doc: Add RFC documents

1 files changed, 675 insertions, 0 deletions

diff --git a/doc/rfc/rfc2501.txt b/doc/rfc/rfc2501.txt
new file mode 100644
index 0000000..8957554
--- /dev/null
+++ b/doc/rfc/rfc2501.txt
@@ -0,0 +1,675 @@
+
+
+
+
+
+
+Network Working Group                                          S. Corson
+Request for Comments: 2501                        University of Maryland
+Category: Informational                                        J. Macker
+                                               Naval Research Laboratory
+                                                            January 1999
+
+
+                   Mobile Ad hoc Networking (MANET):
+   Routing Protocol Performance Issues and Evaluation Considerations
+
+Status of this Memo
+
+   This memo provides information for the Internet community.  It does
+   not specify an Internet standard of any kind.  Distribution of this
+   memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (1999).  All Rights Reserved.
+
+Abstract
+
+   This memo first describes the characteristics of Mobile Ad hoc
+   Networks (MANETs), and their idiosyncrasies with respect to
+   traditional, hardwired packet networks.  It then discusses the effect
+   these differences have on the design and evaluation of network
+   control protocols with an emphasis on routing performance evaluation
+   considerations.
+
+1. Introduction
+
+   With recent performance advancements in computer and wireless
+   communications technologies, advanced mobile wireless computing is
+   expected to see increasingly widespread use and application, much of
+   which will involve the use of the Internet Protocol (IP) suite. The
+   vision of mobile ad hoc networking is to support robust and efficient
+   operation in mobile wireless networks by incorporating routing
+   functionality into mobile nodes.  Such networks are envisioned to
+   have dynamic, sometimes rapidly-changing, random, multihop topologies
+   which are likely composed of relatively bandwidth-constrained
+   wireless links.
+
+   Within the Internet community, routing support for mobile hosts is
+   presently being formulated as "mobile IP" technology.  This is a
+   technology to support nomadic host "roaming", where a roaming host
+   may be connected through various means to the Internet other than its
+   well known fixed-address domain space. The host may be directly
+   physically connected to the fixed network on a foreign subnet, or be
+
+
+
+Corson & Macker              Informational                      [Page 1]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+   connected via a wireless link, dial-up line, etc.  Supporting this
+   form of host mobility (or nomadicity) requires address management,
+   protocol interoperability enhancements and the like, but core network
+   functions such as hop-by-hop routing still presently rely upon pre-
+   existing routing protocols operating within the fixed network. In
+   contrast, the goal of mobile ad hoc networking is to extend mobility
+   into the realm of autonomous, mobile, wireless domains, where a set
+   of nodes--which may be combined routers and hosts--themselves form
+   the network routing infrastructure in an ad hoc fashion.
+
+2. Applications
+
+   The technology of Mobile Ad hoc Networking is somewhat synonymous
+   with Mobile Packet Radio Networking (a term coined via during early
+   military research in the 70's and 80's), Mobile Mesh Networking (a
+   term that appeared in an article in The Economist regarding the
+   structure of future military networks) and Mobile, Multihop, Wireless
+   Networking (perhaps the most accurate term, although a bit
+   cumbersome).
+
+   There is current and future need for dynamic ad hoc networking
+   technology.  The emerging field of mobile and nomadic computing, with
+   its current emphasis on mobile IP operation, should gradually broaden
+   and require highly-adaptive mobile networking technology to
+   effectively manage multihop, ad hoc network clusters which can
+   operate autonomously or, more than likely, be attached at some
+   point(s) to the fixed Internet.
+
+   Some applications of MANET technology could include industrial and
+   commercial applications involving cooperative mobile data exchange.
