“Intra-Network Routing Scheme using Mobile Agents”

byAjay L. Thakur

Outline

Objectives OSPF Overview Mobile Agents Related Works Proposed Best-Effort Routing Scheme Proposed QoS Routing Scheme Simulation Results Conclusion

Objectives

Develop a Routing Scheme using Mobile agents Given a source (s) and destination (d) find a

path Given a source (s) and destination (d) find a

path which satisfies QoS constraints like required Bandwidth ( Breq) and delay

Open Shortest Path First (OSPF)

Overview Uses link state routing algorithm To reduce the routing overhead it divides the full

Autonomous System (AS) into number of areas Each router maintains link state database for

routing domain Area Border Router (ABR) keeps separate database

for each area Routers periodically send Link State Advertisement

(LSA) into the network ABR routers send summary LSA to backbone area

and to the internal routers

OSPF Contd…

0

3

5

2

7

4

10

911

12

13

6

8

15

14

16

Area 1

Area 2

Area 3

Area 0

ABR router Internal Router

OSPF issues Memory Overhead

OSPF uses a link state database to keep track of all routers and networks within each attached area. With a complex topology, this database can be much larger and may limit the maximum size of an area.

Processor Overhead During steady state operation the OSPF CPU usage is

low, mainly due to the traffic between routers. However, when a topology change is detected, there is a large amount of processing required to support flooding of changes, and re-calculation of the routing table. In the existing implementations, the shortest path tree has to be computed from scratch after each link state change.

OSPF issues contd…

Synchronization of Database Database at all routers within area should be

synchronized. After changes in network it takes time to notify the change to all the routers within area. In between database is not synchronized and it may cause looping of packets.

Mobile Agents

Client Server Communication Connection is maintained for full duration If connection breaks due to link/node failure,

connection has to be established once again which consumes network bandwidth

ServerClient

Request

Response

Mobile Agents

ClientServer

Mobile Agent Communication Mobile agent is a program that can be dispatched from one computer and delivered to a remote computer for execution. After execution mobile agent comes back with the result

MA

Result

Some of the advantages of Mobile Agents

Less traffic in the network Good for unreliable networks

Client ServerResult

Link goes down

Link comes up

MA

Related Works Mobile Agents Based Routing

Mobile agents collect the resource status at each node and accordingly the forwarding table is updated at each router

Mobile agent based QoS routing Flooding of mobile agents to find a path It strictly uses call admission control

Topology aggregation approach Divide the topology in groups, and each node

knows the information of resources at the routers within the group

Proposed Work

What are RIMA nodes? RIMA nodes are the subset of nodes such that, each

non-RIMA node should be connected to at least one RIMA node within two hops

RIMA neighborhood RIMA node and its neighbors within 1 hop or 2 hop

distance forms neighborhood RIMA Database

RIMA nodes are capable of managing and collecting information of all the nodes within its neighborhood

e.g. link capacity, reliability of nodes, delay on the path, congestion at the nodes and color of the links

It also collects the information of the nodes which are on the path to neighbor RIMA nodes

RIMA (Routing Intelligent Mobile agent)

In figure nodes 2, 6 and 10 are RIMA nodes Neighborhood of RIMA node 2

Nodes 0, 1, 3, 4, 5 and 7 Neighborhood of RIMA node 6

Nodes 1, 3, 4, 5, 7, 8, 9, 12, 13, 14, 15 and 16

Example

15 166

3

2

7

12

8

10

11

1

5

4

14

0

913

RIMA Placement Algorithm

RIMA nodes are more responsible for routing of packets and it collects the database which is used for routing

RIMA placement algorithm takes into consideration some of the desirable properties Processing power Average normalized link capacity Reliability Connectivity

RIMA Placement Algorithm contd…

• Send node information packet to neighbors• Receive information packet from neighbors

• Calculate weight factor• Send weight factor to neighbors

Weight of node > Weight of all neighbors

Announce itself as RIMA node

Yes

Start timer and wait for RIMA announcement message

RIMA announcement Message received ?

Yes

No

Announce itself as RIMA node

No

Finding path between RIMAs RIMA node sends mobile agents to find

path(s) to neighbor RIMA nodes While traveling mobile agent also collect the

path information like BW available on links When mobile agent reaches at RIMA node it

gives all the information to the RIMA node Mobile agent comes back to source RIMA

node and gives information to source RIMA node

RIMA nodes estimate the path delay by using time stamp in mobile agent

Finding paths between RIMAs

1

2

3

4

5

6

7

8

RIMA PATH Delay

2 4->6->3->2

4

Table at node 4

RIMA PATH Delay

4 2->3->6->4

3

Table at node 2

Communication Among RIMAs

RIMA node periodically sends reachability information to neighbor RIMA nodes

PATH vector protocol is implemented among RIMA nodes

Using the information obtained from neighbor RIMA nodes, RIMA node decides the next hop RIMA node for each destination e.g. tables at RIMA node 2 are, Destination Next hop RIMA

