Optimum Path Computation Algorithms for Multimedia and Real Time Services over IP-Networks
1
Optimum Path Computation Algorithms for Multimedia and Real
Time Services over IP-Networks
Rajiv kumar, Yuvraj Singh, Varun Uppal, Mandeep Rawat and Ankit Bhatt
Department of Electronics and Communication
Jaypee University of Informations and Technology, Waknaghat, Solan, HP
ABSTRACT: Traditional Routing Techniques over internet involves shortest path based on minimum distance,
delay, etc. for various applications including E-mail, instant messaging, voice-over-ip, etc. Such a technique is
based upon connection-less approach where multiple paths are formed between source and destination. Although
such an approach supports faster and less delayed path along with less traffic congestion but, with rapid growth of
multimedia applications such as telesurgery, live video conferencing and various other “mission critical” areas such
connection-less approach dreadfully fails as time delay i.e. start-up delay, increases considerably reducing real time
factor of multimedia applications. In this paper, a routing algorithm is proposed which draw parallels with QoS
requirements of multimedia applications i.e. high bandwidth, minimum start-up delay. Comparative analysis of
routing algorithm based upon connection-less approach against proposed routing algorithm based on connectionoriented approach is also done via a simulation taking an example of a particular network.
Keywords—Traditional Routing Techniques, Multimedia Applications, Mission Critical, Routing Algorithm.
INTRODUCTION
M
ultimedia applications such as digital video and
audio require a connection-oriented approach with
high QoS requirements such as high bandwidth, minimum
start-up delay, maximum throughput. A network has to
pass simultaneously several such constraint in order to
facilitate QoS requirements. In a traditional routing method
e.g ARPANET (provides only connectivity based on
distance), using connection-less approach a path is
computed only on the basis of distance and delay. Such a
connection less oriented approach is substituted by ours
connection-oriented method where maximum bandwidth
allocation is the prior factor in determining the route along
with minimum number of hops [1, 2, 3, 8].
Connectionless means that no effort is made to set up a
dedicated end-to-end connection. Connectionless communication is usually achieved by transmitting information in
one direction, from source to destination without checking
to see if the destination is still there, or if it is prepared to
receive the information. When there is little interference,
and plenty of speed available, these systems work fine. In
environments where there is difficulty transmitting to the
destination, information may have to be re-transmitted
several times before the complete message is received. It
reduces delay time and effective cost. But causes a lot more
problem when a safe and secure data transmission is
required. Although data packets may get transferred from
source to destination but always there are some packet
loses at the receiver end. Various applications like radio
might not need such a high accuracy and hence can be
applied in connection less media. Walkie-talkies, or
citizens band radios are a good examples of connectionless
communication. You speak into the mike, and the radio
transmitter sends out your signal. IP, UDP, ICMP, DNS,
TFTP and SNMP are examples of connectionless protocols
in use on the Internet [8].
Connection-Oriented means that when devices
communicate, they perform handshaking to set up an endto-end connection. Such a technique is the most secure and
guarantees 100% transmission of data. This kind of
accuracy and guarantee is required by various applications
termed as “mission critical”, where dependency on the
system is very high and margin of error reduces to near
zero. This includes along with various real time and
multimedia applications involving space communication,
telesurgery, and teleconferencing [8].
PATH COMPUTATION ALGORITHMS
Routing algorithm is a logic a router uses to decide, for
each incoming packet, which output link, the packet should
be transmitted on. Desirable properties of a routing
algorithm: Correctness, Simplicity, Efficiency, Robustness
Stability, Fairness, Optimality. The two most common
routing algorithms are distance-vector and link-state.
In a distance-vector routing each router exchanges
information about the entire network with neighboring
routers at regular intervals. Neighboring routers are
connected by a direct link (e.g. a LAN) which exchanges in
formation at regular intervals e.g. every 30 seconds.
In a Link-state, each router exchanges information about
its neighborhood with all routers in the network when there
is a change. Here the neighbourhood of a router is a set of
neighbor routers n, where each router’s neighborhood
information is flooded through the network.
