The field of networking is growing in both the deployment and development of new technologies. This makes it difficult for most technical professionals to keep abreast. Although the concept of wireless networking is not particularly new, recent developments within the Navy have made wireless networking a viable solution.
First for a little background. Some years ago a segment of the ham-radio enthusiasts were fascinated with the concept of developing TCP/IP-based wireless networks. Initially, as many dreams do, the idea seemed far fetched. As time passed, it became reality.
The first studies of packet networking were conducted by the Rand Corporation in the mid-1960s. In packet networks, streams of data moving from one computer to another are reduced to chunks and given headers containing the necessary routing information. Computers on the network examine these headers and move the data packets through the network towards their final destination.
Because the routing intelligence is distributed among the network's nodes, packet networks are self-healing. If one node goes out, packets are routed around it. This was of particular value to DoD, which was interested in a network architecture that would survive a nuclear attack. In addition, packet networks provide:
Work began in 1969 on an actual packet network, called ARPANET, which developed and implemented a set of protocols called TCP/IP (Transport Control Protocol/Internet Protocol). The ARPANET ultimately evolved into today's Internet.
In 1970, radio technology and packet networks were brought together for the first time, and a radio network called ALOHANET, based at the University of Hawaii, was put into operation. ALOHANET linked a number of computers and users together with radio. It also had access to satellite relays and the ARPANET. It dealt successfully with the issue of packets colliding in an environment where, potentially, any radio could be trying to talk at any given moment. ALOHANET's approach to the issue of CDMA (collision detection/multiple access) was the basis for the Ethernet standard, now promulgated in local area networks worldwide.
In early 1979, an amateur radio group in Vancouver developed the first hardware devices dedicated to packet-radio communications, called TNCs (terminal node controllers). Development of radio hardware and specialized protocols accelerated after May 1980, when the Federal Communications Commission (FCC) authorized amateur packet radio operations at 220 MHz for ASCII transmissions (text files). By the end of 1983, approximately 650 TNCs were operating in North America, many running a variant of the X.25 packet switched protocol, called AX.25. Five years later, that number had grown to over 35,000.
In 1986, Phil Karn, an active amateur radio operator, developed a software package named KA9Q, which implemented TCP/IP on an IBM PC, and made its code available to the public. This enabled amateur radio hobbyists to use the TCP/IP protocols for packet radio and to interoperate and communicate not only with other packet radio operators, but also with all the computers then on the Internet.
There you have it! It took a large number of associations and developments to make wireless networking what it is today. But enough of this history! How can it be used today when we're concerned with things like DMS and its interrelated X.400/X.500 protocols? The reality is that while some Navy commands have a sincere desire to comply with the requirements for DMS, they have no direct cable network connection.
Let's focus for the moment on the present day Abraham Lincoln battle group (BG) located in the Pacific arena. An unclassified wireless network has been developed within this group. There is wireless networking communications from vessel to vessel on a daily basis. E-mail is regularly exchanged among members of the network along with access to the Internet. Unlike most new communications capabilities provided to Naval vessels in recent years, this one uses high frequency radio, HF e-mail. Previously, intership communications were restricted to teletype nets and voice circuits and no support was provided for computer LAN exchanges. Today, LAN exchanges within the Abraham Lincoln BG can span several hundred miles across the ocean using HF radio technology.
The idea of using HF e-mail was initially introduced by Chief of Naval Operations (CNO N6) and the Space and Naval Warfare Systems Command (SPAWAR PMW-172) with the intent to provide inexpensive intership connectivity.
As a result, Naval Command, Control and Ocean Surveillance Center, RDT&E Division (NRaD) and the Navy's C4I Laboratory were tasked and came up with HF as the answer. Why? Well, besides being inexpensive, it was also the only non-satellite medium capable of meeting the requirements for communications among dispersed Carrier Battle Group and Amphibious Ready Group (ARG) operations.
Everyone liked the idea. When the Wireless Network was used in the Lincoln BG, positive feedback resulted. Perhaps the most notable area for overwhelming support was the fact that a mailhost was introduced on the network providing e-mail for Internet users.
Things went so well that a similar system was installed on a research submarine named the USS Dolphin. The system was set up a little differently because the intent was to provide long-range ship-shore connectivity with direct access to the Internet for purposes of supporting academic research. A radio transceiver was installed with an Automatic Link Establishment (ALE) feature to determine what the best frequency would be for conducting transmissions with an identical system set up at a NRaD shore location. The shore location provided a mail host for the Dolphin. Checks were made on mail several times a day with ranges to 1250 miles from the NRaD site. Again, everything went well and everybody was happy.
So happy in fact, that there has been the selection of yet another candidate to receive the Network in the Sky. The Belleau Wood ARG will receive the HF e-mail installation. This time with the additional requirement that a portable system be assembled for an embarked Marine Expeditionary Unit (MEU) to conduct off shore use with HF radios for an over-the-beach link back to the ARG for e-mail.
