Internet Engineering Task Force                            C. E. Perkins
INTERNET DRAFT                                          Sun Microsystems
                                                        17 November 1998

                  Mobile Ad Hoc Networking Terminology

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 mailing list.

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   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.


         The total capacity of a link to carry information (typically

      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.


         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.


         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.


         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.

      cluster head

         A cluster head is a node (often elected in the cluster
         formation process) that has complete knowledge about group
         membership and link state information in the cluster.  Each
         cluster should have one and only one cluster head.

      cluster member

         All nodes within a cluster EXCEPT the cluster head are called
         members of that cluster.

      communications medium

         A communication channel such as free space, cable or fiber
         through which data can be transmitted

      communications technology

         The means employed by two nodes to transfer data

      control message

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


         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.

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      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


         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


         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.


         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

      home address

         An IP address that is assigned for an extended period of time
         to a mobile node.  It remains unchanged regardless of where
         the node is attached to the Internet [9].  If a node has more

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         than one home address, it SHOULD select and use a single home
         address when participating in the ad hoc network.


         Any node that is not a router.


         A node's attachment to a link.

      interface index

         An 8-bit quantity which uniquely identifies an interface among
         a given node's interfaces.


         The relative physical location of the nodes within the ad hoc


         A communication facility or physical medium that can sustain
         data communications between multiple network nodes, such as an
         Ethernet (simple or bridged).  A link is the layer immediately
         below IP.

      link-layer address

         A link-layer identifier for an interface, such as IEEE 802
         addresses on Ethernet links.

      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).


         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

      mobility security association

         A collection of security contexts, between a pair of routers,
         which may be applied to protocol messages exchanged between


         a "neighbor" is any other node to which data may be propagated
         directly over the communications medium without relying the
         assistance of any other forwarding node


         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.


         A device that implements IP.

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         An IP header plus payload.


         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.


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


         A bit string that consists of some number of initial bits of an

      route table

         The table where ad hoc nodes keep routing (including next hop)
         information for various destinations.

      route entry

         An entry for a specific destination (unicast or multicast) in
         the route table.

      route establishment

         The process of setting up a route between a source and a

      route activation

         The process of putting a route into use after it has been set


         A node that forwards IP packets not explicitly addressed to

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


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

      security context

         A security context between two routers defines the manner in
         which two routers choose to mutually authentication each other,
         and indicates an authentication algorithm and mode.

      Security Parameter Index (SPI)

         An index identifying a security context between a pair of
         routers among the contexts possible in the mobility security

      signal strength

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

      source route

         A source route from node A to node B is an ordered list of home
         addresses, starting with the home address of node A and ending
         with the home address of the node B. Between A and B, the
         source route includes an ordered list of all the intermediate
         hops between A and B, as well as the interface index of the
         interface through which the packet should be transmitted to
         reach the next hop.

      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.

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         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.


         A network can be viewed abstractly as a "graph" whose
         "topology" at any point in time is defined by set of "points"
         connected by "edges."

      triggered update

         An unsolicited route update transmitted by an router along a
         path to a destination.

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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

Author's Address

   Questions about this memo can be directed to:

      Charles E. Perkins
      Advanced Network Development
      Sun Microsystems Laboratories
      901 San Antonio Rd.
      Palo Alto, CA 94303

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