138
Mobile and Pervasive Computing (CoMPC–2008)
To calculate its routing table, a router uses Dijkstra’s
Shortest-Path algorithm [6, 9].
Dijkstra Algorithm
This algorithm builds a shortest-path spanning tree for the
router: such a tree has a route to all possible destinations,
and no loops. First it identifies all link costs in the network:
either from the link-state database or using the fact that the
cost of any link from a network to a router is 0. The router
running the algorithm is the root of its shortest-path
spanning tree. Even if all routers’ link-state databases are
identical, the trees determined by the routers are different
(since the root of each tree is different). A node is either a
network or a router; nodes are connected by arcs. The
algorithm keeps track of 2 sets of nodes and arcs—
Temporary and Permanent. Initially, the Temporary set
contains all neighbor nodes of the router itself, and the arcs
connecting them to the router; only the router is initially
permanent. When all nodes and arcs are in the permanent
set, the algorithm has terminated. Then it identifies the
temporary node whose arc has the lowest cumulative cost
from the root: this node and arc are moved into the
permanent set; any nodes which are connected to the new
permanent node and are not already in the temporary set,
along with the connecting arcs, are made temporary. Also,
if any node already in the temporary set has a lower
cumulative cost from the root by using a route passing
through the new permanent node, then this new route
replaces the existing one; repeat until all nodes and arcs are
permanent.
The Dijkstra’s shortest path algorithm is the most
commonly used to solve the single source shortest path
problem today. This algorithm is the basis of computations
of shortest path according to minimum distance, minimum
delay and maximum bandwidth.
For a graph G (V, E), where V is the set of vertices and
E is the set of edges,
Dijkstra’s shortest path algorithm for each u belongs to
G:
Start
1. d[u] = infinity;
2. parent[u] = NIL;
3. End for
4. d[s] = 0; // s is the start point
5. H = {s}; // the heap
6. while NotEmpty(H) and targetNotFound:
7. u = Extract_Min(H);
8. label u as examined;
9. for each v adjacent to u:
10. if d[v] > d[u] + w[u, v]:
11. d[v] = d[u] + w[u, v];
12. parent[v] = u;
13. DecreaseKey[v, H];
End
Using the above dijkstra algorithm, three programs were
developed in the C++ environment and used for simulation
to compute best suitable path according to certain
requirements like bandwidth, delay, no. of hops etc.
Snapshots of the output of these programs were taken and
are shown in this paper.
A GIVEN UNIDIRECTIONAL NETWORK
TOPOLOGY WITH VARIOUS PARAMETERS
Given in the figure is a network topology with 12 nodes
and 24 links between the nodes. Source is the node no. 9
and the destination is node no. 2. It is required to compute
the optimum path between the source and the destination.
Simulation results are computed and shown with the help
of programs.
12
1
11
9
(Source)
10
(Destination)
2
8
5
3
7
4
6
Fig. 1
Optimum Path Computation Algorithms for Multimedia and Real Time Services over IP-Networks
139
Table: Network Link Metrics
S. No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
Link [u,v]
12,1
11,1
5,1
1,2
11,2
5,2
3,2
10,2
7,2
5,3
4,3
6,4
4,5
11,5
12,5
8,5
7,6
9,8
8,10
9,10
6,10
10,11
6,11
11,12
Distance [D(u,v)]
108
50
30
30
108
50
50
50
30
50
108
50
108
50
50
30
50
50
50
50
50
50
50
50
Bandwidth(in Mbps) [c]
5
4
5
6
4
5
6
7
4
3
4
5
6
8
9
2
4
5
6
3
4
5
3
3
Delay(in secs) [d(u,v)]
10
13
13
4
20
14
14
15
17
9
4
34
21
19
18
3
34
16
15
13
13
12
15
19
Computing Parameters
Connection-Less Routing Algorithm
Various QoS parameters such as delay, bandwidth, number
of hops, capacity, etc are considered in this paper while
computing the optimum path between two nodes. For the
connectionless approach, we have used minimum distance,
minimum delay & bandwidth as the criteria for
optimization. For the connection oriented approach, we
have used maximum bandwidth criteria along with
minimum number of hops.
