Overview of the LEAP Protocols Mohsen Banan public@mohsen.banan.1.byname.net Version 0.2 First Published: August 4, 2000 Last Updated: August 8, 2000 Copyright fcl 2000 Mohsen Banan Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. A Component of The LEAP Manifesto This article is one of a series of articles describing various aspects of the Mobile Messaging industry and the LEAP protocols. For the complete collection of articles see The LEAP Manifesto [4 ], available at http://www.LeapForum.org/LEAP/Manifesto/roadMap/index.html. The LEAP Manifesto is also available at the Free Proto- cols Foundation website at http://www.FreeProtocols.org/LEAP/Manifesto/roadMap/index.html. 1 Contents 1 Introduction 3 2 The Need for Efficiency 3 3 Technical Overview of LEAP 4 3.1 The ESRO Layer: Efficient Transport Ser- vices . . . . . . . . . . . . . . . . . . . .* * 4 3.2 The EMSD Layer: Efficient E-Mail . . . 5 3.3 The EHTD Layer: Efficient Web Browsing 6 3.4 Other Efficient LEAP Applications . . . . 6 4 Efficiency Characteristics of LEAP 7 5 LEAP: A Basis for Convergence 9 6 The End-User's Experience 10 7 The LEAP Development Process 13 7.1 Patent-Freedom . . . . . . . . . . . . . . 13 7.2 RFC Publication . . . . . . . . . . . . . . 13 7.3 Open Maintenance Organizations . . . . . 14 8 LEAPing over WAP 14 9 A Brief History of LEAP 14 List of Figures 1 LEAP Protocol Organization . . . . . . . 5 2 Protocol Efficiency Comparison . . . . . 8 3 Open Mobile Messaging . . . . . . . . . 9 4 The End-User's Experience . . . . . . . . 11 List of Tables 1 WAP versus LEAP . . . . . . . . . . . . 15 2 1 Introduction The key component of the Manifesto is a set of mobile messaging protocols called the Lightweight & Efficient Application Protocols, or LEAP. LEAP is a set of high- performance, efficient protocols which are ideal for mo- bile and wireless applications. This article provides a brief overview of the LEAP protocols; complete details are provided elsewhere in The LEAP Manifesto [4 ]. 2 The Need for Efficiency Engineering is the art of making intelligent trade-offs be- tween conflicting requirements. A perennial engineering trade-off is that which must be made between the need for simplicity, and the need for performance. In the case of wireless data communications, performance means such things as data transfer speed, power efficiency, and band- width efficiency. The 1980s and 1990s were the decades of simple pro- tocols - protocols such as the very aptly named Simple Mail Transfer Protocol (SMTP), and Simple Network Man- agement Protocol (SNMP). A great deal of the success of these and other Internet protocols can be attributed to their simplicity. The first generation of network engineers and net- work operators were only able to view network commu- nications in relatively simple terms. It was appropriate to cater to that simplicity with simple protocols. A key reason for the success of these early protocols is the lack of technical sophistication on the part of first-generation network engineers and operators. Simple protocols are easier to make widespread than "good" protocols (meaning those which have better ca- pabilities and performance), for the basic reason that net- work engineers and operators are able to adopt and im- plement simple protocols much more easily than "good" protocols. However, things have changed. Network communi- cations has now expanded into the wireless and mobile data communications arena, and wireless applications de- mand efficiency. The move to wide-area wireless has significantly shifted the location of the ideal engineering balance between simplicity and performance - moving it away from simplicity, and towards performance. Wireless networks are constrained by bandwidth lim- itations, and the hand-held devices they serve are con- 3 strained by limitations such as display size, battery ca- pacity, and memory capacity. These constraints place an extremely high premium on the efficiency of data trans- fer. Existing Internet protocols do not provide the required efficiency. We therefore need a new generation of high- performance, efficient protocols, to cater to the demands of wireless applications. The point is sometimes made that the need for efficiency in the wireless arena is a tem- porary one - that advances in wireless engineering tech- nology in the form of third generation (3G) systems will eliminate existing bandwidth limitations, obviating the need for efficient protocols. As long as the capacity of wireless networks remains finite, however, the need for efficiency will persist. Efficient usage is an inherent re- quirement for any finite resource, therefore the require- ment for efficient bandwidth usage and battery longevity will remain. 