The Medical Web Project
Technical White Paper
Medical Informatics Engineering, Inc.
7309 W. Jefferson Blvd
Fort Wayne, IN 46804
Phone: (219) 459-6270
APPENDIX B - References
APPENDIX C - InterNIC Recommended Reading
The primary goal of this paper is technical; however, the introduction provides a high level conceptual view of the Med-Web project. The rest of the paper deals with technical aspects, but makes no assumptions about the technical skill of the reader. Specifically the bulk of this paper is intended for those who are tasked with solving the problem of exchanging medical (financial or clinical) information.
The goal of the Medical Web is to build a high speed network to promote the exchange of information. The network solution must be vendor independent, have an open architecture, and be apolitical to encourage inclusion of any medical service provider or client.
The Medical Web is designed to overcome many of the problems facing health care institutions today. The technology of the Medical Web has been available for many years; however, recently it has become inexpensive due to the popularity of wide area networking (WAN) and the Internet. Businesses have been taking advantage of this technology for years and have found it a requirement to compete. It is the goal of the Med-Web Project to apply this technology to the health care industry to address current challenges.
Many health care institutions have not been able to provide information online due to the overwhelming costs of providing these services. In order to provide these services, companies (such as insurance companies) would have to invest in many phone lines and the staff to monitor them. For this purpose, clearing houses have become necessary to make it realistic for most insurance companies to accept electronic claims.
The problem with the existing phone line solution is that is a point-to-point solution. Point-to-point solutions monopolize the connection so that other services can not be utilized. Many health care companies have had to invest in multiple phone lines and modems to get access to required services because they need access simultaneously.
Lack of Security
Because so much is still done by hand and on paper, there is a lack of security. There are not records of who has seen information, or what they have done with it. In addition, many electronic systems are not much better. Many systems provide little or no security; of the systems that do, little is utilized. This means anyone who knows the number of the dial-in lines (which many systems provide) can have free access to sensitive information.
Wide Variety of Systems with no Integration
The requirements made of heath care companies have made it necessary to design and purchase systems to solve their needs. With little standardization in the past, many different implementations have been created to resolve the same problems. This has lead to problems integrating these systems in order to exchange information easily.
Services provided occur over slow modems, which have required systems to "batch" their transactions and transmit them all at once. To make matter worse, the results of these transactions are not known for several hours, so systems must track the transactions and dial-up and get the results at a later time. If the systems are not capable of delayed tracking, there is much work that needs to be done by office personnel to track them manually.
The bulk of the systems that are available now do not allow extraction of data easily. Most solutions that health care software companies have made will only work within their products. There are protocols defined and tested to address these problems; however most companies would rather "re-invent the wheel" and design their own if it locks their customers into their product line.
The Med-Web Projects goals are to overcome the problems listed above. Technology already in existence can be used to solve the difficulties that face the health care industry. The features of a networked environment promote exchange, speed, and accuracy.
Accessibility and Security
The Med-Web project brings everyone together in an Internet-style environment without the security problems of the Internet. Many Internet providers would like to entice the health care community to use the Internet as the source for connectivity. At this time, it is not realistic to have sensitive medical information in such a volatile environment. The Internet has demanded communications make excellent advances in connectivity, and this is why this technology is possible; however, the Internet is no place for sensitive information as many recent headlines have illustrated. The Med-Web project embraces the technology and philosophy of the Internet while isolating the scope to medical institutions only. This adds some security to an otherwise insecure environment. The second security measure is that activity can be tracked and logged, and therefore it now becomes possible to prosecute individuals who violate laws regarding medical information. Currently, there is little to discourage unscrupulous individuals from violating these laws because there are few ways of proving where information was leaked. The Med-Web and the supporting services can now limit who has access to the information and log who and when individuals are getting information.
