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UCLA Undergraduate Research Program in Electrical Engineering

Summer 2003 (June 16 - August 8, 2003)

Integrated System Manager of a Mobile Backbone Network

Jonathan Chan

Professor Izhak Rubin

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Abstract

Given a Mobile Backbone Network (described below), we are implementing an

Integrated System Manager (ISM) to further increase stability, support and the Quality of

Service in the network. Each node will have the ability to become a Network Manager

and all the nodes will be connected in a hierarchical form. Data about the network will

be relayed through the nodes, according to specific routing algorithms; nodes lower in

the hierarchy will update their information to those higher.At the top of the hierarchy will

be a centralized Integrated System Manager. All nodes have the capabilities to convert

itself from a Network Manager into an Integrated System Manager and from an ISM

back into a Network Manager. The difference between the ISM and a Network Manager

is that an ISM is repeatedly updated with information from everyone in the network while

a Network Manager only receives data from those nodes below in on the hierarchy. The

ISM is simply a Network Manager and the top of the hierarchy. With this data, the ISM

will control the network, mainly the stability of the links and the Quality of Service.

Introduction

Mobile Backbone Network

A Mobile Backbone Network (MBN) is an ad hoc wireless mobile network that employs a

hierarchical networking architecture. This is different from usual networks for many

reasons. What separates a MBN from a regular network is its highly decentralized

structure. Because the network is not restricted with a permanent infrastructure, data

can be transferred through different routes in the network. This mobility gives us a huge

advantage over centralized networks. Centralized networks have too much

dependence on its central nodes. If any of those go down, the network collapses. In a

MBN, any node nearby can resume the tasks of the fallen node. Each node can rely on

multiple different routes to send and receive information. The architecture is also

different from a usual ad hoc network because of its multi-leveled structure. A normal ad

hoc network contains only one level. Each node has the same capabilities as each

other. In the network, the nodes are separated into two categories: high power and low

power nodes. Two levels of nodes provide more efficiency and capability within the

network. Certain nodes, usually low powered ones, do not have the capacity or energy

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to act as a hop for other nodes. Low power nodes, or Regular Nodes (RNs), can route

to other low power nodes if within the range or use the high power nodes or Backbone

Nodes (BNs) as hops to their destination.

With these two levels comes a variety of associations and networks that the MBN can

encompass. An association is a possible connection in the network. Because there are

several routes to a destination, associations between nodes provide possible

connections in the network. Through these associations of Regular Nodes and

Backbone Nodes, the MBN supports three different sub-networks. The first is a typical

ad hoc wireless network. This provides the means for Regular Nodes to connect and

communicate with each other. The second sub network needed is the Backbone Node

network comprised of all the Backbone Nodes or Bnet. A Bnet is an ad hoc network on

the second layer of the MBN. This network controls the routing to other Backbone

Nodes as well as the routes to the Regular Nodes. This is done by simply routing to the

Backbone Node that the Regular Node is

associated to. The last sub-network, an

Anet, must be incorporated to provide

each Regular Node with a Backbone

Node association. This sub-network is

formed around the Backbone Node with

one or more associated Regular Nodes.

But what of the Backbone Nodes that

are not associated with any Regular

Nodes?

Imagine a topology of multiple Backbone Nodes with no Regular Nodes; it would be

useless to route through each Backbone Node, when it is easier and safer to route

through one Backbone Node. To save energy, any Backbone Node that is not

associated with any Regular Nodes becomes elected as a Backbone Capable Node

(BCN). These Backbone Capable Nodes have all the capabilities of a Backbone Node

but regulates itself to only capabilities of a Regular Node for efficiency. Backbone

Capable Nodes are associated to the MBN through a Backbone Node as a Regular

Node is. A Backbone Capable Node has the capability to be reelected as a Backbone

Node when a Regular Node moves into the area if needed.

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Both Regular Nodes and Backbone

Nodes can communicate in two ways.

Regular Nodes can communicate to

other Regular Nodes in similar fashion

as in an ad hoc network. If the packets

destination is out of range or not within

neighboring Regular Node capabilities, it

can also route its packet through a

Backbone Node. Backbone

Nodes have two options as well. The first option is through the higher powered

Backbone Nodes. However, if messages are directed to the Regular Nodes and

Backbone Capable Nodes associated to that particular Backbone Node, the message is

routed to its destination.

