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An Enriched Finite State Machine Model-based Formalism for Layer-5 Internet Protocols Modelling – An Investigation on Protocol Performance Alexandru Catalin Ionescu 05.10.2008 Content Surf the MSc Thesis Background, Problems and Methods (Mobile) Internet Communications

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slide1

An Enriched Finite State Machine Model-based Formalism for Layer-5 Internet Protocols Modelling – An Investigation on Protocol Performance

Alexandru Catalin Ionescu

05.10.2008

content
Content
  • Surf the MSc Thesis
    • Background, Problems and Methods
    • (Mobile) Internet Communications
    • Packet Data Access in Mobile Networks
    • Layered Network Architectures
    • Protocol Modelling
    • Protocol Modelling for Performance Measurements
    • Conclusions
  • Personal Experience (How I wrote my MSc. Thesis)
slide3
Surf the MSc Thesis
    • Background, Problems and Methods
    • (Mobile) Internet Communications
    • Packet Data Access in Mobile Networks
    • Layered Network Architectures
    • Protocol Modelling
    • Protocol Modelling for Performance Measurements
    • Conclusions
  • Personal Experience (How I wrote my MSc. Thesis)
background mobile services and applications
BackgroundMobile Services and Applications
  • New Mobile Networks providing High Data Rates
  • Fixed Internet Services are coming into the Mobile Environment
  • It is all about instant access to information
  • Ensure the Quality of Service (QoS)
    • Different applications need different QoS
    • In Mobile Networks resources are never enough 
  • The transition From GSM to UMTS
  • New Internet Engineering Task Force Multimedia Architecture

The need to provide a model that allows a developer to first analyze and eventually optimize the application protocol.

ietf multimedia architecture

Security

SIP

SDP

SDP

RTCP

RSVP

IETF Multimedia Architecture

TCP / IP

UPD / IP

Video Equipment

RTP / RTCP

Encapsulation

Audio Equipment

Packet Network

User Data

Applications

System Control

User Interface

problems and methods
Problems and Methods

Question 1: How could one formally model the communication protocols according to a specific use case?

Question 2: How to estimate the generated network traffic for a specific use case when using a certain communication protocol?

Question 3: How to improve a protocol in order to decrease the generated network traffic?

slide7
Surf the MSc Thesis
    • Background, Problems and Methods
    • (Mobile) Internet Communications
    • Packet Data Access in Mobile Networks
    • Layered Network Architectures
    • Protocol Modelling
    • Protocol Modelling for Performance Measurements
    • Conclusions
  • Personal Experience (How I wrote my MSc. Thesis)
mobile internet communications
Mobile Internet Communications
  • Mobile Communication - A way we see the world
  • Demand for Complete Connectivity
  • Service Evolution
    • First was the voice
    • Then came the basic messaging (SMS)
    • Data transfer followed (FAX)
    • Internet Applications in Mobile handsets
performance in mobile networks

Effective

Resilient

Reliable

Performance in Mobile Networks
  • Performance (efficiency) is hard to define formally, analyze and not easy to accept
  • Performance = Service Efficiency = Service Usability
  • Mobile Communications transmission Media is faulty – Reliable protocols
    • Error detection
    • Error correction
  • Topological Failures in Mobile Networks are common – Resilient protocols
    • Ability to test the Link
  • Effectives is defined as Easy to implement and Use
    • Easy and Use depend on the Context.
resilience in mobile networks
Resilience in Mobile Networks
  • Communication between End-points goes over various different physical media
  • Sending data - the first leg is the radio network
  • Receiving Data - the last leg of physical communication is again the radio wave
  • Level-5 Protocols cannot solve link loss in Mobile Networks
  • Resilience of Level-5 protocols translates to the ability of the protocol to test the availability of the link

Example: A Voice over IP application uses SIP in order to perform the so called Registration. The Client registers its “location” to a Registrar Server. The server then knows how to contact the Client when there is an incoming call. In a GSM / UMTS environment the SIP protocol offers the possibility to both Client and Server to query the availability of each other. In case the Server notices a connection break it can reject all the incoming calls. At the same time a Client can try to re-Register.

