Presented By..
Dipak Kumar Samal

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Abstract
 In mobile ad hoc networks (MANETs) the wireless links are error prone in nature and the mobile devices are highly mobile, therefore traditional Internet QoS protocols like RSVP cannot be easily migrated to the wireless environment
 The management of bandwidth is critical to establish session guarantees for traffic flows
 This paper examines the challenges of incorporating scalable bandwidth management scheme in a mobile adhoc network environment with brief description of some proposals that specifically address this problem.
Introduction
 Bandwidth management in MANETs is much more difficult than in wired networks.
 Extended framework includes local repair mechanism which is used to overcome the problems related to the inertness of resource reservations.
 Here It then introduces to the the concepts of MANET, QoS and QoS models in MANETs.
 It then discusses how traditional QoS techniques fail to scale well in MANETs. It also discusses some schemes that have been specifically designed to address the provision of QoS (specifically) bandwidth in MANET
Mobile Ad Hoc Network (MANET)
Introduction
 A mobile ad hoc network is a self-configuring network of mobile devices connected by wireless links
 Nodes in mobile ad-hoc network are free to move and organize themselves in an arbitrary fashion
 Each user is free to roam about while communicating with others. The path between each pair of the users may have multiple links and the radio between them can be heterogeneous
 This allows an association of various links to be a part of the same network.
Quality of Service (QoS) Introduction
 Quality of Service (QoS) refers to the capability of a network to provide better services to selected network traffic. It is measured in terms of guaranteed amount of data which a network transfers from one place to another in a given time slot.
 In MANETs, its main objective is to achieve a more deterministic network behavior so that information carried by the network can be better delivered and network resources are better utilized, which can be achieved either by raising the priority of a traffic flow or limiting the priority of another flow
Need for QoS in MANETs
 QoS are needed in order to efficiently utilize network resources by identifying which network traffic is critical and allocate appropriate network resources to support those traffic streams
 Traffic behavior and QoS requirement for different applications vary from application to application.
 Different applications require different network performance, based on bandwidth needs and latency sensitivity, if higher the latency sensitivity, higher will be the bandwidth requirement; data transfers can have zero tolerances for packet loss and high tolerances for delay and jitter Quality of Service Models
 Three basic levels of end-to-end QoS can be provided across a heterogeneous network,
1. Best-effort service: Best-effort service is basic connectivity with no guarantee.
2. Differentiated service: Diff Serv is also called soft QoS. Some network traffic is treated better than the rest which is provided by traffic classification.
3. Integrated service: Int Serv is also called hard QoS. This is an absolute reservation of network resources for specific traffic.
Why Existing QoS models fail in
MANET environment
IntServ in MANET The IntServ model is not suitable for MANETs due to following shortcomings in MANET environments:
 Scalability: IntServ provides per-flow granularity, so the amount of state information increases proportionally with the number of flows. This results in a storage and processing overhead on routers, which is the scalability problem of IntServ.
 Signaling: Signaling protocols have three phases: connection establishment, connection maintenance and connection teardown. In highly dynamic networks this is not promising approach since routes may change very quickly and the adaptation process of protocols using a complex handshake mechanism would just be too slow. Moreover, the signaling overhead is a potential problem as well.
Why Existing QoS models fail in
MANET environment
DiffServ in MANET :The main drawbacks of DiffServ approach in MANETs are:
1. SLA (Service Level Agreement): DiffServ is based on the concept of SLA’s. SLA is a contract between a customer and its Internet Service Provider (ISP) which specifies the forwarding service the customer will receive
The SLA includes traffic conditioning rules.
In mobile ad hoc topology there is no obvious scheme for the mobile nodes to negotiate the
traffic rules therefore making SLAs is difficult in MANETs.
Why Existing QoS models fail in
MANET environment
DiffServ in MANET :
2. Ambiguous core network: In DiffServ, traffic
classification and conditioning has to be done at the boundary nodes. This makes QoS provisioning much easier in the core of the network. In MANETs, there is no specific core network because every node is a potential sender, receiver and router
QoS Models for MANETs
1.Flexible QoS Model for Mobile Ad Hoc Network: (FQMM)
FQMM is a QoS model for mobile ad hoc networks which is designed for small to medium sized MANETs, using a flat nonhierarchical topology. It defines three types of nodes exactly as are in DiffServ:
• Ingress node: A mobile node that sends data.
• Interior nodes: The nodes that forward data to the other nodes.
• Egress node: It is a destination node.
QoS Models for MANETs
1.Flexible QoS Model for Mobile Ad Hoc Network: (FQMM)
 The basic idea behind FQQM is that it uses a hybrid per-flow and per-class provisioning policy. In this scheme, traffic of the highest priority is given per-flow provisioning while other traffic with lower priority classes are given per-class provisioning.
 This QoS model is flexible because of the following features:
• Nodes have dynamic roles.
• The provisioning policies are hybrid and flexible.
• FQMM can be combined in a flexible manner to meet different network conditions and QoS requirements.
QoS Models for MANETs
1.Flexible QoS Model for Mobile Ad Hoc Network: (FQMM)
Problems of FQMM in MANETs
In FQMM, as both IntServ and DiffServ schemes are separately used for different priority classes. Therefore, the drawbacks related to IntServ and DiffServ remain to be a drawback in FQMM as well. Although it is attractive model for MANETs but still has following major problems:
• Without an explicit control on the number of services with per-flow granularity, the scalability problem still exists.
• FQMM may not be able to satisfy hard QoS requirements, due to its DiffServ behavior in ingress nodes.
QoS Models for MANETs
II. INSIGNIA:
 It is a signaling protocol which is specially designed for MANETs. INSIGNIA supports algorithms like
fast flow reservation, restoration and adaptation; which are designed to deliver adaptive real-time service.
