[Docs] [txt|pdf] [Tracker] [WG] [Email] [Nits]

Versions: 00 01

Internet Draft                                               M.S. Corson
Expiration: May 26, 1997                          University of Maryland
                                                                 V. Park
                                               Naval Research Laboratory
                                                       November 26, 1997

     An Internet MANET Encapsulation Protocol (IMEP) Specification
                   draft-ietf-manet-imep-spec-00.txt


Status of this Memo

   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
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet- Drafts as reference
   material or to cite them other than as "work in progress."

   To view the entire list of current Internet-Drafts, please check the
   "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
   Directories on ftp.is.co.za (Africa), ftp.nordu.net (Europe),
   munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
   ftp.isi.edu (US West Coast).

   Distribution of this memo is unlimited.

Abstract

   This memo describes a multipurpose network-layer protocol---named the
   Internet MANET Encapsulation Protocol (IMEP)---designed to support
   the operation of many routing algorithms or other upper layer
   protocols intended for use in Mobile Ad hoc Networks (MANET). The
   protocol incorporates mechanisms for supporting link status sensing,
   control message aggregation and encapsulation, broadcast reliability,
   network-layer address resolution and provides hooks for interrouter
   security authentication procedures.  The IMEP also puts forth a
   framework or architecture for MANET router and interface
   identification and addressing.

   The present specification is high-level and incomplete, giving only a
   behavioral protocol description and proposed packet format.  This
   version of this draft is intended primarily to acquaint readers with
   the concept of the protocol. A subsequent revision will detail the
   protocol's mechanisms and data structures.



Corson, Park                                                  [Page 1]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


1. Introduction

   The primary purpose of the Internet MANET Encapsulation Protocol
   (IMEP) is to improve overall network performance by reducing the
   "number" of network control message broadcasts through encapsulation
   and aggregation of multiple MANET control messages (e.g. routing
   protocol packets, acknowledgements, link status sensing messages,
   network-level address resolution, etc.) into larger IMEP messages.
   Usage of the IMEP is desirable because per-message, multiple access
   delay in contention-based schemes such as CSMA/CA, IEEE 802.11, FAMA
   etc. is significant, and thus favors the use of fewer, larger
   messages.  It would also be useful in reservation-based, time-slotted
   access schemes where smaller packets must be aggregated into
   appropriately-sized IP packets for transmission in a given time slot.
   Upper layer protocols *other than routing* may make use of this
   encapsulation functionality for the same purpose.

   Its secondary purpose concerns the commonality of certain
   functionality in many network-level routing algorithms.  Many
   algorithms intended for use in a MANET will require common
   functionality such as link status sensing, security authentication
   with adjacent routers, broadcast reliability of network control
   messages, etc. This common functionality can be extracted from these
   individual protocols and put into a unified, generic protocol useful
   to all.  MANET routing algorithms would also benefit from a common
   approach to router and interface identification and addressing, and
   this protocol provides a framework for unifying the protocols under a
   common architecture.

   The IMEP will run at the network layer (see Figure 1), and will be an
   adjunct to whichever network routing protocol is using it.  Routing
   control packets will be encapsulated in IMEP messages, which will be
   further encapsulated into IP packets.


















Corson, Park                                                  [Page 2]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


      +------+ +-----+ +-----+     +-----+
      |Telnet| | FTP | | TFTP| ... | ... |
      +------+ +-----+ +-----+     +-----+          +---------+
            |   |         |           |             | Routing |
           +-----+     +-----+     +-----+          +---------+
           | TCP |     | UDP | ... | ... |               |
           +-----+     +-----+     +-----+          +---------+
              |           |           |             |  IMEP   |
     +----------------------------------------+     +---------+
     | Internet Protocol & ICMP & IGMP & IMEP |          |
     +----------------------------------------+     +---------+
                          |                         |   IP    |
             +---------------------------+          +---------+
             |   Local Network Protocol  |
             +---------------------------+

           Protocol Relationships                  Encapsulation

                             Figure 1

   2.0 Terminology

   This section provides definitions for the terminology used throughout
   this document.  Many of these definitions may be replaced by or
   merged with those of the MANET working group's terminology draft [1]
   now under development.

