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Network Working Group                                         B. AdamsonRequest for Comments: 1677                     Naval Research LaboratoryCategory: Informational                                      August 1994Tactical Radio Frequency Communication Requirements for IPngStatus of this Memo   This memo provides information for the Internet community.  This memo   does not specify an Internet standard of any kind.  Distribution of   this memo is unlimited.Abstract   This document was submitted to the IETF IPng area in response toRFC1550.  Publication of this document does not imply acceptance by the   IPng area of any ideas expressed within.  Comments should be   submitted to the big-internet@munnari.oz.au mailing list.Executive Summary   The U.S. Navy has several efforts exploring the applicability of   commercial internetworking technology to tactical RF networks.  Some   these include the NATO Communication System Network Interoperability   (CSNI) project, the Naval Research Laboratory Data/Voice Integration   Advanced Technology Demonstration (D/V ATD), and the Navy   Communication Support System (CSS) architecture development.   Critical requirements have been identified for security, mobility,   real-time data delivery applications, multicast, and quality-of-   service and policy based routing.  Address scaling for Navy   application of internet technology will include potentially very   large numbers of local (intra-platform) distributed information and   weapons systems and a smaller number of nodes requiring global   connectivity.  The flexibility of the current Internet Protocol (IP)   for supporting widely different communication media should be   preserved to meet the needs of the highly heterogeneous networks of   the tactical environment.  Compact protocol headers are necessary for   efficient data transfer on the relatively-low throughput RF systems.   Mechanisms which can  enhance the effectiveness of an internet   datagram protocol to provide resource reservation, priority, and   service quality guarantees are also very important.  The broadcast   nature of many RF networks and the need for broad dissemination of   information to warfighting participants makes multicast the general   case for information flow in the tactical environment.Adamson                                                         [Page 1]

RFC 1677             IPng Tactical RF Requirements           August 1994Background   This paper describes requirements for Internet Protocol next   generation (IPng) candidates with respect to their application to   military tactical radio frequency (RF) communication networks.  The   foundation for these requirements are experiences in the NATO   Communication System Network Interoperability (CSNI) project, the   Naval Research Laboratory Data/Voice Integration Advanced Technology   Demonstration (D/V ATD), and the Navy Communication Support System   (CSS) architecture development.   The goal of the CSNI project is to apply internetworking technology   to facilitate multi-national interoperability for typical military   communication applications (e.g., electronic messaging, tactical data   exchange, and digital voice) on typical tactical RF communication   links and networks.  The International Standard Organization (ISO)   Open Systems Interconnect (OSI) protocol suite, including the   Connectionless Network Protocol (CLNP), was selected for this project   for policy reasons.  This paper will address design issues   encountered in meeting the project goals with this particular   protocol stack.   The D/V ATD is focused on demonstrating  a survivable, self-   configuring, self-recovering RF subnetwork technology capable of   simultaneously supporting data delivery, including message transfer,   imagery, and tactical data, and real-time digital voice applications.   Support for real-time interactive communication applications was   extended to include a "white board" and other similar applications.   IP datagram delivery is also planned as part of this demonstration   system.   The CSS architecture will provide U.S. Navy tactical platforms with a   broad array of user-transparent voice and data information exchange   services.  This will include support for sharing and management of   limited platform communication resources among multiple warfighting   communities.  Emphasis is placed on attaining interoperability with   other military services and foreign allies.  Utilization of   commercial off-the-shelf communications products to take advantage of   existing economies of scale is important to make any resulting system   design affordable.  It is anticipated that open, voluntary standards,   and flexible communication protocols, such as IP, will play a key   role in meeting the goals of this architecture.Introduction   Before addressing any IPng requirements as applied to tactical RF   communications, it is necessary to define what this paper means by   "IPng requirements".  To maintain brevity, this paper will focus onAdamson                                                         [Page 2]

