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BLACKER INTERFACE CONTROL DOCUMENT
March 21, 1989
March 21, 1989
Table of Contents
Section Subject Page
1. Introduction 1-1
2. Host/Red-Side Interface 2-1
2.1. Physical Level 2-1
2.2. Link Level 2-4
2.3. Packet Level 2-4
2.4. Internet Protocol Features 2-9
2.5. Internet Control Message Protocol Features 2-11
3. Network/Black-Side Interface 3-1
3.1. Physical Level 3-1
3.2. Link Level 3-3
3.3. Packet Level 3-3
3.4. Internet Protocol Features 3-4
3.5. Internet Control Message Protocol Features 3-4
A. Initial DDN Sensitivity Labels A-1
B. References B-1
C. BLACKER Generated Diagnostic Codes C-1
March 21, 1989
1. INTRODUCTION
1.0.1 The purpose of this document is to define the interface to
the BLACKER Front Ends (BFE). This document will define the
services used on the network or black side where the BFE
interfaces to the Defense Data Network (DDN) and will define the
services offered on the host/gateway or red side.
Host Network
Plaintext Ciphertext
Red-Side Black-Side
+---------+ +---------+ +---------+
| HOST OR |___________| BFE |_______________| DDN |
| GATEWAY | | | | PSN |
+---------+ +---------+ +---------+
1.0.2 The BFE acts as the Data Communication Equipment (DCE) of
an X.25 Network to its attached host. As such, the BFE offers
the host an X.25 interface. This interface is a modified version
of the interface presented in the 1983 DDN X.25 Host Interface
Specification. Because of the additional security functionality
of the BFE, there are additional requirements on the host
interface at levels above the X.25 layer. These additional
requirements as well as the specific details of the X.25
interface are defined in section 2 of this document.
1.0.3 The following terminology will be used in this document.
Units of information at the link (X.25 level 2) level will be
referred to as "frames". Units at the network (X.25 level 3)
level will be referred to as "packets". Units at the Internet
Protocol (IP) level will be referred to as "datagrams". The
information contained in a datagram that is passed on to the
actual destination computer will be referred to as a message,
with an appropriate modifier (e.g., Mail message). A byte is a
unit of data containing eight bits.
1.0.4 The BLACKER System on the DDN uses the X.25 interface as a
local interface only. This means that the type of service
offered does not provide the end-to-end services of X.25. The
BFE will offer a version of the DDN X.25 Standard Service as
defined in the DDN X.25 Host Interface Specification, dated Dec
1983, with the restrictions and modifications defined in this
document. This interface also conforms to FIPS PUB 100 (6 July
1983), and CCITT Recommendation X.25 (1980), as well as the DDN
Host Interface Specification. The BFE will not provide support
for the ARPANET Host Interface Protocol (AHIP), also known as
Bolt, Beranek, and Newman, Inc. (BBN) 1822 interface.
Page 1-1
March 21, 1989
1.0.5 All values for fields defined in this document, unless
otherwise designated, are decimal values. The leftmost bit
(byte) in any field is the high order bit (byte) of the value.
1.0.6 All BFE parameters are loaded via a BLACKER Initialization
Carrier (BIC). These include site identification, Access Control
Center (ACC) and Key Distribution Center (KDC) identification,
security level, protocol parameters, and audit control values.
The BIC is inserted and read when the BFE is first powered on,
and then is only needed after the BFE has been reset, zeroized,
or has completely lost power.
Page 1-2
March 21, 1989
2. RED-SIDE HOST INTERFACE
2.0.1 This section describes the host interface to the BLACKER
Front End. This interface is based upon standards defined for
the 1983 DDN X.25 interface, and requires that the Internet
Protocol (IP) be used as the next layer above X.25. For hosts
which already implement the current set of DDN X.25 protocols
including IP, and use an RS-449 balanced interface, the changes
should be minor.
2.1 PHYSICAL LEVEL
The BFE will conform to the following three specifications:
1. "DEFENSE DATA NETWORK X.25 HOST INTERFACE SPECIFICATION",
DCA, DECEMBER 1983
2. EIA STANDARD RS-449, NOVEMBER 1977
3. MILITARY STANDARD 188-114, MARCH 1976
The BFE will support the signals as listed in Table B-2 of the
DDN X.25 Specification. Optional signals supported will be the
signals identified as CCITT numbers 141 and 142 on the host side.
In RS-449 terms, the BFE will support all Category I circuits in
the balanced mode. The BFE will also support all type Send-
Receive mandatory circuits for synchronous primary channel
operation (see Fig 5.1 in Specification 2). The RS-449 37-
position connector with a GLENAIR, INC., (or equal) backshell
will be used on the host interface.
The BFE will present a DCE interface to the host.
The BFE will operate at speeds from 1.2 to 64 kilobits per
second. Only full duplex synchronous operation will be support-
ed. Data timing will originate from the network DCE to the
BLACKER Data Terminal Equipment (DTE), and then from the BLACKER
DCE to the host. (Note: The signal names used below refer to the
RS-449 names used in the following table.) RT signal will supply
the data strobe for RD, ST will supply the data request for SD,
and TT will supply the data acknowledge/data strobe for SD. The
DTE must use the incoming ST signal to generate the data strobe
signal, TT.
