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Internet Engineering Task Force                               C. Perkins
INTERNET DRAFT                                          Sun Microsystems
                                                         30 October 1997


                  Mobile Ad Hoc Networking Terminology
                      draft-ietf-manet-term-00.txt


Status of This Memo

   This document is a submission by the Mobile Ad Hoc Networking Working
   Group of the Internet Engineering Task Force (IETF).  Comments should
   be submitted to the manet@itd.nrl.navy.mil mailing list.

   Distribution of this memo is unlimited.

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
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Abstract

   This document presents conventional definitions for many terms to be
   used during the discussion of various algorithms for enabling ad hoc
   networks of mobile computers, particularly over wireless media.
















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1. Introduction

   This document presents conventional definitions for many terms to be
   used during the discussion of various algorithms for enabling ad hoc
   networks of mobile computers, particularly over wireless media.  With
   commonly agreed definitions, it is expected that protocol designers
   will be able to discuss more clearly the advantages and disadvantages
   of their algorithms.


2. Definitions for Mobile Ad Hoc Network Terms

      asymmetric link

         A link with transmission characteristics which are different
         depending upon the relative position or design characteristics
         of the transmitter and the receiver of data on the link.  For
         instance, the range of one transmitter may be much higher than
         the range of another transmitter on the same medium.

      bandwidth

         The total capacity of a link to carry information (typically
         bits).

      bandwidth utilization

         The actual amount of information delivered over a link,
         expressed as a percent of the available bandwidth on that link.

      base station

         A centralized node coordinating the channel access of a
         population of mobile nodes within its transmission range.

      beacon

         A control message issued by a node (especially, a base station)
         informing all the other nodes in its neighborhood of the
         continuing presence of the node, possibly along with additional
         status information.

      channel

         A subdivision of the physical medium allowing possibly shared
         independent uses of the medium.  Channels may be made available
         by subdividing the medium into distinct time slots, or distinct
         spectral bands, or decorrelated coding sequences.




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      channel access protocol

         A protocol for mediating access to, and possibly allocation
         of, the various channels available within the physical
         communications medium.  Nodes participating in the channel
         access protocol can communicate only when they have uncontested
         access to the medium, so that there will be no interference.

      cluster

         A group of nodes located within close physical proximity,
         typically all within range of one another, which can be
         grouped together for the purpose of limiting the production and
         propogation of routing information.

      control message

         Information passed between two or more network nodes for
         maintaining protocol state which is not associated to any
         specific application.

      convergence

         The process of approaching a state of equilibrium in which all
         nodes in the network agree on a consistent collection of state
         about the topology of the network, and in which no further
         control messages are needed to establish the consistency of the
         network topology.

      convergence time

         The time which is required for a network to reach convergence
         after an event (typically, the movement of a mobile node) which
         changes the network topology.

      distance vector

         A style of routing protocol in which, for each desired
         destination, a node maintains information about the distance
         to that destination, and a vector (next hop) towards that
         destination.

      fairness

         A property of channel access protocols whereby a medium is
         made fairly equal to all eligible nodes on the link.  Fairness
         does not strictly imply equality, especially in cases where
         nodes are given link access according to unequal priority or
         classification.



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      flooding

         The process of delivering data or control messages to every
         node within the ad hoc network.

      forwarding node

         A node within an ad hoc network which performs the function of
         forwarding datagrams from one of its neighbors to another.

      goodput

         The total bandwidth used, less the volume of control messages
         and protocol overhead from the data packets.

      hidden-terminal problem

         The problem whereby a transmitting node can fail in its attempt
         to transmit data because of destructive interference which is
         only detectable at the receiving node, not the transmitting
         node.

      laydown

         The relative physical location of the nodes within the ad hoc
         network.

      link

         A physical medium which can sustain data communications between
         multiple network nodes.

      link state

         A style of routing protocol in which every node within the
         network is expected to maintain information about every link
         within the network topology.

      link-level acknowledgement

         A protocol strategy, typically employed over wireless
         media, requiring neighbors to acknowledge receipt of packets
         (typically unicast only) from the transmitter.  Such strategies
         aim to avoid packet loss or delay resulting from lack of, or
         unwanted characteristics of, higher level protocols.







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      local broadcast

         The delivery of data to every node on a link (i.e., within
         range of the transmitter).

      loop-free

         A property of routing protocols whereby the path taken by a
         data packet from source to destination never transits the same
         intermediate node twice before arrival at the destination.

      MAC-layer address

         An address (sometimes called the link address) associated with
         the link interface of a node on a physical link.

      mobility factor

         The relative frequency of node movement, compared to the
         convergence time of the routing protocols used in the ad hoc
         network.

      neighborhood

         All the nodes which can receive data on the same link from one
         node whenever it transmits data.

      next hop

         A neighbor which has been designated to forward packets along
         the way to a particular destination.

      pathloss

         A reduction in signal strength caused by traversing the
         physical medium constituting the link.

      pathloss matrix

         A matrix of coefficients describing the pathloss between any
         two nodes in an ad hoc network.  When the links are asymmetric,
         the matrix is also asymmetric.

      payload

         The actual data within a packet, not including network protocol
         headers which were not inserted by an application.





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      scalability

         Wide applicability of a protocol to large as well as small
         populations of nodes participating in the protocol.

      scenario

         The tuple <laydown, pathloss matrix, mobility factor, traffic>
         characterizing a class of ad hoc networks.

      signal strength

         The detectable power of the signal carrying the data bits, as
         seen by the receiver of the signal.

      source route

         A route to a source (i.e., a path with indications of
         intermediate forwarding nodes) made available to a receiver by
         the source of the data arriving at the receiver.

      spatial re-use

         Simultaneous use of channels with identical or close physical
         characteristics, but located spatially far enough apart to
         avoid interference (i.e., co-channel interference)

      system-wide broadcast

         Same as flooding, but used in contrast to local broadcast.

      throughput

         The amount of data from a source to a destination processed
         by the protocol for which throughput is to be measured for
         instance, IP, TCP, or the MAC protocol.
















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Chair's Address

   The working group can be contacted via the current chairs:

      M. Scott Corson                   Joseph Macker
      Institute for Systems Research    Information Technology Division
      University of Maryland            Naval Research Laboratory
      College Park, MD 20742            Washington, DC 20375

      Phone:  +1-301-405-6630           +1-202-767-2001
      E-mail:  corson@isr.umd.edu       macker@itd.nrl.navy.mil



Author's Address

   Questions about this memo can be directed to:

      Charles Perkins
      Advanced Network Development
      Sun Microsystems, Inc.
      901 San Antonio Rd.
      Palo Alto, CA 94303
      +1-650-786-6464
      +1-650-786-6445
      charles.perkins@sun.com


























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