   MANET router or router:
        A device---identified by a "unique Router ID" (RID)---that exe-
        cutes a MANET routing protocol and, under the direction of
        which, forwards IP packets.  It may have multiple interfaces,
        each identified by an IP address.  Associated with each inter-
        face is a physical-layer communication device.  These devices
        may employ wireless or hardwired communications, and a router
        may simultaneously employ devices of differing technologies.
        For example, a MANET router may have four interfaces with
        differing communications technologies: two hardwired (Ethernet
        and FDDI) and two wireless (spread spectrum and impulse radio).

   medium:
        A communication channel such as free space, cable or fiber
        through which connections are established.

   communications technology:
        The means employed by two devices to transfer information
        between them.

   connection:



Corson, Park                                                  [Page 3]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


        A physical-layer connection---which may be through a wired or
        wireless medium---between a device attached to an interface of
        one MANET router and a device utilizing the same communications
        technology attached to an interface on another MANET router.
        From the perspective of a given router, a connection is a
        (interface, adjacency) pair.

   link:
        A "logical connection" consisting of the logical *union* of one
        or more connections between two MANET routers.  Thus a link may
        consist of a heterogeneous combination of connections through
        differing media using different communications technologies.

   neighbor:
        From the perspective of a given MANET router, a "neighbor" is
        any other router to which it is connected by a link.

   adjacency:
        The name given to an "interface on a neighboring router".

   topology:
        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".  (This term comes from the branch of mathematics bear-
        ing the same name that is concerned with those properties of
        geometric configurations (such as point sets) which are unal-
        tered by elastic deformations (such as stretching) that are
        homeomorphisms.)

   physical-layer topology:
        A topology consisting of connections (the edges) through the
        *same* communications medium between devices (the points) com-
        municating using the *same* communications technology.   Multi-
        ple physical-layer topologies may exist for a given medium and
        communications technology if adaptive or proactive power con-
        trol, or other physical-layer mechanisms are employed.

   network-layer topology:
        A topology consisting of links (the edges) between MANET routers
        (the points) which is used as the basis for MANET routing. Since
        "links" are the logical union of physical-layer "connections",
        it follows that the "network-layer topology" is the logical
        union of the various "physical-layer topologies".

   IP routing fabric:
        The heterogeneous mixture of communications media and technolo-
        gies through which IP packets are forwarded whose topology is
        defined by the network-layer topology.



Corson, Park                                                  [Page 4]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


3.0 Protocol Overview

   The mechanisms contained in the IMEP are:

        Link/Connection Status Sensing

        Control Message Aggregation

        Broadcast Reliability

        Network-layer Address Resolution

        Security Authentication

3.1 Link/Connection Status Sensing

3.1.1 Definition of Link/Connection Status

   Many routing protocols require accurate knowledge of the status of
   links/connections between neighboring routers. "Link status" in the
   IP routing fabric is determined from the union of the status of
   physical-layer "connections" between interfaces.

   The relationship of interfaces, adjacencies, connections and links is
   depicted in Figure 2 from the perspective of router i.  Router i has
   two interfaces f1 and f2, each of which has a physical-layer connec-
   tion with multiple interfaces attached to other routers---these
   interfaces are referred to as adjacencies from router i's perspective
   and are numbered with c's. In this figure, there are two connections
   (f1,c1) and (f2,c2), the logical union of which composes the logical
   link (i,k) between routers i and k.




