Interface signal electrical characteristics will be as defined by
MIL-STD-188-114. The single deviation from this specification is
the Open Circuit Balanced Voltage Driver Output, which is 8 volts
+/- 2 volts, instead of 6 volts +/- 2 volts. Interface signal
Page 2-1
March 21, 1989
functions, directions, and pin assignments will be as defined in
RS-449.
LISTING OF SIGNALS SUPPORTED BY THE BFE RED-SIDE
PIN RS-449 ABBREVIATION DCE IS
1 SHIELD NO CONNECTION
2 SI +5
3 SPARE
4 SD BALANCED RECEIVER
5 ST BALANCED GENERATOR
6 RD BALANCED GENERATOR
7 RS BALANCED RECEIVER
8 RT BALANCED GENERATOR
9 CS BALANCED GENERATOR
10 LL UNBALANCED RECEIVER
11 DM BALANCED GENERATOR
12 TR BALANCED RECEIVER
13 RR BALANCED GENERATOR
14 RL IB-
15 IC -5
16 SF/SR IB+
17 TT BALANCED RECEIVER
18 TM UNBALANCED GENERATOR
19 SG CIRCUIT GROUND
20 RC DCE CIRCUIT GROUND
21 SPARE
22 SD ( see pin 4 )
23 ST ( see pin 5 )
24 RD ( see pin 6 )
25 RS ( see pin 7 )
26 RT ( see pin 8 )
27 CS ( see pin 9 )
28 IS IB+
29 DM ( see pin 11 )
30 TR ( see pin 12 )
31 RR ( see pin 13 )
32 SS IB-
33 SQ +5
34 NS IB-
35 TT ( see pin 17 )
36 SB -5
37 SC DTE CIRCUIT GROUND
ABBREVIATIONS OTHER THAN RS-449 SIGNAL NAMES
IB- PIN IS OPEN, INTERNAL BIAS OF MINUS FIVE VOLTS (OPTIONAL)
IB+ PIN IS OPEN, INTERNAL BIAS OF FIVE VOLTS (OPTIONAL)
Page 2-2
March 21, 1989
2.2 LINK LEVEL
The BFE will conform to the following Link Level specifications:
1. "DEFENSE DATA NETWORK X.25 HOST INTERFACE SPECIFICATION",
DCA, DECEMBER 1983
2. "INTERFACE BETWEEN DATA TERMINAL EQUIPMENT (DTE) AND
DATA CIRCUIT TERMINATION EQUIPMENT (DCE) FOR TERMINALS
OPERATING IN THE PACKET MODE ON PUBLIC DATA NETWORKS",
RECOMMENDATION X.25, CCITT, 1980
3. "WD2512 X.25 PACKET NETWORK INTERFACE (LAPB)", WESTERN
DIGITAL CORP., SEPT. 1988 (PRELIMINARY),
APRIL 1989 (EXPECTED FINAL PUBLICATION).
At level 2, the BFE will use the DDN X.25 High Level Data Link
Control, Link Access Procedure - Balanced (HDLC-LAPB) interface
protocol.
On the host/red side the BFE will be a DCE.
The HDLC-LAPB interface in the BFE will be implemented using the
Western Digital WD2512 Packet Network Interface Chip. This chip
handles bit oriented, full duplex serial data communications on
its Level 1/Level 2 interface side. The computer interface side
uses direct memory access.
The "Transparent Modes" of the WD2512 chip, as described in
specification three above, will not be used.
2.3 PACKET LEVEL
2.3.1 The BFE will conform to the following Packet Level
specifications. Restrictions and extensions are described below.
(Note: All page and paragraph references refer to the DDN
specification as number one below. Paragraph references begin
with the letter 'D').
