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rfc:ien:ien192
                                                        IEN 192
                    HOST/SATNET  PROTOCOL
                Bolt Beranek and Newman Inc.
                          July 1981

Host/SATNET Protocol IEN 192

                      TABLE OF CONTENTS

1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 1

2. Satellite IMP Implementation Details . . . . . . . . . . . 4

2.1  Initialization  . . . . . . . . . . . . . . . . . . . .  5
2.2  Host-to-Satellite IMP Input . . . . . . . . . . . . . .  6
2.3  Satellite IMP-to-Host Output  . . . . . . . . . . . . .  8

3. DATAGRAM ACCESS PROTOCOL . . . . . . . . . . . . . . . . . 10

3.1  Overview  . . . . . . . . . . . . . . . . . . . . . . . 10
3.2  Types of Service  . . . . . . . . . . . . . . . . . . . 11
3.3  Addressing  . . . . . . . . . . . . . . . . . . . . . . 12
3.4  Message Length  . . . . . . . . . . . . . . . . . . . . 12
3.5  Host/SATNET Flow Control  . . . . . . . . . . . . . . . 13
3.6  Status Messages . . . . . . . . . . . . . . . . . . . . 14
3.7  Hello Messages  . . . . . . . . . . . . . . . . . . . . 14
3.8  Message Reference Numbers . . . . . . . . . . . . . . . 15
3.9  Initialization  . . . . . . . . . . . . . . . . . . . . 15
3.10  Format Errors  . . . . . . . . . . . . . . . . . . . . 16
3.11  Loop Detection . . . . . . . . . . . . . . . . . . . . 16
3.12  Piggybacked Control Messages . . . . . . . . . . . . . 17
3.13  Formats  . . . . . . . . . . . . . . . . . . . . . . . 17
  3.13.1  Control Codes  . . . . . . . . . . . . . . . . . . 17
  3.13.2  Data Messages  . . . . . . . . . . . . . . . . . . 18
    3.13.2.1  Type of Service Word . . . . . . . . . . . . . 19
    3.13.2.2  Acceptance Status Word . . . . . . . . . . . . 20
  3.13.3  ACCEPTED Messages  . . . . . . . . . . . . . . . . 21
  3.13.4  REFUSED Messages . . . . . . . . . . . . . . . . . 21
  3.13.5  STATUS REQUEST Messages  . . . . . . . . . . . . . 22
  3.13.6  STATUS MESSAGES  . . . . . . . . . . . . . . . . . 23
  3.13.7  HELLO Message  . . . . . . . . . . . . . . . . . . 23
  3.13.8  FORMAT ERROR Message . . . . . . . . . . . . . . . 23
  3.13.9  RESTART REQUEST Message  . . . . . . . . . . . . . 24
  3.13.10  RESTART COMPLETE Message  . . . . . . . . . . . . 25

4. STREAM ACCESS PROTOCOLS . . . . . . . . . . . . . . . . . 26

4.1  Overview  . . . . . . . . . . . . . . . . . . . . . . . 26
4.2  Stream Data Messages  . . . . . . . . . . . . . . . . . 27
4.3  Stream Request Replies and Notifications  . . . . . . . 28
  4.3.1  CREATE  . . . . . . . . . . . . . . . . . . . . . . 31
  4.3.2  DELETE  . . . . . . . . . . . . . . . . . . . . . . 32
  4.3.3  JOIN  . . . . . . . . . . . . . . . . . . . . . . . 33
  4.3.4  LEAVE . . . . . . . . . . . . . . . . . . . . . . . 34
  4.3.5  CHANGE  . . . . . . . . . . . . . . . . . . . . . . 34
4.4  SATNET Termination and Suspension of Streams  . . . . . 35
  1. i -

Host/SATNET Protocol IEN 192

5. Land Modem Interface . . . . . . . . . . . . . . . . . . . 37

6. Local Host Interface . . . . . . . . . . . . . . . . . . . 37

APPENDIX A. . . . . . . . . . . . . . . . . . . . . . . . . 38

A.1   Table 1 -- Request Codes . . . . . . . . . . . . . . . 38
A.2   Table 2 -- Reply Codes . . . . . . . . . . . . . . . . 38
A.3   Table 3 -- Error Codes in D3 . . . . . . . . . . . . . 39
A.4   Table 4 -- Notification Codes  . . . . . . . . . . . . 39
A.5   Table 5 -- SATNET Data Message Types . . . . . . . . . 39
A.6   Table 6 -- SATNET Logical Address Map  . . . . . . . . 40

APPENDIX B. . . . . . . . . . . . . . . . . . . . . . . . . 43

B.1   Figure 1.  Restart State Diagram . . . . . . . . . . . 43
B.2   Figure 2.  General Message Format  . . . . . . . . . . 44
B.3   Figure 3.  Block DATA Message  . . . . . . . . . . . . 45
B.4   Figure 4.  Type of Service Word  . . . . . . . . . . . 46
B.5   Figure 5.  Acceptance Status Word  . . . . . . . . . . 46
B.6   Figure 6.  ACCEPTED Message  . . . . . . . . . . . . . 46
B.7   Figure 7.  REFUSED Message . . . . . . . . . . . . . . 46
B.8   Figure 8.  STATUS REQUEST Message  . . . . . . . . . . 47
B.9   Figure 9.  STATUS Message  . . . . . . . . . . . . . . 47
B.10   Figure 10.  HELLO Message . . . . . . . . . . . . . . 48
B.11   Figure 11.  FORMAT ERROR Message  . . . . . . . . . . 48
B.12   Figure 12.  RESTART REQUEST Message . . . . . . . . . 48
B.13   Figure 13.  RESTART COMPLETE Message  . . . . . . . . 48
B.14   Figure 14.  Stream Data Format  . . . . . . . . . . . 49
B.15   Figure 15.  Request Message Format  . . . . . . . . . 50
B.16   Figure 16.  Reply Message Format  . . . . . . . . . . 51
B.17   Figure 17.  Notification Message Format . . . . . . . 52
B.18   Figure 18.  Create Request Words  . . . . . . . . . . 53
B.19   Figure 19.  Delete, Join, Leave Request Words . . . . 54
  1. ii -

Host/SATNET Protocol IEN 192

                           PREFACE
   This document  describes  the  current  SATNET  Host  Access

protocol. This supersedes PSPWN #100 (SATNET Host Access protocol) and PSPWN #104 (Host/SATNET Stream Access protocol). The differences are:

   (1)  The initialization  state  diagram  has  been
        changed  so  that neither side will enter the
        ON state unless both sides of the  connecting
        transmission line are working.
   (2)  A "Host type" field was added to the  Restart
        Request and Restart Complete messages.
   (3)  The numeric values of some error  codes  have
        been  changed,  as have the detailed meanings
        of some of those codes.
   (4)  Some Stream Reply Codes have been changed.
   (5)  Some significant changes have  been  made  to
        the  information  supplied by hosts in Stream
        Create and Change request messages.
   (6)  Hosts must use  the  acceptance/refusal  flow
        control strategy in response to data messages
        from  Satellite IMPs (i.e., this is no longer
        an option).
  1. iii -

Host/SATNET Protocol IEN 192

1. Overview

   In determining an appropriate host access protocol,  several

factors must be considered. One set of factors concerns

regulation of transfers in either direction across the

host-network interface. A second set of factors concerns actions

associated with the transmission of messages across the network.

