As per Relevance of the word broadcast, we have this rfc below:
Network Working Group C.
Request for Comments: 1770 US Army
Category: Informational March 1995
IPv4 Option for Sender Directed Multi-Destination
Status of this
This memo provides information for the Internet community. This
does not specify an Internet standard of any kind. Distribution
this memo is unlimited
This memo defines an IPv4 option to provide a sender directed multi
destination delivery mechanism called Selective Directed
Mode (SDBM). The SDBM provides unreliable UDP delivery to a set
IP addresses included in the option field of an IPv4 datagram.
reliability if required will be provided by the application layer
This approach was developed to support sender directed multi
destination delivery to sparsely populated groups with no
control traffic. This approach will find application in
extremely bandwidth constrained tactical military environment,
well as in some commercial applications requiring sender control
data delivery
The Selective Directed Broadcast Mode (SDBM) is an integral part
the U.S. Army standard for tactical data communication networks
defined in MIL-STD-188-220() (Reference 1). The MIL-STD-188-220()
defines a protocol architecture for the lower four layers of
ISO-OSI Reference model. The MIL-STD-188-220() is
undergoing a reformatting to be consistent with other DoD
that deal with IP networking. These efforts will provide tactical
internetting of tactical Army broadcast radio networks, and
support fully IP compliant internetworking to other types of
networks via commercial IP routers. It is the goal of the U.S.
to move toward a fully IP compliant internetwork architecture for
tactical battlefield data communications. The Army does, however
have a critical need for a reliable, sender directed multi
destination data transfer capability that is not currently
by the existing or emerging internet standards. The SDBM IP
was developed to meet this need. The required data reliability
be provided by incorporating an acknowledgement strategy at
application layer. It is hoped that this IP option, providing multi
destination capability not currently provided by the current
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RFC 1770 Selective Directed Broadcast Protocol March 1995
emerging internet standards, will be embraced by the
community and become an integal part of the IP family of
and be incorporated in commercial IP software products
SDBM
The SDBM provides the ability for an application to explicitly list
set of intended IP destinations. This capability will be
as an option in the IP layer, as shown in Figure 1. This option
is variable in length, up to a maximum of 40 octets due to
limitation of the HLEN field as specified in STD 5, RFC 791
(Reference 2). Under this option 38 of the 40 octets would be used
contain the 2 octet control field and a maximum of 9 IP addresses
1 8 16 31
***************************************************
| | | |
| | | |
| TYPE | LENGTH | IP ADDRESS 1 |
| | | |
| | | |
|*************************************************|
| | |
| IP ADDRESS 1(Cont) | IP ADDRESS 2 |
| | |
| | |
|*************************************************|
| | |
| IP ADDRESS 2(Cont) | .......... |
| | |
| | |
|*************************************************|
| | |
| | |
| .......... | IP ADDRESS N |
| | |
| | |
|*************************************************|
| | |
| IP ADDRESS N(Cont) | UNUSED |
| | |
| | |
***************************************************
Figure 1 IP Option Field
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RFC 1770 Selective Directed Broadcast Protocol March 1995
The TYPE field specifies the copy flag, class, and option number
The copy field indicates whether or not this option field is to
copied into each fragment if the IP datagram is fragmented. The
field and option number field are set to 0 and 21 respectively.
format of the TYPE field is shown at Figure 2.
1 8
**************************************************
| | | |
| COPY | CLASS | OPTION NUMBER | = 149
| | | |
**************************************************
Figure 2 Type Field
Since the IP multi-address list shall always be copied to all
headers during fragmentation, the COPY bit should be set to 1.
Returning to Figure 1, the LENGTH octet indicates how many octets
in the option field. It is calculated as
LENGTH = 2 + 4*(number of IP addresses
The remaining octets contain the IP addresses of the
destination hosts. Each IP address occupies 4 octets
Transmission of SDBM
The procedures for a source host, transit router, and
router are provided below. When a source host has a message to
to multiple destination hosts, it shall
a. Group the destination host internet addresses by their
identifiers (Net IDs). If there are N distinct Net IDs, there
be at least N distinct directed broadcast packets. If there
more that 9 destination hosts on a single net, multiple
broadcast datagrams must be sent to that net
b. For each Net ID, form the directed broadcast address as defined
STD 3, RFC 1122 (Reference 3) for that network. The
broadcast address is used as the destination address in the
datagram and the source address is the address of the host
the message
c. Place the entire IP address for up to 9 destination hosts in the
the same net in the option field defined above. The total length
all IP options in a given datagram is limited to 40 octets
determined by the HLEN (Header Length) field which defines
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RFC 1770 Selective Directed Broadcast Protocol March 1995
number of 32 bit words in the header. If other options are to
included in addition to the SDBM option, the number of addresses
the option field must be reduced accordingly
d. The thusly formed datagram shall be transmitted and
according to normal datagram handling procedures
When a IP SDBM datagram encounters a transit router (router
connected to the destination network), the datagram shall
processed in accordance with normal IP datagram handling procedures
When encountering the destination router (the destination network
directly attached to the router), the destination router
perform a, b or c below
a. If the local subnet has a broadcast capability, broadcast to
hosts in the network and let the hosts perform address filtering
b. If the local subnet does not support broadcast, form a local
packet for each destination host in the SDBM datagram and
into the network
c. If the local subnet supports reliable layer 2 multi-
capability as provided by MIL-STD-188-220() networks, use a layer 2
multi-address frame to deliver the datagram to addresses found
the IP option field
Reception of SDBM
In processing received SDBM datagrams, receiving hosts shall
inside the IP option field for their address. Processing
continue only if the host's IP address is found inside this
field. Thus the source host has explicit control over which
will process its datagrams. Since SDBM uses a broadcast address
its destination field, the SDBM can only be used with UDP (
4) and not TCP (Reference 5) as the TCP supports only point-to-
connections and not point-to-multi-point
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RFC 1770 Selective Directed Broadcast Protocol March 1995
Source for MIL-STD-188-220()
The above mentioned MIL-STD-188-220() may be obtained by
US Army Communications Electronics
AMSEL-RD-SE-AIN-E (ATTN: Mr. Ted Dzik
Fort Monmouth, NJ 07703
Comm: (908) 532-1780
Fax: (908) 532-3398
EMail: DZIK@ain3.monmouth.army.
The author wishes to acknowledge the major contributions to this
made by Mr. Dave Macauley of ATT and Ms. Barbara Denny of
International. Other contributions were made by members of the 188-
220() committee
(1) "MIL-STD-188-220() For Task Force XXI, Interoperability
for Digital Message Transfer Device Subsystems, 23 December 1994.
(2) Postel, J., "Internet Protocol - DARPA Internet Program
Specification", STD 5, RFC 791, DARPA, September 1981.
(3) Braden, R., Editor, "Requirements for Internet Hosts --
Communication Layers" STD 3, RFC 1122, IETF, October 1989.
(4) Postel, J., "User Datagram Protocol", STD 6, RFC 768,
USC/Information Sciences Institute, August 1980.
(5) Postel, J., "Transmission Control Protocol - DARPA
Program Protocol Specification", STD 7, RFC 793, September 1981.
Security
Security issues are not discussed in this memo
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RFC 1770 Selective Directed Broadcast Protocol March 1995
Author's
US Army Communications Electronics
AMSEL-RD-ST-LA-L ( ATTN: Charles Graff )
Ft. Monmouth, NJ 07703
Phone: (908) 544 3264
Fax: (908) 544 2150
EMail: bud@fotlan5.fotlan.army.
Graff [Page 6]
if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
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