1. "DEFENSE DATA NETWORK X.25 HOST INTERFACE SPECIFICATION",
DCA, DECEMBER 1983
2. "INTERFACE BETWEEN DATA TERMINAL EQUIPMENT (DTE) AND
DATA CIRCUIT TERMINATING EQUIPMENT (DCE) FOR TERMINALS
OPERATING IN THE PACKET MODE ON PUBLIC DATA NETWORKS",
RECOMMENDATION X.25, CCITT, 1980
Page 2-3
March 21, 1989
3. "INTERFACE BETWEEN DATA TERMINAL EQUIPMENT (DTE) AND
DATA CIRCUIT TERMINATING EQUIPMENT (DCE) FOR OPERATIONS
WITH PACKET-SWITCHED DATA COMMUNICATIONS NETWORKS",
FED-STD 1041; FIPS PUB 100, 6 JULY 1983
2.3.2 Standard Service Restriction: Only DDN "Standard Service"
X.25 will be offered on the host interface. No provisions for
"Basic Service" will be made. Any call requests from the host
indicating "Basic Service" will be rejected. (pg. 3)
2.3.3 Physical Address Restriction: Only physical addressing
will be supported. All BFE ports will be assigned a physical
address by the Defense Communications Agency. The address will
conform to the format defined in D2.1.1.1 with the following
constraints. All addresses will be 12 binary coded decimal (BCD)
digits. Sub-addresses will not be supported. The 'F' flag will
be set to zero. Requests for Logical Addressing facilities will
result in a CLEAR INDICATION with an appropriate diagnostic code
(146) being sent to the host. Early serial number BFEs may
return an Invalid Called Address (68) or Invalid Calling Address
(69) diagnostic code. (pg. 6)
2.3.4 Standard Service Restriction: In D2.1.2.1 for the Type of
Service Facility on a CALL REQUEST, DDN "Standard Service" must
always be selected. Failure to specify DDN "Standard Service"
will result in a CLEAR INDICATION packet with a diagnostic code
of (155) being sent to the host. (pg. 8)
2.3.5 Call User Data Restriction: In the Protocol Identifi-
cation Field of a CALL REQUEST packet, as defined in D2.1.3, a
DTE must indicate the use of the DoD Internet Protocol (IP). The
value defined for IP (11001100 binary, CC hex) must be the first
and only byte present in the Call User Data Field of the CALL
REQUEST Packet. A Call User Data field that is not exactly one
byte long will result in a CLEAR INDICATION with a diagnostic of
either a packet too short (38) or packet too long (39). Selection
of a different value will result in a CLEAR INDICATION packet
with a diagnostic code of (156) being sent to the host. (pg. 10)
2.3.6 Packet Sizes Supported: A maximum packet sizes of 128,
256, 512, or 1024 octets will be supported by the BFE. A maximum
packet size of 1024 octets is required for hosts accredited to
operate at multiple security levels. A maximum packet size of
1024 octets is strongly recommended for all hosts, in order to
allow an IP datagram to fit within a single packet. IP Datagram
Size limitation is discussed in section 2.4.4 of this document.
(pg. 11)
2.3.7 Packet Size Limitation: The maximum permissible number of
data bits in a complete packet sequence must be no more than 896
Page 2-4
March 21, 1989
bytes (7168 bits). An attempt to send more than 896 bytes will
result in a CLEAR INDICATION with an appropriate diagnostic code
(39) being sent to the host. (pg. 11)
2.3.8 D and Q Bit Restriction: The D-bit and Q-bit have no
significance to the BFE and are not passed to the destination.
These should be set to zero by the host. (pg. A6)
2.3.9 Logical Addressing: There is no support for logical
addressing. Requests for logical addressing facilities will
receive a CLEAR INDICATION packet with an appropriate diagnostic
code (146) being sent to the host. Early serial number BFEs may
return an Invalid Called Address (67) or Invalid Calling Address
(68) diagnostic code. (pg. A7)
2.3.10 Derivation of X.25 addresses in BLACKER: (pg. A9)
For devices directly connected to a BLACKER Front End, the IP
address is a 32-bit quantity that consists of two parts, the
first part defining a network, and the second being network
specific. The DDN Red Virtual Network (DDN-RVN) will be a class
A network, having a network identifier field eight bits wide, and
a network specific portion 24 bits wide. The network number for
the DDN-RVN will be 21. The 24-bit network specific part will be
defined as follows. The first bit is zero. The next three bits
are a port number of the BFE. The following ten bits are the
domain number of the BFE, and the last ten bits are the BFE's
number within its domain. This is shown graphically as:
IP 0 1 2
ADDRESS 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NETWORK |0|PORT | DOMAIN ID | BFE ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The port field specifies a routing for the BFE. It may take on
values between zero and seven. The currently defined values are:
0 for the computer attached to the host port, 1 for the internal
Access Control Module, and 2 for the internal Internet Control
Message Protocol (ICMP) Server. The domain ID and BFE ID fields
may take on the values 000 to 999, inclusive.
At the X.25 level, the DDN-RVN is an X.25 network supporting the
version of DDN "Standard Service" described in this section. For
devices directly connected to the DDN-RVN, the X.25 address
consists of 12 BCD digits in the form ZZZZ F DDDDDDD. (See
D2.1.1.1.) The sub-address feature, defined in D2.1.1.1, is
never used. For the DDN-RVN, ZZZZ is a value to be decided by
the administration. It will initially be set to 0000. F will be
zero to indicate physical addressing. DDDDDDD is directly mapped
from the network specific portion of the IP address, where the
Page 2-5
March 21, 1989
first digit is the port ID, the next three digits are the domain
ID, and the last three digits are the intra-domain BFE ID. The
mapping is a value conversion from the binary representation to
the BCD representation. This is shown graphically as:
0 1 2 2
0 0 0 3
IP: BBBBBBBBBBBBBBBBBBBBBBBB (bits)
|\ /\ /\ /
x | -------- --------
| | |
X.25: 0000 0 D DDD DDD (BCD digits)
For example, if your host was host number 45 in domain 10, and
you wish to talk to the internal ICMP echo port, you would
address your message to network 21, domain 10, host 45, port 2.
