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IETF MANET Working Group                                    T. Ramrekha
Internet-Draft                                             E. Panaousis
Intended status: Experimental                                C. Politis
Expires: February 2011                               WMN Research Group
                                             Kingston University London
                                                           AUG 25, 2010


  ChaMeLeon (CML): A hybrid and adaptive routing protocol for Emergency
                               Situations
                      draft-ramrekha-manet-cml-01.txt


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   This Internet-Draft will expire on February 27, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
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Abstract

   This document describes the ChaMeLeon (CML) routing protocol
   designed for Mobile Ad hoc NETworks (MANETs) supporting emergency
   communications. CML is a hybrid and adaptive routing protocol
   operating within a defined disaster area denoted as the Critical
   Area (CA). The main concept behind CML is the adaptability of its
   routing mechanisms towards changes in the physical and logical state
   of a MANET. For autonomous emergency communications, there is a
   likelihood that the network size will vary whenever more rescuers
   join or leave the network. In addition, battery exhaustion of
   lightweight mobile communication devices used by rescuers could
   stipulate another reason for changes in the network size. Hence,
   this version of CML adapts its routing behavior according to changes
   in the network size within a pre-defined CA. For small networks, CML
   routes data proactively using the Optimized Link State Routing
   (OLSR) protocol whereas for larger networks it utilizes the reactive
   Ad hoc On-Demand Distance Vector (AODV) Routing protocol so that
   overall routing performance is improved. These transitions occur via
   the CML oscillation phase. This document focuses on the description
   of the processes involved in the CML Cognitive and Adaptive Module
   (CAM), CML Oscillation phase and transition between phases.

Table of Contents

   1. Introduction ................................................ 3
   2. Conventions used in this document............................ 4
      2.1. CML Terminology......................................... 4
   3. Applicability ............................................... 8
   4. Protocol Overview ........................................... 8
      4.1. CML operation with CAM.................................. 9

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         4.1.1. CAM core .......................................... 9
         4.1.2. Monitor Component................................. 10
         4.1.3. Adaptive Component................................ 11
      4.2. O-phase ............................................... 12
   5. Protocol Operation ......................................... 13
      5.1. P-phase ............................................... 14
      5.2. R-phase ............................................... 14
      5.3. O-phase ............................................... 14
         5.3.1. The Oscillation Problem........................... 14
         5.3.2. Operation ........................................ 15
   6. CML Packet and Message Formats.............................. 15
      6.1. Packet Format ......................................... 15
      6.2. Change Phase (CP) Message.............................. 15
      6.3. Hop Count Request (HCReq) Message...................... 16
      6.4. Hop Count Request (HCRep) Message...................... 16
   7. CML tables ................................................. 16
      7.1. CML Change Phase table................................. 16
   8. CML Timers ................................................. 17
      8.1. Oscillation timer...................................... 17
   9. Constants .................................................. 17
      9.1. Network Threshold Values............................... 17
      9.2. Oscillation Interval (Osc_Interval).................... 18
      9.3. Parameter Values....................................... 18
   10. Message Emission and Jitter................................ 18
   11. IPv6 Considerations........................................ 18
   12. Security Considerations.................................... 19
   13. IANA Considerations........................................ 19
   14. Conclusions ............................................... 20
   15. References ................................................ 21
      15.1. Normative References.................................. 21
      15.2. Informative References................................ 21
   16. Acknowledgments ........................................... 22


1. Introduction

   This protocol is an adaptive and hybrid routing protocol for MANETs
   designed to be used by rescuers within the realm of extreme
   emergency communications. It consists of 3 phases of operation
   namely Proactive, Oscillation and Reactive. The Proactive (p-) and
   Reactive (r-) phases operate in the same way as the core functions
   of [3] and [6] respectively and are discrete from each other. The
   Oscillation phase (o-phase), therefore, acts as an intermediate
   between p- and r-phases and decides on whether a shift from p-phase
   to r-phase is appropriate based on criteria defined in section 4.2.

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   The main purpose of the o-phase is to avoid the oscillation problem
   as described in section 5.3. In addition, ChaMeLeon (CML) uses the
   Cognitive and Adaptive module (CAM) specified in [4]. The module is
   designed to segment routing protocols into logical parts for an
   easier and . monitor relevant MANET characteristics, detect a
   certain quantitative threshold exhibited by specific monitored
   characteristics and in such an event, transfer the control to the o-
   phase.