3 Technical Overview of LEAP The LEAP protocols are intended to be an enabling cata- lyst for the growth of the wireless-IP based Mobile Mes- saging industry, and have been designed with this goal in mind from the outset. They have been designed as a genuine enabling technology which will bring enormous benefits to the industry and the consumer. They are a sound engineering construction based on true openness and patent-freedom. The LEAP protocols a general-purpose solution to the problem of efficient message transfer, and their use is not limited to any particular device type or network. In particular, LEAP is compatible with all wireless-IP net- works. Examples of wireless networks which provide na- tive support for LEAP are CDPD, GSM, packet CDMA, and PCS. The basic organization of the LEAP protocols is shown in Figure 1. 3.1 The ESRO Layer: Efficient Transport Services As shown in Figure 1, the LEAP protocols are layered. The lower layer is called Efficient Short Remote Opera- tions, or ESRO. The ESRO layer provides reliable con- nectionless transport services which can be used for a va- riety of applications. For example, in addition to mobile 4 Figure 1: LEAP Protocol Organization messaging services, ESRO can also be used as a trans- port service for credit card verification applications and efficient micro browsers. For more information on ESRO see the article ESRO: A Foundation for the Development of Efficient Protocols within The LEAP Manifesto, or visit the ESRO website at http://www.esro.org/. 3.2 The EMSD Layer: Efficient E-Mail One of the efficient application layers built on top of ESRO is called Efficient Mail Submission & Delivery, or EMSD. EMSD is the component of LEAP that addresses the Mo- bile Messaging application. EMSD is a specialized native Internet messaging pro- tocol. It defines a similar set of services to the existing SMTP protocols. It defines a complete set of rules for message submission (end-user device to server) and mes- sage delivery (server to end-user device). EMSD meets or exceeds the level of functionality, reliability and security provided by the existing SMTP protocols. Though its use is not limited to wireless networks, EMSD has been designed specifically to address the re- quirements of wireless networks, such as CDPD, Wireless- IP, Mobile-IP. In particular, EMSD has been designed with a very strong and clear emphasis on efficiency. EMSD is highly optimized for the submission and 5 delivery of short (typically 4 kilobytes or less) Internet e-mail messages, and is therefore extremely well suited to the wireless environment. EMSD improves on exist- ing messaging protocols by optimizing the exchange be- tween the server and the end-user device, both in terms of the number of bytes transferred and the number of trans- missions. Because of the required timeliness of the mes- sages, mailbox access protocols like POP and IMAP are not used. EMSD is the only truly open messaging proto- col that is specifically designed for the wireless network environment. EMSD is a natural extension of the existing Inter- net e-mail environment, and accommodates the two-way paging model of usage, in which time-critical messages are "pushed" to the recipient. Any network or network operator which faces signifi- cant bandwidth and capacity limitations can benefit from the use of EMSD. Any user of a network who must bear high costs for measured network usage can benefit from the use of EMSD. The initial use of EMSD is expected to be primarily to provide Mobile Messaging services over IP-based wire- less networks. However, EMSD can also function as an adjunct to Mail Access Protocols for "Mail Notification Services." For more information on EMSD see the article EMSD: The LEAP E-Mail Component within The LEAP Mani- festo, or visit the EMSD website at http://www.emsd.org/. 3.3 The EHTD Layer: Efficient Web Brows- ing The Efficient Hyper Text Delivery (EHTD) layer is a hy- pertext transfer protocol which is optimized for the effi- cient transfer of short markup pages. EHTD is the com- ponent of the LEAP protocols which facilitates web brows- ing. Along with EMSD, EHTD also benefits from the reliable efficient services of ESRO. A multiplicity of effi- cient markup languages can be used in conjunction with EHTD. Development of the EHTD protocol is currently in progress. 