In graphic form this IP address is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1 0 1 0 1|0|0 1 0|0 0 0 0 0 0 1 0 1 0|0 0 0 0 1 0 1 1 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 21 | | 2 | 10 | 45 |
The X.25 address for this port would be: 0000 0 2010045.
2.3.11 Interrupt Restriction: INTERRUPT and INTERRUPT
CONFIRMATION packets are not supported.
2.3.12 Datagram Restriction: DATAGRAM service as it is defined
in reference two above is not supported.
2.3.13 Permanent Virtual Circuit Restriction: There will be no
support for PERMANENT VIRTUAL CIRCUITS. All calls will need to
be established via CALL REQUEST Packets.
2.3.14 X.25 Facilities
The following facilities described in reference two above WILL BE
supported by the BFE:
1980 CCITT paragraph
Nonstandard default window size 7.1.2
Nonstandard default packet size 7.2.1
Flow control parameter negotiation 7.2.2
Page 2-6
March 21, 1989
The following facilities described in reference two above WILL
NOT BE supported by the BFE:
1980 CCITT paragraph
Extended packet sequence numbering 7.1.1
Default Throughput Class Assignment 7.1.3
Packet Retransmission 7.1.4
Incoming Calls Barred 7.1.5
Outgoing Called Barred 7.1.6
One-way logical channels outgoing 7.1.7
One-way logical channels incoming 7.1.8
Closed user group (all varieties) 7.1.9-7.1.15
Reverse charging 7.1.16
Reverse charging acceptance 7.1.17
RPOA selection 7.1.18
Throughput class negotiation 7.2.3
Fast select 7.2.4
Fast select acceptance 7.2.5
D-bit modification 7.2.6
Datagram facilities (all varieties) 7.3
2.3.14.1 Packet and Window Sizes: For selection of Flow Control
Parameters the BFE will default to a packet size of 128 octets
and a window size of 2 packets. These default parameters may be
changed if approved by the Defense Communications Agency. When
requesting a BIC, a host administrator may specify non-standard
defaults for packet sizes between 128 and 1024 octets, and for a
window size of between 2 and 7 packets. The host administrator
must also specify whether or not the BFE should negotiate these
values on a call by call basis. If the host administrator
chooses not to negotiate, the BFE will use the values specified
by the host administrator for all calls, incoming and outgoing.
If negotiation is selected, the BFE will offer a packet size of
1024 and a window size of 7 for incoming calls, and the host may
then respond with a smaller size if desired.
2.3.14.2 Emergency Mode Addressing: One new facility code has
been defined for use with BLACKER. It is called the Emergency
Mode Addressing Facility, and is defined in section 2.3.17.3.
2.3.15 Precedence: The BFE does not reallocate resources based
on the precedence facility supplied in a call request. It does
carry the precedence of a packet across the BFE to the call
request on the opposite interface. If the host does not supply
precedence on a CALL REQUEST packet, the BFE will assume that
precedence zero is requested, and send the CALL REQUEST out to
the network with precedence zero. This allows the host or
network to continue to act upon the precedence of a call.
Page 2-7
March 21, 1989
2.3.16 Diagnostics Codes
2.3.16.1 The BFE passes certain diagnostic information back to
the host to indicate status information on the communication path
and to provide security related information. Diagnostic informa-
tion is provided when the BFE becomes aware of a reportable
event. Two examples of such reportable events are a notice that
the BFE's network interface has come up, and that the BFE has
lost contact with its Access Control Center. However, there is
no guarantee that the BFE will be able to detect, or report,
anomalous situations that occur in the underlying black network.
2.3.16.2 Diagnostic information is sent in the diagnostic field
of an X.25 packet. For the X.25 diagnostic codes, the BFE will
use the values defined in the CCITT Recommendation and in the DDN
Specification with the following interpretations. DDN diagnostic
code (128), PSN Unavailable, will indicate that the DDN packet
switching node to which the BFE is connected is unavailable. DDN
diagnostic code (137), Remote PSN dead, will indicate that the
destination BFE is unreachable. See Appendix C for a full list
of diagnostic codes that may be generated by BLACKER.
2.3.16.3 Diagnostic information related to Emergency Mode status
(see section 2.3.17 below) will also be passed to the host at the
X.25 level.
DIAGNOSTIC packets may be sent by the BFE with the following
diagnostic codes:
Code
Entering Emergency Mode 224
Leaving Emergency Mode 225
Emergency Mode Window Open 226
CLEAR INDICATION packets may be sent by the BFE with the follow-
ing diagnostic codes:
Code
Call Failed--Address Translation Information Required 227
Call Failed--Emergency Window Open, BFE not in Emergency Mode 228
2.3.17 EMERGENCY MODE
2.3.17.1 One aspect of the BLACKER System operation is the ability
to communicate between BFEs in the absence of Access Control
Centers (ACCs) and/or Key Distribution Centers (KDCs). This
capability is referred to as Emergency Mode. The use of Emergency
Page 2-8
March 21, 1989
Mode may involve the host in some of the processing. When the
conditions exist which could result in the BFE entering Emergency
Mode, the BFEs action depends upon a start-up parameter contained
in the BIC. This parameter specifies one of three possible courses
of action. These actions are 1) remain in normal mode, i.e., not
communicate with BFEs that are operating in Emergency Mode, 2)
automatically enter Emergency Mode and so notify the host, or 3)
notify the host that conditions exist which allow the BFE to enter
Emergency Mode, but do not make the transition into Emergency Mode
until directed by the host. Paragraphs 2.3.16.3 and 2.3.17.3
provide further information on Emergency Mode diagnostic codes and
addressing.
