HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Peer to Peer Applications in Ad hoc
Networks
Author: Jesús Hijas
jhijas@netlab.hut.fi
Networking Laboratory
Helsinki University of Technology
Supervisor: Professor
Raimo Kantola
Instructor: LSc. José CostaRequena
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Outline
• Problem overview
– Ad Hoc Networks
– Peer to Peer applications
• P2P architectures
• Study of the problem
– Limitations when using P2P applications in Ad Hoc networks.
• Solution
– P2P application proposal for Ad Hoc networks
• Verification
– Tests and results
• Conclusions
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Problem
• The problem to be solved in this Thesis is
how to discover and use Peer to Peer
applications in Ad Hoc networks.
• We also study their performance and
scalability problems when running in
nodes that are part of an Ad Hoc network.
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Problem (II)
• Ad Hoc networks are wireless, self-organizing
systems that provide functionality without
infrastructure support.
• Peer to Peer (P2P) applications are those that
do not rely on elements as servers or clients
• Inherent symbiosis:
– P2P applications: distributed, running in the nodes of
the network, not in central servers
– Ad hoc networks: all nodes are peers (equals) that
have to act both as clients and servers (P2P
paradigm).
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Problem (III)
• P2P architectures: Centralized (e.g. Napster)
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Problem (IV)
• P2P architectures: Distributed and unstructured (e.g.
Gnutella)
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Problem (V)
• P2P architectures: Distributed but structured (e.g.
Kazaa)
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Study of the problem
• Problem description: to achieve the goal of this Thesis,
we need to study which problems appear when
integrating P2P applications and Ad Hoc networks:
– Service Discovery: P2P architecture is fully distributed, which
means that applications are available in concrete nodes of the
network and not centralized in servers. In Ad Hoc networks, one
node does not know the others beforehand. Thus, applications
have to be discovered before they can be used.
– P2P architecture: should not rely on central nodes, since in Ad
Hoc networks one node can be down at anytime.
– P2P applications: may act both as client and server with high
reliability.
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Solution
• We need to implement a Service Discovery
mechanism so that peers can find each other
and the services they provide. It will be
implemented over UPnP.
– Chosen among others such as JINI, Salutation, SLP,
etc.
• P2P architecture must be distributed and
unstructured.
• P2P application must include both client and
server entities in a single piece of software that
will run in every node in the Ad Hoc network.
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Solution (II)
• P2P application proposal for Ad Hoc
networks:
– P2P application: Presence Service.
• Chosen among others such as Instant Messaging,
Voice over IP, file sharing, etc. due to its simplicity.
• Will run over SIP.
– Service Discovery module: in charge of
solving the problem of service discovery in Ad
Hoc networks.
• Will run over UPnP.
Solution (III)
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
• P2P application proposal for Ad Hoc networks:
design of the system.
SIP
HTTP, TCP, IP, SSDP, UDP, XML…
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Solution (IV)
• Presence Service functionality:
– Service that allows the user to know about the
reachability, availability and willingness of
communication of another user (i.e. his
status).
– Users subscribe to others’ presence
information.
– When the presence status of one user
changes, it has to notify all the subscribers
this user has.
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Solution (V)
• UPnP functionality:
– We use UPnP discovery step, in which control points and
devices multicast SSDP discovery messages (to address
239.255.255.250).
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Verification
• Tests scope: estimate the performance of the
P2P application developed in a real Ad Hoc
Network.
• Test method: prepare test cases with different
number of nodes in the network and measure
the total traffic generated by the application in
one node.
• Test conclusions: consider scalability problems
based on the results obtained in the tests and
the previous analytic study.
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Verification (II)
• The Ad Hoc network
is formed by iPAQ
PDAs with with one
wireless adapter
• Linux OS
• Wireless link
bandwidth: 2Mbps
• 1 iPAQ 3900 and 2
iPAQ 3800
Verification (III)
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
• Analytic study:
– Excluding unavoidable traffic, such as IGMP, TCP or ARP, the total
traffic of the application is:
T  TSIP  TUPnP
– SIP traffic, TSIP, is the number of SIP messages sent by one node.