While there are several different protocols in existence which

deal with link and network access (e.g., SDLC and X.25), none

satisfies the totality of user services and other factors unique

to SATNET. Thus to allow flexible exploration of access issues,

a special protocol was developed for the network transmission

level. (For implementation convenience, however, an existing

ARPANET link error control protocol was used to provide reliable

interface transfers.)

   The  network-level  access  factors  include  the passing of

type-of-service information such as priority and delay class, the

passing of flow and congestion control information, coordination

of stream data messages with their scheduled times, and

mechanisms for dynamic stream and addressing setups.

   The type-of-service information is dealt with by defining an

appropriate field in the message headers. This field currently

consists of eight bits in SATNET: Two bits for message type

(datagram/stream and internet designations), two bits to specify

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Host/SATNET Protocol IEN 192

one of four priorities, two bits to specify one of four delay

classes, one bit to specify a holding time choice, and one bit to

specify reliability. The delay class choices presently consist

of one second, five seconds, twenty seconds, and two minutes.

The holding time choice consists of either twice the specified

delay class or two minutes. The reliability choice consists of

"high", which causes channel retransmissions to be used, or

"standard", which inhibits the use of retransmissions and allows

messages with bad data checksums (but good checksums on their

control information) to be delivered to users. Standard

reliability is designed for applications which can tolerate

occasional bit errors, but cannot tolerate lost or out-of-order

packets (e.g. packet speech).

   Flow and congestion control information is passed by the use

of two distinct mechanisms. First, status information reflecting

current congestion control is sent in all data and related

control messages; in the absence of other traffic, a special

status message is sent periodically. This information indicates

which priority and delay classes are currently being accepted by

the network.

   The  second  mechanism  consists  of  specific   information

concerning the disposition of each data message passed to the

network. Each data message is numbered (modulo 128) by the

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Host/SATNET Protocol IEN 192

sending host for identification purposes. Upon receipt, the

network returns an "acceptance" or "refusal" indication to the

host. An acceptance implies the network believes it can deliver

the message to its destination and is proceeding to do so;

delivery, however, is not guaranteed. A refusal means the

network has discarded the message; in this case a refusal subcode

is included to indicate the reason. Messages may be refused

because, for example, the destination is down or does not exist,

because its priority or delay class is not being accepted, or

because of temporary flow control reasons associated with source

or destination buffering. In the latter case the message is

assigned to one of several categories used for subsequent

notification purposes. A bit representing each category is

passed along with the priority-delay class status information in

all messages. When the message is refused the number of the

assigned category is returned to the sender, with the values of

subsequent category status bits indicating when messages of that

category will again be accepted.

   In  order  to minimize message delays and to schedule stream

slots efficiently, the coordination of stream data messages

involves establishment of the correct time window in which the

host should pass each message to the network. The present system

uses explicit accept/refuse messages to accomplish this. Stream

and addressing setups are accomplished by using datagram messages

between the hosts and the network.

  1. 3 -

Host/SATNET Protocol IEN 192

2. Satellite IMP Implementation Details

   For  each physical host port the software uses the following

data structures:

             Protocol state word,
             Category queues,
             Host output queue,
             Accept/refuse queue (HAQ),
             Interface property table,
             Last-heard word (LSTHRD).
   The protocol state word indicates whether the protocol is in

initialization or running state. If in initialization state, no

messages will be accepted or delivered until the necessary

handshaking procedure, as described below, is completed.

   The four category queues are used  to  store  messages  that

have been refused by a host. If a host refuses a message and

provides an appropriate category indication, the message will be

stored on the specified category queue until the host indicates

it is willing to accept messages of that category. If a message

reaches its maximum holding time before the host will accept it,

it will be dropped from the queue.

   The host output queue is a queue of data messages waiting to

be delivered to the appropriate host. Ordered by urgency, all

messages remain on this queue until they are transferred into the

HAQ just prior to being sent to the host or until their holding

time expires.

  1. 4 -

Host/SATNET Protocol IEN 192

   The HAQ is a storage location for a message  that  has  been

sent to the host and is awaiting an accept or refuse response.

If a response is received, the message is removed from the queue.

If no response is received, the message will be removed when its

maximum holding time has expired.

   The  interface  property table (IPT) is used to indicate any

of the various protocol options selected by a host. One such

option is whether to allow piggybacking of Host/SATNET control

messages. Another option is that the host may decline to do

accept/reject decisions on traffic that it receives from SATNET.

   The last-heard word indicates when the host was  last  heard

from. The host is declared down if it has not been heard from in

a specified time, currently about thirty seconds. The host will

remain down until the necessary handshaking is completed.

2.1 Initialization

   Whenever a host or Satellite IMP is restarted,  it  sends  a

RESTART-REQUEST control message to the other party. This message

will be repeated periodically until a RESTART-COMPLETE message is

received from the other party. When the RESTART-COMPLETE message

is received by the first party, it will then also send a

RESTART-COMPLETE message.

  1. 5 -

Host/SATNET Protocol IEN 192

2.2 Host-to-Satellite IMP Input

   For  datagram  traffic,   SATNET   accepts   variable-length

messages of up to a fixed maximum length (currently 128 16-bit

words). The host prefixes each message with a header which

provides addressing and control information. The control

information specifies priority, desired delivery delay, maximum

holding time, and selection of message control options such as

reliability. Each datagram message from a host is accepted or

rejected by the Satellite IMP according to the current network

loading and other factors. The Satellite IMP always returns a

control message indicating acceptance or refusal.

   The  message  control parameters have the following possible

values: Priority is an integer from zero to three, with three

being the lowest priority and zero the highest. There are four

possible delay classes: 1 second, 5 seconds, 20 seconds, and 120

seconds. There are two possible choices for maximum holding

time: twice the delay class or the maximum system holding time.

Reliability may be either normal or high reliability (zero or

one).

   Initially,  when  a  message is offered by a host, a minimal

amount of buffer is requested at high priority, and the header of

the message is copied into this buffer in SATNET internal format.

The information in the header is then presented to the

  1. 6 -

Host/SATNET Protocol IEN 192

Accept/Reject module. If the message is accepted the additional

buffer needed is obtained, the rest of the message is copied into

the buffer, and an accept message is placed on the accept/reject

notification list (ARN). If the message is rejected, the

appropriate rejection code is placed on the ARN and the buffer

space is freed. It is left for the host to decide whether to

resubmit the message at a later time. The rejection code will

also inform the host of which priority and delay classes are

currently being accepted, to assist the host in making message

offering decisions.

   The  accept/reject  decision  is  performed as follows:  The

first checks are made to ensure a valid source ID, adequate

buffer in the Satellite IMP, and a message size not exceeding the

maximum allowed size. The Satellite IMP must also be in the

In-Sync state to be able to accept the message. For any message

passing these tests, its TTG and priority are calculated, and

used to form its urgency value.

   Next a check is made to see if the message can be  delivered

to the destination, which involves checking a table of

destination parameters. The Satellite IMP verifies that the

destination Satellite IMP and host are up and are receiving

messages of the same category as the offered message.

  1. 7 -

Host/SATNET Protocol IEN 192

   Although  not  implemented,   the   following   checks   are

considered useful. If the reservation-making queue contains too

much traffic of higher urgency or if the number of free buffers

is below a fixed threshold, the message will be refused. Also, a

maximum buffer usage may be assigned to each host for messages of

each category; messages will be refused if the threshold is

exceeded for messages of the same category.