3.4 Other Efficient LEAP Applications Various other efficient application protocols are either un- der development, or anticipated for future development. One of these is the Efficient Dictionary protocol, or E- DICT, which will enable efficient access to dictionaries 6 and other look-up data structures. A starting point for the E-DICT protocol is currently being created. In devel- oping E-DICT, we intend to build on the existing work already done in the context of the DICT protocol. We anticipate that additional protocols will be needed for a variety of future applications, not all of which can be foreseen at this time. These applications will include such things as efficient implementations of ESRO-based instant messaging, chat, white pages, and others. 4 Efficiency Characteristics of LEAP All LEAP protocols are designed with efficiency in mind. In this section we describe the efficiency characteristics of EMSD, the LEAP e-mail protocol. Other LEAP pro- tocols deliver similar efficiency benefits. Most existing Internet e-mail protocols are designed with simplicity, and continuity with SMTP traditions, as two of the primary design requirements. These require- ments are in conflict with efficiency of data transfer, and for this reason most existing Internet e-mail protocols are not efficient. EMSD, on the other hand, has been designed with efficiency as its primary requirement. For this reason, EMSD is a great deal more efficient than existing Internet e-mail protocols. A detailed efficiency study of the LEAP protocols is provided in the article entitled Efficiency of EMSD [2 ] within The LEAP Manifesto. That article presents var- ious efficiency studies which compare the efficiency of EMSD to other e-mail protocols such as SMTP, POP and IMAP, and which demonstrate the efficiency advantages of EMSD. In this section we provide a brief summary of EMSD's efficiency characteristics. A comparison of the efficiency of the EMSD protocol to other messaging protocols is provided in Figure 2, which shows the delivery traffic overhead for EMSD and three other e-mail protocols: SMTP, IMAP and POP. As the figure shows, EMSD is much more efficient than SMTP, POP and IMAP. For submission and deliv- ery of short e-mail messages, EMSD is up to five times more efficient than the ubiquitous SMTP e-mail messag- ing protocols, both in terms of the number of packets transmitted, and in terms of number of bytes transmitted. Even with pipelining and other possible optimizations of SMTP, EMSD remains up to three times more efficient 7 Figure 2: Protocol Efficiency Comparison than SMTP, both in terms of the number of packets trans- mitted, and in terms of number of bytes transmitted. By minimizing the network traffic required to send and receive messages, EMSD meets the needs of the mo- bile communicator. The extreme efficiency of the EMSD protocol translates into bandwidth efficiency, which in turn translates into: - Efficient use of carrier bandwidth, and therefore in- creased capacity for network operators - Longer battery life for mobile phones, PDAs and other wireless Internet devices - Cheaper network usage costs for the end-user - Reduced latency for the end-user - Improved support for marginal coverage areas 8 5 LEAP: A Basis for Convergence An illustration of how LEAP works is shown in Figure 3. As the figure shows, LEAP provides complete openness of interoperability among Mobile Messaging devices, mes- sage centers, and wireless networks. Figure 3: Open Mobile Messaging LEAP will thus have the effect of unifying the en- tire Mobile Messaging industry under a set of open Inter- net Protocol ("IP") standards and protocols so that, in the manner of the World Wide Web, all of the Mobile Mes- saging networks will effectively operate as one. In order to achieve this convergence, it is not suffi- cient for the Mobile Messaging industry merely to adopt a set of common protocols. Many would claim that WAP is in fact just such a set of common protocols. However, a further essential attribute of the required protocols is that they must be a truly integral, "end-to-end" part of the Internet, as opposed to "gateways" which accommodate unnecessary gatekeepers and middlemen. 