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This network has also been expanded to cover larger areas with the help of UAVs and

UGVs. Unmanned Aircraft Vehicles and Unmanned Ground Vehicles are used to create

direct lines of communications between Bnets if regular Backbone Node nodes are

incapable of a certain distance. Both UAVs and UGVs perform as a Backbone Node. If

stationed between two Bnets within range, it could provide a connection between the two

networks. These mobile nodes are mostly used as the Backbone Nodes to connect

Regular Nodes in Anets and as Backbone Nodes to connect Backbone Nodes in Bnets.

A sensor network is also incorporated in the network to identify objects. It alerts the

network allowing the nodes to check out what was sensed by the sensor network.

Integrated System Manager

Now with the network in place with all its association and routing capabilities, how is the

network controlled? The easiest way would be to define a simple algorithm that all the

nodes would have such as sending messages on a first come first serve basis or by

electing Backbone Nodes based on the node ID. However, this is certainly not the most

optimal solution especially in a mobile network. For every association, every movement,

every Backbone Capable Node election there is change in the network. How can a node

route through a network if it doesnt know where the destination is without flooding the

network with queries?

The answer to these questions is to create an Integrated System Manager (ISM). The

ISM controls the Mobile Backbone Network by enforcing Quality of Service (QoS) in the

network. This included congestion control, priority and the ability to connect and

associate in the network.

The ISM adds additional levels to the network. Each Backbone Node includes an

application called a Network Manager (NM). A Network Manager simply maintains

information about the network as seen through its node and collects data from nearby

nodes. One Network Manager is selected to become the ISM and collects data from all

the other Network Managers. This works in a hierarchy of Network Managers. Since

the ISM is only a Backbone Node, it can only collect data from all its neighboring nodes

through their Network Managers. Those Network Managers in turn collect data from

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their neighboring nodes and the cycle continues until all Backbone Nodes that can be

connected are collected. Each Network Manager not only collects all the information

from its neighboring nodes but all the information they have of other nodes as well. This

allows each Network Manager to only talk to its neighbors but receive information from

everyone under it in the hierarchy. The ISM contains all the information of all the nodes

connected in the network.

With the data received, we are able to control the network. To control the ISM we use

the principles of the Simple Network Management Protocol (SNMP) over UDP (User

Datagram Protocol).

User Datagram Protocol

UDP is very simple transport protocol. It simply adds the source and destination port

and IP address and lets the IP layer handle everything else. However, its

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straightforwardness allows us to manipulate certain aspects to better control our

network. UDP is unreliable because it is connectionless and doesnt contain states. If a

node wanted to receive information from another node, it would just take the information

instead of asking for permission. Because the other node doesnt know if that node

wants information, if the packet is lost or damaged, nothing is done. However, this

allows the ISM to control the network without waiting for a certain node that could be lost

or cannot be connected. UDP also has small overhead and an unregulated send rate.

This is imperative for communication speed and priority. Because humans can

understand audio and video even if a few packets are lost, this tremendously increases

the speed of the packet rate due to packets not being resent because or packet loss or

errors. The unregulated send rate allows the ISM to control the flow of the network.

Simple Network Management Protocol

SNMP is a management protocol comprised of agents and managers written for network

devices such as hubs and routers. An SNMP Agent is any device that runs a program

that understands the SNMP language. A manager is an agent the collects the data.

Each agent has a database called a Management Information Base (MIB). Although our

application modifies SNMP to better assist our network, several properties are used.

Everything the ISM needs to know is stored in the MIB and is collected when queried by

other Network Managers. In our MIBs, each entry has a key and value. This simplifies

the SNMP MIB database which uses a tree system where each value is stored in certain

directories which you can choose from.

SNMP 1.0 uses five simple functions to control its operations which we mimic. The first

four functions are relatively simple are great for data collection. The most common

function is the SNMP Get function. This simply queries the node for a particular value of

a MIB key. The SNMP GetNext function calls for the value of the next key in the MIB.

When the function reaches the end of the MIB after several GetNext function calls, the

MIB returns the value of the first key which alerts the manager that all the information

has been collected. The SNMP GetResponse function is the response of a Get or a

GetNext function call. The SNMP Set function simply sets a value of a MIB to a specific

key. The most interesting function is the last of the five: the SNMP Trap function. The

Trap function is its own process, sent out by an agent when a set of circumstances

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occurs. Usually a trap is triggered by a threshold: a value that the key cannot go above

or cannot go below. When the Trap is set off, it alerts the Network Manager, which will

respond accordingly. This can be very useful in determining several aspects of our

routing protocol. Traps can set thresholds on anything from the number of RN

associations to the maximum traffic flow. The use of a Trap is essential to help regulate

the nodes and ensuring Quality of Service. Thresholds can be put on each node to

maintain certain standards on the network such as congestion or maximum associations.