   A stream packet undergoes a different set of  checks  before

it is accepted by the Satellite IMP. The stream must exist, the

length of the message must not exceed the maximum allowable for

that stream, and there must be room available on the stream queue

for another packet. Also, the offering host must be designated

as a member of that stream.

2.3 Satellite IMP-to-Host Output

   Whenever there is an opportunity to  send  a  message  to  a

host, the Satellite IMP will examine every eligible queue to

determine which message should be sent first. This includes the

host output queue, the four category queues, and the control

message waiting queue (ARN). If ARN is longer than a specified

threshold, sending of control messages will take precedence over

sending of data messages, until the ARN length falls below the

threshold. Otherwise, if piggybacking is allowed, a data message

will be sent to the host with a control message piggybacked. If

  1. 8 -

Host/SATNET Protocol IEN 192

no piggybacking is allowed, then control messages and data

messages will compete. Competition is always on the basis of

urgency (priority and TTG). A category queue may be ineligible

if the host is not accepting messages of that category. In the

absence of other traffic, a Satellite IMP will send a 'HELLO'

message every second. Once a data message has been selected it

is queued in HAQ and transmitted to the host.

   If the host fails to respond in time, the  message  will  be

deleted from HAQ when its holding time expires. If the host

accepts, the message will be removed from HAQ and discarded. If

the host refuses and specifies a category, the message will be

removed from HAQ and placed on the specified category queue. If

the message is refused for urgency reasons, the message will be

requeued on the host output queue.

   HAQ, the category queues, the host output  queues,  and  ARN

are all kept ordered by urgency, so that testing for the most

urgent message consists of testing only the first message on each

queue.

  1. 9 -

Host/SATNET Protocol IEN 192

3. DATAGRAM ACCESS PROTOCOL

3.1 Overview

   For  datagram  traffic,   SATNET   accepts   variable-length

messages of up to 128 words of data. The source host prefixes

each message with a leader which provides addressing and control

information. The control information specifies message priority,

desired delivery delay, delay at which the message should be

discarded if not yet delivered ("maximum holding time"), and

selection of one or more message control options.

   Each  datagram  message  from  a  source host is accepted or

refused by the source Satellite IMP according to current network

loading and other factors, with a control message always returned

by the source Satellite IMP indicating the acceptance or refusal.

Upon acceptance, SATNET then attempts to deliver the message

within its specified delay. However, it will continue trying to

deliver if late, until its maximum holding time is exceeded.

Datagram messages always have at least a two-hop delay (about 0.6

seconds) within SATNET.

   A  lower-level  protocol  is  assumed  to  provide  reliable

exchanges of data and control messages on the link connecting a

host and Satellite IMP, and is assumed transparent to the

protocol defined in this document. The Honeywell 316 Satellite

IMPs use the ARPANET VDH protocol for this purpose. The new BBN

  1. 10 -

Host/SATNET Protocol IEN 192

C/30 Satellite IMPs support in addition ARPANET 1822 local host

and distant host protocol.

3.2 Types of Service

   The type-of-service fields in  the  SATNET  leader  of  each

datagram message allows the following choices to be specified to

SATNET for each message:

        Priority:  4 choices.  This is used in conjunction with
        the acceptable delivery delay to arbitrate  for  SATNET
        resources.
        Acceptable  Delivery  Delay:   1  second, 5 seconds, 20
        seconds, and 120 seconds.
        Holding Time:  This is the maximum time an  undelivered
        message should be held within SATNET before discarding.
        There   are  two  choices:   (1)  twice  the  specified
        delivery delay, or (2) the maximum system holding  time
        (currently about two minutes).
        Reliability:   There  are  two  choices, "standard" and
        "high".  If standard is specified, a satellite  channel
        acknowledgment  is  not used for the message, and it is
        not retransmitted by the source Satellite IMP  in  case
        of errors; if the packet is received at the destination
        Satellite  IMP with a good message leader but errors in
  1. 11 -

Host/SATNET Protocol IEN 192

        the data portion of the message, it is marked  as  such
        and delivered to its destination.
        If "high" is specified, the message is retransmitted as
        many times as necessary until a positive acknowledgment
        is  received  by  the  source  Satellite IMP, up to the
        specified message holding time (duplicate copies may be
        delivered to the destination host in this case).

3.3 Addressing

   SATNET uses logical addressing, with each  host  assigned  a

16-bit permanent address. Each data message sent to SATNET must

contain both a source and destination logical address, and is

delivered to the specified destination(s) with these addresses

unchanged. Table 6 in Appendix A contains the current list of

addresses.

3.4 Message Length

   Datagrams may have variable lengths, where these lengths are

integer multiples of 16-bit words. Maximum length of the data

portion of a datagram message is 128 words. The "data portion"

excludes the SATNET leader but includes an internet header if

present.

  1. 12 -

Host/SATNET Protocol IEN 192

3.5 Host/SATNET Flow Control

   Each message sent by a host is accepted or  refused  by  the

Satellite IMP based upon various network and local congestion and

status factors. If accepted, an ACCEPTED control message is

returned to the host containing the message ID assigned by the

host in the data message leader. If refused, a REFUSED control

message is returned containing the message ID and a refusal code

C. If the message itself is bad, a FORMAT ERROR control message

is returned containing the message ID.

   The value of C is used to  indicate  to  the  host  when  it

should subsequently retry the message. This is accomplished by

also sending the host an "acceptance status" word at frequent

intervals to inform it of the categories currently being

accepted. The host may ignore the category information if it

chooses, or map the categories into a smaller subset if

convenient. The use of the categories allows the host to retry

those messages first which are most likely to be accepted by the

Satellite IMP.

   The  "acceptance  status"  word  also  contains  information

indicating which message priorities and delivery delay classes

are currently being accepted, allowing the host to also avoid

unnecessarily sending new messages which will be refused. The

acceptance status word is sent to the host in every data and

  1. 13 -

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control message from the Satellite IMP; in the absence of regular

traffic, a "Hello" message containing the acceptance status word

is sent once per second.

   Hosts must return an explicit acceptance or refusal for each

message received from the Satellite IMP. Note that a "refusal"

by the host is a request to the Satellite IMP to requeue the

message in question and submit it again later. Currently,

refused messages are immediately discarded, so as to eliminate a

line congestion problem seen with the catenet.

3.6 Status Messages

   A host can request current status information from SATNET by

sending a "Status Request" control message. The Satellite IMP

will return a status message containing the acceptance status

word, SATNET global time, and an indicator of the current delay

expected for each delivery delay class. (Inclusion of host

status information is still under study.)

3.7 Hello Messages

   When it  is  not  sending  data  or  control  messages,  the

Satellite IMP or host must send a "Hello" control message once

every second. In addition to providing frequent updating of

acceptance status, the hello message allows the receiver to

maintain the up/down status of the sender. The Satellite IMP

  1. 14 -

Host/SATNET Protocol IEN 192

will do this by resetting a timeout counter whenever anything is

received from the host; if the timeout expires, the host will be

declared down and the Satellite IMP will begin sending restart

messages as described in the next section. The timeout value

used by the Satellite IMP is thirty seconds.

3.8 Message Reference Numbers

   To  support  message-by-message  acknowledgements, each data

message is assigned a 7-bit "message reference number" by its

sender. Its purpose is to allow referencing of the message in a

subsequent acknowledgement (ACCEPTED, REFUSED, or FORMAT ERROR)

message. Reference numbers may be assigned in any order, except

that a particular number may not be reused until the message it

refers to has been acknowledged. All reference numbers are

automatically released whenever the Host/SATNET interface is

reinitialized.