2.3.17.2 Additionally, since the address translation table
contained in a BFE is maintained by the ACC, and in Emergency Mode
the BFE may not be able to communicate with the ACC, a host may be
limited as to what other hosts it can communicate with. In
Emergency Mode, the BFE will continue to be able to communicate
with all other hosts for which it has address translations,
providing all other access controls are passed. The optional X.25
facility defined in 2.3.17.3 allows a host to provide address
translation information to its BFE, and must be used if a host
requires flexibility while in Emergency Mode.
2.3.17.3 An additional optional user facility will be supported.
This facility will allow the DTE to provide the DDN address (Black
Internet Address) of the destination BFE for the address specified
in the CALL REQUEST. This facility will be accepted only when
Emergency Mode is enabled. The format is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1 0 0 0 0 0 1|0 0 0 0 0 1 0 0| 32 bit Black |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Internet Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The first byte in the facility is the identification code, 193 for
Black Internet Address. The second byte contains the length of the
following parameter value field. It must always contain the value
four. The remaining bytes contain the Black IP Address of the
destination host for this call. This address will be stored with
bits 0-7 in octet 3, bits 8-15 in octet 4, bits 16-23 in octet 5
and bits 24-31 in octet 6. Bit 0 will be the leftmost bit of octet
3, etc. A supplied address of all zeros is used to tell the BFE
that it should enter Emergency Mode and is sent in response to the
BFE message advertising the opening of the Emergency Mode Window
(2.3.16.3). If it is necessary for the host to provide the enter
Page 2-9
March 21, 1989
Emergency Mode command along with address translation information,
this facility must appear twice in the CALL REQUEST packet, with
the enter Emergency Mode command appearing first.
2.3.17.4 When a host administrator has requested that his BFE
never enter Emergency Mode, the host is not notified when the
Emergency Mode window opens or closes. A host whose administrator
has requested that his BFE always enter Emergency Mode is notified
via the diagnostic codes described in 2.3.16.3 when the BFE enters
and exits emergency mode. If a host administrator has requested
that his host participate in the BFE's decision to enter Emergency
Mode, the BFE will send the Emergency Mode Window Open diagnostic
to the host when the conditions for Emergency Mode exist. If the
host desires the BFE to enter Emergency Mode, it responds by using
the Emergency Mode Address Facility (2.3.17.3) with the address set
to all zeros. If the host does not wish to enter Emergency Mode,
no response is necessary. When the BFE restores contact with its
administrative nodes, it will send the host a Leaving Emergency
Mode diagnostic message.
2.3.18 Logical Channels: The BFE will support up to 128 simul-
taneous open logical channels. A logical channel for the BFE is
defined as the intersection of a source X.25 address, a destination
X.25 address, and an X.25 precedence.
2.4 INTERNET PROTOCOL FEATURES
2.4.1 In addition to the X.25 interface, the BFE requires the use
of IP as defined in MIL STD 1777. The only restrictions on the use
of IP are as follows:
2.4.2 The IP address is a 32-bit value consisting of a network
identifier and a network specific host field. There are different
formats for this address. The DDN Red Virtual Network (RVN) is a
class A network (net number 21) with the following format (see also
2.3.10):
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NETWORK | HOST |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2.4.3 The host connected to the BFE will provide the Red IP
destination address for the actual destination of each datagram.
The host will also supply the appropriate DDN-RVN X.25 address to
the BFE. In most cases, the X.25 address supplied by the host will
correspond to the actual destination red IP address, but in some
cases (e.g., IP devices not directly connected to a BFE) may be an
Page 2-10
March 21, 1989
X.25 address corresponding to a red gateway which is the next hop
to the actual red IP destination.
2.4.4 The maximum BLACKER IP datagram size is 896 eight-bit bytes
(octets). As required by MIL-STD 1777 (Para 9.2.2.2), IP datagrams
of more than 576 octets should only be sent if there is assurance
that the destination is prepared to accept the larger datagram. An
IP datagram must be sent as an X.25 complete packet sequence if the
datagram does not fit within a single X.25 packet. A packet or
complete packet sequence must contain exactly one IP datagram. If
IP datagrams are sent in multiple X.25 packets, no more than 32
incomplete datagrams (unfinished packet sequences) may be sent at
one time. Only single level hosts are allowed to send datagrams as
packet sequences. Hosts accredited to send datagrams at multiple
security levels must send and receive datagrams in single packets.
Any packet received from such a host with the 'more' bit set will
result in the call being CLEARed.