RFC 1677             IPng Tactical RF Requirements           August 1994   criteria related specifically to the design of an OSI model's Layer 3   protocol format and a few other areas suggested byRFC 1550.  There   are several additional areas of concern in applying internetwork   protocols to the military tactical RF setting including routing   protocol design, address assignment, network management, and resource   management.  While these areas are equally important, this paper will   attempt to satisfy the purpose ofRFC 1550 and address issues more   directly applicable to selection of an IPng candidate.Scaling   The projection given inRFC 1550 that IPng should be able to deal   with 10 to the 12th nodes is more than adequate in the face of   military requirements.  More important is that it is possible to   assign addresses efficiently.  For example, although a military   platform may have a relatively small number of nodes with   requirements to communicate with a larger, global infrastructure,   there will likely be applications of IPng to management and control   of distributed systems (e.g., specific radio communications equipment   and processors, weapons systems, etc.) within the platform.  This   local expansion of address space requirements may not necessarily   need to be solved by "sheer numbers" of globally-unique addresses but   perhaps by alternate delimitation of addressing to differentiate   between globally-unique and locally-unique addressing.  The   advantages of a compact internet address header are clear for   relatively low capacity RF networks.Timescale, Transition and Deployment   The U.S. Navy and other services are only recently (the last few   years) beginning to design and deploy systems utilizing open systems   internetworking technology.  From this point of view, the time scale   for selection of IPng must be somewhat rapid.  Otherwise, two   transition phases will need to be suffered, 1) the move from unique,   "stove pipe" systems to open, internetworked (e.g., IP) systems, and   then 2) a transition from deployed IP-based systems to IPng.  In some   sense, if an IPng is quickly accepted and widely implemented, the   transition for tactical military systems will be somewhat easier than   the enterprise Internet where a large investment in current IP   already exists.  However, having said this, the Department of Defense   as a whole already deploys a large number  of IP-capable systems, and   the issue of transition from IP to IPng remains significant.Security   As with any military system, information security, including   confidentiality and authenticity of data, is of paramount importance.   With regards to IPng, network layer security mechanisms for tacticalAdamson                                                         [Page 3]

RFC 1677             IPng Tactical RF Requirements           August 1994   RF networks generally important for authentication purposes,   including routing protocol authentication, source authentication, and   user network access control.  Concerns for denial of service attacks,   traffic analysis monitoring, etc., usually dictate that tactical RF   communication networks provide link layer security mechanisms.   Compartmentalization and multiple levels of security for different   users of common communication resources call for additional security   mechanisms at the transport layer or above.  In the typical tactical   RF environment, network layer confidentiality and, in some cases,   even authentication becomes redundant with these other security   mechanisms.   The need for network layer security mechanisms becomes more critical   when the military utilizes commercial telecommunications systems or   has tactical systems inter-connected with commercial internets.   While the Network Encryption Server (NES) works in this role today,   there is a desire for a more integrated, higher performance solution   in the future.  Thus, to meet the military requirement for   confidentiality and authentication, an IPng candidate must be capable   of operating in a secure manner when necessary, but also allow for   efficient operation on low-throughput RF links when other security   mechanisms are already in place.   In either of these cases, key management is extremely important.   Ideally, a common key management system could be used to provide key   distribution for security mechanisms at any layer from the   application to the link layer.  As a result, it is anticipated,   however, that key distribution is a function of management, and   should not dependent upon a particular IPng protocol format.Mobility   The definition of most tactical systems include mobility in some   form.  Many tactical RF network designs provide means for members to   join and leave particular RF subnets as their position changes.  For   example, as a platform moves out of the RF line-of-sight (LOS) range,   it may switch from a typical LOS RF media such as the ultra-high   frequency (UHF) band to a long-haul RF media such as high frequency   (HF) or satellite communication (SATCOM).   In some cases, such as the D/V ATD network, the RF subnet will   perform its own routing and management of this dynamic topology.   This will be invisible to the internet protocol except for   (hopefully) subtle changes to some routing metrics (e.g., more or   less delay to reach a host).  In this instance, the RF subnetwork   protocols serve as a buffer to the internet routing protocols and   IPng will not need to be too concerned with mobility.Adamson                                                         [Page 4]