+   In addition,  mesh-based mobile networks can be operated as robust,
+   inexpensive alternatives or enhancements to cell-based mobile network
+   infrastructures. There are also existing and future military
+   networking requirements for robust, IP-compliant data services within
+   mobile wireless communication networks [1]--many of these networks
+   consist of highly-dynamic autonomous topology segments. Also, the
+   developing technologies of "wearable" computing and communications
+   may provide applications for MANET technology. When properly combined
+   with satellite-based information delivery, MANET technology can
+   provide an extremely flexible method for establishing communications
+   for fire/safety/rescue operations or other scenarios requiring
+   rapidly-deployable communications with survivable, efficient dynamic
+   networking. There are likely other applications for MANET technology
+   which are not presently realized or envisioned by the authors.  It
+   is, simply put, improved IP-based networking technology for dynamic,
+   autonomous wireless networks.
+
+
+
+
+
+Corson & Macker              Informational                      [Page 2]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+3. Characteristics of MANETs
+
+   A MANET consists of mobile platforms (e.g., a router with multiple
+   hosts and wireless communications devices)--herein simply referred to
+   as "nodes"--which are free to move about arbitrarily. The nodes may
+   be located in or on airplanes, ships, trucks, cars, perhaps even on
+   people or very small devices, and there may be multiple hosts per
+   router. A MANET is an autonomous system of mobile nodes.  The system
+   may operate in isolation, or may have gateways to and interface with
+   a fixed network. In the latter operational mode, it is typically
+   envisioned to operate as a "stub" network connecting to a fixed
+   internetwork.  Stub networks carry traffic originating at and/or
+   destined for internal nodes, but do not permit exogenous traffic to
+   "transit" through the stub network.
+
+   MANET nodes are equipped with wireless transmitters and receivers
+   using antennas which may be omnidirectional (broadcast), highly-
+   directional (point-to-point), possibly steerable, or some combination
+   thereof. At a given point in time, depending on the nodes' positions
+   and their transmitter and receiver coverage patterns, transmission
+   power levels and co-channel interference levels, a wireless
+   connectivity in the form of a random, multihop graph or "ad hoc"
+   network exists between the nodes.  This ad hoc topology may change
+   with time as the nodes move or adjust their transmission and
+   reception parameters.
+
+   MANETs have several salient characteristics:
+
+      1) Dynamic topologies: Nodes are free to move arbitrarily; thus,
+      the network topology--which is typically multihop--may change
+      randomly and rapidly at unpredictable times, and may consist of
+      both bidirectional and unidirectional links.
+
+      2) Bandwidth-constrained, variable capacity links: Wireless links
+      will continue to have significantly lower capacity than their
+      hardwired counterparts. In addition, the realized throughput of
+      wireless communications--after accounting for the effects of
+      multiple access, fading, noise, and interference conditions,
+      etc.--is often much less than a radio's maximum transmission rate.
+
+      One effect of the relatively low to moderate link capacities is
+      that congestion is typically the norm rather than the exception,
+      i.e.  aggregate application demand will likely approach or exceed
+      network capacity frequently. As the mobile network is often simply
+      an extension of the fixed network infrastructure, mobile ad hoc
+      users will demand similar services. These demands will continue to
+      increase as multimedia computing and collaborative networking
+      applications rise.
+
+
+
+Corson & Macker              Informational                      [Page 3]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+      3) Energy-constrained operation: Some or all of the nodes in a
+      MANET may rely on batteries or other exhaustible means for their
+      energy. For these nodes, the most important system design criteria
+      for optimization may be energy conservation.
+
+      4) Limited physical security: Mobile wireless networks are
+      generally more prone to physical security threats than are fixed-
+      cable nets.  The increased possibility of eavesdropping, spoofing,
+      and denial-of-service attacks should be carefully considered.
+      Existing link security techniques are often applied within
+      wireless networks to reduce security threats. As a benefit, the
+      decentralized nature of network control in MANETs provides
+      additional robustness against the single points of failure of more
+      centralized approaches.
+
+   In addition, some envisioned networks (e.g. mobile military networks
+   or highway networks) may be relatively large (e.g. tens or hundreds
+   of nodes per routing area).  The need for scalability is not unique
+   to MANETS. However, in light of the preceding characteristics, the
+   mechanisms required to achieve scalability likely are.