   This version of CML monitors the number of nodes in MANETs within a
   defined Critical Area (CA) where extreme emergency rescue operations
   take place. In such a situation, rescuers tend to join or leave the
   network according to the severity of the situation. CML aims to
   adapt its routing mechanism to the size of such MANETs, thus
   enhancing overall efficiency and effectiveness (both terms defined
   in [5]) as compared to [3] and [6]. CML uses [6], [3], [9], [11]
   and, optionally, [1]. CML makes no assumptions about the underlying
   link layer.

2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC-2119 [1].

2.1. CML Terminology

   This section defines terminology associated with CML that is not
   already defined in or that differs from the meaning of the
   terminology in [9], [6] [4]and [3].

   o Node - A MANET router that implements the CML protocol as
      specified in this document.

   o CML interface - A network device that participates in a MANET
      that runs CML. A node may have several CML interfaces. Each
      interface SHOULD be assigned a unique IP address. Each interface
      SHOULD have a unique IP address.

   o Non CML interface - A network device that does not participate in
      a MANET that runs CML. A node MAY have several non CML
      interfaces.

   o Single CML interface node - A node in a MANET that has only one
      CML interface.

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   o Multiple CML interface node - A node in a MANET that has more
      than one CML interface.

   o Link - A pair of CML interfaces, from two different nodes, within
      the same radio range that can communicate directly with each
      other. A node has a link to another node when at least one of its
      interfaces has a link to one of the interfaces of the other node.

   o Symmetric link - A verified bi-directional link between two CML
      interfaces.

   o Asymmetric link - A verified link between two CML interfaces in
      one direction only.

   o Main address - The main address of a node, to be used in CML
      packet as the "originator address" for all control messages
      generated by the node. It MUST be the address of one of the CML
      node interfaces.

   o Neighbor node - A node X is a neighbor node of node Y if node Y
      can hear node X.

   o MANET Context - A set of characteristics describing the MANET and
      its environment as defined in [5]. This includes node mobility
      levels, small and large node groups as well as technological and
      environmental constraints such as limited battery life of devices
      and bandwidth limitations of wireless links.

   o Source - A node that initiates data communication in the network
      or a node which generates control packets.

   o Sink - A node that is the intended recipient of data sent by
      source nodes.

   o Router - A node that implements the CML protocol. All
      collaborating nodes are potential routers. Router nodes are
      intermediate nodes located on routes between source and
      destination nodes. They are responsible for forwarding packets
      according to the CML routing algorithm.

   o Source address - An address that is unique (within the MANET) to
      each individual source node. A node MUST select an originator
      address; it MAY choose one of its interface addresses as its
      originator address.


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   o Destination address - An address that is unique (within the
      MANET) to each individual sink node.

   o Operation phase - A state of node operation that results from a
      number of logical parts of the routing protocol being active.

   o Stable phases - The set of CML routing phases that operates
      efficiently for a given MANET context. In this CML version, r-
      phase and p-phase are the only stable phases.

   o R-phase - A routing phase where the protocol adopts routing
      mechanisms from [3].

   o P-phase - A routing phase where the protocol adopts routing
      mechanisms from [6].

   o CML Oscillation phase - A routing phase where the protocol
      continues to operate in the current stable phase. It also checks
      whether the network size or hop threshold has been genuinely
      exceeded or whether node oscillation has taken place. It also
      alerts neighbors whenever it decides that the network has to
      shift phases. This phase is initiated by the CML Adaptive module.

   o Phase-shift - A shift from r-phase routing to p-phase routing via
      the o-phase.

   o Oscillation - An event where at least one node regularly joins
      and leaves a MANET so that the CML Network Size Threshold is each
      time exceeded by such activity.

   o Cognitive and Adaptive Module (CAM) - A module that encompasses
      all the logics of CML functionality including Monitoring and
      Adaptation. This module activates logics according to network
      contexts. It MAY be used to determine the number of nodes in the
      network and check whether this number has breached Network Size
      Limits. It also change the node phase to o-phase if the threshold
      is exceeded. A generic CAM is described in [4].








