IETF MANET Working Group T. Ramrekha
Internet-Draft E. Panaousis
Intended status: Experimental C. Politis
Expires: August 2011 WMN Research Group
Kingston University London
FEB 28, 2011
ChaMeLeon (CML): A hybrid and adaptive routing protocol for Emergency
Situations
draft-ramrekha-manet-cml-02.txt
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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.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. If the protocol phase changes from
P-phase to R-phase, and a HELLO packet is received, the information
about next hop is stored in the routing table. A TC packet information
is used to either reset a timeout in the routing table or populate
routing table information for potential data to be sent. In the case
where the transition occurs from the R-phase to the P-phase, and RREQ
are requested, if the destination is already in the routing table, a
RREP is sent back with this information. Otherwise, the RREQ is stored
until 2 *TC_INTERVAL before sending a RREP.
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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