+
+   These characteristics create a set of underlying assumptions and
+   performance concerns for protocol design which extend beyond those
+   guiding the design of routing within the higher-speed, semi-static
+   topology of the fixed Internet.
+
+4. Goals of IETF Mobile Ad Hoc Network (manet) Working Group
+
+   The intent of the newly formed IETF manet working group is to develop
+   a peer-to-peer mobile routing capability in a purely mobile, wireless
+   domain.  This capability will exist beyond the fixed network (as
+   supported by traditional IP networking) and beyond the one-hop fringe
+   of the fixed network.
+
+   The near-term goal of the manet working group is to standardize one
+   (or more) intra-domain unicast routing protocol(s), and related
+   network-layer support technology which:
+
+      * provides for effective operation over a wide range of mobile
+      networking "contexts" (a context is a set of characteristics
+      describing a mobile network and its environment);
+
+      * supports traditional, connectionless IP service;
+
+      * reacts efficiently to topological changes and traffic demands
+      while maintaining effective routing in a mobile networking
+      context.
+
+
+
+
+Corson & Macker              Informational                      [Page 4]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+   The working group will also consider issues pertaining to addressing,
+   security, and interaction/interfacing with lower and upper layer
+   protocols. In the longer term, the group may look at the issues of
+   layering more advanced mobility services on top of the initial
+   unicast routing developed.  These longer term issues will likely
+   include investigating multicast and QoS extensions for a dynamic,
+   mobile area.
+
+5. IP-Layer Mobile Routing
+
+   An improved mobile routing capability at the IP layer can provide a
+   benefit similar to the intention of the original Internet, viz. "an
+   interoperable internetworking capability over a heterogeneous
+   networking infrastructure". In this case, the infrastructure is
+   wireless, rather than hardwired, consisting of multiple wireless
+   technologies, channel access protocols, etc.  Improved IP routing and
+   related networking services provide the glue to preserve the
+   integrity of the mobile internetwork segment in this more dynamic
+   environment.
+
+   In other words, a real benefit to using IP-level routing in a MANET
+   is to provide network-level consistency for multihop networks
+   composed of nodes using a *mixture* of physical-layer media; i.e. a
+   mixture of what are commonly thought of as subnet technologies.  A
+   MANET node principally consists of a router, which may be physically
+   attached to multiple IP hosts (or IP-addressable devices), which has
+   potentially *multiple* wireless interfaces--each interface using a
+   *different* wireless technology.  Thus, a MANET node with interfaces
+   using technologies A and B can communicate with any other MANET node
+   possessing an interface with technology A or B.  The multihop
+   connectivity of technology A forms a physical-layer multihop
+   topology, the multihop connectivity of technology B forms *another*
+   physical-layer topology (which may differ from that of A's topology),
+   and the *union* of these topologies forms another topology (in graph
+   theoretic terms--a multigraph), termed the "IP routing fabric", of
+   the MANET.  MANET nodes making routing decisions using the IP fabric
+   can intercommunicate using either or both physical-layer topologies
+   simultaneously.  As new physical-layer technologies are developed,
+   new device drivers can be written and another physical-layer multihop
+   topology can be seamlessly added to the IP fabric.  Likewise, older
+   technologies can easily be dropped.  Such is the functionality and
+   architectural flexibility that IP-layer routing can support, which
+   brings with it hardware economies of scale.
+
+   The concept of a "node identifier" (separate and apart from the
+   concept of an "interface identifier") is crucial to supporting the
+   multigraph topology of the routing fabric. It is what *unifies* a set
+   of wireless interfaces and identifies them as belonging to the same
+
+
+
+Corson & Macker              Informational                      [Page 5]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+   mobile platform.  This approach permits maximum flexibility in
+   address assignment.  Node identifiers are used at the IP layer for
+   routing computations.