2.4.5 All IP datagrams must contain a sensitivity label as defined
by the Revised IP Security Option (IPSO) described in change 1 to
MIL-STD 1777. This must be the first option on all IP datagrams.
BLACKER is designed to make cryptographic distinctions on up to
eight hierarchical levels and sixteen non-hierarchical categories.
Appendix A provides the configuration to be used for the initial
BLACKER deployment on DSNET I.
2.4.6 The BFE has a limited amount of space available to buffer
datagrams. Datagrams for which authorizations already exist in the
BFE, are subject to normal flow control procedures, and are not a
problem. Outgoing datagrams that require new authorizations,
however, must be buffered until the proper permissions (or denials)
are received from the ACC. Up to five of these datagrams can be
buffered by the BFE at any time. The receipt of additional
outgoing datagrams requiring communication with the ACC will
overflow available buffer space, and such datagrams will be
discarded without notice. In order to minimize the likelihood of
such an event, a host administrator should ensure that the keys for
essential and high volume destinations are marked for preplacement
at the time the BIC is ordered from the ACC administrator.
2.4.7 The BLACKER System can support dual or multiple homing of a
host. The host must have one BFE for each port that is to be
connected to the network. Each BFE connected to this host must
have a different network and internet addresses. It is the
responsibility of two hosts to select which BFE of a multi-homed
host will be used for a connection between those hosts. (BLACKER
ACCs and KDCs can not be set up to have multiple addresses.)
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March 21, 1989
2.5 INTERNET CONTROL PROTOCOL FEATURES
2.5.1 The BFE also makes use of ICMP messages to indicate certain
information to the host.
2.5.2 The BFE will respond to ICMP ECHO REQUEST messages with ICMP
ECHO REPLY messages.
2.5.3 The BFE passes diagnostic information back to the host to
indicate status information on the communication path and to
provide security related information. Diagnostic information is
provided when the BFE becomes aware of a reportable event.
However, there is no guarantee that the BFE will be able to detect,
or report, all anomalous situations.
2.5.4 Diagnostic information will be passed in ICMP messages. A
DESTINATION UNREACHABLE (type 3) message will be sent when a
Request Denied message is received by the BFE from the ACC. Code
1, Host Unreachable, will be sent if the Request Denied message
indicates that the destination BFE is down. Code 10, Communication
with Destination Host Administratively Prohibited, will be sent if
the Request Denied message indicates that access is denied.
Page 2-12
March 21, 1989
3. BLACK-SIDE NETWORK INTERFACE
3.0.1 This section describes the DDN interface of all BLACKER
equipment connecting to the DDN. Host implementors need not
concern themselves with this section, except as background, or to
assist in ordering the proper type of interface line from DCA.
3.1 PHYSICAL LEVEL
The BFE will confirm to the following specifications:
1. "DEFENSE DATA NETWORK X.25 HOST INTERFACE SPECIFICATION",
DCA, DECEMBER 1983
2. EIA STANDARD RS-449, NOVEMBER 1977
3. MILITARY STANDARD 188-114, MARCH 1976
The BFE will support the signals as listed in Table B-2 of the DDN
X.25 Specification. No optional signals will be supported on the
network side.
In RS-449 terms, the BFE will support all Category I circuits in
the balanced mode. The BFE will also support all type Send-Receive
mandatory circuits for synchronous primary channel operation (see
Fig 5.1 in Specification 2). The RS-449 37-position connector with
a GLENAIR, INC., (or equal) backshell will be used on the network
interface.
The BFE will present a DTE interface to the network.
The BFE will operate at speeds from 1.2 to 64 kilobits per second.
Only full duplex synchronous operation will be supported. Data
timing will originate at the DCE. (Note: The signal names used
below refer to the RS-449 names used in the following table.) RT
signal will supply the data strobe for RD, ST will supply the data
request for SD, and TT will supply the data acknowledge/data strobe
for SD. This implies that the DCE will control data transfer rates
via RT and ST, and the DTE will use ST to generate the data strobe
signal, TT. The network DCE supplies timing to the BLACKER DTE and
the BLACKER DCE supplies timing to the host DTE.
Interface signal electrical characteristics will be as defined by
MIL-STD-188-114. The single deviation from this specification is
the Open Circuit Balanced Voltage Driver Output, which is 8 volts
+/- 2 volts, instead of 6 volts +/- 2 volts. Interface signal
functions, directions, and pin assignments will be as defined in
RS-449.