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   o CML Network Size Threshold (NST) - A threshold for the number of
      nodes in the network. Below the NST point, p-phase routing is
      more efficient and effective (both terms defined in [5]) than the
      r-phase routing. Beyond the NST point, r-phase routing
      outperforms p-phase. The NST varies according to the context of
      the MANET such as transmission range of the devices and node
      density (for a given critical area). NST is exceeded in the r-
      phase when the number of nodes is less than NST. In the p-phase,
      this occurs when the number of nodes is greater than NST.

   o CML Network Size Limit (NSL) - The NSL is a couple of values
      which deviate by an equal amount greater/less than the NST. The
      Upper value of NST is denoted by (U-NST) and the Lower value by
      (L-NST). The deviation value from Network Size Threshold is
      selected based on node oscillation properties.

   o CML Change Phase (CP) packet - A control packet unique to CML
      that is sent during the o-phase to alert other nodes in the
      network that a phase-shift has occurred locally. In p-phase mode,
      CML CP packets are only forwarded by MPR nodes whereas in r-phase
      mode, the CP packets are flooded by all nodes in an RREQ flooding
      fashion.

   o CML Change Phase (CP) Table - The CP Table is used to make sure
      that the originator sequence number and originator IP information
      of processed CML control packets are available for a given
      timeout period. This will help in ensuring loop free
      communication.

   o Network Hop Threshold (NHT) - A hop count value which indicates
      that the NST has been reached. The relationship between NHT and
      NST is defined in section 9.1.

   o CML Hop Count Request (HCReq) Packet - A CML control packet sent
      to probe whether the Network Hop Threshold (NHT) has been
      exceeded.

   o CML Hop Count Reply (HCRep) Packet - A CML control packet sent as
      a unicast reply to a HCReq packet. When it is received by the
      originator node, it indicates that the Network Hop Threshold
      (NHT) has not been exceeded.






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3. Applicability

   This protocol has been designed with Ad hoc Communications in
   extreme emergency scenarios in mind, where rescuers are equipped
   with lightweight communication devices. The autonomous nature of
   MANETs is very suitable for extreme emergency communications within
   the CA because communication infrastructures in such disaster sites
   are usually incapacitated. Also, in such a context, the number of
   MANET nodes varies depending on the severity of the rescue
   operations. In such extreme emergencies:

       . Battery limitation of nodes is a very important consideration.
         Node failure as a consequence of battery drainage MAY result
         in network segmentation and thus compromise rescue operations.

       . Nodes MAY join or leave the network according to the urgency
         of the situation and vary network size

       . A certain quality of service (QoS) level has to be maintained
         to allow for multimedia communication. Mainly, certain delay
         bounds have to be established while also maintaining effective
         routing by minimizing battery consumption.

       . Rescuers MAY not always desire to communicate with each other,
         therefore, maintaining proactive routes in all situations MAY
         not always be the best routing option.

   CML has the ability to adapt its routing behavior to changes in
   MANET size. Hence, it is a more suitable routing alternative than
   pure routing approaches for small, large as well as variable sized
   MANETs operating in a defined CA. A MANET including but not limited
   to such unique contextual considerations is defined as an emergency
   MANET (eMANET) in [7]. Future versions of CML will include functions
   in the Adaptive module to adapt to some of the other eMANET contexts
   such as mobility and those described in [5]. In this document, it is
   assumed that nodes are uniformly distributed in the CA so that
   rescuers can cover the maximum CA.

   In addition, CML MAY also be used for general purpose MANETs as it
   utilizes CAM to adapt to specific network contexts.

4. Protocol Overview

   This protocol is designed to work as a hybrid and adaptive routing
   protocol for eMANETs. The normal mode of operation is under one of


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   the stable phases. The default stable operating phase is the p-
   phase. This section describes the various processes and structures
   introduced by CML. Thus, it focuses on the interaction between the
   routing logics encompassed by CAM most notably the operation during
   the o-phase. The routing behaviors of the r-phase and p-phase have
   been described in [3] and [6] respectively. Here, these routing
   states are described with respect to usage within CAM.