+
+5.1. Interaction with Standard IP Routing
+
+   In the near term, it is currently envisioned that MANETs will
+   function as *stub* networks, meaning that all traffic carried by
+   MANET nodes will either be sourced or sinked within the MANET.
+   Because of bandwidth and possibly power constraints, MANETs are not
+   presently envisioned to function as *transit* networks carrying
+   traffic which enters and then leaves the MANET (although this
+   restriction may be removed by subsequent technology advances).  This
+   substantially reduces the amount of route advertisement required for
+   interoperation with the existing fixed Internet. For stub operation,
+   routing interoperability in the near term may be achieved using some
+   combination of mechanisms such as MANET-based anycast and mobile IP.
+   Future interoperability may be achieved using mechanisms other than
+   mobile IP.
+
+   Interaction with Standard IP Routing will be greatly facilitated by
+   usage of a common MANET addressing approach by all MANET routing
+   protocols. Development of such an approach is underway which permits
+   routing through a multi-technology fabric, permits multiple hosts per
+   router and ensures long-term interoperability through adherence to
+   the IP addressing architecture.  Supporting these features appears
+   only to require identifying host and router interfaces with IP
+   addresses, identifying a router with a separate Router ID, and
+   permitting routers to have multiple wired and wireless interfaces.
+
+6. MANET Routing Protocol Performance Issues
+
+   To judge the merit of a routing protocol, one needs metrics--both
+   qualitative and quantitative--with which to measure its suitability
+   and performance.  These metrics should be *independent* of any given
+   routing protocol.
+
+   The following is a list of desirable qualitative properties of MANET
+   routing protocols:
+
+      1) Distributed operation:  This is an essential property, but it
+      should be stated nonetheless.
+
+      2) Loop-freedom:  Not required per se in light of certain
+      quantitative measures (i.e. performance criteria), but generally
+      desirable to avoid problems such as worst-case phenomena, e.g. a
+      small fraction of packets spinning around in the network for
+      arbitrary time periods.  Ad hoc solutions such as TTL values can
+
+
+
+Corson & Macker              Informational                      [Page 6]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+      bound the problem, but a more structured and well-formed approach
+      is generally desirable as it usually leads to better overall
+      performance.
+
+      3) Demand-based operation:  Instead of assuming an uniform traffic
+      distribution within the network (and maintaining routing between
+      all nodes at all times), let the routing algorithm adapt to the
+      traffic pattern on a demand or need basis.  If this is done
+      intelligently, it can utilize network energy and bandwidth
+      resources more efficiently, at the cost of increased route
+      discovery delay.
+
+      4) Proactive operation:  The flip-side of demand-based operation.
+      In certain contexts, the additional latency demand-based operation
+      incurs may be unacceptable.  If bandwidth and energy resources
+      permit, proactive operation is desirable in these contexts.
+
+      5) Security: Without some form of network-level or link-layer
+      security, a MANET routing protocol is vulnerable to many forms of
+      attack.  It may be relatively simple to snoop network traffic,
+      replay transmissions, manipulate packet headers, and redirect
+      routing messages, within a wireless network without appropriate
+      security provisions. While these concerns exist within wired
+      infrastructures and routing protocols as well, maintaining the
+      "physical" security of of the transmission media is harder in
+      practice with MANETs. Sufficient security protection to prohibit
+      disruption of modification of protocol operation is desired. This
+      may be somewhat orthogonal to any particular routing protocol
+      approach, e.g. through the application of IP Security techniques.
+
+      6) "Sleep" period operation:  As a result of energy conservation,
+      or some other need to be inactive, nodes of a MANET may stop
+      transmitting and/or receiving (even receiving requires power) for
+      arbitrary time periods.  A routing protocol should be able to
+      accommodate such sleep periods without overly adverse
+      consequences. This property may require close coupling with the
+      link-layer protocol through a standardized interface.
+
+      7) Unidirectional link support:  Bidirectional links are typically
+      assumed in the design of routing algorithms, and many algorithms
+      are incapable of functioning properly over unidirectional links.
