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ATM for Naval Applications
Rodney A. Colton, CDR USNR (Ret), RF Microsystems, Inc.
4900 Seminary Road, Suite 210
Alexandria, Virginia 22311-1811
(703) 671-2777
coltonr@rfmdc.com
J. Airst, David Aschkenasy, Deborah L. Goldsmith, Ph.D.
The MITRE Corporation
c/o SSC SD, Bldg. 626
49185 Transmitter Road
San Diego, CA 92152-7335
(619) 758-7829
mairst@mitre.org, daschken@mitre.org, deborah@mitre.org
Abstract- As a tactical user of network services, the Navy
is distinguished by its mobility and its use of low-
bandwidth wireless links. ATM technology optimizes
bandwidth usage and guarantees QoS for high priority
applications. However, wireless and low data rate ATM
specifications are just beginning to have commercial
availability. This paper discusses the status of emerging
ATM specifications that will satisfy Navy tactical
communications requirements.
I. INTRODUCTION
Modern and developing communications technology
allows a single network infrastructure to transport voice,
video, and data. Asynchronous Transfer Mode (ATM)
technology is an enabler of integrated services networks
that also provides the Quality of Service (QoS)
necessary to guarantee reliability for critical military
applications.
The Navy is a tactical user of network services, and
as with other tactical users, it is distinguished by its
mobility. Mobility introduces low-bandwidth wireless
links into the networking architecture. An important
concern therefore is that the capacity of these links be
used in an optimal manner, consistent with the Navy’s
Communications Plan of priority and precedence.
Through the use of ATM technology, bandwidth usage
is optimized, since ATM connections only use
bandwidth when there is data to be transmitted. ATM
QoS ensures that high priority data will access wireless
links before low priority data, and, if no high-priority
data is present, that the link capacity will be made
available to lower-priority applications.
Today, integrated services networks and commercial
ATM products are targeted at mainstream fixed users.
Mobile users enjoy the support of few commercial
products. However, additional standards and products
are under development and will be available shortly.
The purpose of this paper is to describe specific ATM
standards that will be the mainstay of Navy tactical
communications. ATM networks are being deployed on
mobile platforms such as ships and airplanes to support
onboard operations, and on the shore backbone Wide
Area Network (WAN), the Defense Information System
Network (DISN).
II. DISA ATM MANDATE
The backbone of the Navy-Wide Intranet (NWI) is
the DISN. The DISN is defined as the subset of the
Defense Information Infrastructure (DII) that provides
information transport services both within the DII and
across DII boundaries (i.e., with Academia, Industry,
and other Government, as well as with Allied and
Coalition Forces). The DISN includes Sustaining Base,
Long Haul, and Tactical/Deployed information transport
services components of the DII. In order to ensure
DoD-wide interoperability of ATM systems and
services, the Joint Interoperability and Engineering
Organization (JIEO) arm of the Defense Information
Systems Agency (DISA) has mandated compliance with
DoD ATM specifications [1] – [3], for all ATM systems
and services that are integral to or that inter-operate
with the DISN1
. The DISA ATM specifications must be
supported on all Navy platforms and on the tactical
WAN connection in order for the DISN to be the
backbone of the Navy’s end-to-end joint tactical
communications.
III. TACTICAL ATM EMERGING STANDARDS
Emerging ATM standards and specifications will play
an essential role in enabling Navy tactical
communications. Standards and specifications relevant
to tactical communications include: ATM Trunking
using AAL2 for Narrowband Services (LLT2), Low
1
DISA Memorandum dtd April 20, 1998
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Speed Circuit Emulation Services (LS-CES), the Real-
Time Multimedia over ATM (RMOA) Technical
Committee Working Group specification Gateway for
H.323 Media Transport over ATM, Wireless ATM
(WATM, btd-watm-01.10), Mobility Extensions for
Private Network to Network Interface (M-PNNI), and
PNNI Transportable Address Stack (TAS).
A. LLT2
For voice applications requiring bandwidth
efficiency, the DoD ATM Standards document has
mandated LLT2. This specification utilizes voice
compression with optional silence detection over
variable bit rate ATM service, to carry voice calls at
rates as low as 2.4 kilobits per second (Kbps). While a
number of voice compression algorithms are optionally
available through this specification, DISA has recently
adopted G.729 (8-Kbps) as the default compressed
voice algorithm for use with non-secure (bulk
encrypted) military voice. Users are responsible to
ensure that all their LLT2-capable ATM edge switches
support the default G.729 and G.711 algorithms.