4.1. CML operation with CAM

   The operation of CML is described in this section. An overview of
   the protocol is shown in Figure 1.
+------------------------------------------------------------------------+
| +-----+ +-------+  +------+ +-------+     +------+   +----+    +------+|
| |Net. | |Size   |  |L-NST | |U-NST  |     |OLSR  |   |AODV|    |Tables||
| |Size | |O-phase|  |Limit | | Part  |     |      |   |    |    |      ||
| +-----+ +-------+  +------+ +-------+     +------+   +----+    +------+|
|  A  |     A  |       A  |      A  |          A  |      A |       A |   |
|  |  v     |  v       |  v      |  v          |  v      | v       | v   |
|+--------------+   +-----------------+   +-----------------+ +--------+ |
||    Monitor   |   |     Adaptive    |   |  Routing Algo.  | |  Repo. | |
|+--------------+   +-----------------+   +-----------------+ +--------+ |
|  A          |            A     |              A       |        A   |   |
|  |          |            |     |              |       |        |   |   |
|  |          v            |     v              |       v        |   v   |
| +-------------------------------------------------------------------+  |
| |                            CAM CORE                               |  |
| | Fine Variables                                                    |  |
| | Coarse Variables                                                  |  |
| | In/Out Component Interfaces                                       |  |
| | In/Out Packet interfaces                                          |  |
| +-------------------------------------------------------------------+  |
+------------------------------------------------------------------------+


   Figure 1 : Overview of the updated CML protocol with CAM




4.1.1. CAM core

   The CAM core contains variables that identify at least one active
   part from each component. Thus, as defined in [4], a bitwise scheme
   can be used to assign IDs to active components. The required
   variables include the Monitor ID, Adaptive ID, Routing Algorithm ID,


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   Security ID, Repository Routing Table IDs and Repository packet
   definition IDs. The o-phase variable is defined and maintained to
   signal whether the o-phase processes have to be activated as
   described in later sections.

4.1.2. Monitor Component

   When a control message is received at the CAM core interface, the
   node MUST:

      1. Send a copy of the packet to the monitor part of the module.
        The monitor component has a network size part that MUST check
        the number of nodes in the network. This is accomplished
        differently depending on the current stable phase of operation
        (as described later).

      2. Send the the packet to the regular control message processing
        by the stable phase, as described in [3] or [6]. The current
        active routing part.

   The monitor part determines the network size as follows. In the p-
   phase (where the OLSR routing algorithm is active), this task
   consists of calculating the number of reachable hosts from the
   routing table as defined in [6]. This calculation is done by
   counting the number of rows in the proactive routing table. Each row
   includes fields of; possible destination nodes, the next hop to
   reach the destination as specified in the possible destination field
   and its distance from the current source node. These field values
   are computed using periodical Topology Control (TC) and HELLO
   message broadcasts by each node in the network. If the number of
   nodes is found to exceed the NST, this monitor part must contact the
   L-NST part of the Adaptive Component.

   In the r-phase (where the AODV routing algorithm is active), the
   number of nodes in the network is estimated using the maximum value
   of the hop count from a source node to a destination. As defined in
   [3], a source finds a route to a destination 'on-demand' by flooding
   a Route Request (RReq) packet throughout the network using an
   expanding ring approach until a RRep is received from the
   destination. The monitor function in the source node must use this
   RRep message to obtain the value of Hop Count (HC) towards the
   destination node. It then compares this with the U-NST, which is
   calculated according to the relationship defined in section 9.1. The
   monitor function MUST act as follows:



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   1. If HC in RRep is greater or equal to U-NST, it decides that the
      NST is not exceeded.

   2. If HC in RRep is less than the U-NST, the data packets are
      transmitted through the established route. After data
      transmission, the CML Hop Count Request (HCReq) packet described
      in section 6.3. MUST be generated and flooded in the network to
      probe for the network HC (as opposed to destination HC). The HC
      is said to be less than the NHT, if after 4*NET_TRAVERSAL_TIME,
      no HCRep has been received. If the HC is less than the U-NST, the
      monitor function decides that the r-phase NST (calculated using
      the relationship in section 9.1. ), has been exceeded and calls
      the U-NST part of the Adaptive component.