Page 3-1
March 21, 1989
LISTING OF SIGNALS SUPPORTED BY THE BFE BLACK-SIDE
PIN RS-449 ABBREVIATION DTE IS
1 SHIELD NO CONNECTION
2 SI IB+
3 SPARE
4 SD BALANCED GENERATOR
5 ST BALANCED RECEIVER
6 RD BALANCED RECEIVER
7 RS BALANCED GENERATOR
8 RT BALANCED RECEIVER
9 CS BALANCED RECEIVER
10 LL -5
11 DM BALANCED RECEIVER
12 TR BALANCED GENERATOR
13 RR BALANCED RECEIVER
14 RL -5
15 IC IB-
16 SF/SR +5
17 TT BALANCED GENERATOR
18 TM IB-
19 SG CIRCUIT GROUND
20 RC DCE CIRCUIT GROUND
21 SPARE
22 SD ( see pin 4 )
23 ST ( see pin 5 )
24 RD ( see pin 6 )
25 RS ( see pin 7 )
26 RT ( see pin 8 )
27 CS ( see pin 9 )
28 IS +5
29 DM ( see pin 11 )
30 TR ( see pin 12 )
31 RR ( see pin 13 )
32 SS -5
33 SQ IB+
34 NS -5
35 TT ( see pin 17 )
36 SB IB-
37 SC DTE CIRCUIT GROUND
ABBREVIATIONS OTHER THAN RS-449 SIGNAL NAMES
IB- PIN IS OPEN, INTERNAL BIAS OF MINUS FIVE VOLTS (OPTIONAL)
IB+ PIN IS OPEN, INTERNAL BIAS OF FIVE VOLTS (OPTIONAL)
Page 3-2
March 21, 1989
3.2 LINK LEVEL
The BFE will conform to the following Link Level specifications:
1. "DEFENSE DATA NETWORK X.25 HOST INTERFACE SPECIFICATION",
DCA, DECEMBER 1983
2. "INTERFACE BETWEEN DATA TERMINAL EQUIPMENT (DTE) AND
DATA CIRCUIT TERMINATION EQUIPMENT (DCE) FOR TERMINALS
OPERATING IN THE PACKET MODE ON PUBLIC DATA NETWORKS",
RECOMMENDATION X.25, CCITT, 1980
3. "WD2512 X.25 PACKET NETWORK INTERFACE (LAPB)", WESTERN
DIGITAL CORP., SEPTEMBER 1988 (PRELIMINARY),
APRIL 1989 (EXPECTED FINAL DATE).
At level 2, the BFE will use the DDN X.25 High Level Data Link
Control, Link Access Procedure - Balanced (HDLC-LAPB) interface
protocol.
On the PSN/black side the BFE will be a DTE.
The HDLC-LAPB interface in the BFE will be implemented using the
Western Digital WD2512 Packet Network Interface Chip. This chip
handles bit oriented, full duplex serial data communications on its
Level 1/Level 2 interface side. The computer interface side uses
direct memory access.
The "Transparent Modes" of the WD2512 chip, as described in
specification three above, will not be used.
3.3 PACKET LEVEL
3.3.1 The BFE network interface to DDN conforms to the DDN
interface specification dated December 1983.
3.3.2 Type of Service: The BFE interface offers a DDN Standard
Service interface to the network. It may operate with a DDN Basic
Service interface on the network side only.
3.3.3 Packet Size: The BFE is designed to operate with a maximum
packet size of 1024 bytes but will also operate at 128, 256, or 512
bytes. Operating with a maximum packet size of less than 1024 bytes
may significantly degrade performance.
3.3.4 The BFE does NOT make use of INTERRUPT service and does not
set the D-bit or Q-bit.
Page 3-3
March 21, 1989
3.3.5 Call User Data Restriction: For the protocol identification
information in the X.25 call, the BFE will use CC hex (11001100
binary) to indicate that IP is the next higher level protocol.
When IP is not used on the network interface, the value C5 hex
(11000101 binary) is used to indicate that the next layer of
protocol is the encryption layer. IP is only used on the black
side of the BFE when the connection will have to pass through a
gateway on the black network.
3.3.6 Call Request: The BFE supports INCOMING CALL and CALL
REQUEST packets that specify either a logical or physical address.
However, it has no capability to issue declarative CALL REQUEST
packets which add or delete logical names.
3.4 INTERNET PROTOCOL (IP) FEATURES
3.4.1 The BFE will send IP datagrams of up to 1024 bytes.
3.4.2 IP Header: The BFE may include or omit an IP header on the
network side when sending various types of datagrams. These
datagrams will be marked in accordance with section 3.3.5. The BFE
will use an IP header when sending datagrams through a gateway on
the black network, or when sending traffic that is not encrypted
(e.g., ICMP ECHO REPLIES to a black network host).
3.4.3 IP Address: The BFE takes the DDN-RVN address (2.3.10) and
generates the Black IP address via a table lookup. This table in
the BFE contains address translations for the BFE's domain, and
some interdomain BFE address translation information. This table
is normally maintained by the Access Control Center (ACC) for the
BFE. However, information for this table may also be provided by
the host when the BFE is in Emergency mode (2.3.17.3).
3.4.4 X.25 Address: The Black X.25 network address is generated
from the Black IP address via the algorithm defined for DDN. The
BFE will support the full DDN address translation algorithm for
both physical and logical addresses.
3.5 INTERNET CONTROL MESSAGE PROTOCOL (ICMP) FEATURES
3.5.1 The BFE will be capable of receiving all ICMP message types
and of generating at least ECHO REPLY, PARAMETER PROBLEM, and
DESTINATION UNREACHABLE messages.