– UPnP traffic, TUPnP, varies with the expression:
TUPnP ( packs / sec) 
1
 N  N tx
CC
– With:
• CC = Value of control-cache header
• N = number of nodes in the network
• Ntx = number of transmissions of one packet
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Verification (IV)
• Tests case 1: one node in the network
– Scope: measure the UPnP traffic in one iPAQ when it
does not interact with other devices and estimate the
value of CC to complete the analytic formula.
– Results:
Test case 1
UPnP Total
Time between first and last packet (sec) 6,719 7,348
Packets
29
33
Avg. Traffic (Kbit/s)
9
10
– CC: time between UPnP announcements (expiration
time)
CC 
time
6,719s

 0,232s
packets 29 packs
Verification (V)
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
• Analytic study:
– We will assume no UPnP retransmissions, i.e.
N tx  1
– With these data the general analytic model for the traffic of the
application is:
1
1
T ( packs / s)  TSIP 
 N  N tx  0 
 N 1  4,31 N
CC
0,232
– The capacity consumed by the application is:
BW (bits / s)  Traffic(bytes / s)  Avg. packsize(bytes)  8(bits / byte)
– Considering the average UPnP packet size measured in the test
cases (309 bytes):
BW (bits / s)  4,31 N  309  8  10654,32  N
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Verification (VI)
• Test case 2: two nodes in the network. Scenario.
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
• Test case 2: capture.
Verification (VII)
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
• Test case 2: Traffic.
Verification (VIII)
Verification (IX)
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
• Test case 2: Result analysis.
– Initial IGMP and ARP traffic.
– SIP traffic (red) is very low compared to UPnP traffic
(green).
– Data and comparison:
Test case 2
Avg. Traffic (Kbit/s)
SIP
1
UPnP Total
22
24
– Analytic results for test case 2:
TUPnP  10654,32  2  21,308Kbit / s
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Verification (X)
• Test case 3: three nodes in the network. Scenario.
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
• Test case 3: Traffic.
Verification (XI)
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Verification (XII)
• Test case 3: Result analysis.
–
–
–
–
–
IGMP and ARP traffic peaks in the initialization.
UPnP traffic: predomines during all the test.
SIP traffic (red) is very low.
Total traffic increases softly compared to test case 1.
Data:
Test case 3
Avg. Traffic (Kbit/s)
SIP UPnP Total
1
35
36
– Analytic results for test case 3:
TUPnP  10654,32  3  31,926Kbit / s
Verification (XIII)
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
• Result analysis:
Bandwidth (Kbit/s)
Bandwith of the Presence Service Application
450
400
350
300
250
200
150
100
50
0
Analytic function
Measured values
1
4
7
10
13
16
19
22
25
Number of nodes (N)
28
31
34
37
40
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Verification (XIV)
• Result analysis:
– If we consider the total capacity of the channel
provided by the wireless card in the iPAQ devices
(2Mbit/s), we could accept that the Presence
application would consume the 20% of this capacity.
Therefore, the maximum acceptable capacity of the
application in one device would be:
BWMAX ( KBit / s)  20%  2MBit / s  400KBit / s
– This maximum is reached with 37 nodes in the
network. This number can be taken as the maximum
acceptable number of nodes in the Ad Hoc network
so that the application is efficient.
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Conclusions
• In this Thesis we have developed a Peer to Peer
application that will run in an Ad Hoc network.
• Attending to the results got, we can conclude that Peer
to Peer applications are suitable for Ad Hoc networks,
providing a fully-distributed service and automatic
service discovery in every node, without relying in central
servers and with a reasonable scalability.
• Possible future work:
– Reducing the UPnP traffic to improve the scalability of the
application.
– Integrating the Presence Service with any other P2P application
such as VoIP or IM to allow users a wider way of communication.
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Questions?
HELSINKI UNIVERSITY OF TECHNOLOGY
Peer to Peer Applications in Ad Hoc Networks
Jesús Hijas
Thank you