3.9 Initialization

   Since   the   Host/SATNET   protocol  requires  an  explicit

acknowledgement for each message, the initialization procedure

ensures that full two-way communication is possible before

allowing either side to begin transmitting data. Whenever a host

or a Satellite IMP is restarted, it sends a RESTART REQUEST

control message to the other party once every ten seconds until a

RESTART COMPLETE is received, at which time it sends a RESTART

  1. 15 -

Host/SATNET Protocol IEN 192

COMPLETE. The procedure in initializing the interface is shown

in Figure 1 in Appendix B.

   The  initialization action indicated in Figure 1 consists of

flushing all queued control messages waiting to be sent, and of

flushing all received data messages for which an ACCEPTED or

REFUSED message has not already been sent. Note that data

messages waiting to be sent need not be flushed; they can

continue to be queued during the 'waiting' state and their

transmission begun once the 'on' state is entered.

3.10 Format Errors

   Whenever  an invalid leader field value or message length is

detected in a received message a FORMAT ERROR control message is

returned to the sending host or Satellite IMP. An error code is

returned in this message to indicate the detected condition

(these codes are defined in the Formats section of this document,

section 3.13).

3.11 Loop Detection

   To  allow  a  Satellite  IMP or host to detect situations in

which the interface may be externally looped (crosspatched), a

Host/Satellite IMP address bit is included in all data and

control messages, identifying the sender of each message.

  1. 16 -

Host/SATNET Protocol IEN 192

3.12 Piggybacked Control Messages

   Control messages of the ACCEPT, REFUSE,  FORMAT  ERROR,  and

RESTART COMPLETE types may be piggybacked onto data messages by

including the control message in the 16-bit "piggyback" field of

the data message header. The Satellite Imp interprets all

piggybacked control information before examining the rest of the

data message, so, for example, a piggybacked RESTART COMPLETE

takes effect immediately.

3.13 Formats

   The general format used for Host/SATNET interface  exchanges

is shown in Figure 2 (all figures are in Appendix B). The

control code always defines the message format; for all except

data messages, it also implicitly defines the message length.

Exact data message length is assumed to be derived from the host

or Satellite IMP interface transfer, and is always an integer

multiple of 16-bit words.

3.13.1 Control Codes

   Each distinct message type is identified by a  unique  4-bit

control code. Codes currently defined are:

  1. 17 -

Host/SATNET Protocol IEN 192

             1 = DATA
             2 = ACCEPTED
             3 = REFUSED
             4 = STATUS REQUEST
             5 = STATUS
             6 = HELLO
             7 = DATA WITH ERRORS
            13 = FORMAT ERROR
            14 = RESTART REQUEST
            15 = RESTART COMPLETE

3.13.2 Data Messages

   Figure  3  shows  the format for datagram DATA messages (the

width of each word in this and subsequent figures is 16 bits).

Words 1, 2, and 3 are defined by the interface sender (host or

Satellite IMP); words 4, 5, and 6 are defined by the source host.

     Word 1, datagram message control word:
  1. H/S, bit 1: 0 = from Satellite IMP, 1 = from host
  1. message ID, bits 2-8: defined in Section 3.6
  1. block length, bits 9-12: the number of 64-word
     blocks of data words following the message leader:  a
     block  length of 1 means the message contains between
     1 and 64 data words; a length of 2 means 65  and  128
     data  words,  etc.   The  maximum  datagram length is
     defined by Section 3.2.  A length of 0 means  a  null
     DATA message.
  1. Control Code, bits 13-16:
     1 = DATA (no detected errors)
  1. 18 -

Host/SATNET Protocol IEN 192

     7 = DATA  WITH  ERRORS  --  used  only  if  "standard
         reliability"  service  is  designated  and one or
         more data errors were detected by SATNET  in  the
         data  portion  of  the  message.  Applies only to
         packets delivered by SATNET to hosts.
     Word 2, acceptance status:  (defined below).
     Word 3, piggyback field:  This word may  contain  any
     of  the one-word control messages defined by codes 2,
     3, 13, and 15.  A value of zero means the word is not
     used.
     Word 4, Type of Service Word:  (defined below).
     Word 5, destination host:  a  16-bit  SATNET  logical
     address.
     Word   6,  source  host:   a  16-bit  SATNET  logical
     address.

3.13.2.1 Type of Service Word

   Figure 4 shows the  details  of  word  4  of  datagram  DATA

message leaders.

   M, bits 1-2:  DATA message type;
                 0 = datagram, internet format
                 1 = stream, internet format
                 2 = datagram, local format
                 3 = stream, local format
  1. 19 -

Host/SATNET Protocol IEN 192

   P, bits 3-4:  priority; 0 = highest priority, 3 = lowest.
   D, bits 5-6:  acceptable delivery delay ("delay class");
                 delay class      value
  1. ———- —–
                      0          1 second
                      1          5 seconds
                      2         20 seconds
                      3        120 seconds
   H, bit 7:     holding time; 0 = maximum (120 seconds*),
                               1 = twice the specified delay class.
   R, bit 8:     reliability;  0 = high, 1 = standard

3.13.2.2 Acceptance Status Word

   Figure  5  shows  the  details for this word.  If the entire

word equals 0, everything is being accepted.

   Category bits, bits  1-4:   each  bit  defines  the  current
   acceptance/refusal  status for the category corresponding to
   the bit number (e.g., bit 3 represents category 3).
        0 = accepting for this category
        1 = refusing
   Delay Class Priority, bits 5-16 (not currently implemented):
   each delay class is identified by its  position  within  the
   acceptance status word; e.g., bits 14-16 contain information
   for delay class 3.  The content of each three-bit field is a
   binary number defining the current priorities being accepted
   for that delay class, interpreted as follows:
  1. 20 -

Host/SATNET Protocol IEN 192

             0 = all priorities accepted
             1 = lowest priority (3) not accepted
             2 = lowest two priorities (2,3) not accepted
             3 = lowest three priorities (1,2,3) not accepted
             7 = none accepted

3.13.3 ACCEPTED Messages

   Figure  6  shows  the  format  of  ACCEPTED  messages.   (An

acceptance status word, as defined in Figure 5, is always the

second word of this and all other messages.)

   H/S, bit 1:  same as for Data messages.
   Data  message ID, bits 2-8:  The message ID of the DATA
   message being accepted.
   Control Code, bits 13-16:  ACCEPTED = 2.

3.13.4 REFUSED Messages

   Figure 7 shows the format of REFUSED messages.
   H/S, bit 1:  same as for DATA messages.
   Data message ID, bits 2-8:  The message ID of the  DATA
   message being refused.
   C,  bits  9-12:   refusal  category.  A value of 0 to 4
   means  a  refusal  due   to   temporarily   unavailable
   resources.   Messages refused with category values 1 to
   4 will not be accepted until the corresponding category
  1. 21 -

Host/SATNET Protocol IEN 192

   bit  in  the  acceptance  status  word  becomes  0.   A
   category value of 0 means the refusal is because of the
   message   priority   and/or   delay  class;  acceptance
   information for this case is given by the  delay  class
   priority bits in the acceptance status word.  Values of
   C  have  the following meanings (acceptance status word
   information does not apply to values 8 to 15):
               0 = refused for priority/delay class
               1 = category 1  refusal
               2 = category 2  refusal
               3 = category 3  refusal
               4 = category 4  refusal
               5 = undefined
               6 = undefined
               7 = undefined
              *8 = data length greater than stream length
               9 = destination host has been declared in a
                   "refusing" state
              10 = destination host is not reachable
              11 = destination host's Satellite IMP is not reachable
              12 = unrecognized destination address
              13 = destination host access not allowed
              14 = illegal source host
             *15 = no active stream with that stream ID
                   *(See Section 4 on stream access)
   Control Code, bits 13-16:  REFUSED = 3.