Vendors have stated that they will support this recently
approved specification (March ’99).
B. LS-CES
Low Speed Circuit Emulation Services using CBR-
AAL1 (approved June’99) allows dynamic circuit setup
at selectable rates between 75 bps and 2.048 Mbps (E1).
This protocol is capable of switching low speed
synchronous serial interfaces (e.g., EIA-RS449 and
EIA-530) used for Navy baseband equipment (e.g.,
cryptographic equipment and radio modems), and can
be used for switching encrypted, synchronous voice.
C. Gateway for H.323 Media Transport over ATM
The ATM Forum and the ITU-T are developing a set
of standards and specification titled Gateway for H.323
Media Transport over ATM. Products implementing
these documents will be able to efficiently carry H.323
multimedia traffic over ATM using header translation
and compression. Today, H.323 over IP results in
extremely inefficient transport due to the combination
of Real Time Protocol (RTP), Real Time Control
Protocol (RTCP), H.225 Call Signaling, H.245 Control
Signaling, User Datagram Protocol (UDP), Internet
Protocol (IP), and others. Using header translation and
mapping, H.323 overhead via ATM is far lower than
over IP. H.323 over ATM can also make use of ATM's
QoS. Gateway for H.323 Transport over ATM removes
redundant header information, and uses ATM signaling
to set up Switched Virtual Circuits (SVCs) that utilize
ATM’s QoS guarantees.
D. Forward Error Correction (FEC) for ATM over
Radio Frequency (RF)
ATM over satellite techniques include forward error
correction (FEC) with adaptive and per Virtual Circuit
(VC) encoding, and physical layer multicasting. Lucent,
COMSAT, GTE and others are working on a
specification for FEC at the ATM layer ([4], [5], [7]).
The TR34.1 section of the Telecommunications
Industries Association (TIA) has formed a liaison with
the ATM Forum to develop a Common ATM Satellite
Air Interface Interoperability Specification (CASI) to
deal with FEC at the data link layer, and other satellite
related issues. This document has a scheduled
completion date of Q2/99.
E. WATM and M-PNNI
The ATM Forum is developing standards that support
location management and traffic handover for mobile
users. Cellular telephone service provides an excellent
model on which to base the evolving standards.
Location management allows users to move about the
fixed infrastructure (roam) and maintain the ability to
make calls to and receive calls from a static address.
Boeing and IBM are active participants in the Wireless
ATM (WATM) Working Group (WG) and the Routing
and Addressing (RA) WG. The mobility extensions to
PNNI (M-PNNI) were approved in June 99. M-PNNI
provides a robust connectivity service that eliminates
the impact of mobility on new and existing connections
as long as connectivity exists. A WATM draft
specification defines mechanisms to allow active ATM
virtual circuits (VCs) to be dynamically rerouted when
an ATM switch changes its connectivity, i.e., enters a
new “cell” (mobility is hidden from users and
applications). Shipboard Navy ATM switches will
change connectivity as ships move between satellite
footprints. In addition, the Boeing Company has
developed a phased array antenna system that provides
trigger information to M-PNNI enhanced ATM switches
([8]). In this way, circuits can be rerouted prior to losing
the connection, when the RF signal becomes weak. The
proposed standards optimize use of scarce resources
such as the bandwidth of low-capacity satellite links.
Other applications of mobile PNNI include circuit
migration after switch or link failure or in preparation
for switch or link maintenance. The migration technique
used by the mobility extensions to PNNI has wide
applicability.
Another mobility enhancement is in the area of ATM
addressing. Addresses are used to locate end-stations.
Current DoD strategy does not directly support either
end-station mobility or network mobility, as in the case
of ships. DISA has drafted an addressing plan that
allocates addresses in a hierarchical manner based on
geographical location. Using today’s ATM routing
standards and the DISA addressing plan, tactical
network users would have to readdress their systems
each time they relocate, placing a burden on the end
user. Routing exceptions (generated when users are no
longer reachable through their old routes) are not
handled by the DISA network. Direct support for
mobile networks is the focus of the WATM Working
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Group, and includes “transportable addresses” and
“gateway” or “edge” networks to support the mobile
users, such as is described in the Boeing/IBM White
Paper ([6]).