   If a node receives HCReq, it must first make sure that the sequence
   number of the packet is greater than that stored in the Change Phase
   (CP) table for the same originator address. Then, it checks if the
   TTL = 0. If the latter is true, it MUST store HCReq originator IP
   and packet sequence number information in the CP table and send back
   an HCRep to the originator, as described in section 6.4. Otherwise,
   it decreases the TTL value and floods back the HCReq packet in the
   network. It then generates and floods its own HCReq to probe for the
   HC with TTL value set to NHT. The value of the originator address of
   the original HCReq packet (triggering the probing locally) is stored
   in the CP table along with the sequence number. The message type
   field is set equal to the value of message type "HCReq" as which is
   equal to '9' as mentioned in section 13. If for that particular
   HCReq, an HCRep is received, the node must send an additional HCRep
   to that HCReq originator address.

   If a node receives a CML CP Packet described in section 6.2. , it
   MUST flood the packet in the network after decreasing its TTL count.
   Then, the active routing algorithm part of the node MUST call the
   relevant Adaptive part from its Adaptive component.

4.1.3. Adaptive Component

   The Adaptive component, when called by the monitor or core (in case
   a CP packet is received) component MUST sure of the following:

   1. The Adaptive part ID used in the calling message is valid.

   2. The Adaptive part ID corresponds to the appropriate part with
      respect to the active routing component if contacted from the
      monitor part as described in the above section.


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   3. In the case where the CP packet requires that an inappropriate
      (see point 2 above) Adaptive part be contacted, this action is
      ignored and the CP is flooded back in the network.

   Any of the activated Adaptive part, subsequent to the above steps,
   MUST change operation to o-phase.

   In any other situation, the Adapt function terminates and the
   appropriate stable phase operation is resumed.

4.2. O-phase

   In the o-phase, the Adaptive component checks the o-phase validity
   time, "Osc_Interval" of the oscillation timer described in section
   8.1. , is first checked. If the timer is still valid, the o-phase
   variable in the core is cleared and consequently the stable phase of
   operation is maintained. If the timer has expired, the o-phase
   variable is set and:

   1. If the routing algorithm ID (RID) is set to OLSR:

      The OLSR mechanism will continue to operate. At the same time,
      the node will check the number of nodes in the network as
      described in section 4. for 2*TC_Intervals (TC_Interval is
      described in [6]). If the number of nodes is then found to be
      greater than L-NST at least once, the o-phase switches to r-phase
      and resets the oscillation timer. It also generates and floods a
      CML CP Packet. The CP packet includes its address as originator
      address and its incremented sequence number. The CP field value
      of the CML packet is set as "AODV RID".

      Otherwise, the node returns to operating in the p-phase.

   2. If the routing algorithm ID (RID) is set to AODV:












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      The routing mechanism of AODV will continue to operate. At the
      same time, the Monitor and Adaptive component will check the HC
      of the network using two more HCReq packets, as described in
      section 6.3. , waiting for 4*NET_TRAVERSAL_TIME
      (NET_TRAVERSAL_TIME is explained in [3]) each time. If in at
      least one occurrence, no HCRep is obtained for the HCReq with
      TTL=U-NHT, it is implied that the network size is smaller than
      the NST. In this case, the o-phase switches to p-phase by
      clearing the o-phase variable and setting the RID to the OLSR
      RID. The oscillation timer is also reset. It also generates and
      floods a CML CP packet. The CP packet includes its address as
      originator address and its incremented sequence number. The value
      of the CP field in the packet is set to "OLSR RID".

      Otherwise, stable r-phase routing is resumed.

   3. If this phase shift is initiated using a CML CP packet:

      The node core  MUST check the value of the sequence number in the
      packet and compare it to any stored sequence number having the
      same originator address in the CP table. If no match is found n
      the CP table, a new entry is created with the aforementioned
      values obtained from the CP packet before further processing.
      Otherwise, if a match is found and the packet sequence number is
      less than the sequence number stored in the table, the message is
      silently discarded and the node returns to the stable phase
      specified by its core RID variable.

   For non-discarded packets, the node MUST check the CP field value in
   the CP packets and compare it with its own RID:

   1. If they are equal, the CP packet is silently discarded and the
      node returns to the phase specified by its core RID.

   2. If they are not equal, the o-phase changes the RID to the value
      specified in the CP field of the CP message and resets the
      oscillation timer.

   In both cases, the CP packets are flooded back in the network.

5. Protocol Operation

   This section describes the behavior CML MUST follow in the p-phase,
   r-phase and o-phase.