3.13.5 STATUS REQUEST Messages

   Figure 8 shows the format of STATUS  REQUEST  messages.
   H/S bit 1:  same as DATA messages.
   Control code, bits 13-16:  STATUS REPORT = 4.
  1. 22 -

Host/SATNET Protocol IEN 192

3.13.6 STATUS MESSAGES

   Figure 9 shows the format of STATUS messages.
   Word 1:  H/S bit, bit 1 = same as DATA messages.
   Control Code, bits 13-16:  STATUS = 5.
   Word 2:  ACCEPTANCE STATUS
   Word   3,   SATNET  global  time:   current  internally
   synchronized clock time used by Satellite IMPs; unit of
   time = 10.24 milliseconds, maximum value  equals  2{16}
  1. 1 units.
   Words  4-7:   current  expected delay for the indicated
   delay class (values to be defined).

3.13.7 HELLO Message

   Figure 10 shows the status of Hello messages.
   H/S bit 1:  same as DATA messages.
   Control Code, bits 13-16:  HELLO = 6.

3.13.8 FORMAT ERROR Message

   Figure 11 shows the format of FORMAT ERROR messages.
  1. 23 -

Host/SATNET Protocol IEN 192

   H/S bit 1:  same as DATA messages.
   Error Message ID, bits 2-8:  ID of  DATA  message  with
   format error (if applicable, otherwise = 0).
   Error Code, bits 9-12:
        0 = undefined error
        1 = data message length exceeds SATNET maximum size
        2 = illegal control code
        3 = block length disagrees with message length.
        4 = illegal control code in piggyback
            word of data message.
        5 = undefined category value (5-7)
            in REFUSED message.
   Control Code, bits 13-16:  FORMAT ERROR = 13.

Note: Implementation of error codes 2 to 5 is optional; however,

a FORMAT ERROR message should be returned with (at least) error

codes 0 and 1 for illegal conditions.

3.13.9 RESTART REQUEST Message

   Figure 12 shows the format of RESTART REQUEST  message.
   H/S bit 1:  same as DATA messages.
   Host Type, bits 9-12:  presently undefined.
   Control Code, bits 13-16:  RESTART REQUEST = 14.
  1. 24 -

Host/SATNET Protocol IEN 192

3.13.10 RESTART COMPLETE Message

   Figure   13   shows  the  format  of  RESTART  COMPLETE
   messages.
   H/S bit 1:  same as DATA messages.
   Host Type, bits 9-12:  presently undefined.
   Control Code, bits 13-16:  RESTART COMPLETE = 15.

Note: All Restart Request and Complete messages sent by the

Satellite IMP have bits 9 to 12 set to zero.

  1. 25 -

Host/SATNET Protocol IEN 192

4. STREAM ACCESS PROTOCOLS

4.1 Overview

   In  addition  to datagram message service, SATNET provides a

service called 'stream'. A stream is a sort of virtual circuit

in which information must be established within Satellite IMP

tables for the duration of the stream use. This information

maintains an outstanding reservation for the stream, causing

channel time to be scheduled at more or less regular intervals

specified in the stream setup. This mechanism provides one of

the important performance properties of a stream which motivates

its use: one-hop for each stream data packet (as opposed to at

least two hops for datagrams).

   Any number of hosts can use the same stream; host membership

is accomplished by special Host/SATNET messages. Each stream is

identified by a SATNET-assigned Stream ID, which has two distinct

functions. The first is to allow Satellite IMPs to identify the

transmission properties being used for each stream data message

including verification that the sending host is a stream member.

The second Stream ID function is its optional use as a

destination address in a stream or datagram data message, causing

delivery to the Stream ID members. (Its use in datagram messages

allows "out of band" signaling messages to be sent while the

stream data messages are also being sent.)

  1. 26 -

Host/SATNET Protocol IEN 192

   The destination address in a  stream  data  message  is  not

limited to the Stream ID, however; any SATNET address may be

used. Thus, a host can set up a simplex stream in which it is

the only member, and therefore the only sender, and send messages

to different hosts using the single stream. Or, a set of hosts

can use a single stream in an arbitrarily shared manner

(determined by the hosts) to send to arbitrary destinations.

   More typically, a stream would be used by a set of hosts for

voice conferencing, in which the Stream ID would be used as the

destination address. Note that, in all cases of shared use,

hosts must provide a protocol to determine how the stream is

shared. If every member host presented a stream data packet to

its Satellite IMP at the same time, they would all be sent

simultaneously in the satellite channel with resultant

destructive interference. (Note: the addressing use of a Stream

ID is not presently implemented – only permanent SATNET

addresses, either point or group, are allowed.)

4.2 Stream Data Messages

   Stream data messages have the format  shown  in  Figure  14.

The message type (bits 1 and 2 of word H4) may be either 1

(stream data, internet format) or 3 (stream data, local

format).(1) Bits 3 to 16 of word H4 contain a Stream ID,

_ (1) Table 5 in Appendix A defines all SATNET message types.

  1. 27 -

Host/SATNET Protocol IEN 192

assigned by SATNET as described in the next section. The

destination address in word H5 can be any SATNET address. The

source host address in word H6 must be assigned to the Satellite

IMP port used to send the message into SATNET, and must be a

member of the Stream ID.

   An ACCEPTED or REFUSED  message  will  be  returned  by  the

Satellite IMP for each stream data message, the same as for

datagrams. Stream data messages will normally always be accepted

unless they are greater than (to be determined) seconds early

relative to the next stream slot time, or the stream is being

preempted by higher priority traffic.

   Internal SATNET channel acknowledgments  are  not  used  for

stream data messages.

4.3 Stream Request Replies and Notifications

   Streams  can  be  used  by a Host only by first establishing

certain information within SATNET. The following requests are

used:

                            CREATE
                            DELETE
                            JOIN
                            LEAVE
                            CHANGE

Each request is sent by the host, along with supplemental

information, in the data portion of a datagram message to the

  1. 28 -

Host/SATNET Protocol IEN 192

SATNET Service Host. A Request message is accepted or refused by

the local Satellite IMP the same as any other datagram message;

if accepted it is delivered to an internal host within the local

Satellite IMP which acts on the request, returning a datagram

message reply to the source host indicating its disposition. The

reply always contains a Request ID supplied by the host in its

Request message, allowing the host to relate the response to its

earlier request (more than one Request message may be outstanding

from a host; the maximum number outstanding will be limited

implicitly by the datagram message refusal mechanism).

   Figure  15 shows the format used for Request messages, which

are always local datagram (type 2). The Request message priority

PR in header word H4 may be assigned the same as for other

datagram traffic. The source host address must be assigned to

the Satellite IMP port used for the message. The first data word

D1 contains one of the Request Codes defined in Table 1. The

Request ID in word D2 is chosen by the host, and should not be

re-used until a Reply message is received with the same ID to

avoid ambiguity.