Reduction of Administration Costs
Automation has eliminated or reduced the amount of time required for many tasks in the health care industry already; however, there is still very much that can be done. The Med-Web project promotes the exchange of information electronically because of its ease of operation. The information exchange eliminates time re-keying information in by hand, helps verbally communicating difficult information, provides faster response time, and requires less time waiting. The section in this paper called Savings illustrates some of these advantages.
The technology used for the Med-Web project allows for communication at speeds which make it practical to transmit images. Even the slowest optional speed is three times faster than the fastest modems. What is more impressive is the cost for the speed is 27% less for the bandwidth. See the Savings section.
Recently the medical industry has been criticized by the media for mistakes made due to inaccuracy. Not only is there a financial benefit to the reduction of manpower needed for data entry, there is the additional benefit of accuracy. Even with all the medical systems available, there is no infrastructure to aid in the transfer of information between them accurately. The Med-Web project will build that infrastructure.
Cross Platform, Vendor Independence
The solution that the Med-Web promotes is an open architecture and vendor independent. This translates to less dependence on a particular vendor's solution and means there is more opportunity for information exchange. Because MIE is not keeping this technology within our company but is free publishing it, it allows other companies to implement a standard rather than invest in developing their own. It will be important for the health care companies to demand systems that can utilize the open architecture of the Med-Web.
Eliminate Hospital/Physician Relations
The Med-Web project only makes the exchange of information much easier. It cannot replace the programs that hospitals and insurance companies have put in place to develop relationships with physicians and affiliates. These programs will be vital to not only the success of the Med-Web project, but also the growth of the hospitals and insurance companies.
Maintain Local Systems The Med-Web project is not meant to replace the systems that most hospitals, physicians, payers, and clinics support. In fact, the systems will have to become network aware. This is the challenge of the community-- to embrace the concept of the web, an interwoven network, stronger than the individual parts.
Claims can be submitted directly to Payers bypassing clearinghouses. Payers do not need to maintain any phone lines to allow many clinics and hospitals to submit claims. Problems can be resolved online and e-mail can be utilized for communication between the payer and the clinic.
Referral letters can be sent out to physicians directly without the need to print and mail them. The turn-around time can be milliseconds. Improved communication between physicians improves patient care. Additionally, because the referral letters are processed electronically, the task of document management becomes easier.
Electronic Mail and Internet E-Mail
Access to Internet mail allows physicians and companies to communicate efficiently with the entire world. Doctors and office staff can be brought up to date with the latest research.
Centralized Billing / MSO Management
A high speed network allows a company to centralize redundant tasks such as billing. These tasks which are being performed at several locations can be combined to consolidate costs and improve efficiency.
Managed care is becoming very popular in recent years. A medical network can help physicians to track patient care more effectively by allowing the physician to be in better contact with referring physicians. Detailed information must be tracked in order for the physician to know whether or not money is being lost. The Medical Web makes data acquisition much easier.
Insurance Eligibility Verification
Insurance companies can now provide valuable eligibility information to physicians without the expense of developing complicated software and hardware. The Medical Web allows insurance companies to develop an eligibility system once, and have it available to everyone on the network.
Lab Ordering and Results
Lab can use the Medical Web to provide information to physicians at the same time reducing the amount of effort that they invest in data entry. Programs can be provided to physicians to allow them to order labs. Because the physicians are already connected, Lab companies do not need to sell a separate PC and modem to get them connected, they can utilized existing hardware and the connection to the Med-Web.
Radiology and Pathology
Without a high-speed network, providing anything more than a report would be unreasonable. The cost of building a high-speed network just for imaging also would be unreasonable. The Med-Web can operate at extremely high speeds; making it ideal for transmission of X-ray, MRI, PET and other high definition images. Because the Med-Web is multi-purposed, the cost is offset be other services that can be accessed and provided though the same network.
Physician Directory Services
The services listed above become efficient with the potential to warehouse data in a place that many people can contribute and utilize. The Med-Web provides a means of accessing a centralized database for community information. Community information may include demographics and medical information.