RFC 1677             IPng Tactical RF Requirements           August 1994   In other cases, however, the platform may make a dramatic change in   position and require a major change in internet routing.  IPng must   be able to support this situation.  It is recognized that an internet   protocol may not be able to cope with large, rapid changes in   topology.  Efforts will be made to minimize the frequency of this in   a tactical RF communication architecture, but there are instances   when a major change in topology is required.   Furthermore, it should be realized that mobility in the tactical   setting is not limited to individual nodes moving about, but that, in   some cases, entire subnetworks may be moving.  An example of this is   a Navy ship with multiple LANs on board, moving through the domains   of different RF networks.  In some cases, the RF subnet will be   moving, as in the case of an aircraft strike force, or Navy   battlegroup.Flows and Resource Reservation   The tactical military has very real requirements for multi-media   services across its shared and inter-connected RF networks.  This   includes applications from digital secure voice integrated with   applications such as "white boards" and position reporting for   mission planning purposes to low-latency, high priority tactical data   messages (target detection, identification, location and heading   information).  Because of the limited capacity of tactical RF   networks, resource reservation is extremely important to control   access to these valuable resources.  Resource reservation can play a   role in "congestion avoidance" for these limited resources as well as   ensuring that quality-of-service data delivery requirements are met   for multi-media communication.   Note there is more required here than can be met by simple quality-   of-service (QoS) based path selection and subsequent source-routing   to get real-time data such as voice delivered.  For example, to   support digital voice in the CSNI project, a call setup and resource   reservation protocol was designed.  It was determined that the QoS   mechanisms provided by the CLNP specification were not sufficient for   our voice application path selection.  Voice calls could not be   routed and resources reserved based on any single QoS parameter   (e.g., delay, capacity, etc.) alone.  Some RF subnets in the CSNI   test bed simply did not have the capability to support voice calls.   To perform resource reservation for the voice calls, the CLNP cost   metric was "hijacked" as essentially a Type of Service identifier to   let the router know which datagrams were associated with a voice   call.  The cost metric, concatenated with the source and destination   addresses were used to form a unique identifier for voice calls in   the router and subnet state tables.  Voice call paths were to be   selected by the router (i.e. the "cost" metric was calculated) as aAdamson                                                         [Page 5]

RFC 1677             IPng Tactical RF Requirements           August 1994   rule-based function of each subnet's capability to support voice, its   delay, and its capacity.  While source routing provided a possible   means for voice datagrams to find their way from router to router,   the network address alone was not explicit enough to direct the data   to the correct interface, particularly in cases where there were   multiple communication media interconnecting two routers along the   path.  Fortunately, exclusive use of the cost QoS indicator for voice   in CSNI was able to serve as a flag to the router for packets   requiring special handling.   While a simple Type of Service field as part of an IPng protocol can   serve this purpose where there are a limited number of well known   services (CSNI has a single special service - 2400 bps digital   voice), a more general technique such as RSVP's Flow Specification   can support a larger set of such services.  And a field, such as the   one sometimes referred to as a Flow Identification (Flow ID), can   play an important role in facilitating inter-networked data   communication over these limited capacity networks.   For example, the D/V ATD RF sub-network provides support for both   connectionless datagram delivery and virtual circuit connectivity.   To utilize this capability, an IPng could establish a virtual circuit   connection across this RF subnetwork which meets the requirements of   an RSVP Flow Specification. By creating an association between a   particular Flow ID and the subnetwork header identifying the   established virtual circuit, an IPng gateway could forward data   across the low-capacity while removing most, if not all, of the IPng   packet header information.  The receiving gateway could re- construct   these fields based on the Flow Specification of the particular Flow   ID/virtual circuit association.   In summary, a field such as a Flow Identification can serve at least   two important purposes:         1)      It can be used by routers (or gateways) to identify                 packets with special, or pre-arranged delivery                 requirements.  It is important to realize that it may                 not always be possible to "peek" at internet packet                 content for this information if certain security                 considerations are met (e.g., an encrypted transport                 layer).         2)      It can aid mapping datagram services to different                 types of communication services provided by                 specialized subnet/data link layer protocols.Adamson                                                         [Page 6]