   Figure  16  shows  the format used for Reply messages, which

are always local datagram (type 2). The values of PR and the

Request ID are those used by the host in the Request messages;

the source host address of the Request message is used as the

destination host address. Word D1 contains a Reply Code in bits

  1. 29 -

Host/SATNET Protocol IEN 192

2 to 16 indicating the action taken on the request; bit 1 is

always zero. The contents of words D3-D6 depends on the Reply

Code; whether used or not, all Reply messages will contain six

data words. Table 2 lists the possible Reply Codes.

   In addition to Reply messages, a Notification message may be

sent to a host by SATNET concerning streams for which the host

has previously established membership. The Notification message

format is shown in Figure 17, and is also a local datagram type

message. The notification message priority PS in word H4 is that

assigned to the stream; the Stream ID involved in the

notification is contained in data word D2. A Notification Code

is contained in bits 2 to 16 of word D1; bit 1 of this word is

always set to 1 to distinguish Notification messages from Reply

messages. As in the case of Reply messages a Notification

message always contains words D3 to D6, whose contents depend on

the Notification Code. Table 4 lists the Notification Codes.

(Notifications not implemented.)

   Except  when a request is refused as a result of information

local to the source Satellite IMP, Notification messages have a

delay of at least one satellite hop (about 0.25 seconds) relative

to the request message, and are initiated at approximately the

same global SATNET time by Satellite IMPs to their involved

hosts. A Reply indicating successful completion of a stream

request requires at least five seconds' delay after receipt of

the request.

  1. 30 -

Host/SATNET Protocol IEN 192

4.3.1 CREATE

   The  words  used in the data portion of a CREATE request are

shown in Figure 18. Word D3 contains a zero if a new stream is

being requested (the use of non-zero values will be defined in a

later version of the Host/SATNET access protocol). Words D4-D6

contain a Key which is used to authenticate subsequent requests

from any host concerning the stream. Any 48-bit value may be

used, including zero; however, all subsequent Request message

Keys for this stream must equal this Key to be honored.

   Words D7-D9 define the parameters to be used for the  stream

by SATNET. Ps is the priority to be used for the stream data

messages. Bits 7 to 16 of word D7 indicate the maximum number L

of 16-bit data words which will be sent in any data message using

the stream. The queue length, bits 1-4 of D8, is the maximum

number of messages that may be queued at once awaiting

transmission using the stream. The stream interval is a 24-bit

quantity indicating the time (in ten microsecond units) between

stream messages. The high order eight bits are in D8, bits 9-16,

and the low 16 bits are in D9. A suitable time for messages in

this stream will be computed using the stream interval given.

   If the CREATE is honored, Stream Started Reply message  will

be returned with the Stream ID assigned by SATNET in word D3

(words D4-D6 are not used). The first stream channel allocation

  1. 31 -

Host/SATNET Protocol IEN 192

is begun approximately one stream interval I following generation

of the Reply message. If refused, a Stream Creation Refused will

be returned with a reason code in Word D3.

   Each  CREATE  message received with word D3 set to zero will

cause the creation of a new stream (resources permitting),

independently of the Key or other field values contained in the

CREATE message. Note that different streams may use the same

Key; the SATNET-assigned Stream ID supplied by hosts in

subsequent Request messages provides unique referencing to the

stream in question.

4.3.2 DELETE

   Figure  19  shows  the  data words sent in a DELETE Request.

Word D1 contains the DELETE STREAM Request Code; word D2 contains

the host's Request ID (this ID need not relate to any previous

Request message); word D3 contains the Stream ID; words D4-D6

contain the Key.

   If the DELETE STREAM request is honored, the stream  channel

allocations will be terminated and a Stream Deleted Reply message

will be returned with the Stream ID in word D3; words D4-D6 are

not used. In addition, a Notification message ("Stream Deleted

by Host X") will be sent to all other member hosts, with the

address of the requesting host in D3 (not implemented yet); words

D4-D6 are not used. All Satellite IMP table entries concerning

  1. 32 -

Host/SATNET Protocol IEN 192

the stream will be cleared and the Stream ID released for re-use.

   If  the  DELETE  STREAM  request  is  not  honored, a Stream

Deletion Refused Reply will be returned. Word D3 will indicate

why the request was refused. Table 3 indicates the refusal

reasons that can appear in D3.

4.3.3 JOIN

   A JOIN Request (not implemented yet) is used by  a  host  to

establish membership in a stream previously created by another

host. (It is the responsibility of the creating host to

distribute the assigned Stream ID and Key to those hosts it

wishes to have participate in the use of the stream.) The format

shown in Figure 19 is used for a JOIN, with the JOIN STREAM

Request Code in word D1.

   If  the  stream  exists  and  the correct Key is supplied, a

Stream Joined Reply message is returned approximately one stream

interval prior to the next scheduled channel allocation for the

stream. Word D3 of the reply message contains the Stream ID;

words D4-D6 contain the parameters currently used for the stream,

formatted according to words D7 to D9 of Figure 5. Also, a

Notification Code 3 Message ("Stream Joined by Host X") is sent

to all other member hosts–word D3 contains the address of the

newly joined host; words D4-D6 are not used.

  1. 33 -

Host/SATNET Protocol IEN 192

   If the JOIN is not honored, a  Join  Refused  Reply  message

will be returned with a Table error code as appropriate.

4.3.4 LEAVE

   A  host may leave a stream of which it is a member by use of

a LEAVE Request (not implemented yet). The format of Figure 19

is again used, with the Request Code = 4. If the stream exists

and the host is entered as a member in Satellite IMP tables, a

Stream Left Reply message will be returned. Note that the Key is

not used for this request. Also, a Notification Code 4 message

("Stream Left by Host X") is sent to all member hosts; word D3

contains the address of the departed host; words D4-D6 are not

used.

   A Leave request will always succeed.  However, in some cases

it may be impossible to notify other stream members of the event.

If so, a Leave Without Notification Reply message will be

returned. Word D3 will indicate why notification could not be

made.

4.3.5 CHANGE

   A host can request changes  to  the  parameters  defining  a

stream by use of a CHANGE request (not implemented yet). This

message is identical to the CREATE message format of Figure 18,

except that the Request code is set to 5 in word D1 and word D3

  1. 34 -

Host/SATNET Protocol IEN 192

contains the Stream ID. All parameters of words D7-D9 must be

defined, whether or not their values are being changed – if

allowed, the parameters will be used to re-define the stream

characteristics just as if they were being supplied in a CREATE

request.

   If the changes  can  be  honored,  a  Stream  Changed  Reply

message will be returned with the Stream ID in word D3; words

D4-D6 are not used. Also, a Notification code 5 message ("Stream

Changed by Host X") is sent to the other member hosts; word D3

contains the address of the requesting host; words D4-D6 contain

the new parameters.

   If the changes cannot be  made,  a  Stream  Changes  Refused

Reply message is returned to the requesting host, with a reason

code in word D3 (see Table 3).

4.4 SATNET Termination and Suspension of Streams

   A stream termination will be initiated by SATNET  if  (1)  a

data message is not sent in the stream by any of the member hosts

for sixty seconds, or (2) if the stream's channel allocation

cannot be honored for N (to be determined) consecutive stream

intervals I due to higher priority traffic (not implemented yet).

If either of these occurs, a Notification code 1 message ("Stream

Deleted by SATNET") will be sent to all member hosts with an

appropriate reason code in word D3; words D4-D6 are not used.

  1. 35 -

Host/SATNET Protocol IEN 192

All Satellite IMP table entries concerning the stream will be

deleted and the Stream ID released for re-use.