Medical Record Exchange
Getting medical information from doctor to specialist, or from lab to doctor is time-consuming, expensive, and unreliable. The Medical Web is a wide area network that makes exchange of medical information much easier. Without a wide area network, information must be relayed over the phone, carried by hand, or sent by mail. A wide area network allows systems to send the information electronically.
Remote Office Connectivity
The Medical Web also has the ability to reduce the cost of remote locations. The only connection that a remote office needs is a connection to the Med-Web. With that single connection, the remote office can stay in touch with the home office and utilize services on the Med-Web.
The Internet has become an excellent way of communicating with anyone in the world. Med-Web's connection to the Internet allows e-mail to be sent or received from anywhere in the world. In addition to the Internet's ability to connect people, it has become a vast resources for all types of information including medical information. All machines connected to the Medical Web have the potential of accessing the Internet. What is equally important is that no one from the Internet can access computers or information on the Med-Web. Security is accomplished via a special router called a firewall.
In the interest of consolidating resources, Internet access is available for a nominal fee on the Med-Web.
The approach of the Medical Web has benefit of reducing the costs of communication. Because the costs of access to the Medical Web are fixed, and do not vary based on distance or usage, the time and cost of placing long distance calls to companies on the Med-Web can be greatly reduced. Messages can be communicated via e-mail instead of waiting on hold. The reduction of time on the phone can increase office productivity and decrease costs. As an example, a problem with an insurance claim could completely resolved via e-mail between a doctor's office an insurance company. In this scenario, both the doctor's office and the insurance company benefit from the power of e-mail.
The Medical Web can also reduce the cost of remote offices because of the consolidation of resources. Instead of having a connection to the hospital, one for the remote office, and others, all can be served through one connection. Each connection is still secure, it is just divided into virtual separate connections.
Because of the nature of telecommunications, tremendous savings can be obtained by sharing bandwidth all over the community. The table below shows some of the potential savings.
|Cost of Bandwidth as Bandwidth Increases|
|Circuit Type||Monthly Line Cost||Number of 64Kbs channels||Monthly Cost per channel|
Modem Cost and Support
A network such as the Med-Web has the potential to allow companies to offer many more services than though other means. In many cases, digital information is provided though dial-up means. There are few companies willing to absorb the cost of an Information System department to administrate the number of modems to make on-line services available. Furthermore, there is great cost in dedicating phone lines to on-line services. If very few lines are used, then customers complain about busy signals. If too many phone lines are used the cost is prohibitive.
The Medical Web solves the problems of offering on-line services to customers. Because there is only one line, and all the customers access the services across that line, there is a reduction in the time to administrate lines and deal with complaints of busy signals. Problems with modem compatibility or modems not connecting eliminated.
Propriety Vendor Solution and Fees
The Medical Web project is based on standard published technology. Because the network is based on standards, it does not lock customers into one vendors solution. It also means that multiple vendors can be utilized where it makes sense.
As more information is handled in an automated fashion, the dependency on large office staff to manage information becomes less necessary. Also because the information becomes more accurate, less people are needs to track down problems due to information or typing errors.
The Med-Web is a high speed wide area network (WAN). The connection into the WAN is not exclusive. Three methods of access are planned and they are outlined in the configuration section below. As more methods of access become available, they will be added as options. Factors affecting the method of access will be the location of the company, services to be accessed or provided, and price.
The primary method of access will be a new service offered called Frame Relay. This is a high speed digital line connected to specialized routing equipment owned by the phone company. The routing equipment is capable of routing information through Permanent Virtual Circuits (PVCs). Depending on the phone company, the cost for Frame Relay varies; however, it is the most attractive method because it offers the fastest speeds for the cheapest rates. Another feature of Frame Relay is that it is expandable; as the bandwidth is required, the lines and equipment can easily be upgraded.
Access to the Frame Relay Network can be attained via one of three popular connections: 56k DDS lines, T1, or T3 lines. The need for the speed of a T3 line would be very rare.
