16-05-2012, 03:10 PM
Security and QoS Self-Optimization in Mobile Ad Hoc Networks
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INTRODUCTION
NETWORK quality of service (QoS) and network security
have been considered as separate entities and research
in these areas have largely proceeded independently with
few exceptions. However, security impacts the overall
network QoS as more security usually means more message
overheads for authentication and other security functions,
as well as additional delays imposed due to overheads
caused by encryption, etc. This is especially true in an
ad hoc network environment where security mechanisms
such as authentication services are proposed to protect the
communication on open mediums in wireless networks,
thus introducing overheads that affect the QoS of communications
significantly. It is therefore essential to consider
both security and QoS together when designing protocols
for ad hoc environments as one impacts the other.
SECURITY AND QOS FEEDBACK CONTROL LOOP
We use the PID feedback control loop to manage network
security and QoS self-optimization. Fig. 5 shows the
distributed optimization architecture present at each node
in the network. Each application has one of three QoS
requirements as input: Guaranteed, Controlled load, or
Best effort. In the network, the QoS plant is a module of
the routing protocol to handle the QoS request. Security
policies are considered as another input to the network; all
the security policies are implemented by the security plant,
which is another module of the routing protocol. The QoS
plant is responsible for creating new paths as well as
managing the state information of any existing path and
the state information of each node. It outputs the QoS path
state information to the PID controller. The security plant
is responsible for managing, adding, and removing
security policies. Network security is controlled by a
policy-based security management. The network security
level can be adapted by the security plant module by
adding or removing security policies at runtime.
MEASURING NETWORK RESOURCE AVAILABILITY
We first describe the QoS plant. QoS routing in an ad hoc
network is difficult because the network topology changes
constantly, and the available state information for routing is
inherently imprecise. In this paper, we propose a holistic
multilayer QoS surface-guided routing which separates
metrics at the different layers. In our model, each layer
manages its own QoS and communicates with other layers
through its QoS interface. Network layer metrics determine
the quality of links in order to generate the paths with good
quality. On the other hand, application layer metrics select
exactly one path out of the paths that are most likely to meet
the application requirements. Our model considers not only
the QoS requirement, but also the cost optimality of the
routing path to improve the overall network performance.
The goal of QoS routing is twofold: 1) Selecting a network
path that has sufficient resources to meet the QoS
requirements of all admitted connections and 2) achieving
global efficiency in resource utilization.
Multilayer QoS Interface Guided Routing
We propose a multilayer QoS interface guided routing,
which separates metrics at the different layers: Medium
Access Control (MAC) layer metrics, network layer metrics,
and application layer metrics. In our model, each layer
manages its own QoS and communicates with other layers
through its QoS interface. At the application layer, we
propose to classify the QoS requirements into a set of
three QoS priority levels with their corresponding application
layer metrics. Level I guaranteed service corresponds
to applications that have strong delay constraints such
as voice.