   Whenever a stream's channel allocation has not been  honored

by SATNET for M (to be determined) consecutive stream intervals I

following the last allocation, a Notification Code 6 message

("Stream Suspended") is sent to all member hosts (M will be much

smaller than N). If the allocations are resumed before N

consecutive non-allocations, a Notification Code 7 message

("Stream Resumed") is sent to all member hosts. (These are not

implemented yet.)

  1. 36 -

Host/SATNET Protocol IEN 192

5. Land Modem Interface

   A Satellite IMP communicates with other IMPs and  with  Very

Distant Hosts via communication circuits, such as those provided

by the various common carriers (Bell, Western Electric, etc.)

The exact nature of the synchronous modems and dedicated full

duplex lines varies from site to site. The hardware interface to

the modem is the standard BBN IMP-modem interface which is

logically identical to the Bell 303 interface with the exception

that the mark and space convention is inverted for characters

sent to the modem (i.e., binary "one" equals high current). The

control lines, however, are not inverted.

6. Local Host Interface

   Local Host computers interface to the Satellite  IMP  via  a

hardware interface which is electrically equivalent to that used

in the ARPANET between hosts and IMPs. The electrical

specification for this interface appears in BBN Report No. 1822

entitled "Specifications for the Interconnection of a host and an

IMP".

  1. 37 -

Host/SATNET Protocol IEN 192

APPENDIX A.

A.1 Table 1 – Request Codes

        1 -- Create Stream
        2 -- Delete Stream
        3 -- Join Stream
        4 -- Leave Stream
        5 -- Change Stream Parameters

A.2 Table 2 – Reply Codes

        1 -- Stream Started
        2 -- Stream Deleted
        3 -- Stream Joined
        4 -- Stream Left
        5 -- Stream Changed
        6 -- Stream Creation Refused
        7 -- Stream Deletion Refused
        8 -- Join Refused
        9 -- Leave without Notification
       10 -- Stream Changes Refused
       11 -- Illegal Request Code
  1. 38 -

Host/SATNET Protocol IEN 192

A.3 Table 3 – Error Codes in D3

        0 -- System busy; unable to handle request
        1 -- Unimplemented function
        2 -- Invalid protection Key
        3 -- Not member of stream
        4 -- Stream does not exist
        5 -- Net trouble
        6 -- Insufficient resources to handle request
        7 -- Improper format for request
        8 -- Channel protocol does not support streams
        9 -- Illegal argument in stream request
       10 -- Channel access not allowed

A.4 Table 4 – Notification Codes

        1 -- Stream Deleted by SATNET
        2 -- Stream Deleted by Host X
        3 -- Stream Joined by Host X
        4 -- Stream Left by Host X
        5 -- Stream Changed by Host X
        6 -- Stream Suspended
        7 -- Stream Resumed

A.5 Table 5 – SATNET Data Message Types

        0 -- Datagram, internet format
        1 -- Stream data, internet format
        2 -- Datagram, local format
        3 -- Stream data, local format
  1. 39 -

Host/SATNET Protocol IEN 192

A.6 Table 6 – SATNET Logical Address Map

        0 -- 0 SATNET Service Host
        1 -- Etam EXPAK fake host
        2 -- Goonhilly EXPAK fake host
        3 -- Tanum EXPAK fake host
        4 -- Clarksburg EXPAK fake host
        5 -- Etam Message Generator/Sink #0
        6 -- Etam Message Generator/Sink #1
        7 -- Etam Message Generator/Sink #2
        8 -- Etam Message Generator/Sink #3
        9 -- Goonhilly Message Generator/Sink #0
       10 -- Goonhilly Message Generator/Sink #1
       11 -- Goonhilly Message Generator/Sink #2
       12 -- Goonhilly Message Generator/Sink #3
       13 -- Tanum Message Generator/Sink #0
       14 -- Tanum Message Generator/Sink #1
       15 -- Tanum Message Generator/Sink #2
       16 -- Tanum Message Generator/Sink #3
       17 -- Clarksburg Message Generator/Sink #0
       18 -- Clarksburg Message Generator/Sink #1
       19 -- Clarksburg Message Generator/Sink #2
       20 -- Clarksburg Message Generator/Sink #3
       21 -- Etam Internal Gateway
       22 -- Goonhilly Internal Gateway
       23 -- Tanum Internal Gateway
       24 --   unused
       25 --   unused
       26 --   unused
       27 --   unused
       28 --   unused
       29 --   unused
       30 -- Clarksburg Internal Gateway
       31 --   unused
       32 --   unused
       33 --   unused
       34 --   unused
       35 --   unused
       36 --   unused
       37 -- Universal Message Sink (equivalent name)
       38 -- Tanum NDRE Gateway
       39 -- Clarksburg COMSAT Gateway
       40 -- Universal Satellite Echo (equivalent name)
       41 -- Etam Monitor Fake Host
       42 -- Goonhilly Monitor Fake Host
       43 -- Tanum Monitor Fake Host
       44 -- Clarksburg Monitor Fake Host
       45 -- Etam Packet Core Fake Host
       46 -- Goonhilly Packet Core Fake Host
  1. 40 -

Host/SATNET Protocol IEN 192

       47 -- Tanum Packet Core Fake Host
       48 -- Clarksburg Packet Core Fake Host
       49 -- Etam TTY Fake Host
       50 -- Goonhilly TTY Fake Host
       51 -- Tanum TTY Fake Host
       52 -- Clarksburg TTY Fake Host
       53 -- Etam DDT Fake Host
       54 -- Goonhilly DDT Fake Host
       55 -- Tanum DDT Fake Host
       56 -- Clarksburg DDT Fake Host
       57 --   unused
       58 --   unused
       59 --   unused
       60 -- Goonhilly UCL Gateway
       61 -- Etam BBN Gateway
       62 -- Etam Echo Fake Host
       63 -- Goonhilly Echo Fake Host
       64 -- Tanum Echo Fake Host
       65 -- Clarksburg Echo Fake Host
       66 --   unused
       67 --   unused
       68 --   unused
       69 --   unused
       70 --   unused
       71 --   unused
       72 -- Raisting External Gateway
       73 --   unused
       74 --   unused
       75 --   unused
       76 -- Raisting Internal Gateway
       77 -- Raisting Echo Fake Host
       78 -- Raisting Monitor Fake Host
       79 -- Raisting EXPAK Fake Host
       80 -- Raisting Packet Core Fake Host
       81 -- Raisting DDT Fake Host
       82 -- Raisting TTY Fake Host
       83 -- Raisting Message Generator/Sink #0
       84 -- Raisting Message Generator/Sink #1
       85 -- Raisting Message Generator/Sink #2
       86 -- Raisting Message Generator/Sink #3
       87 --   unused
       88 -- Fucino External Gateway
       89 --   unused
       90 --   unused
       91 --   unused
       92 -- Fucino Internal Gateway
       93 -- Fucino Echo Fake Host
  1. 41 -

Host/SATNET Protocol IEN 192

       94 -- Fucino Monitor Fake Host
       95 -- Fucino EXPAK Fake Host
       96 -- Fucino Packet Core Fake Host
       97 -- Fucino DDT Fake Host
       98 -- Fucino TTY Fake Host
       99 -- Fucino Message Generator/Sink #0
      100 -- Fucino Message Generator/Sink #1
      101 -- Fucino Message Generator/Sink #2
      102 -- Fucino Message Generator/Sink #3
      103 --   unused
  1. 42 -