Furthermore, plans are now to consider the making of a true at sea Metropolitan Area Network and to even investigate the possibility of hub spoke e-mail communications for smaller units. The hubs would provide smaller units with automatic relay over SHF SATCOM links to related stateside parent commands.
There is the possibility of using a number of standard TCP/IP based protocols for wireless communications; TELNET, PPP, UDP, SLIP, SMTP, FTP, etc. If it were warranted by some situation, a mail gateway host could be used to convert SMTP correspondence to X.400 or vice versa. That means DMS could be used! Skip that mail gateway host stuff since that would probably be covered by an Multifunction Interface (MFI) at another location. Yes, the possibilities are all there for a DMS wireless connection. Even X.400 and X.500 over TCP/IP using the RFC 1006 capability is a possibility.
At the bottom of all this wireless network technology is AX.25. The variant of the X.25 packet switched protocol. That means that the standard TCP/IP applications like TELNET, FTP, SMTP, and so forth, could just well be replaced by the OSI applications of VT, FTAM, X.400, etc. Plus it has the added enhancement of directory services (X.500) to perform secure messaging and lookups. Just read in your Fortezza card and you're off and running. More importantly, there is no directly cabled network connection.
All of this can be done through wireless technology as we know it today. Okay, so what's the drawback to all this wonderfulness? If going wireless is so terrific, then why not do it all the time? It's the speed. Radiomen are familiar with the 75 baud data rate of the teletype. By comparison, the potentially whiz bang data rate of 4.8 The kbps for present day HF technology seems fast indeed. Is this data rate fast enough to do anything we desire? Absolutely not! I shudder to think of what the results would be if someone would set up a WEB secession over a wireless network and decided to run an mpeg display over the connection. Anybody got a lot of time?
There's more to come from wireless systems. As higher-performance wireless networks are established, users will access the full panoply of Internet services, including bandwidth-intensive resources like FTP and the World-Wide Web.
The reason wireless data has so far failed to attract millions of subscribers is that most service providers have not set sufficiently high goals. Wishing to believe that users would be satisfied with low throughput and high latency (because such networks are easier to construct), much of the industry wasted the last few years trying to convince users to rewrite their applications and downgrade their expectations. Nobody else really cared for the idea.
The first nationwide mobile data services on the air were low-speed packet radio networks - ARDIS (Advanced Radio Data Information Service) and RAM Mobile Data. These networks provide what could be described as wireless telex service. Like the clunky telex terminals common in the days before fax machines, ARDIS and RAM Mobile Data services let users send and receive short messages. The major difference is that these packet radio networks have been closely integrated with modern computer networks.
Although the packet radio companies talk about speeds ranging from 4.8 Kbps to 19.2 Kbps, users almost never see throughput that high. The networks assemble each user's data in packets containing origin and destination addresses, error checking and correction data, and other supervisory data. Over ARDIS and RAM networks, 40 to 60 percent of the raw data rate is consumed by protocol overhead. Therefore, 2.4 Kbps to 9.6 Kbps is the maximum instantaneous throughput users can expect. But, there's more bad news. These networks hoped to make money by forcing users to share a single radio channel. Average throughput depends on the number of users active on a channel at any given time. With even modest channel contention, throughput can quickly plummet to less than 1,200 bps.
There certainly are legitimate uses for low-speed, two-way wireless messaging, and the paging industry is pursuing this market. Indeed, two-way wireless messaging is a powerful enhancement to conventional paging, and a few paging operators are promoting the integration of paging with personal digital assistants (PDAs), palmtops and notebook computers.
The day is dawning when users will be able to access cyberspace from the beach or a remote village in central Africa. More importantly, wireless technology will inspire a myriad of new applications. For example, to interact with local offices/commands and transportation systems (virtually all of which will be tied into the Internet) via pocket-size personal communicators.
Because wireless computing is still in its infancy, there clearly are many present-day limitations to its use as a networking panacea. While several mobile data services already exist, many more are on the way. The mobile radio industry has for decades exclusively catered to industrial users and has now finally awakened to opportunities posed by the PC. Within the last few years portable computers have begun to sprout antennas.
Today, with a little extra effort, you can log on wirelessly to the Net from practically any major city in the United States. All you need is a cellular-ready modem and cellular telephone. There also are two nationwide mobile data networks that offer wireless access to Internet e-mail. And other wireless technologies can be employed to extend access to locations that are difficult to reach via wire, such as parks, boats, or rural sites.
Admittedly, most existing wireless services offer only limited coverage, do not perform as well as their wireline counterparts, and can be expensive to use. But development activity has reached a fever pitch, and we will soon be able to enjoy the fruits resulting from competition in the wireless arena. Significant breakthroughs in coverage, performance and cost are in the offing.
About the Contributor: Rick Reyes