 INSIGNIA implements an in-band approach by encapsulating some control signals in the IP option of every data packet, which is now called INSIGNIA option. Moreover flow state information is kept in every node and this information is refreshed periodically
QoS Models for MANETs
II. INSIGNIA:
Although INSIGNIA presents very promising approach to QoS support in MANETs but the
system still lacks a few essential features:
• The most frequently mentioned drawback of INSIGNIA is scalability problem due to
the flow state information which is kept within the nodes of a certain path.
• Bandwidth usage in INSIGNIA is not efficient. The extra reservation on the path from the sending node to the bottleneck is a waste of bandwidth. MANET’s topology changing will make this reservation waste propagate frequently.
• INSIGNIA imposes a major processing overhead on the network as there is no mechanism to dynamically change the frequency by which control signals are inserted into the data packets.
• INSIGNIA offers only two bandwidth levels to be used, MINIMUM and MAXIMUM. A better approach would be needed in order to satisfy application requirements and to fully utilize the available resources.
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
ASAP provides adaptive QoS support to real time applications in infrastructure based wireless IP networks. The purpose of this analysis is to extend the ASAP framework which can be used in mobile ad hoc networks.
Soft/Hard Reservation:
 Soft reservation can be considered as the claim of a traffic flow for a certain bandwidth to be used in future.
 Hard reservation enables a traffic flow to exclusively reserve some bandwidth.
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
Soft/Hard Reservation:
 When a new real-time flow is about to start, a soft reservation request is sent first. If there are enough resources available, the requested bandwidth will be soft reserved for that flow.
 After a soft reservation is established,the end node sends a hard reservation message requesting the same amount of bandwidth. This hard reservation will remove all the traffic occupying the corresponding soft reserved bandwidth.
 Introducing these two kinds of reservations is to achieve good performance in QoS monitoring.
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
 Adaptive QoS Monitoring:
QoS monitoring packets periodically investigates the QoS situation on every node within a certain path. Hard reservation messages are sent whenever the end-to-end QoS changes.
Monitoring interval can be changed dynamically
 ASAP Signaling System
ASAP also provides efficient in-band signaling for resource reservation, management, adaptation and releasing. The signaling is designed to produce minimum possible overhead and to provide maximum flexibility.
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
Problems of ASAP in MANETs
Although ASAP makes use of in-band signaling and fast adaptation but the protocol still fails to meet some MANET specific demands. Few problems of ASAP in a mobile ad hoc environment are:
• Flow Restoration Problem
• Reverse Path Problem
• Lost Hard-Reservation Messages
Ad Hoc Extensions for ASAP
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
Ad Hoc Extensions for ASAP
Based on above listed shortcomings ASAP needs to be extended which can provide fast flow restoration and short reaction time to topology changes. To achieve this following new mechanisms are identified:
• Local Repair
• Dynamic Virtual Path
• Flexible Timing Control
• Congestion Control
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
• Local Repair:
 It is triggered by a soft reservation message. Upon receiving a soft reservation message the node reserves some bandwidth within the specified range and updates table entries as usual.
 Before passing the message to the next hop the node checks whether its actual hard reservation corresponds to the hard reservation specified within the received message or not.
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
• Local Repair:
1. If both values are equal nothing has to be done and the soft reservation message is sent along the path
2. In case, if the actual hard reservation specified is smaller than its own hard reservation for that flow, the node releases additional reservation
3. if the specified value is greater than its own, the node tries to allocate additional resources
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
• Dynamic Virtual Path :
Unsymmetrical routes and links causing difficulties for hard reservation messages to follow the reverse path, established during soft reservation can be addressed by dynamic virtual path mechanism. • • Flexible Timing Control
In ASAP, there are two timing parameters which
are related to the efficiency and performance of ASAP; the SR (Soft Reservation) sending interval and the soft state time-out period
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
Flexible Timing Control
 The interval between SR messages is critical in determining the speed with which ASAP adapts changes. This time interval may cause excessive messages and high processing load
 Larger intervals are preferable when the network is relatively stable and has enough resource. A smaller interval is helpful in case of high mobility of network nodes.
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
Flexible Timing Control
 The SR interval should not be smaller than the timeout period in order to keep the flow path alive. And the timeout period should not go too far beyond the SR interval.
 The reason is that too large a soft state time-out will keep reservations on broken paths alive for a long time, thereby preventing other traffic from accessing those resources..
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
Congestion Control:
 It can be done by detecting it and reducing transmission rate
 In MANETs, the queue length is not a valid indication of congestion. We need to detect congestion in a node’s neighborhood by monitoring the wireless channel utilization ratio.
 This information can be obtained by defining a threshold value, and when the channel utilization ratio is larger than this threshold, we can assume that this node’s neighborhood is getting congested
QoS Models for MANETs
III. Adaptive Bandwidth Reservation and Pre-allocation QoS Architecture: ASAP
Congestion Control:
 The channel utilization ratio is defined as the fraction of time within which a node is sensing the channel as being utilized.
 Normally a wireless radio has four states; (1) Busy state, (2) Carrier sensing channel busy, (3) Virtual carrier sensing busy and (4) idle state.
 Each node will constantly monitor the channel state changes and record the time period that the radio is in eachstate. For each time period, we then calculate the channel utilization ratio
Conclusion
 Three major problems of using ASAP in MANETs were presented in the paper that were related to flow restoration, reverse path and lost hard reservation messages.
 Thereafter, the paper identified and explained a solution to address these specific problems.
 To be specific, a local repair mechanism is used to overcome the problems related to the inertness of two pass based reservations like the big latency during flow restorations. The reverse path problem is addressed by using dynamic virtual paths while
flexible timing control and congestion control will help in improving efficiency and performance of ASAP.