Page 3-4
March 21, 1989
A. Initial DDN Sensitivity Labels
Hierarchical Levels
Value Code Name
7 0000 0001 (undefined)
6 0011 1101 TOP SECRET
5 0101 1010 SECRET
4 1001 0110 CONFIDENTIAL
3 0110 0110 (undefined)
2 1100 1100 (undefined)
1 1010 1011 Unclassified
0 1111 0001 (undefined)
Non-Hierarchical Compartments
Value Option Type *Bit number Name
0 BASIC 0 GENSER
1 BASIC 1 SIOP-ESI
2 BASIC 2 SCI
3 BASIC 3 NSA
4 - 15 (undefined) (undefined) (undefined)
*numbered from left to right
Page A-1
March 21, 1989
B. REFERENCES
1. "DEFENSE DATA NETWORK X.25 HOST INTERFACE SPECIFICATION",
DCA, DECEMBER 1983, available from the Defense Technical
Information Center, Cameron Station, Alexandria Va 22314, (202)
274-7633, order number AD-A137 427.
2. EIA STANDARD RS-449, NOVEMBER 1977, available from The
Electronic Industries Association, 2001 Eye Street, N.W.,
Washington, DC 20006.
3. MILITARY STANDARD 188-114, MARCH 1976, available from the
Naval Publications and Forms Center, 5801 Tabor Avenue,
Philadelphia, PA 19120.
4. "INTERFACE BETWEEN DATA TERMINAL EQUIPMENT (DTE) AND DATA
CIRCUIT TERMINATING EQUIPMENT (DCE) FOR TERMINALS OPERATING IN THE
PACKET MODE ON PUBLIC DATA NETWORKS", RECOMMENDATION X.25, CCITT,
1980, available from the National Technical Information Center,
U.S.Department of Commerce, Springfield, VA 22161, order number
PB82-187766.
5. "INTERFACE BETWEEN DATA TERMINAL EQUIPMENT (DTE) AND DATA
CIRCUIT TERMINATING EQUIPMENT (DCE) FOR OPERATIONS WITH PACKET-
SWITCHED DATA COMMUNICATION NETWORKS", FED-STD 1041; FIPS PUB 100,
6 JULY 1983, also available from the National Technical Information
Center, U.S.Department of Commerce, Springfield, VA 22161.
6. "WD2512 X.25 PACKET NETWORK INTERFACE (LAPB)", WESTERN
DIGITAL CORP., SEPT. 1988 (PRELIMINARY), APRIL 1989 (FINAL),
available from Western Digital, 2445 McCabe Way, Irvine CA 92714,
(714) 474-2033.
7. "REVISED INTERNET PROTOCOL SECURITY OPTION", Department of
Defense, to be issued, (change 1 to MIL STD Internet Protocol / MIL
STD 1777, 12 Aug 1983), available from the Naval Publications and
Forms Center, 5801 Tabor Avenue, Philadelphia, PA 19120.
Page B-1
March 21, 1989
C. BLACKER Generated Diagnostic Codes
Diagnostic Code Value
No additional information 0
Invalid P(S) 1
Invalid P(R) 2
Packet type invalid -
for state r1 17
for state r3 19
for state p1 20
for state p3 22
for state p7 26
for state d1 27
for state d3 29
Packet not allowed 32
Packet too short 38
Packet too long 39
Restart with nonzero LCGN and LCN 41
Timer expired 48
for incoming call 49
for clear indication 50
for reset indication 51
for restart indication 52
Call set-up problem 64
Facility code not allowed 65
Facility parameter not allowed 66
Invalid called address 67
Invalid calling address 68
Invalid facility length 69
Local PSN Unavailable 128
Network side interface came up 130
Remote BFE dead 131
Local resources not available 133
Remote resources not available 134
Remote host (or red gateway) unavailable 136
Remote PSN (or black gateway) unavailable 137
Calling logical address not enabled 141
Calling logical name incorrect for this DTE 142
Called logical name not authorized 143
Called logical name not enabled 144
Called logical name has no DTEs 145
Page C-1
March 21, 1989
Diagnostic Code Value
Logical addressing invalid for the Black network 146
Standard Service not requested (see 2.3.4) 155
Invalid protocol identification (see 2.3.5) 156
Cleared due to higher precedence call 192
Requested precedence too high 194
Entering Emergency Mode (see 2.3.17) 224
Leaving Emergency Mode (see 2.3.17) 225
Emergency Mode Window Open (see 2.3.17) 226
Address translation needed (see 2.3.17) 227
Emergency Mode Window Open but not in
Emergency Mode (see 2.3.17) 228
Diagnostic Code 0 will be sent in:
- a CLEAR INDICATION when
- more than 32 calls have unfinished packet sequences.
- a multilevel host uses the M bit.
- BFE table resources are at full capacity.
- a logical channel idle timer expires.
- the host sends a non-zero CLEAR REQUEST code.
- a RESET INDICATION when
- a packet reassembly timer expires.
- the host sends a non-zero RESET REQUEST code.
Page C-2