If these traps are set off, they immediately alert the Integrated System Manager which

has the power to reroute and move nodes to ease high association of nodes. This puts

the power of the network into the hands of the user who can manipulate the network into

a form he sees fit.

ISM operations

The ISM is a three pronged network manager. Its operations can be split up into three

clusters. The first is the integration with the other gateways. To become completely

integrated and control the network, the ISM must know more than just what each BNs

has in its MIB. Specialized BNs such as UGVs and UAVs have more functioning than

regular BNs and can be better utilized if they were not treated as regular BNs. The

Sensor Network has other qualities that can be maximized as well with proper

integration. The ISMs second main operation is the association algorithm between each

nodes. This includes the Anet and Bnet. Each node must know its neighbors to create

a well routed network. And finally, the ISM must control the actual routing of packets to

ensure Quality of Service within the MBN.

ISM Integration

MBN

The ISMs integration with the MBN is mainly to collect data from each MIB. Each MIB

contains the information of each Backbone Nodes RN associations as well as the

neighboring BNs. It also contains routing information such as traffic flow. This data is

very important for routing purposes as will be seen later.

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UGV

Unmanned Ground Vehicles are great in the sense that they are unmanned and can be

controlled directly by the ISM. UGVs are like an insurance policy on the network. They

are used mainly to keep all the nodes associated in the network. Because they have the

same qualities as a Backbone Node, UGVs insure connections in both the Anet and the

Bnet. Any node that strays far from the network, whether it is a Regular Node or a

Backbone Node, can easily be re-associated with a UGV properly placed between that

node and the network. New implementation is made in the ISM to accommodate

instructions to relocate the UGV to specific coordinates.

UAV

Unmanned Air Vehicles are similar to a UGV without any ground limitations such as

mountains or lakes. Because the UAVs fly and are without restriction, their reception as

a Backbone Node is increased. Normal Backbone Nodes are limited in wireless

communication by physical structures and cannot travel as quickly. UAVs present the

ability to associate quickly and in a broad fashion, covering much more ground than a

normal BN.

UAVs also add increased implementation to the ISM. The UAVs use the CloudCap

Protocol to calculate a variety of aspects in flying. This protocol provides the ISM with a

gateway to communicate with the UAV. Unlike UGVs, where the ISM controls mostly

the coordinates it wants the UGV to reside at, UAVs have enhanced features, including

calculating speed, direction and altitude.

Sensor Network

The Sensor Network is a group of sensors designed to detect targets in the network.

By using actual SNMP, it floods the area of sensors with predefined traps. Each sensor

acts as its own SNMP agent and sets off the trap when it senses a target. The Sensor

Network Gateway acts as a manager and collects all these responses. When two or

more sensors set off the same trap, the Sensor Network Gateway relays a message to

the ISM which records these trap responses. Each message the Sensor Network

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Gateway sends includes in its value the location of the target and the Sensor IDs that

detected the target. This provides the ISM with a timeline of where targets are sensed

as well as their movements in the network.

This implementation of the Sensor Network is very interesting in a mobile network. The

ISM control can execute a number of options including sending UGVs and UAVs to a

specified target that set off a trap. The Sensor Network can also detect lost BNs and

RNs that are out of range from the MBN. When the UAVs or UGVs relocate to the

correct coordinates, the sensor network confirms their movement solidifying the network

associations. With the Sensor Network implementation intact, the topography of the

overall network is more precise.

One factor in nodal movement is the Quality of Service of a node. Too much movement

in a node results in less stability. Although any slight nodal movements wont result in

increased packet loss, too much nodal movement could result in the loss of an

association. The Sensor Network provides additional judgment to routing. Important

video feed sent over the network might want the most stable connection available.

Because the Sensor Network continuously senses targets, the movement of nodes can

be detected and the ISM can relay a message to the other nodes rerouting packets if

necessary.

Nodal Association

A query system is used to incorporate each node into the network. Regular Nodes

associate itself with a BN in the Anet by querying BNs until one answer. This can be

done with a Hello echoed back and forth to establish an association. Any BN that

does not hear from an RN is automatically reverts to its BCN functioning until an RN

associates with it.

The Network Managers and Backbone Nodes associate themselves in the Bnet also by

sending messages. Backbone Nodes themselves know all the possible connections

through a similar querying method as the Regular Nodes. Since every Backbone Node

can also be a Network Manager, each Network Manager knows two things: its Network

Manager and all the nodes it is managing. If the node does not hear from its Network

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Manager for a specified period of time, it immediately un-associates itself with its

Network Manager and queries the network asking for all other possible Network

Managers in the area. The node in turn waits a period of time for all the responses.