+      Nevertheless, unidirectional links can and do occur in wireless
+      networks. Oftentimes, a sufficient number of duplex links exist so
+      that usage of unidirectional links is of limited added value.
+      However, in situations where a pair of unidirectional links (in
+      opposite directions) form the only bidirectional connection
+      between two ad hoc regions, the ability to make use of them is
+      valuable.
+
+
+
+Corson & Macker              Informational                      [Page 7]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+   The following is a list of quantitative metrics that can be used to
+   assess the performance of any routing protocol.
+
+      1) End-to-end data throughput and delay: Statistical measures of
+      data routing performance (e.g., means, variances, distributions)
+      are important. These are the measures of a routing policy's
+      effectiveness--how well it does its job--as measured from the
+      *external* perspective of other policies that make use of routing.
+
+      2) Route Acquisition Time: A particular form of *external* end-
+      to-end delay measurement--of particular concern with "on demand"
+      routing algorithms--is the time required to establish route(s)
+      when requested.
+
+      3) Percentage Out-of-Order Delivery: An external measure of
+      connectionless routing performance of particular interest to
+      transport layer protocols such as TCP which prefer in-order
+      delivery.
+
+      4) Efficiency:  If data routing effectiveness is the external
+      measure of a policy's performance, efficiency is the *internal*
+      measure of its effectiveness.  To achieve a given level of data
+      routing performance, two different policies can expend differing
+      amounts of overhead, depending on their internal efficiency.
+      Protocol efficiency may or may not directly affect data routing
+      performance.  If control and data traffic must share the same
+      channel, and the channel's capacity is limited, then excessive
+      control traffic often impacts data routing performance.
+
+      It is useful to track several ratios that illuminate the
+      *internal* efficiency of a protocol in doing its job (there may be
+      others that the authors have not considered):
+
+         * Average number of data bits transmitted/data bit delivered--
+         this can be thought of as a measure of the bit efficiency of
+         delivering data within the network.  Indirectly, it also gives
+         the average hop count taken by data packets.
+
+         * Average number of control bits transmitted/data bit
+         delivered--this measures the bit efficiency of the protocol in
+         expending control overhead to delivery data.  Note that this
+         should include not only the bits in the routing control
+         packets, but also the bits in the header of the data packets.
+         In other words, anything that is not data is control overhead,
+         and should be counted in the control portion of the algorithm.
+
+
+
+
+
+
+Corson & Macker              Informational                      [Page 8]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+         * Average number of control and data packets transmitted/data
+         packet delivered--rather than measuring pure algorithmic
+         efficiency in terms of bit count, this measure tries to capture
+         a protocol's channel access efficiency, as the cost of channel
+         access is high in contention-based link layers.
+
+   Also, we must consider the networking *context* in which a protocol's
+   performance is measured.  Essential parameters that should be varied
+   include:
+
+      1) Network size--measured in the number of nodes
+
+      2) Network connectivity--the average degree of a node (i.e. the
+      average number of neighbors of a node)
+
+      3) Topological rate of change--the speed with which a network's
+      topology is changing
+
+      4) Link capacity--effective link speed measured in bits/second,
+      after accounting for losses due to multiple access, coding,
+      framing, etc.
+
+      5) Fraction of unidirectional links--how effectively does a
+      protocol perform as a function of the presence of unidirectional
+      links?
+
+      6) Traffic patterns--how effective is a protocol in adapting to
+      non-uniform or bursty traffic patterns?
+
+      7) Mobility--when, and under what circumstances, is temporal and
+      spatial topological correlation relevant to the performance of a
+      routing protocol?  In these cases, what is the most appropriate
+      model for simulating node mobility in a MANET?
+
+      8) Fraction and frequency of sleeping nodes--how does a protocol
+      perform in the presence of sleeping and awakening nodes?