A very important bandwidth-conservation and stealth
technique for the Navy is multicasting and the passive
broadcast. One of the multicast support issues
identified in the WATM Portland meeting, October
1998, was the ATM over satellite issue ([9]). IP
multicasting routing protocols can provide a tunnel for
multicast stream forwarding between IP routers, but this
does not provide a single multicast tunnel to all mobile
platforms in the same satellite footprint, to conserve the
air-to-ship bandwidth. Although multicast support can
be achieved at different layers of the protocol stack,
including ATM layers, it is clear that a MAC layer
approach is the only approach that can take full
advantage of the satellite broadcast media
characteristics. With this approach, for each multicast
local identifier associated with a multicast group, a
point-to-multipoint VC is set up between the multicast
controller and the stations in the group, but because of
the broadcast nature of the medium, no cell duplication
is necessary.
Since the ATM layer was initially defined for the
point-to-point environment (terrestrial telephone
networks), extensions to PHY and MAC service are
required to take into account the shared media
environment of the satellite RF. ATM multicast over
satellite can be accomplished if a multicast addressing
scheme (similar to RFC 1112 extensions of IP
multicasting to Ethernet or IEEE 802.14) can be
incorporated into the WATM radio level of the
mobility-enhanced ATM switch. Close coordination has
been ongoing with TIA TR34.1 in view of the TR34.1
mandate to address the MAC layer issues for satellite
access.
IV. DOD ATM ADDRESSING
Recognizing the current limitations of the DoD
ATM Addressing Plan for deployable and fixed network
interfaces, DoD has adopted the following strategic
policy:
1. For the interim, DISN deployable systems will
adopt the addressing instructions described in
Section 5.1.3 of the Addressing Plan, and
2. The DISN objective architecture for interfacing to
commercial, deployable and foreign national
networks shall employ the Bi-Level addressing
method currently under development by the ATM
Forum.
Prefix Rt Dmain G Rs Area SysID nS
47:00:06/01/XX:XX:00:XX/81/00/12:34:56/XX:XX:XX:XX:XX:XX/XX
Fig. 1. DOD ATM Addressing
Neither the equipment nor the standards required to
develop such equipment support the Bi-Level
addressing method exist today. Several years must pass
before standards are completed and additional years
may be required for products to appear and then several
budget cycles will be required to deploy a complete
infrastructure. The interim addressing plan chosen by
the DOD will be in use for several years.
V. THE ATM FORUM PROCESS
ATM originated in the International
Telecommunications Union (ITU), which sets standards
for the world’s telephone and other public networks.
The ATM Forum augments the ITU as the
specifications setting body for public and private ATM
networking. Officially known as an implementers'
agreement body, its role is to push the development of
specifications that drive early availability of ATM
products and services.
Approval by the ATM Forum of a specification
must follow a rigorous procedure. The steps of this
procedure consist of Baseline Text Document, Straw
Ballot, Final Ballot and Letter Ballot. Two to nine
months after the approval of an ATM specification,
vendors tend to incorporate the specification into
commercial products. Interoperability testing is
sometimes performed among vendors, but is ultimately
the responsibility of the customer (e.g., DISA). The
approval process is as follows:
A. Baseline Text Document
The relevant Technical Committee Working Group (TC
WG) agrees that it has substantially completed the
Baseline Text Document.
B. Straw Ballot
The WG then votes for the document to go to the Straw
Ballot process at the ATM Forum Working Group level.
At this time, the technical content is thought to be
complete, and all the working group members have had
a chance to comment. If all comments have been
resolved, it is assumed the members will vote “yes” in
the Straw Ballot. (Members with no comments are
assumed to vote “yes”.) Once the comments are
adjudicated, then the document is submitted to final
ballot.
C. Final Ballot
Submission to Final Ballot is a three-step process:
1) Working group approval: All comments are resolved
at the working group level. A vote is then taken at the
working group level by the representatives of the
Principal Member companies. Principal Member
companies are those organizations with authority to
write and modify Forum specifications by virtue of their
paying the requisite membership fee. A two-thirds
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majority vote is required for approval by the working
group.
2) Technical committee approval: Upon approval, the
specification is put before the complete Technical
Committee. All Principal Member companies are
represented at the complete technical committee. Again,
a two-thirds majority vote is required by the Technical
Committee for approval.
3) Board of Directors approval: The proposed
specification must be approved by the ATM Forum’s
Board of Directors. This to ensure that editorial quality
is maintained, and to de-conflict efforts with those of
other standards’ groups. This vote is usually pro-forma,
and happens very quickly.
D. Letter Ballot
Letter Ballot is the final formal vote process. A two-
thirds majority vote by the Principal Members by a
formal written or e-mail vote is required for approval by
the ATM Forum. This process can last up to one month.