Shortest Path According to Distance Only
Associated weights of delay wd , bandwidth wc , no. of
hops
wh are computed for each case. For the case of
connection oriented approach wc is the is the minimum
capacity in the whole path. The capacity of link less than
wc is not used for computing the path. For the case of
Below is the snap shot of the program based on Dijkstra
Algorithm for computing minimum distance path between
two points in network taken above taking a single
parameter of distance [D(u,v)] between two nodes. a
shortest length is hence calculated between source node no.
9 to node no. 2. The path is 9..10..2 and minimum distance
is 100. This route is often changed as connectionless
approach might require. Depending on traffic, the shortest
path is computed taking new path where distance parameter
is minimum.
wc can be derived as follows: An
equivalent of whole path is assumed to be C eq .
connection less
As we know that,

Ceq
= Total Delay. Hence the net
value of
Ceq 

[d (u, v) 

c(u, v)
(1)
]
Simulation no. 1: optimum path according to distance only
140
Mobile and Pervasive Computing (CoMPC–2008)
This routing algorithm uses Dijkstra algorithm to find
best path depending on minimum delay (d(u,v) in sec). This
program computes minimum delayed path according to
bandwidth (c(u,v)) and delay (d(u,v)) linked with each
node. The best path is calculated on the basis of traffic to
data to be sent (  = 5 mbps).
Here the formula used for minimum delay is =

 (u, v)[ c(u, v)  d (u, v)]
(2)
As said above, the path would change according to the
traffic of data to be send. Here the best path is calculated
between node no. 9 to node no. 2 and minimum delay is
31 seconds.
Simulation no. 3: optimum path according to bandwidth
Simulation no. 2: optimum path according to delay and
bandwidth
Connection-Oriented Routing Algorithm
Shortest Path According to Bandwidth and Number
of Hops
As the path is dedicated one there is no loss of data packets
here. Only criteria for above program algorithm is the
maximum bandwidth. This is calculated on the basis of
traffic of data to be sent. If under any circumstances any
node is witnessed with bandwidth less than traffic of data
() then a condition called bottle neck is reached. Under
such a condition the node (u, v) with less bandwidth than
the traffic () would be truncated or the different path
would be chosen removing the node (u, v) from the
decision tree. After that path with minimum no. of hops is
selected from source to destination. As shown below for
traffic () 4 mbps shortest path is selected from node
no. 9 to node no. 2 in minimum of three hops.
Above is the comparative analysis of the various
parameters taken separately in the above three different
cases. The following inference were drawn:
1. High Bandwidth requirement for the multimedia
applications is only satisfied by the last row where the
value of equivalent bandwidth is highest among the
three values.
2. Although the value of distance, no. of hops and delay is
far less in case of first two cases still for dedicated
applications only bandwidth value reigns more than all
other parameters to give a secure and guarantee stable
communication.
3. Also the path was changed between node no. 9 and node
no. 10 as “bottle neck” was encountered as the
bandwidth of between 9 and 10 is less as compared to
traffic requirement.
c(9, 10) = 3 <  = 4
CONCLUSION
By using the simulation programs it is shown that for the
multimedia and real-time application over ip-networks, it
was mandatory to use the bandwidth efficiently. The
traditional routing method which depended only on delay
and distance has proven incompetent for high bandwidth
requirement applications. Also shown is the adaptive
routing, where route is changed in accordance with the
traffic load.
A COMPARISON
CASE
NO.
1.
2.
3.
ROUTE
9..10..2
9..10..2
9..8..10..2
TRAFFIC ()
IN Mbps
3
5
4
DISTANCE (WD)
DELAY (Wd)
IN Secs
BANDWIDTH (WC)
IN Mbps
NO. OF
HOPS
100
100
150
30
31
49
0.102
0.164
5
2
2
3
Optimum Path Computation Algorithms for Multimedia and Real Time Services over IP-Networks
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141
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