A very popular service called ISDN (Integrated Services Digital Network) is another method to access the Medical Web. This is a digital service that is like a fast digital phone line. The line can be dialed and connected in under a quarter second. The digital line also offers the speed of 128kbs. The fast dialing time and high bandwidth of ISDN has made it a versatile choice in wide area networking. However, the "point-to-point" nature of ISDN has made it expensive for enterprise wide networking. The availability of the service is also a problem. Even with these things in mind, ISDN is still a good choice for connections-- most likely for doctors who wish to have residential connections.
The third option of access is conventional modems running SLIP or PPP protocol. The slowness and lack of reliability makes this the least attractive option; however for some, it can be the most inexpensive. A modem can dial into the network, and many services can be accessed at the same time. The ability to access several services at the same time makes this attractive for offices who don't want to invest in any hardware, but are having problems getting to all the services needed though the one phone line. This type of service would be offered in a limited basis to very small offices or to individuals who required residential access.
The Medical Web Network is only as good as the ability of everyone on the network to exchange information. To accomplish this, strict adherence to WAN, LAN, and application protocols are strictly enforced and monitored.Network Protocol Conformance
The hardware that is recommended and installed by MIE conforms to popular networking and routing protocol. Because of the Med-Web policy of open architecture, organizations and companies are free to use their own hardware. However, any equipment that compromises the integrity of the Med-Web will be removed.
All TCP/IP addresses on the Medical Web are assigned by InterNIC Registration Services in order to guarantee network compatibility. MIE will assign network address or sub-nets as required. If machines are already assigned numbers by InterNIC, then MIE will modify routing table to accommodate the current number scheme. InterNIC can be contacted at:
Organizations who have an existing network in place who are not registered by InterNIC must conform prior to gaining access to the Medical Web. Non-conformance of this policy cannot be tolerated without the potential of degrading network performance or interruption of service. See the Recommended Reading in the appendix for more information on the importance of IP number registration.
It is important to note that registering IP addresses is getting increasingly difficult. InterNIC recommends getting registered IP addresses with an Internet Service Providers (ISP) because routing tables are becoming overloaded for many ISPs. InterNIC is hesitant to issue IP addresses that may not be routed when there is already a shortage of routable IP addresses.
Some firewalls have the capability to translate unregistered IP addresses into registered addresses. Using firewall software may prevent having to re-address an entire network.
All hardware installed and supported by MIE supports IPX routing.
The second factor affecting the ease of information exchange is protocol conformance at the application level. Because MIE is not the only vendor that will offer services on the network, quality control of the application is left to the vendor supplying the service. The applications that MIE will provide on the network will conform to documented standards. The inclusion of the popular standards in this document is to urge other vendors to conform to these standards. Deviation from these standards would risk the ability to exchange information easily and could even cause unforseen errors in many applications. For these reasons, these application level protocols are listed here.Application Conformance
Since March 1987, a working group of health care institutions, vendors and consultants have been developing the Health Level 7 (HL7) Standard. The primary goal of the HL7 standard is to "provide a standard for the exchange of data among health care computer applications that eliminate or substantially reduce the custom interface programming and program maintenance that is currently required" .
The term "Level 7" refers to the highest level of the Open System Interconnection (OSI) model of the International Standards Organization (ISO). The HL7 standard is primarily focused on the issues that occur within the seventh, or application layer. HL7 does not identify a set of ISO approved specifications to occupy layers 1 to 6 under HL7's abstract message specifications. HL7 does, however, conform to the conceptual definition of an application to application interface placed in the seventh layer of the OSI model. As a matter of practicality, the HL7 defines the Lower Level Protocol (LLP), which allows the exchange of messages in less robust communications, such as over a RS-232 connection .
The American College of Radiology (ACR) and the National Electrical Manufacturers Association (NEMA) formed to develop an interface standard for the interconnection of two pieces of imaging equipment. The standard was created so that a group of devices, each of which meets this standard, may be organized into a system to meet user needs. The standardization process has produced three versions to date. This section will describe the main features of each version.