9 LEAP is based on the concept of the Internet end-to- end model, in which direct communication between the client and the server assumes that the role of the network service provider is merely that of a pipe - i.e. a passive communication conduit. The Internet end-to-end model assumes that both ends are under the control and choice of the user, and that the servers are widespread, from a variety of providers, and under no specific administra- tion or control. The Internet end-to-end model is in sharp contrast to the traditional phone company and telecom- munications approach, which inserts gateways between the two ends, and creates control and exploitation oppor- tunities for the telecommunication operators. Bearing in mind that the natural convergence of all wireless networks to IP at Layer 3 is well under way and rapidly progressing, the key remaining requirements are: efficiency, lightweightness, miniaturization, and confor- mance to the Internet end-to-end model. LEAP fulfils all of these requirements. By serving as the necessary missing link, LEAP will become the ultimate basis for convergence. The mobile e-mail component of LEAP is EMSD. In the spirit of the Internet end-to-end model, the EMSD protocol will facilitate the convergence of the IP-based two-way paging industry, and Internet e-mail, in a natural and transparent manner. 6 The End-User's Experience The entire LEAP family of protocols bring efficiency and functionality benefits to the user of miniaturized mobile devices. In this section we describe the user's experience of an EMSD-enabled device. Mobile users may not always have the benefit of a wired connection, because of their frequent mobility. They may have a permanent computing system elsewhere, at which they can review large messages at their leisure (for example, messages containing Word documents, Excel spreadsheets, images, etc.). While on the move, however, they need to be kept apprised of important information that requires their immediate attention. Such information cannot wait for them to find the time to set up a laptop and dial in to check for messages. They must be able to ac- cept messages immediately, at any time, and on a device that they can carry anywhere. The experience of the end-user in using LEAP-based Mobile Messaging technology is illustrated in Figure 4. 10 Figure 4: The End-User's Experience The user equips him/herself with an EMSD device. The EMSD device could be a dedicated two-way pager, or a hand-held device (such as a PalmPC) with a wire- less (for example CDPD) modem. While the device can be turned off, the modem will remain on at all times to accept incoming messages. Anyone with access to the Internet can now send a message to this user. The EMSD Service Provider ac- cepts the message from the Internet e-mail system via standard Internet protocols, then delivers the message to the user's device via EMSD protocols. Since the modem is always on, the message can be accepted at any time, and the user can be notified immediately (in any of the ways commonly used for pager notification) that a mes- sage has arrived. The user will then activate the EMSD device and read the message. To send a message the user enters the message, then submits it to the EMSD Service Provider via the EMSD protocols. The Service Provider then acts like a standard 11 Internet Service Provider and sends the message to its destination. The end-user device may have a limited display area and a limited keyboard. This is very much the case for today's cell phones, for example. If so, both the end- user and his/her correspondents may wish to make use of canned messages to facilitate their communication. These canned messages may be defined by the system or end- user device, or they may defined by the message origina- tor as embedded multiple-choice responses. Figure 4 illustrates how the Mobile Messaging needs of a typical user (we'll call him Joe) are provided by the LEAP technology. This figure includes all the required technological components, and shows how they interop- erate to satisfy Joe's needs. The figure includes three ma- jor components: 1. Joe requires some form of handheld mobile device, such as a cell phone or a PDA. This component is shown on the left side of the figure. The device must include the appropriate LEAP device software, allowing it to use the LEAP protocols to commu- nicate with LEAP-enabled Message Centers, either directly over the Internet, or via a Subscriber Ser- vice system. 2. Joe requires a set of Subscriber Services to support his Mobile Messaging capability. This component is shown in the center of the figure. 