Corson, Park                                                  [Page 5]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


                +----------+
                | Router i |
                +----------+
    +--------------+    +--------------+
    | Interface f1 |    | Interface f2 |
    +--------------+    +--------------+
            |                   |
            |                   |
            |                   |
            |                   |
            |                   |
            |                   |
    +--------------+    +--------------+
    | Adjacency c1 |    | Adjacency c2 |
    +--------------+    +--------------+
                +----------+
                | Router k |
                +----------+

   Figure 2: Shown from router i's perspective, interfaces f1 and f2 are
   connected  to  adjacencies  c1  and  c2  via  connections (f1,c1) and
   (f1,c2)---the union of which forms link (i,k).

   The status of an connection may be INcoming or OUTgoing (either of
   which meaning it is unidirectional) or BIdirectional.  A unidirec-
   tional link is composed from one or more similarly-directed, uni-
   directional connections.  A BIdirectional link may be composed from
   the union of one or more bidirectional connections, or two or more
   oppositely-directed, unidirectional connections, or some combination
   thereof.  A link which is present (i.e. which has a non-null status,
   and is either uni or bidirectional), is referred to as "UP".  A link
   which is not present (i.e. which has a null status) is referred to as
   "DOWN".

   The IMEP may be configured to run in the following "connection notif-
   ication" modes:

   BI-directional:
        This mode requires that physical-layer connectivity between two
        interfaces be established in *both* IN and OUT directions before
        an connection is considered *present* and the upper layer rout-
        ing protocol is subsequently notified.

   UNI-directional:
        This mode requires that physical-layer connectivity between two
        interfaces need only be established in one direction (IN or OUT)
        before an connection is considered present and the upper layer
        routing protocol is subsequently notified.



Corson, Park                                                  [Page 6]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


   As determined by the connection notification mode, the upper layer
   routing protocol is notified whenever there is a change (addition,
   modification, deletion) in the status of an interface's connections.
   This notification is implemented via a callback functions defined in
   the MANET routing policy/IMEP interface (more on this later)

3.1.2 Link/Connection Status Sensing Packet Exchange Mechanism

   The IMEP uses a combination of BEACON and HELLO packets (and other
   packets to be described shortly) to ascertain connection (and
   indirectly link) status.  On initialization, an interface under the
   control of IMEP broadcasts (the format of a BEACON packet is speci-
   fied in section 4.0) to all adjacencies; i.e. interfaces that are
   only one hop away such as those on the same Ethernet subnet, or those
   within wireless transmission range of the broadcasting interface.
   (Note:  Usage of the term "broadcast" here means to transmit a *sin-
   gle* copy of a packet to *all* interfaces reachable over one hop.  As
   is the convention with other Internet routing protocols, this is done
   using IP multicast. An IP multicast address "ALL_IMEP_ROUTERS" will
   be reserved, and all MANET router interfaces will be configured to
   listen for this address.)  a BEACON packet The purpose of a BEACON
   packet is to alert any adjacencies of the existence and identity of
   the broadcasting interface; an interface's identity is its IP
   address. The interface must ensure that a BEACON packet (or other
   "equivalent" packet, more on this later) is transmitted at least once
   every BEACON_PERIOD (BP) time units; i.e. no more than BP time units
   may pass between subsequent transmissions of a BEACON (or "BEACON-
   equivalent") packet.

   Reception of a BEACON at an interface implies either reconfirmation
   or creation of "IN" (read "INcoming") status of a connection at that
   interface, depending on whether or not the connection already exists,
   respectively.  Thus, BEACONs serve to tell a receiving interface that
   "someone else is out there."  Once present, the status remains for
   MAX_BEACON_TIME (MBT) time units, at which time it expires (i.e.
   times out) if no subsequent BEACONs have been received; i.e. the link
   is declared DOWN and is removed from the data structures.  Creation
   or loss of IN status may require notification of the upper level
   routing protocol, depending on whether or not the logical link status
   to which this connection is associated has been affected.