Version 1 and Version 2: Version 1 was published in 1985. It specifies data formatting and provides a data dictionary, a set of commands and hardware interface. It supports transmission of data between two pieces of medical imaging equipment (i.e., only point-to-point message transmission). It provides for a variety of functions such as data integrity checking, media access, flow control as well as fragmenting and reconstruction. ACR-NEMA is patterned after the ISO/OSI Reference Model. However, it is a six layer protocol since the transport layer and the network layer were consolidated. The transport/network layer, data link layer and physical layer all follow very specific protocols. These protocols were defined by state transitions, timing, and cable activity diagrams. Version 2 is an expanded version of Version 1 but still supports only point-to-point message exchange. The data dictionary syntax rules are identical to those of Version 1. It added some features like controlling display devices (e.g. laser printers).
Version 3: This version is known as digital imaging and communications in medicine (DICOM) and was published in 1992. This version is a complex standard structured in a tagged format using a pseudo-object oriented description. It attempts to maintain compatibility with Version 2.0 where possible. The major enhancements of version 3 include:
a) Network applications were designed so that it did not remain a point-to-point protocol.
b) It specifies levels of conformance. Previous versions only indicated a minimum level of conformance.
c) The specification is a structured multi-part document which facilitates evolution by simplifying the addition of new features.
DICOM is has been further expanded by the University Hospital of Geneva with the Papyrus format. The Papyrus format defines on the DICOM tags as a multiple image section. This extends the DICOM standard to include multi-dimension images.
American Society of Testing and Materials (ASTM) Medical
ASTM's committee E-31 was started in 1970 as the "committee on computerized laboratory systems" and was originally designed to write standards for computer automation of laboratory instruments . Later the name was changed to "committee on computerized systems" and the scope broadened to include other kinds of computerized systems. In 1975, a subcommittee to deal with clinical laboratory systems was formed, beginning E-31's interest in medical computer systems. There are now six active subcommittees dealing with different aspects of computer applications in medicine .
The primary goal of the sub-committee on data exchange for clinical results E-31.11 is as stated in the mission statement : "the specification for transferring clinical laboratory data messages between independent computer systems E 1238" . In relationship to networking protocols this ASTM standard deals with the application layer, the seventh layer in the ISO/OSI model. The lower layers can be any set of reliable protocols (TCP/IP, X.400, Kermit, RS 232). However, the messages are composed of a restricted ASCII character set (the printable ones). Furthermore, the message consists of an unlimited number of lines. However, each line can't be longer than 220 characters .
Hypertext protocol has become and excellent method to allow access to systems and information. HTTP is a protocol that defines the transmission of HTML documents. HTML (hypertext Markup Language) is a method of displaying information with "hot links" to other related information. The real power of HTML is the ability to reach so many different platforms and operating system. The time it takes to implement cross-platform information systems is greatly reduced.
There are many third party productivity tools that may be utilized to get information from the Medical Web. The optimal method of passing information on the Med-Web is though customized interfaces; however, it can be expensive to develop these interfaces depending on what is needed. All services on the network that have a general audience should have gateways that allow everyone to use them. The best method to do this is to use HTTP. The bulk of this section will deal with productivity tools for HTTP and the WWW.
Most of the advances being made today are in the arena of graphical technology. Graphical environments have proven to be very powerful, easier to use, and easier to learn. The biggest asset of graphical environments is their ability to display a wide variety of information an different ways.
There are many inexpensive UNIX web browser available for X-windows. The type of browser will depend on the host of the X-terminal, but most browsers are available for several different UNIX platforms.
Windows 3.1, Windows 95
Graphical Web application for the Windowed environments have become quite popular. They are easy to use, easy to configure, and there are many options to choose from. Netscape Communication Corporation produces the Netscape Navigator which has set the standard in hypertext browsers. Microsoft has announced that it will begin shipping a browser with Windows95. There are many other browsers that are available, however it is expected that Netscape and Microsoft will set the standard. Both companies have licensed JAVA from Sun Microsystems.