RFC 1677             IPng Tactical RF Requirements           August 1994Multicast   Tactical military communication has a very clear requirement for   multicast.  Efficient dissemination of information to distributed   warfighting participants can be the key to success in a battle.  In   modern warfare, this information includes imagery, the "tactical   scene" via tactical data messages, messaging information, and real-   time interactive applications such as digital secure voice.  Many of   the tactical RF communication media are broadcast by nature, and   multicast routing can take advantage of this topology to distribute   critical data to a large number of participants.  The throughput   limitations imposed by these RF media and the physics of potential   electronic counter measures (ECM) dictate that this information be   distributed efficiently.  A multicast architecture is the general   case for information flow in a tactical internetwork.Quality of Service and Policy-Based Routing   Quality of service and policy based routing are of particular   importance in a tactical environment with limited communication   resources, limited bandwidth, and possible degradation and/or denial   of service.  Priority is a very important criteria in the tactical   setting.  In the tactical RF world of limited resources (limited   bandwidth, radio assets, etc.) there will be instances when there is   not sufficient capacity to provide all users with their perception of   required communication capability.  It is extremely important for a   shared, automated communication system to delegate capacity higher   priority users.  Unlike the commercial world, where everyone has a   more equal footing, it is possible in the military environment to   assign priority to users or even individual datagrams.  An example of   this is the tactical data exchange.  Tactical data messages are   generally single-datagram messages containing information on the   location, bearing, identification, etc., of entities detected by   sensors.  In CSNI, tactical data messages were assigned 15 different   levels of CLNP priority.  This ensured that important messages, such   as a rapidly approaching enemy missile's trajectory, were given   priority over less important messages, such as a friendly, slow-   moving tanker's heading.Applicability   There will be a significant amount of applicability to tactical RF   networks.  The current IP and CLNP protocols are being given   considerable attention in the tactical RF community as a means to   provide communication interoperability across a large set of   heterogeneous RF networks in use by different services and countries.   The applicability of IPng can only improve with the inclusion of   features critical to supporting QoS and Policy based routing,Adamson                                                         [Page 7]

RFC 1677             IPng Tactical RF Requirements           August 1994   security, real-time multi-media data delivery, and extended   addressing.  It must be noted that it is very important that the IPng   protocol headers not grow overly large.  There is a sharp tradeoff   between the value added by these headers (interoperability, global   addressing, etc.) and the degree of communication performance   attainable on limited capacity RF networks.  Regardless of the data   rate that future RF networks will be capable of supporting, there is   always a tactical advantage in utilizing your resources more   efficiently.Datagram Service   The datagram service paradigm provides many useful features for   tactical communication networks.  The "memory" provided by datagram   headers, provides an inherent amount of survivability essential to   the dynamics of the tactical communication environment.  The   availability of platforms for routing and relaying is never 100%   certain in a tactical scenario.  The efficiency with which multi-cast   can be implemented in a connectionless network is highly critical in   the tactical environment where rapid, efficient information   dissemination can be a deciding factor.  And, as has been proven,   with several different Internet applications and experiments, a   datagram service is capable of providing useful connection-oriented   and real-time communication services.   Consideration should be given in IPng to how it can co-exist with   other architectures such as switching fabrics which offer demand-   based control over topology and connectivity.  The military owns many   of its own communication resources and one of the large problems in   managing the military communication infrastructure is directing those   underlying resources to where they are needed.  Traditional   management (SNMP, etc.) is of course useful here, but RF   communication media can be somewhat dynamically allocated.  Circuit   switching designs offer some advantages here.  Dial-up IP routing is   an example of an integrated solution.  The IPng should be capable of   supporting a similar type of operation.Support of Communication Media   The tactical communication environment includes a very broad spectrum   of communication media from shipboard fiber-optic LANs to very low   data rate (<2400 bps) RF links.  Many of the RF links, even higher   speed ones, can exhibit error statistics not necessarily well-   serviced by higher layer reliable protocols (i.e., TCP).  In these   cases, efficient lower layer protocols can be implemented to provide   reliable datagram delivery at the link layer, but at the cost of   highly variable delay performance.Adamson                                                         [Page 8]

RFC 1677             IPng Tactical RF Requirements           August 1994   It is also important to recognize that RF communication cannot be   viewed from the IPng designer as simple point-to-point  links.   Often, highly complex, unique subnetwork protocols are utilized to   meet requirements of survivability, communications performance with   limited bandwidth, anti- jam and/or low probability of detection   requirements.  In some of these cases IPng will be one of several   Layer 3 protocols sharing the subnetwork.   It is understood that IPng cannot be the panacea of Layer 3   protocols, particularly when it comes to providing special mechanisms   to support the endangered-specie low data rate user.  However, note   that there are many valuable low data rate applications useful to the   tactical user.  And low user data rates, coupled with efficient   networking protocols can allow many more users share limited RF   bandwidth.  As a result, any mechanisms which facilitate compression   of network headers can be considered highly valuable in an IPng   candidate.Security Considerations   Security issues are discussed throughout this memo.Author's Address   R. Brian Adamson   Communication Systems Branch   Information Technology Division   Naval Research Laboratory   NRL Code 5523   Washington, DC 20375   EMail: adamson@itd.nrl.navy.milAdamson                                                         [Page 9]