3. Joe may also wish to have LEAP-based Mobile Mes- saging capability on a Personal Desktop system at home, or on a Corporate Intranet system at his of- fice. These components are shown on the right side of the figure. If Joe receives a generic (i.e. non-LEAP) e-mail mes- sage over the Internet, then this will be fielded by his Sub- scriber Service provider, then forwarded to Joe's mobile device using the LEAP protocols. Meanwhile, e-mails for Joe may be received in ei- ther his home or office mailbox systems. Joe may con- figure either of these systems to forward certain e-mails to his mobile device on a selective basis. If so, the qual- ifying e-mails will be forwarded to him directly over the Internet, using the LEAP protocols. The Subscriber Ser- vices system need not be involved in the transmission of these forwarded e-mails, since they are being sent from one LEAP-enabled system to another. 12 In summary, the end-user experience described above represents a superset of the capabilities of the RIM Black- Berry [tm] system. The market success of BlackBerry clearly demonstrates the large user demand for this kind of service. By providing the same functionality of Black- Berry in a completely open fashion, the benefits to the consumer will be that much greater. For further discus- sion, see the article Operation WhiteBerry in The LEAP Manifesto. 7 The LEAP Development Process The LEAP protocols are intended to be open in the fullest sense of the word; they are intended to be freely and per- manently available, subject to public review and revision, and without usage restrictions of any kind. Therefore the processes and procedures used throughout the develop- ment and maintenance of the LEAP protocols have been such as to endow them with these characteristics, and to ensure their integrity as public protocols. A detailed description of the LEAP development pro- cess is provided in the article entitled The LEAP Protocol Development Model within The LEAP Manifesto. In the following sections we provide a brief summary of the ma- jor development principles. 7.1 Patent-Freedom The development and maintenance of the LEAP proto- cols conforms fully to the policies and procedures of the Free Protocols Foundation. In particular, Neda has de- clared to the Free Protocols Foundation that the LEAP protocols are patent-free to the best of its knowledge, and that it intends to keep them patent-free permanently. For more information see http://www.FreeProtocols.org. 7.2 RFC Publication Both protocols have been published as Internet RFCs; ESRO in September 1997 as RFC-2188 [6 ], and EMSD in March 1999 as RFC-2524 [1 ]. RFC publication is the mainstream Internet publishing procedure, ensuring that the protocols are freely, easily and permanently accessi- ble to anyone who wishes to use them. 13 7.3 Open Maintenance Organizations To provide an open forum for the continued development and maintenance of the LEAP protocols, Neda has estab- lished a public organization for each protocol. The ESRO and EMSD protocols are maintained, re- spectively, by ESRO.org at http://www.esro.org/, and by EMSD.org at http://www.emsd.org/. Each of these organizations allows public review of the respective protocol, and provides mechanisms for en- hancement of the protocol as a result of collective expe- rience. Any interested person may participate in the further development of the protocols. Participation in the devel- opment process is entirely open and non-exclusive; there are no membership fees. 8 LEAPing over WAP A set of specifications called the Wireless Application Protocol, or WAP, exists already, and purports to do the same things that LEAP does. However, the WAP speci- fications are entirely unfit for their claimed purpose, and are doomed to technological and political failure. A de- tailed criticism of WAP and justification of these state- ments is provided in an article called The WAP Trap [5 ] within The LEAP Manifesto. LEAP is an alternative to WAP, that does in fact what WAP does only in fiction. For a point-by-point compari- son of LEAP to WAP, see the article entitled LEAP: One Alternative to WAP [3 ] within The LEAP Manifesto. Those characteristics of WAP that make it wholly un- fit to be the industry standard are summarized in Table 1, along with the corresponding characteristics of the LEAP protocols. 