM
	WORD	PT.PKO			;PACKETS WAITING OUTPUT I/O COMPLETION
	BUFFER	PT.RC,32.		;RCV COUNTERS FOR EACH MESSAGE TYPE
	BUFFER	PT.SC,32.		;SND COUNTERS FOR EACH MESSAGE TYPE
PT.LEN	=..OFST