Host/SATNET Protocol IEN 192

                              +-------+
                              |       |
                              |  OFF  |
                              |       |
 TO = TIMEOUT                 +-------+
 RR = RESTART REQUEST             |
 RC = RESTART COMPLETE            |INIT & SEND RR
                                  |
                                  V
                              +-------+
                          --->|       |---------------
                        /     |       |                \
                       |      |       |                 \
                       |      |  INIT |                  |
                       |      |       |<---              |
                        \     |       |     \            |
                          ----|       |      |           |
                    10 SEC TO +-------+      |           |
                     -------      |          |           |
                     SEND RR      |RCVD RR   |           |
                                  | -----    |           |
                                  |SEND RC   |           |
                                  V          |           |
                              +-------+      |           |
               -------------->|       |      |           |
             /                |       |     /            |
            /             --->|       |----              |
           |            /     |WAITING| 100 SEC TO       |
           |           |      |       |  --------        |
           |            \     |       |  SEND RR         |
           |              ----|       |                  |
           |        10 SEC TO +-------+                  |
           |         -------      |                      |
           |         SEND RC      |                      |
           |                      |RCVD RC               |
           |                      |                      |
            \                     V                     /
             \                +-------+                /
               ---------------|       |<--------------
             RCVD RR          |   ON  |       RCVD RC
           ------------       |       |        -----
          INIT & SEND RC      +-------+       SEND RC

B.1 Figure 1. Restart State Diagram

  1. 43 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| | CONTROL CODE |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
 |                                                               |
 |                                                               |
 |                                                               |
 |                                                               |
 |                                                               |
 |                                                               |
 |                                                               |
 |                                                               |
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.2 Figure 2. General Message Format

  1. 44 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| MESSAGE ID | BLOCK LENGTH | CODE = 1 or 7 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H3 | PIGGYBACK WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H4 | TYPE OF SERVICE |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H5 | DESTINATION HOST(S) ADDRESS |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H6 | SOURCE HOST ADDRESS |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D1 | |

 |                                                               |
 |                             DATA                              |
 |                                                               |

DN | |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.3 Figure 3. Block DATA Message

  1. 45 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H4 | M | P | D | H | R | (unused) |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.4 Figure 4. Type of Service Word

   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | C | D0 | D1 | D2 | D3 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.5 Figure 5. Acceptance Status Word

   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| DATA MESSAGE ID | (unused) | CODE = 2 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.6 Figure 6. ACCEPTED Message

   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| DATA MESSAGE ID | C | CODE = 3 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.7 Figure 7. REFUSED Message

  1. 46 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| (unused) | CODE = 4 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.8 Figure 8. STATUS REQUEST Message

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| (unused) | CODE = 5 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H3 | SATNET GLOBAL TIME |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H4 | CURRENT DELAY FOR CLASS 0 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H5 | CURRENT DELAY FOR CLASS 1 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H6 | CURRENT DELAY FOR CLASS 2 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H7 | CURRENT DELAY FOR CLASS 3 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.9 Figure 9. STATUS Message

  1. 47 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| (unused) | CODE = 6 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.10 Figure 10. HELLO Message

   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| ERROR MESSAGE ID | ERROR CODE | CODE = 13 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.11 Figure 11. FORMAT ERROR Message

   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| (unused) | HOST TYPE | CODE = 14 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.12 Figure 12. RESTART REQUEST Message

   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| (unused) | HOST TYPE | CODE = 15 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.13 Figure 13. RESTART COMPLETE Message

  1. 48 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| MESSAGE ID | BLOCK LENGTH | CODE = 1 or 7 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H3 | PIGGYBACK WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H4 | 1 or 3| STREAM ID |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H5 | DESTINATION HOST(S) ADDRESS |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H6 | SOURCE HOST ADDRESS |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
 |                                                               |
 |                                                               |
 |                  (INTERNET HEADER IF TYPE=1)                  |
 |                                                               |
 |                                                               |
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D1 | |

 |                                                               |
 |                           STREAM DATA                         |
 |                                                               |

DN | |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.14 Figure 14. Stream Data Format

  1. 49 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| MESSAGE ID | BLOCK LENGTH | CODE = 1 or 7 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H3 | PIGGYBACK WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H4 |0 or 2 | PR | 0 | 0 | 0 | (unused) |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H5 | SATNET SERVICE HOST (CURRENT ADDRESS = 0) |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H6 | SOURCE HOST ADDRESS |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
 |                                                               |
 |                                                               |
 |                  (INTERNET HEADER IF TYPE=0)                  |
 |                                                               |
 |                                                               |
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D1 | REQUEST CODE |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D2 | REQUEST ID |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D3 | |

 |                                                               |
 |                      REQUEST INFORMATION                      |
 |                                                               |

DN | |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.15 Figure 15. Request Message Format

  1. 50 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| MESSAGE ID | BLOCK LENGTH | CODE = 1 or 7 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H3 | PIGGYBACK WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H4 |0 or 2 | PR | 0 | 0 | 0 | (unused) |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H5 | REQUESTING HOST |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H6 | SATNET SERVICE HOST (CURRENT ADDRESS = 0) |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
 |                                                               |
 |                                                               |
 |                  (INTERNET HEADER IF TYPE=0)                  |
 |                                                               |
 |                                                               |
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D1 | 0 | REPLY CODE |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D2 | REQUEST ID |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D3 | |

 |                                                               |
 |                       REPLY INFORMATION                       |
 |                                                               |

D6 | |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.16 Figure 16. Reply Message Format

  1. 51 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H1 |H/S| MESSAGE ID | BLOCK LENGTH | CODE = 1 or 7 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H2 | ACCEPTANCE STATUS WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H3 | PIGGYBACK WORD |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H4 |0 or 2 | PS | 0 | 0 | 0 | (unused) |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H5 | MEMBER HOST |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

H6 | SATNET SERVICE HOST (CURRENT ADDRESS = 0) |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
 |                                                               |
 |                                                               |
 |                  (INTERNET HEADER IF TYPE=0)                  |
 |                                                               |
 |                                                               |
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D1 | 1 | NOTIFICATION CODE |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D2 | STREAM ID |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D3 | |

 |                                                               |
 |                    NOTIFICATION INFORMATION                   |
 |                                                               |

D6 | |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.17 Figure 17. Notification Message Format

  1. 52 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D1 | REQUEST CODE = 1 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D2 | REQUEST ID |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D3 | STREAM ID = 0 |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D4 | |

 |                                                               |

D5 | KEY |

 |                                                               |

D6 | |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D7 | (unused) | PS | MAXIMUM DATA LENGTH (L) |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D8 | QUEUE LENGTH | (unused) | STREAM INTERVAL (HIGH BITS) |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D9 | STREAM INTERVAL (LOW BITS) |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.18 Figure 18. Create Request Words

  1. 53 -

Host/SATNET Protocol IEN 192

 MSB                                                           LSB
   1   2   3   4   5   6   7   8   9   10  11  12  13  14  15  16
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
 |                                 = 2:  DELETE                  |

D1 | REQUEST CODE = 3: JOIN |

 |                                 = 4:  LEAVE                   |
 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D2 | REQUEST ID |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D3 | STREAM ID |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

D4 | |

 |                                                               |

D5 | KEY |

 |                                                               |

D6 | |

 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

B.19 Figure 19. Delete, Join, Leave Request Words

  1. 54 -
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