15 6

11 10

- -

RIMA PATH

6 2->4->62->1->7->6

10 2->3->5->102->4->5->10

Path finding in RIMA based routing

Consider source (s) and destination (d) s sends a packet to connected RIMA node (R1) At R1 : if destination is in neighborhood it

sends directly to d otherwise it sends the packet to next hop RIMA node R2

Suppose at a RIMA node Rn destination is in neighborhood. In that case RIMA node directly sends packet to destination node

Path of packet can be represented as s R1 R2 … Rn d

RIMA Based Best-Effort Routing

15 166

9

3

2

7

12

8

10

11

1

5

4

14

0

13

Source=1 and Destination=11

Source=9 and Destination=14

Dynamic Network Behavior After link/node failure corresponding

node sends update message to only connected RIMA nodes and one hop neighbor nodes

RIMA node updates its neighborhood If there is change in cost to reach some

node in neighborhood Send reachability information to neighbor

RIMA nodes If neighborhood is unchanged

No need to send messages

Quality of Service (QoS) Need of QoS

Internet provides Best-Effort service New Emerging real time applications need

Guaranteed QoS; specially in case of interactive application like IP telephony, video conferencing

Metrics used in QoS routing Bandwidth, Delay, Delay jitter, packet loss

Issues in QoS Knowledge propagation and maintenance: When to

send the link state information to other network Periodic: Router periodically send Threshold based: When significant change in resources

Metric and path computation How to measure and collect network state information How to compute routes based on the information collected

RIMA based QoS Routing Scheme

On-Demand Routing algorithm QoS metrics used are bandwidth and

delay RIMA based QoS routing is same as RIMA

based Best-effort routing but only difference is that each RIMA node strictly selects a path according to QoS constraints

Consider source s , destination d , requested bandwidth Breq and delay Δmax

RIMA based QoS Routing Scheme

Source node sends mobile agent to a connected RIMA node on the path with sufficient bandwidth and minimum delay

At RIMA node: If destination is within a neighborhood or it is on the path to other RIMA node and feasible path exist, then RIMA node directly sends the mobile agent to

destination node otherwise RIMA node sends the mobile agent to next

hop RIMA node on the path which satisfies QoS constraints

When mobile agent reaches to destination, destination node sends reservation request on the same path

When source node gets mobile agent it finds the time taken by mobile agent to setup the connection and it estimates delay to destination. If application can sustain that much delay then it sends the packet. Otherwise it releases the resources

QoS Routing

15 166

9

3

2

7

12

8

10

11

1

5

4

14

0

13

Source=1 and Destination=11

Reservation successful

Modified RIMA based QoS Routing

In previous algorithm Source sends request to only one RIMA node

In modified RIMA based QoS routing Source sends the path request to all the connected

RIMA nodes Advantage

More than one mobile agent reaches at destination hence possibility of finding path increases i.e. increase in success ratio

Disadvantage Cost per connection increases as more requests are

send in the network Destination will choose one path and sends

the reservation request on that path

Modified QoS Routing

15 166

9

3

2

7

12

8

10

11

1

5

4

14

0

13

Source=1 and Destination=11

Reservation successful

Simulation of Intranet

Different Simulation Methods Waxman Method

P (x ,y) =e -d/(Lβ)

Regular Method Regular topologies are used for simulation e.g.

star, mesh, ring Hierarchical Method

Transit-Stub Method

Hierarchical Method

Transit-Stub model

Example

OSPF Simulation

Topology is generated using Transit-Stub model and edges are added using Waxman’s method

Total domain is divided into NA areas + backbone area.

Each area has more than one ABR ( Area Border Router)

Topology size is changed by changing Number of areas and Number of routers per area

Simulation

RIMA topology simulation We consider topology as Flat topology Generate the topology using Transit-Stub

model and added edges using Waxman’s method

RIMA placement algorithm decides RIMA nodes

Assumption and Features of Intranet Simulation

Assumptions Propagation delay considered to be 1 unit time Error free transmission Links are symmetric No packet loss at the router due to insufficient buffer

Features Simulated up to 800 nodes At each router two queues one for best effort service

and other for guaranteed service Best effort traffic is background traffic Weighted fair queue is used at each router Processing delay, transmission delay and queuing

delays are considered

RIMA Placement

• Number of RIMAs required

RIMA-to-RIMA average number of paths

Node Convergence: Number of messages

10

Node Convergence Time

Path Convergence: Number of messages

Path Convergence Time

RIMA based QoS Routing: Path setup

Success ratio Vs Number of connections

Connections Rejected Vs Breq

Number of update messages generated Vs connection generated

Connection Blocking Probability Vs number of hops

Conclusion

Developed RIMA based Best-effort routing scheme

Developed RIMA based QoS routing scheme

Comparisons of the performance of proposed routing scheme and OSPF routing

Publications (submitted) Ajay L. Thakur and P. Venkataram , "RIMA Based

Intra-Network QoS Routing Scheme", Computer Communications Journal (Elsevier)

Ajay L. Thakur and P. Venkataram , "Intra-Network

Routing Scheme using Mobile Agents”, SPCOM 2004

Thank You!