One of the assets of Hypertext is the ability to reach such a wide audience. By using hypertext, it is possible to share information to many different platforms and devices. Obviously graphical information such as images, cannot be viewed; however, in most cases the images just slow things down when accessing text information. The advantages of graphical technology are aesthetics and the ability to view information such as X-rays or other important graphical images. The primary advantage to character technology is the cost. Many clinics and hospitals have invested in character terminals which would be expensive to replace. Furthermore, most of the information can generally be displayed on a character terminal.
Lynx is a character based browser that enables dumb terminals access to hypertext information and other Internet-type resources.
Training for applications should be performed by the companies that offer services on the network. MIE will offer classes on how to access information on the Medical Web and the Internet.
Because most technical information is only available via the Internet, MIE is providing most of the documentation referenced on in the paper on-line though the Medical Web or via fax.
Developer Programs are available for software programmers and engineers who wish to develop applications for the Medical Web.
MIE, Inc. is providing the required hardware at special rates; however Med-Web members who wish to purchase their equipment though their own channels may do so. Hardware not purchased from MIE, Inc. is not guaranteed, and will not be supported in the event of hardware failure or incompatibility. Hardware purchased from MIE will be supported and maintained by MIE, Inc. Warrantees for such hardware are outlined below.
The hardware required to access the Medical Web will depend on the method of access and the required bandwidth. The following separate components are required to gain access the frame relay. Many companies offer a single unit that contain some or all of the components required to route traffic across frame relay. Each required component can also be purchased separately.
All of the components are listed to show access seekers which components they may already own and which may need to be purchased. The most cost effective solution for those access seekers whom do not own any single component will be to purchase an integrated unit.
A CSU/DSU (Channel Switching Unit / Digital Switching Unit) is required to interface the Bridging unit to the frame relay line. The type of CSU/DSU will depend on the speed of the frame relay service. A 56/64kbs CSU/DSU will be required for connection speeds less than 128kbs. A T1 CSU/DSU will be required for connection speeds equal or greater than 128kbs.
A bridge is a device that "bridges" to different types of networks. A bridge with frame relay software is required to get packets from the LAN to the WAN. Many manufacturers make devices called "Brouters" which are bridges and routers combined.
A device that will keep local traffic within the office is needed so that the slower speed of the WAN is not overwhelmed by faster, more frequent local traffic.
The hardware specified in the Hardware Recommendation section can be purchased directly from MIE, Inc. for a reduced rate. Installation of the hardware is optional. MIE will not install hardware not recommended; however, the Med-Web members may install by themselves any hardware they see fit.
Medical Related Purposes
Any institution or organization can gain access to the Medical Web provided that the purpose for access is medically related. Institutions and organizations will not be excluded based on types of services provided or utilized by that institution or organization.
Services Independent of Network
Network services will remain independent of the network itself. The purpose for this policy is to allow the network to grow free from the politics of competition of services. No institute or organization will be refused access because of duplication of services. It is desirable to have many institutions and organizations offering competing services to drive costs down. Ultimately services should translate to a benefit to the community though reduction of costs, quality of care, or offering of a new service.
Anyone can offer Health related services
The policy of the Med-Web project is not to deny any organization or institute access to provide services on the Medical Web for any other member(s) of the Med-Web.
Changes to the Med-Web Project
Information in this document is subject to change. Registered members of the Med-Web Project will be notified in writing of any changes 30 days prior to the implementation of the changes.