At the end of this process, the specification is
approved.
VI. STATUS OF EMERGING SPECIFICATIONS
Table 1 indicates where emerging “tactical” ATM
specifications sit in the ATM Forum standards process.
These documents are available on-line to ATM Forum
Principal Members.
VII. CONCLUSION
ATM is a viable technology that is capable of
supporting the needs of military communications. This
paper has presented a brief look at emerging ATM
standards and specifications that will play an important
role in the Navy’s architecture for tactical
communications. It is extremely important that the Navy
establishes and maintains involvement in the ATM
standards development process in order to be assured
that future implementation of ATM technologies can be
achieved using commercially available equipment. The
alternative, proprietary, sole source commercial
equipment or costly and lengthy government-sponsored
special development, is unacceptable in today’s military
environment.
TABLE 1
STATUS OF EMERGING ATM SPECIFICATIONS
Spec Name Spec Number Description Status Expected Approval
ATM Security Framework af-ra-0096.00 Enhances security of user data Approved 2/98
ATM Trunking Using AAL2 for
Narrowband Services
af-vtoa-
0113.000
Used to compress and multiplex
voice calls on narrowband RF links.
Approved 2/99
Inverse Multiplexing over ATM (IMA)
V1.1
af-phy-
0086.001
Combines multiple T1’s into an
aggregate output.
Approved 4/99
PNNI Mobility Extensions V1.0 af-ra-0123.00 Reroutes connections as the user
transitions satellite spot beams or
base stations.
Approved 6/99
PNNI Transported Address Stack, V1.0 af-phy-
0086.001
Used for mobile forces address
tunneling.
Approved 6/99
Multi-Protocol over ATM, V1.1 af-mpoa-
0114.000
Allows ATM to interconnect
multiple logical IP subnets (LISs) or
LANs without an IP Router.
Approved 6/ 99
PNNI V1 Security Signaling Addend. af-cs-0116.000 Enhances PNNI signaling security. Approved 6/ 99
UNI Signaling 4.0 Security Addendum af-cs-0117.000 Enhances UNI signaling security. Approved 6/99
Low Speed Circuit Emulation Service
(LS-CES)
af-vtoa-
0119.000
Allow low speed synchronous serial
devices (75 bps to 2.048 Mbps) to be
connected to an ATM network.
Approved 6/99
Traffic Management V4.1
(Include Guaranteed Frame Rate (GFR)
af-tm-0121.000 Guarantees QoS and maximizes
efficiency of IP over ATM.
Final Ballot July-99
H.323 Media Transport over ATM af-saa-0124.000 Efficient H.323 over ATM using
header translation and compression.
Final Ballot Q2/CY99
Wireless ATM V1 (WATM) N/A WATM WG supports mobility,
handoff, & ATM over satellite.
Draft, in prog. Q2/FY00
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REFERENCES
[1] L. Bowman, “DoD DISN ATM Specification”,
Version 1.2c, 17 April 1998,
bowmanl@ncr.disa.mil,
http://www.disa.atd.net/DISNATM_DOCS/
[2] G. Bradshaw, “DoD ATM Addressing Plan,”
Version 1.0, 17 April 1998, bradshag@ncr.disa.mil,
http://www.disa.atd.net/DISNATM_DOCS/
[3] D. Choi, “DoD ATM Standards,” Version 1.0, 17
April 1998, choid@ncr.disa.mil,
http://www.disa.atd.net/DISNATM_DOCS/
[4] COMSAT Corporation ,“COMSAT Innovation
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http://209.207.228.58/company_info/index_set.htm
[5] COMSAT Corporation, “COMSAT Link
Accelerators (CLA-2000)”, Copyright© 1997-99,
http://209.207.228.58/company_info/index_set.htm
[6] IBM Corporation, “IBM Mobile ATM Networking
Technology Overview”, White Paper, Version 2,
August 1998
[7] Lucent Technologies, “LANET: Adapting ATM in
Low Speed Environments”, Copyright © 1999,
http://www.lucent.com/dns/library/white_papers/la
net.html
[8] C. Ramey and D. Sloan, “Boeing Demonstrates
Advanced Communications Capabilities At EFX
'98”, Sept. 11, 1998,
http://www.boeing.com/news/releases/1998/news_r
elease_9809b.html
[9] WATM SWG, “Applicability of Existing
Techniques for ATM Multicast over Highly
Asymmetric Satellite Links”, Document No.
ATM_Forum/98-0711
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