+
+   A MANET protocol should function effectively over a wide range of
+   networking contexts--from small, collaborative, ad hoc groups to
+   larger mobile, multihop networks.  The preceding discussion of
+   characteristics and evaluation metrics somewhat differentiate MANETs
+   from traditional, hardwired, multihop networks.  The wireless
+   networking environment is one of scarcity rather than abundance,
+   wherein bandwidth is relatively limited, and energy may be as well.
+
+   In summary, the networking opportunities for MANETs are intriguing
+   and the engineering tradeoffs are many and challenging.  A diverse
+   set of performance issues requires new protocols for network control.
+
+
+
+Corson & Macker              Informational                      [Page 9]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+   A question which arises is "how should the *goodness* of a policy be
+   measured?". To help answer that, we proposed here an outline of
+   protocol evaluation issues that highlight performance metrics that
+   can help promote meaningful comparisons and assessments of protocol
+   performance.  It should be recognized that a routing protocol tends
+   to be well-suited for particular network contexts, and less well-
+   suited for others. In putting forth a description of a protocol, both
+   its *advantages* and *limitations* should be mentioned so that the
+   appropriate networking context(s) for its usage can be identified.
+   These attributes of a protocol can typically be expressed
+   *qualitatively*, e.g., whether the protocol can or cannot support
+   shortest-path routing.  Qualitative descriptions of this nature
+   permit broad classification of protocols, and form a basis for more
+   detailed *quantitative* assessments of protocol performance. In
+   future documents, the group may put forth candidate recommendations
+   regarding protocol design for MANETs. The metrics and the philosophy
+   presented within this document are expected to continue to evolve as
+   MANET technology and related efforts mature.
+
+7. Security Considerations
+
+   Mobile wireless networks are generally more prone to physical
+   security threats than are fixed, hardwired networks. Existing link-
+   level security techniques (e.g. encryption) are often applied within
+   wireless networks to reduce these threats.  Absent link-level
+   encryption, at the network layer, the most pressing issue is one of
+   inter-router authentication prior to the exchange of network control
+   information.  Several levels of authentication ranging from no
+   security (always an option) and simple shared-key approaches, to full
+   public key infrastructure-based authentication mechanisms will be
+   explored by the group.  As an adjunct to the working groups efforts,
+   several optional authentication modes may be standardized for use in
+   MANETs.
+
+8. References
+
+   [1] Adamson, B., "Tactical Radio Frequency Communication Requirements
+       for IPng", RFC 1677, August 1994.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Corson & Macker              Informational                     [Page 10]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+Authors' Addresses
+
+   M. Scott Corson
+   Institute for Systems Research
+   University of Maryland
+   College Park, MD 20742
+
+   Phone: (301) 405-6630
+   EMail: corson@isr.umd.edu
+
+
+   Joseph Macker
+   Information Technology Division
+   Naval Research Laboratory
+   Washington, DC 20375
+
+   Phone: (202) 767-2001
+   EMail: macker@itd.nrl.navy.mil
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Corson & Macker              Informational                     [Page 11]
+
+RFC 2501                MANET Performance Issues            January 1999
+
+
+Full Copyright Statement
+
+   Copyright (C) The Internet Society (1999).  All Rights Reserved.
+
+   This document and translations of it may be copied and furnished to
+   others, and derivative works that comment on or otherwise explain it
+   or assist in its implementation may be prepared, copied, published
+   and distributed, in whole or in part, without restriction of any
+   kind, provided that the above copyright notice and this paragraph are
+   included on all such copies and derivative works.  However, this
+   document itself may not be modified in any way, such as by removing
+   the copyright notice or references to the Internet Society or other
+   Internet organizations, except as needed for the purpose of
+   developing Internet standards in which case the procedures for
+   copyrights defined in the Internet Standards process must be
+   followed, or as required to translate it into languages other than
+   English.
+
+   The limited permissions granted above are perpetual and will not be
+   revoked by the Internet Society or its successors or assigns.
+
+   This document and the information contained herein is provided on an
+   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Corson & Macker              Informational                     [Page 12]
+