   HELLO (or "HELLO-equivalent") packets are used to respond to BEACONs.
   The purpose of a HELLO packet is to let a "BEACONing" node know that
   someone hears its BEACON.  A HELLO packet contains the identity (i.e.
   IP interface) of the interface broadcasting the HELLO and the iden-
   tity of the BEACONing interface to which it is responding.  A HELLO
   packet is generated immediately in response to a BEACON reception,
   and is placed in the "Awaiting Broadcast" (AB) buffer (more on the



Corson, Park                                                  [Page 7]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


   functioning of this buffer later).  Subsequently, as long as the
   interface is considered UP (i.e. IN or BI), a HELLO packet must be
   generated at least once every BP time units; i.e. no more than BP
   time units may pass between subsequent generations of a HELLO packet.

   Reception of a HELLO at an interface implies either reconfirmation or
   creation of "BIdirectional" status of an connection at that inter-
   face, depending on whether or not the connection already exists,
   respectively.  This is because reception of HELLO packet confirms
   that someone hears this interface (i.e. that is has OUTgoing status),
   and simultaneously confirms that it itself can receive them and,
   hence, also has INcoming status for that connection.

   HELLO packets may be broadcast in one of two "Hello" modes:

   Single Interface (SI):
        An interface only sends HELLOs in response to BEACONs it
        receives.  This is the standard mode which permits efficient
        link-layer detection of IN and BI connections.  It also permits
        "network-layer detection" (by a routing protocol) of BIdirec-
        tional links composed of oppositely-directed, unidirectional
        links on the same or differing routers.

   Multiple Interface (MI):
        An interface sends HELLOs in response to BEACONs it receives,
        and it also sends HELLOS in response to the BEACONs received by
        *all* other interfaces attached to its router.  This mode is
        necessary to permit "link-layer detection" of BIdirectional
        links composed of oppositely-directed, unidirectional connec-
        tions between neighboring routers.  Note that only by using this
        Hello mode can an interface determine that it itself has "OUTgo-
        ing" status without also having "INcoming" and, hence, BIdirec-
        tional status.

        To make this clear, consider Figure 3.
















Corson, Park                                                  [Page 8]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


                           +----------+
                           | Router i |
                           +----------+
               +--------------+    +--------------+
               | Interface f1 |    | Interface f2 |
               +--------------+    +--------------+
                       |             IN    ^
                       |                   |
                       |                   |
                       |                   |
                       |                   |
                 IN    V                   |
               +--------------+    +--------------+
               | Adjacency c1 |    | Adjacency c2 |
               +--------------+    +--------------+
                           +----------+
                           | Router k |
                           +----------+

        Figure 3: A bidirectional link  consisting  of  two  oppositely-
        directed connections.

        Assume that SI Hello mode is being used, and the wireless direc-
        tional connectivity is as shown.  From router i's perspective,
        it can only receive over interface f2, and thus classifies con-
        nection (f2,c2) as IN.  It is unaware that its BEACON packets
        being broadcast from interface f1 are being received at inter-
        face c1 on router k.  However, if MI mode is used, then router k
        will advertise the reception of BEACON packers from f1 at c1
        over connection (f2,c2) thereby informing router i that connec-
        tion (f1,c1) should be classified as OUT.  Of course, the
        reverse but same is true from router k’s perspective.

        The additional functionality provided by the MI mode comes at
        the cost of broadcasting a HELLO out *every* interface instead
        of only the interface over which the corresponding BEACON was
        received.  This creates more HELLO overhead.  For a given net-
        work, this cost must be balanced against the frequency of
        occurrence of the situation depicted in figure 3.


3.2 Control Message Aggregation

   MANET routing protocols exchange control information in the form of
   routing control messages or "objects". To minimize the number of
   channel accesses generated by routing control traffic, the IMEP
   aggregates and encapsulates these objects into larger "IMEP object
   blocks".  The objects are treated as "opaque" objects by the IMEP



Corson, Park                                                  [Page 9]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


   protocol; i.e. IMEP is not aware of the contents of the objects, only
   of the protocol "type" of the object block (necessary for protocol
   demultiplexing at a receiver) and the length of each object. These
   object blocks are contained in yet larger "IMEP messages" which are
   passed to the IP layer for encapsulation and forwarding.