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5.1. P-phase

   In the p-phase, the node core receives packets with all message
   types but only processes packets with message types 1-4 and routes
   data packets as described in [6]. It also processes packets with
   message types 9-11 as described in this document. In addition, it
   sends a copy of the packet to the Monitor component each time a TC
   routing packet is received.

   In this phase, NST is equal to U-NST to cater for group oscillation
   as described in section 5.3.1.

5.2. R-phase

   In the r-phase, the node core receives packets with all message
   types but processes only packets with message types 5-8 and routes
   data packets as specified in [3]. It also processes packets with
   message types 9-11 as described in this document. In addition, it
   sends a copy of the packet to the Monitor component each time it
   receives RRep routing packets as a source node.

   In this phase, NST is equal to L-NST to cater for group oscillation.

5.3. O-phase

   In this subsection we describe the oscillation problem and the
   operation of the o-phase as a mechanism to counteract oscillation
   effects in eMANETs that use CML. The o-phase can only be initiated
   by the Adaptive module as described in section 4.1. The basic
   operations of the current stable phase still apply in the o-phase.
   However, there are added phase dependent sampling processes to check
   for oscillation instances.

5.3.1. The Oscillation Problem

   Oscillation occurs when nodes join and leave the network repeatedly
   so that the total number of nodes fluctuates, exceeding and
   returning below the NST, on a sequential basis. This causes
   performance degradation in CML due to frequent phase shifts. The
   oscillation level is characterized by:

      1. The number of nodes that oscillates

      2. The frequency at which nodes oscillate



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5.3.2. Operation

   CML proposes a twofold solution to the oscillation problem.
   Appropriate NSL values (acting as NST) can restrain the effects of
   group oscillations whereas the right "Osc_Interval" value for the
   oscillation timer limits the impact of frequent oscillations.

   In addition, during the o-phase, the monitor component samples more
   instances of the 'number of nodes' count or the network HC
   (depending on the current stable phase of operation) as described in
   section 4. In this way, it can confirm whether the NST or NHT has
   actually been exceeded. Otherwise, it determines that an oscillation
   has occurred and the stable phase of operation is resumed. If the
   NST is found to have been actually exceeded in the o-phase, the
   appropriate part of the Adaptive component (identified as explained
   above) resets the oscillation timer and generates CP packets. These
   CP packets are flooded into the network to alert neighboring nodes
   of such a phase shift. The o-phase is then terminated by the
   Adaptive Component part that then shifts routing operation to the
   relevant stable phase of operation.

   Furthermore, during the o-phase, the core and active Adaptive
   component part are responsible for phase shifting if a valid CP
   packet is received from a neighboring node (as explained above). In
   such a case, it floods back the CP packet in the network.

6. CML Packet and Message Formats

6.1. Packet Format

   The basic layout of a CML packet is as recommended in [9]. The
   message type field indicates the type of message found in the
   "MESSAGE" section. This could be a CML message or messages from [6]
   or [3] or the CP message.

6.2. Change Phase (CP) Message

   The Change Phase message format is shown below:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             CP containing RID                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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   o Change Phase (CP) - The CP field contains the RID to which the
      originator node has shifted to and subsequently requests neighbor
      nodes to shift to.

6.3. Hop Count Request (HCReq) Message

   The HCReq message has an empty message body. It can be identified as
   a CML packet with:

   o Message Type - The value of message type is set to 9.

   o TTL - The TTL value is set to NHT.

6.4. Hop Count Request (HCRep) Message

   The message format for the HCRep message is:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Destination IP address                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Destination Sequence Number                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   o Destination IP address - Originator IP address in corresponding
      HCReq packet.

   o Destination Sequence Number - Originator Sequence Number of
      corresponding HCReq packet.

7. CML tables

7.1. CML Change Phase table

   The CML CP Table fields are listed below:

   o Originator IP Address - The IP address of the node which
      generated the packet.

   o Originator Sequence Number - The Sequence number of the message
      that was sent by the node which generated the packet. This is
      incremented monolithically for each message generated by a node.


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   o Message Type - The message type value of the message through
      which the table row was populated.

8. CML Timers

8.1. Oscillation timer

   The Oscillation timer is used in the o-phase to prevent phase shifts
   within the time period of "Osc_Interval". This timer prevents phase
   shift due to frequent oscillations.