9 A Brief History of LEAP LEAP originated in 1994 as part of the research and de- velopment initiatives of McCaw Cellular's wireless data group (now AT&T Wireless Services). The development work that would eventually lead to LEAP was initially undertaken in the context of the CDPD network; its scope was later expanded to include the Narrowband PCS net- work also. 14 _ _ ___ ___ ____ _____ _____ ______ _______ _______ _______ _______ ________ ________ ________ _________ _________ __________ ___________ ___________ ____________ ____________ _____________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ ______________ _____________________ ____________________ _______________ ___________________ ______________________ WAP ______ * * LEAP _____ ___________ _______Subject_to_known_patent_restrictions________ Pat_____e* *nt-free _____ _______Self-published_by_the_WAP_Forum___________ Pub_____l* *ished as Internet RFCs _____ _______Revisions_subject_to_change_without_notice_______ All_____r* *evisions permanently fixed _____ _______Maintained_by_the_WAP_Forum_____ Mai_____n* *tained by open working groups _____ ________ Re-invention of existing protocols Efficienc* *y-optimizing extensions to existing _______ _________________ protoco__* *_______ls _________ ______ Tailored to mobile phone user interface char- User inte* *rface independent ______ ___________acteristics______ __* *_______ _________ _______Inherent_security_vulnerability____ Imp_____o* *ses no security assumptions _____ _______Inconsistent_protocol_number_assignment_ Con_____s* *istent protocol number assignment _____ _______Poor_technical_design_ Goo_____d* * technical design _____ _______Initial_focus: web browsing Ini_____t* *ial focus: messaging _____ ______ Treats wireless as a special case Tre_____a* *ts wireless as an extension of Internet _____ Table 1: WAP versus LEAP By 1996 McCaw Cellular was fully committed to pag- ing, had recently purchased two nationwide narrowband wireless PCS licenses, and wished to develop an efficient wireless message transport and delivery system. Neda Communications, Inc., an independent consulting com- pany working under contract to McCaw Cellular, played a significant role in the development of the required sys- tem. Neda Communications had also been involved from the outset in the development of the CDPD specification. In 1997 however, soon after the purchase of McCaw Cellular by AT&T Wireless, the latter company aban- doned the wireless messaging project. Prior to this event, Neda had secured from AT&T the necessary rights to continue independent development of the protocols. There- fore, recognizing the eventual future need for these pro- tocols, Neda then undertook to continue development of them independently of AT&T. They were eventually com- pleted by Neda, published as RFCs, and now form the basis of the LEAP protocols. Prior to abandoning wireless messaging, AT&T Wire- less Services invested several million dollars in related development work. In creating LEAP, therefore, Neda was able to build upon a large abandoned investment by AT&T Wireless. References [1] M. Banan. Neda's Efficient Mail Submission and Delivery (EMSD) Protocol Specification Ver- sion 1.3. Request for Comments (Informational) 15 2524, Neda Communications, Inc., February 1999. Online document is available at ftp://ftp.isi.edu/in- notes/rfc2524.txt. [2] Mohsen Banan. Efficiency Study of EMSD vs. SMTP/POP3/IMAP. Neda Published Document 103-101-01.01, EMSD Organiza- tion, 1996. Online document is available at http://www.emsd.org/pubs/biblio/103-101-01- 01/index.html. [3] Mohsen Banan. LEAP: One Alternative to WAP. A component of LEAP Manifesto 108- 102-02, LEAP Forum, Bellevue, WA, Febru- ary 2000. Online document is available at http://www.freeprotocols.org/pubs/biblio/108-102- 02/index.html. [4] Mohsen Banan. Lightweight & Efficient Applica- tion Protocol (LEAP) Manifesto. Technical Re- port 108-101-01, LEAP Forum, Bellevue, WA, January 2000. Online document is available at http://www.freeprotocols.org/pubs/biblio/108-101- 01/index.html. [5] Mohsen Banan. The WAP Trap. FPF Pub- lished Document 108-102-01, Free Proto- cols Foundation, Bellevue, WA, January 2000. Online document is available at http://www.freeprotocols.org/pubs/biblio/108- 102-01/index.html. [6] M. Taylor, J. Cheng, and M. Banan. AT&T/Neda's Efficient Short Remote Operations (ESRO) Protocol Specification Version 1.2. Request for Comments (Informational) 2188, Neda Communications, Inc., September 1997. Online document is available at ftp://ftp.isi.edu/in-notes/rfc2188.txt. 16