After that period is over, it selects its Network Manager based off an algorithm and

sends a message setting that Network Manager as its Network Manager. This algorithm

can be anything from selecting the Network Manager with the smallest ID to selecting

the closest Network Manager in the network.

If a Network Managers periodic update requests are not being replied to, it assumes the

node has moved or is not within range. It un-associates itself with that node and ceases

its periodic update requests.

Routing

The MBNs routing capabilities are perhaps the most important part of the MIB updates.

As associations change, the topography of the network is stored in a connectivity matrix.

The connectivity matrix displays each possible connection within the network as well as

the stability of each link. The stability of the link refers to many aspects of routing. To

be stable, a node must have set associations and good traffic flow. Any node that

repeatedly loses its associations is less stable and will induce more packet loss. This

goes the same for nodes with congested links. Their ability to pass packets is

decreased and a different route would be better corresponding to other nodes. Each

time an association is made or a dropped the connectivity matrix is updated. When the

ISM is informed of a change in the association or stability of a link, the ISM broadcasts

the new connectivity matrix to its nodes. Each Network Manager sends the connectivity

matrix to the BNs that are associated with it until everyone receives the new matrix.

When a new connectivity matrix is received, each node calculates the route needed to

send packets to any node in the network. It uses these calculations until a new

connectivity matrix is broadcasted.

There are several other options looked upon to route packets. The first is priority.

Certain packets from different routes are more important than others. Smaller audio

messages might be more important than a long video feed. Adding a priority to each

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packet guarantees the importance of a packet. Packets with higher priority take the

faster routes while packets are relayed slower depending on traffic. In a congested

network, packets sent regardless of traffic get to their destination faster but has less

reliability on a route due to congestion. The second option is the algorithm used to

route packets. The ISM associates two algorithms that packets can route in. Robust

routing is the safer, reliable route. It sends packets through links with high values in the

connectivity matrix. Dijkstras Algorithm is used as a second algorithm. It chooses the

fastest route regardless of reliability. These selections help nodes route packets

depending on the packet.

ISM Election Algorithm

A Mobile Backbone Network is more efficient than a regular network because of its

structure and decentralized nodes. Because every network is different, an MBN is more

manageable and is easier to establish and maintain based on the circumstances of the

environment it is run on. This must also be true of the Integrated System Manager.

The ISM itself is a centralized administration. It can manage every node in the network

and receives updates from every node to create topographies in both the eyes of the

Backbone Nodes and the Sensor network. However, each Backbone Node has the

capabilities from converting itself from a Network Manager into an Integrated System

Manager and vice versa. There is no enforced structure on which node has to act as the

ISM. The ISM is controlled by a simple algorithm: any node that is its own Network

Manager (it stands at the top of the hierarchy) is an Integrated System Manager. While

an ISM, it queries other nodes periodically to see if there is any node willing to be its

Network Manager. The network is constantly querying itself, wanting to establish more

associations and to improve its service.

Each node can also set itself as the ISM. It un-associates itself with its Network

Manager and then queries all surrounding nodes telling them to set the ISM as their new

Network Manager. These nodes un-associate themselves with their previous Network

Manager and sets the ISM as their new Network Manager.

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These new associations work because each Network Manager only is aware of its

Network Manager and all the other associations it has below it on the hierarchy. To

change Network Managers, it simply un-associates itself from the old Network Manager

and associates itself with the new one.

Conclusion

This paper describes the implementation of an Integrated System Manager onto a

Mobile Backbone Network. This application will support the network and control it to

generate maximum efficiency and more effectiveness. The Quality of Service on a

network is very important and the ISM situates the owner of the network to control it as

to how he sees fit. This is imperative as this Mobile Backbone Network can be utilized in

a variety of fashions.

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References

[1] I. Rubin, A. Behzad, R. Zhang, H. Luo, E. Caballero, "TBONE: a mobile-backbone

protocol for ad hoc wireless networks",Aerospace Conference Proceedings,

2002. IEEE , Volume: 6 , 2002, Page(s): 2727 -2740

[2] Kurose, James F., Ross, Keith W. Computer Networking: A Top-Down Approach

Featuring the Internet (2nd edition). Pearson Addison Wesley. 2002.

[3] SUNY Institute of Technology. SNMP For Dummies.

http://www.tele.sunyit.edu/snmp4dum.pdf Accessed 2003 June 12.