9. Constants

9.1. Network Threshold Values

   The Network threshold values for CML are described below:

   o NST - The theoretical Network size threshold "Nt" of a network
      depends on the number of nodes N in the network, the critical
      area A of the network and the radio coverage area of each node.
      NST marks the point after which a reactive routing approach will
      be more effective (in terms of end to end packet delivery
      latency) and efficient (in terms of battery usage) compared to a
      reactive routing approach. Below the NST point, proactive routing
      approaches outperform reactive routing approaches.

   o U-NST - The Upper limit network size threshold "Nu" is given by:

      Nu = Nt + Nosc

      where "Nosc" is the number of nodes in the network which are
      expected to oscillate.

      When operating in the p-phase the actual value of NST is equal to
      "Nu".

   o L-NST - The Lower limit network size threshold "Nl" is given by:

      Nl = Nt - Nosc

      When operating in the r-phase the actual value of NST is equal to
      "Nl".

   o NHT - The network hop threshold value "Nht" is directly
      proportional to the square root value of the NST:


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      Nht = Function (sqrt (Nt))

The optimal values for "Nt", "Nosc", "Nu", "Nl" and "Nht" as well as an
accurate relationship between NST and NHT can be derived through
experimentation and mathematical modeling for a given critical area,
'A' and node coverage radius 'R'.

9.2. Oscillation Interval (Osc_Interval)

   The Osc_Interval is a time period for which no phase shift is
   allowed. While the U-NST and L-NST values cater for group
   oscillations, the Osc_Interval prevents unnecessary phase shift
   overheads due to regular oscillations. Thus, the Osc_Interval SHOULD
   be set according to the time period of node oscillations. The
   optimal value for Osc_Interval can be derived through
   experimentation and mathematical modeling for a given critical area,
   'A' and node coverage radius 'R'.

9.3. Parameter Values

   Parameter values used by the CML protocol and also defined in [3]
   and [6] are:

   Parameter Name           Value
   ----------------------   -----
   NET_DIAMETER             35
   NET_TRAVERSAL_TIME       2 * NODE_TRAVERSAL_TIME * NET_DIAMETER
   NODE_TRAVERSAL_TIME      40 milliseconds
   PATH_DISCOVERY_TIME      2 * NET_TRAVERSAL_TIME
   HELLO_INTERVAL           2 seconds
   TC_INTERVAL              5 seconds

10. Message Emission and Jitter

   Synchronization of control messages SHOULD be avoided as mentioned
   in [2].

11. IPv6 Considerations

   All the operations and parameters described in this document can be
   used for both IP version 4 and IP version 6. For IPv6 networks, the
   IPv4 addresses in CML packets and messages need to be replaced by



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   IPv6 addresses. The packet and message sizes will also increase
   accordingly.

12. Security Considerations

   CML does not specify any special security countermeasures. Although,
   different secure versions of AODV and OLSR have been proposed in the
   literature [12], CML introduces new vulnerabilities. Firstly, any
   malicious node can generate a change phase packet to call the o-
   phase of CML and the routing behaviors will accordingly change. In
   this way, CML will not operate in the proper routing mode and the
   MANET's performance will not be optimal considering the real number
   of nodes in the network. Apart from that, legitimate nodes will
   flood the network with the CML CP packet generating traffic overhead
   within the MANET. Furthermore, a set of malicious nodes that
   coordinate their actions against the CML may periodically come into
   and depart from the network. In this way, CML recognizes that the
   number of nodes in the MANET has changed and oscillates from the
   proactive phase to the reactive or vice-versa. The continuous
   oscillation of CML can result in draining the battery level of the
   emergency devices rapidly. Another version of the above attack is
   launched when malicious nodes change the "hop value" in the CML
   HCReq Packet. In this case, legitimate nodes believe that the size
   of the network has changed and CML oscillates unreasonably. On the
   other hand, if a phase shift should take place (due to a real change
   of the number of nodes) but malicious nodes succeed to drop some or
   all of the Change Phase packets the performance of MANET will not be
   optimized. Therefore, security intelligent approaches have to be
   integrated into CML to avoid the aforementioned attacks and to
   provide eMANET nodes with basic security requirements such as
   confidentiality, authentication, integrity and availability.