3.3 Broadcast Reliability

   IMEP supports reliable and unreliable delivery of opaque protocol
   objects, where reliable delivery is also guaranteed to be delivery
   "in order" of transmission.  IMEP uses a "point-to-multipoint selec-
   tive repeat" algorithm to guarantee broadcast or multicast reliabil-
   ity and ordered delivery.  This approach eliminates unnecessary
   retransmissions of the type commonly associated with "go back n"
   algorithms, and is in keeping with the greater IMEP goal of minimiz-
   ing the number of required channel accesses.

   To support reliability, each object block is given a SEQUENCE number,
   and is broadcast with that number and with a set of its intended
   receivers referred to as its "response list".  When broadcast, a copy
   of the object block and its associated response list (i.e. the set of
   neighbors that are required to acknowledge this block) are stored.  A
   retransmission timer is set to RETRANS_PERIOD (RP) time units which,
   upon expiration, will cause the object to be rebroadcast to any
   neighbors which have not acknowledged the object (this causes the
   retransmission timer to be set again to RP).  The time the packet was
   initially broadcast is also stored.  If the object’s response list is
   not empty (i.e it has not been acknowledged by some adjacencies)
   after MAX_RETRANS_TIME (MRT) time units, the connections to those
   adjacencies are declared DOWN.

   Acknowledgements (ACKs) are sent in response to object block recep-
   tions when (i) reliable delivery is indicated and (ii) when the
   receiver is contained in the response list.  Once a node has ACKed a
   given block, it will be removed from the block's response list so
   that it will not be required to ACK any future retransmissions.

3.4 Network-level Address Resolution

   IMEP puts forth a framework or architecture for MANET router and
   interface identification and addressing.  IMEP operates simultane-
   ously on two different topological levels: the "logical network"
   topology level---which is concerned with interrouter connectivity---
   and the "physical" topology level---which is concerned with interface
   connectivity.  Router IDs (RID) identify routers in the logical
   topology, and IP addresses identify interfaces in the physical topol-
   ogy. There may be *multiple* IP addresses associated with a given
   RID.



Corson, Park                                                 [Page 10]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


   The purpose of the Network-level Address Resolution Protocol (NARP)
   incorporated within IMEP is to dynamically discover the mapping
   between RIDs and IP addresses when necessary.  This is envisioned
   typically only to occur when a new connection is discovered, as it is
   necessary to be able to associate an interface (an IP address) with a
   router (an RID).

                    +----------+
                    |  Router  |                      RID
                    +----------+
                     |        |
         +--------------+   +--------------+
         |  Interface   |   |  Interface   |       IP Address
         +--------------+   +--------------+
                |                   |
         +--------------+   +--------------+
         | Phys Device  |   | Phys Device  |       MAC Address
         +--------------+   +--------------+

                Figure 4: RIDs, IP and MAC addresses


   While it is true that---as currently defined---RIDs are not
   "addresses" in the strict sense, they do uniquely identify a router
   for purposes of internal routing computations and somewhat resemble a
   logical "router address".  Thus, the IP address-to-RID mapping is
   similar in spirit to IP address-to-MAC address mapping performed by
   the present ARP protocol.  Each mapping simply associates an IP
   address with another identifier as shown in Figure 4.  As with ARP, a
   "reverse" mapping is also defined as the Reverse Network-level
   Address Resolution Protocol (RNARP).  The two mappings are shown in
   Figure 5.

      ARP:  IP --> MAC     RARP:  MAC --> IP

      NARP: IP --> RID     RNARP: RID --> IP

        Figure 5: ARP/RARP and NARP/RNARP

   When necessary, NARP/RNARP packets are generated, aggregated with
   other network control traffic and reliably broadcast within the
   object block of a IMEP message.  However, unlike other control
   traffic, the NARP/RNARP objects are not opaque with respect to IMEP
   as they are generated and consumed by the IMEP protocol.