The following information is included to show how to obtain the latest technical details and programs to best utilize the Med-Web. Most of the programs and information can freely be obtained from the Internet. If access is not available to the Internet, MIE is providing the information across the Med-Web on our local servers.WWW Organizations
European Laboratory for High Energy Physics
H O 1211 Geneva 23
Organization Europeenee pour la Recherche Nucleaire
F-01631 CERN Cedex
+41 22 767 6111
World Wide Web Consortium
Paul C. Powell, Coordinator
Office of Sponsored Programs, E19-702
Massachusetts Institute of Technology
77 Massachusetts Avenue
Cambridge, MA 02139
FAQ or Frequently Asked Questions about the World Wide Web
How to write HTML
The Official HTML Specification
Official List of Web Clients
Web Server Lists
Latest NCSA Hypertext Server Software
HTTPS for Windows NT
OS2HTTPD for OS/2
KANQ NOS for DOS
The following information is recommended reading by InterNIC. All RFC can be obtained by fax from MIE on request, or by anonymous FTP from mie.webmed.org on the Medical Web.Gerich, E. Guidelines for Management of IP Address Space, Ann Arbor, MI: Merit Network, Inc.; May 1993; RFC 1466. 10 p. (DS.INTERNIC.NET RFC1466.TXT).
Rekhter, Y., Moskowitz. B., Karrenberg, D., de Groot, G. Address Allocation for Private Internets, IBM Corp., Chrysler Corp., RIPE NCC; March 1994; RFC 1597. 8 p. (DS.INTERNIC.NET RFC1597.TXT).
Braden, R.T.; Postel, J.B. Requirements for Internet Gateways. Marina del Rey, CA: University of Southern California, Information Sciences Inst.; 1987 June; RFC 1009. 55 p. (DS.INTERNET.NET POLICY RFC1009.TXT).
Internet Engineering Task Force, Braden, R.T. Requirements for Internet Hosts -- Communication Layers. Marina del Rey, CA: University of Southern California, Information Sciences Inst.; October 1989; RFC 1122. 116 p. (DS.INTERNIC.NET RFC1122.TXT).
Internet Engineering Task Force, Braden, R.T. Requirements for Internet Hosts -- Application and Support. Marina del Rey, CA: University of Southern California, Information Sciences Inst.; October 1989; RFC 1123. 98 p. (DS.INTERNIC.NET RFC1123.TXT).
Internet Activities Board. Internet Official Protocol Standards. 1994 March; RFC 1600. 34p. (DS.INTERNIC.NET POLICY RFC1600.TXT). [Note: the current version is always available as "STD 1".]
Mogul, J.; Postel, J.B. Internet Standard Subnetting Procedure. Stanford, CA: Stanford University; 1985 August; RFC 950. 18 p. (DS.INTERNIC.NET POLICY RFC950.TXT).
Postel, J.B. Internet Control Message Protocol. Marina del Rey, CA: University of Southern California, Information Sciences Inst.; 1981 September; RFC 792. 21 p. (DS.INTERNIC.NET POLICY RFC792.TXT).
Postel, J.B. Transmission Control Protocol. Marina del Rey, CA: University of Southern California, Information Sciences Inst.; 1981 September; RFC 793. 85 p. (DS.INTERNIC.NET POLICY RFC793.TXT).
Postel, J.B. Address Mappings. Marina del Rey, CA: University of Southern California, Information Sciences Inst.; 1981 September; RFC 796. 7 p. (DS.INTERNIC.NET POLICY RFC796.TXT). Obsoletes: IEN 115 (NACC 0968-79)
Postel, J.B. User Datagram Protocol. Marina del Rey, CA: University of Southern California, Information Sciences Inst.; 1980 August 28; RFC 768. 3 p. (DS.INTERNIC.NET POLICY RFC768.TXT).
Postel, J.B. Internet Protocol. Marina del Rey, CA: University of Southern California, Information Sciences Inst.; 1981 September; RFC 791. 45 p. (DS.INTERNIC.NET POLICY RFC791.TXT).
Reynolds, J.K.; Postel, J.B. Assigned Numbers. Marina del Rey, CA: University of Southern California, Information Sciences Inst.; 1992 JUly; RFC 1340. 139p. (DS.INTERNIC.NET POLICY RFC1340.TXT). [Note: the current version is always available as "STD 2".]