13. IANA Considerations

   The IANA consideration section is required as recommended by [7] and
   [9]. The following values for the corresponding message types would
   be required:



      Message Type             Value
     --------------------      -----

      HELLO_MESSAGE             = 1


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      TC_MESSAGE                = 2

      MID_MESSAGE               = 3

      HNA_MESSAGE               = 4

      ROUTE REQUEST (RREQ)      = 5

      ROUTE REPLY   (RREP)      = 6

      ROUTE ERROR   (RERR)      = 7

      ROUTE-REPLY ACK (RREP-ACK)= 8

      HOP COUNT REQUEST (HCREQ) = 9

      HOP COUNT REPLY   (HCREP) = 10

      CHANGE PHASE (CP)         = 11

14. Conclusions

   This I-D introduced the CML routing protocol. In extreme emergency
   situations, rescuers tend to join and/or leave the network
   frequently, thus changing network size. CML is a hybrid protocol
   which combines the functionalities of OLSR and AODV protocols in an
   adaptive manner. The motivation behind CML is the enhancement of the
   overall routing performance for varying size networks. The main
   features of CML include the Adaptive Module, which monitors and
   adapts to the changing network state, and the o-phase which
   considers the case of node oscillation. Future CML versions will
   augment the Adaptive module and make CML adaptive to additional
   MANET contexts.

   Furthermore, more security aspects of CML will be discussed towards
   the provision of security against adversaries that try to launch
   different types of network layer attacks.






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15. References

15.1. Normative References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate
         Requirement Levels", BCP 14, RFC 2119, March 1997.

   [2]  Clausen, T., Dearlove, C., and B. Adamson, "Jitter
         considerations in MANETs", RFC 5148, February 2008.

   [3]  Perkins, C., Belding-Royer, E., and Das S., "Ad hoc On-Demand
         Distance Vector (AODV) Routing", RFC 3561, July 2003.

   [4]  Ramrekha, T., Emmanouil, E., and Politis, C., "A Generic
         Cognitive Adaptive Module (CAM) for MANETs", draft-ramrekha-
         manet-cam-00, June 2010.

   [5]  Macker, J. and S. Corson, "Mobile Ad hoc Networking (MANET):
         Routing Protocol Performance Issues and Evaluation
         Considerations", RFC 2501, January 1999.

   [6]  Clausen, T. and P. Jacquet, "The Optimized Link State Routing
         Protocol", RFC 3626, October 2003.

15.2. Informative References

   [7]  PEACE team, "First draft of the emergency framework" PEACE,
         ICT-SEC-2007.1.7, Deliverable 2.2 (Public), June 2009.

   [8]  Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
         Considerations Section in RFCs", RFC 5226, BCP 26, May 2008.

   [9]  Clausen, T., Dean, J., Dearlove, C., and Adjih, C.
         "Generalized MANET Packet/Message Format", RFC 5444, February
         2009.

   [10] Chakeres, I., "IANA Allocations for MANET Protocols", RFC
         5498, March 2009.

   [11] Clausen, T. and C. Dearlove, "Representing multi-value time in
         MANETs", RFC 5497, March 2009.

   [12] Anjum, F. and Mouchtaris, P. "Security for Wireless Ad Hoc
         Networks", ISBN: 978-0-471-75688-0, John Wiley & Sons, March
         2007.


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16. Acknowledgments

   The authors wish to acknowledge the support of the ICT European 7th
   Framework Program and all the partners in PEACE (IP-based Emergency
   Applications and services for next generation networks) project with
   contract number 225654.

   This document was prepared using 2-Word-v2.0.template.dot.

Authors' Addresses

   The following researchers who have contributed to this I-D are
   members of the Wireless Multimedia and Networking (WMN) Research
   Group at Kingston University London:

   Tipu Arvind Ramrekha
   Researcher, WMN Research Group
   Kingston University London
   UK KT1 2EE

   Phone: (+44) 02084177025
   Email: a.ramrekha@kingston.ac.uk

   Emmanouil A. Panaousis
   Researcher, WMN Research Group
   Kingston University London
   UK KT1 2EE

   Phone: (+44) 02084177025
   Email: e.panaousis@kingston.ac.uk

   Christos Politis
   Head of WMN Research Group
   Kingston University London
   UK KT1 2EE

   Phone: (+44) 02084172653
   Email: c.politis@kingston.ac.uk









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