3.5 Security Authentication

   It is expected that the IMEP protocol will include hooks for security



Corson, Park                                                 [Page 11]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


   authentication in a fashion similar to that already performed by OSPF
   and other routing protocols.  This will include, among others, an
   authentication type field in the IMEP message header.

3.6 BEACON and HELLO "Equivalency"

   As stated earlier, BEACON and HELLO packets are necessary for ascer-
   taining current connection status.  From the perspective of a given
   router, BEACONs announce the presence of a broadcasting interface,
   and HELLOs simultaneously announce the presence of an adjacency and
   that the adjacency can receive from the broadcasting interface.  How-
   ever, it should be clear that the same information can be gleaned
   from other IMEP packets.  Specifically, OBJect block transmissions
   (which may contain routing, NARP/RNARP and/or security objects) sig-
   nal the presence of a broadcasting interface and are, in this sense,
   "equivalent" to BEACON packets.  Similarly, ACKnowledgements both
   announce the presence of an adjacency and, through the process of
   acknowledgement, confirm that the adjacency recently received from
   the broadcasting interface.  Thus, in this sense, ACKs are equivalent
   to HELLOs.  The equivalency is depicted in the Figure 6.

                                 BEACON-->
                                 OBJ   -->
   +----------+ +-------------+              +-------------+
   | Router i |-| Interface f |  -  -  -  -  | Adjacency c |
   +----------+ +-------------+              +-------------+
                                 <-- HELLO
                                 <--   ACK

              Figure 6: BEACON and HELLO Equivalency
   Transmission or reception of a BEACON or HELLO equivalent packet
   affects the link status sensing timers as would transmission or
   reception of a BEACON or HELLO, respectively.  Thus, during periods
   of heavy data, it is expected that BEACONs and HELLOs will rarely be
   transmitted as their respective "equivalent" packets will serve their
   role in link status sensing.  During periods of light or no traffic,
   BEACONs or HELLOs will be transmitted as necessary to satisfy the
   aforementioned timing requirements.

3.7 Connection Failure Detection

   It should be noted here that there are two events that can signal
   connection failure: expiration of the MRT timer or expiration of the
   BPT timer.  Thus the CONN_DEAD_TIME (CDT) value---the time at which a
   connection, once UP (i.e. IN, OUT/BI), will be declared DOWN if its
   UP status is not confirmed---is CDT = min(MBT,MRT).  Note that
   separate timers are used to monitor IN and OUT connection status.
   Thus, a connection may lose its OUT status while still retaining IN



Corson, Park                                                 [Page 12]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


   status and vice versa.  Obviously, a connection satisfying both IN
   and OUT timing requirements is marked at BI.

4.0 Protocol Message Format

   The following describes the message format of the proposed protocol.
   An IMEP message format consists of several  fixed,  mandatory  fields
   followed  by  a  self-formatting  byte stream.  The stream is aligned
   along  "byte"  boundaries---not  32-bit  word  boundaries---to   save
   transmission  overhead  at  the cost of extra processing at a router.
   An IMEP message typically contains at least one of  several  optional
   blocks.  A message containing no blocks is a BEACON message.

   <IMEP message> ::= <IMEP_VERSION> <BLOCK_FLAGS> <IMEP_LENGTH>
                    [Ack Block]
                    [Hello Block]
                    [Object Block]

The fixed field formats are:

        31           24 23           16 15            8 7             0
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   1   |  (a)  |  (b)  |              (c)              | Opt. blocks...
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   (a) IMEP_VERSION (4-bit unsigned integer):
        This field specifies the protocol version number, which may
        range from 0-15.  The initial protocol version number is zero.

   (b) BLOCK_FLAGS (4-bit bitmask):
        This field contains single-bit flags, each of which specifies
        the presence (flag = 1) or absence (flag = 0) of a block.  All
        bits set equal to zero indicates that this is a BEACON packet--a
        packet intended only to announce the existence of this interface
        (whose IP address is contained in the IP header) to any poten-
        tial adjacencies.

        bit 27: Ack block flag

        bit 26: Hello block flag

        bit 25: Object block flag

        bit 24: unused

   (c) IMEP_LENGTH (16-bit unsigned integer):
        This field specifies the total length of an IMEP message



Corson, Park                                                 [Page 13]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


        (measured in bytes) which must lie in the following range:

                3 < IMEP_LENGTH <= MAX_IMEP_LENGTH <= 65535



The ACK Block format is:

   <Ack Block> ::= <NUM_ACKS> <Ack List>

   <Ack List> ::= <ACK> |
                  <Ack List> <ACK>


   NUM_ACKS (8-bit unsigned integer):
        This field indicates the length of the Ack List which may range
        from 0-255.

   The ACK format is:
        31           24 23           16 15            8 7             0
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   1      ...self-formatting bytestream contents       |      (a)      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   2   |              (b) Ack'ed IP Interface Address                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        (a) SEQUENCE (8-bit unsigned integer):
             Indicates the sequence number of the protocol object block
             being ack'ed, which may range from 0-255.

        (b) ACKIPADDR (32-bit unsigned integer):
             IP interface address of the interface which originally sent
             the protocol object block that is being acknowledged.


The Hello Block format is:

   <Hello Block> ::= <NUM_HELLOS> <Hello List>

   <Hello List> ::= <HELLO> |
                    <Hello List> <HELLO>


   NUM_HELLOS (8-bit unsigned integer):
        This field indicates the length of the Hello List which may
        range from 0-255.

   HELLO (32-bit unsigned integer):



Corson, Park                                                 [Page 14]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


        This field contains the IPv4 address of the interface being
        "hello'ed".


   The Object Block format consists of a set of fixed fields followed by
   an Object List and an optional Response List:

   <Object Block> ::= <SEQUENCE> <PROTOCOL_TYPE>
                      <NUM_OBJECTS> <NUM_RESPONSES>
                      <Object List> [ <Response List> ]

   <Object List> ::= <OBJECT> |
                     <Object List> <OBJECT>

   <OBJECT> ::= <LENGTH_FLAG> <OBJECT_LENGTH> <OBJECT_DATA>

   <Response List> ::= <RESPONSE> |
                       <Response List> <RESPONSE>

   The fixed fields format is:

        31           24 23           16 15            8 7             0
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   1   |      (a)      |  (b)  |     (c)     |   (d)   | Object List...
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   (a) SEQUENCE (8-bit unsigned integer):
        A sequence counter uniquely indicating the Object Block ID
        within a sender's transmission queue, ranging from 0-255.  This
        value may rollover, but for the envisioned applications, the 8-
        bit value should be large enough so that no two Object Blocks in
        the retransmission queue ever have the same SEQUENCE number.

   (b) PROTOCOL_TYPE (4-bit unsigned integer):
        This field indicates the protocol responsible for the opaque
        objects in the object block--necessary for demultiplexing the
        Object Block at a receiver.  The field may range from 0-15.

        value 0: reserved

        value 1: NARP/RNARP

        value 2: TORA

        values 3-15: unassigned




Corson, Park                                                 [Page 15]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


   (c) NUM_OBJECTS (7-bit unsigned integer):
        This field indicates the length (i.e. number of objects) of the
        Object List contained in the Object Block, which may range from
        0-127.

   (d) NUM_RESPONSES (5-bit unsigned integer):
        This field indicates the length (i.e. number of responses) of
        the Response List contained in the Object Block, which may range
        from 0-31. The value 0 indicates unreliable delivery is desired,
        and that no interfaces need respond.  The value 31 indicates
        BROADCAST, and that ALL receiving interfaces should respond.  In
        both cases, the Response List is omitted.

   The OBJECT format is:

        31           24 23           16 15            8 7             0
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   1   |0|OBJECT_LENGTH|  OBJECT_DATA...
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   or

        31           24 23           16 15            8 7             0
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   1   |1|       OBJECT_LENGTH         |  OBJECT_DATA...
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   LENGTH_FLAG (1-bit field, bit 31 in format figures):

        0: indicates 7-bit OBJECT_LENGTH

        1: indicates 15-bit OBJECT_LENGTH

   OBJECT_LENGTH (7 or 15-bit unsigned integer):
        May range from 0-127 or 0-32767 as required indicating the
        length of the OBJECT_DATA in bytes.

   OBJECT_DATA:
        Opaque bytestream of data of length OBJECT_LENGTH.











Corson, Park                                                 [Page 16]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997



   NARP/RNARP Packet Format (> 10 bytes):

        31           24 23           16 15            8 7             0
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   1   ...self-formatting bytestream   |  (a)  |  (b)  |  (c)  |  (d)  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   2   |              (e) Sender IP Interface Address                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   3   |              (f) Target IP Interface Address                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              (g) Sender Router Identifier...
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   ...(h) Target Router Identifier...
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Both NARP and RNARP packets share the same format  which  is  similar
   but not identical to traditional link-layer ARP/RARP packets:

   (b) VERSION (4-bit unsigned integer):
        This field  specifies  the  version  number  of  the  NARP/RNARP
        protocol.   The  current  version maps 32-bit IPv4 addresses.  A
        future version would be required to map 128-bit IPv6 addresses.

        0 (IPv4)

        1 (IPv6)

        2-15 (unused)

   (b) PROTOCOL_TYPE (8-bit unsigned integer):
        This field specifies the  network-layer  routing  protocol  type
        being mapped.

   (c) PROTOCOL_LENGTH (4-bit unsigned integer):
        This field specifies length of the  protocol  Router  IDentifier
        (RID) in bytes.

   (d) FRAME_TYPE (4-bit unsigned integer):
        Indicates whether packet is a NARP or RNARP, and whether it is a
        request or reply.

        0x00 (NARP Request)

        0x01 (NARP Reply)

        0x02 (RNARP Request)




Corson, Park                                                 [Page 17]


Internet Draft   Internet MANET Encapsulation Protocol November 26, 1997


        0x03 (RNARP Reply)

   (e) SENDER_INTERFACE_ADDR (32-bit unsigned integer):
        IP interface address of the sender of the NARP/RNARP message.

   (f) TARGET_INTERFACE_ADDR (32-bit unsigned integer):
        IP interface address of the target of the NARP/RNARP message.

   (g) SENDER_ROUTER_ADDR (length specfied in (c):
        Router identifier of the sender of the NARP/RNARP message.

   (h) TARGET_ROUTER_ADDR (length specfied in (c):
        Router identifier of the target of the NARP/RNARP message.


5. Summary

   The preceding gives only a high-level protocol description, specify-
   ing what is to be exchanged and, generally, why. Details on how the
   protocol is to be implemented will be given in a subsequent version
   of this draft.

6. References

[1] C. Perkins, "Mobile Ad Hoc Networking Terminology," draft-ietf-
    manet-term-00.txt, October 1997.

Authors' Addresses:

   M. Scott Corson
   Institute for Systems Research
   A.V. Williams Building (115)
   University of Maryland
   College Park, MD 20742
   (301) 405-6630
   corson@isr.umd.edu

   Vincent Park
   Information Technology Division
   Code 5540
   Naval Research Laboratory
   Washington, DC 20375
   (202) 767-5098
   vpark@itd.nrl.navy.mil







Corson, Park                                                 [Page 18]


Html markup produced by rfcmarkup 1.129c, available from https://tools.ietf.org/tools/rfcmarkup/