reliability in mobile networks
Reliability in Mobile Networks
  • Radio resources in Mobile Networks are the most likely to create connectivity problems (e.g. bad signal or signal loss)
  • Bad signal quality – lower level protocols solve the reliability problem
    • Correction
    • Retransmission
    • All these at Level-4 and lower
  • Signal loss
    • No ability to handle correction and retransmissions
    • Level-5 needs to cope with these case
  • One could observe that Resilience and Reliability have the similar meaning in case of Level-5 protocols in mobile networks.
effectiveness in mobile networks
Effectiveness in Mobile Networks
  • Monetary vs. Non-monetary aspects
  • An effective Level-5 protocol is network friendly
    • Light
    • Not to case “too much” traffic
  • Monetary aspect
    • Direct – the amount of data sent and received is to expensive –
    • Indirect – the amount of data is too high and consumes resources that will otherwise be useful to other services
  • Non-monetary aspects need to be considered as well.
    • Mobile device resources are not costly but limited (e.g. processing power, battery)
slide13
Surf the MSc Thesis
    • Background, Problems and Methods
    • (Mobile) Internet Communications
    • Packet Data Access in Mobile Networks
    • Layered Network Architectures
    • Protocol Modelling
    • Protocol Modelling for Performance Measurements
    • Conclusions
  • Personal Experience (How I wrote my MSc. Thesis)
resource allocation in mobile networks
Resource Allocation in Mobile Networks
  • QoS classes
    • Conversational – Conversational pattern
    • Interactive – preserves the time relation between the informational elements
    • Streaming – Request / Response pattern
    • Background – Data is not expected with strict time limits
  • Protocol performance within a QoS class
    • Performance of a protocol needs to be considered in the context of the QoS class (e.g. A protocol can offer good performance when used by applications running under the Conversational Class but could be the wrong tool for the job within the Interactive Class)
  • Mobile Networks allocate the communication resources differently, depending on the QoS class.
    • In practice, means that an application running within the Conversational Class has more resources to spare compared to an application running within the Interactive Class
    • Protocols that have already been defined and perform well are not necessarily the best choice for the new applications being deployed.
communication channels
Communication Channels
  • Common Channels
    • Caring the signalling within the network but In some cases they are also used for user data
    • Low setup time - Fast to establish in order to send and receive data and then tear-down
    • Cannot handle the so called soft handover – no cell to cell hoping
    • The network will not allocate them when the data amounts to be sent or received is high - work with small individual packets
  • Dedicated Channels
    • Exact opposite of the Common Channels
    • Long time to set up
    • High bit rates and the bit rate can be changed during the transmission
    • Improved radio performance
    • Any protocol can be used on these channels
    • Issues can arise only when the entities involved in the communication expect responses to their request within a certain time interval
  • Shared Channels
communication channels cont
Communication Channels (cont)
  • Shared Channels
    • Share a channel in time between different users
    • Bit rate is lower in comparison with the achieved rates on the dedicated channels
    • Good for applications that generate bursty traffic
    • Capacity of the air interface is shared among many users at the same time
slide17
Surf the MSc Thesis
    • Background, Problems and Methods
    • (Mobile) Internet Communications
    • Packet Data Access in Mobile Networks
    • Layered Network Architectures
    • Protocol Modelling
    • Protocol Modelling for Performance Measurements
    • Conclusions
  • Personal Experience (How I wrote my MSc. Thesis)
ip suite stack host to host communication over internet
IP Suite Stack Host to Host communication over Internet

Application

Application

PEER TO PEER Communication

Transport

Transport

Network

Network

Network

Network

Data Link

Data Link

Data Link

Data Link

Internet

Internet

Internet

Physical Layer

internet reference model in mobile networks
Internet Reference Model in Mobile Networks

Application Server

Mobile Device

Application

Application

PEER TO PEER Communication

Transport

Transport

Network

Network

Network

Ethernet

GPRS

Data Link

Data Link

Data Link

Radio Network

Internet

Gateway GPRS

Support Node

slide22
Surf the MSc Thesis
    • Background, Problems and Methods
    • (Mobile) Internet Communications
    • Packet Data Access in Mobile Networks
    • Layered Network Architectures
    • Protocol Modelling
    • Protocol Modelling for Performance Measurements
    • Conclusions
  • Personal Experience (How I wrote my MSc. Thesis)
protocol modelling
Protocol Modelling
  • Informal methods
    • Successfully used
    • Do not handle well high complexity
  • Formal methods
    • Analyze rigorously and efficiently
    • Several papers in the literature
    • Extremely valuable for Validation and Verification
  • Performance evaluation has not been addressed much
    • Done in an informal manner
    • Acknowledge issues but do not offer clear fact and figures
    • Lack of formalism makes comparison between two set of results impossible
protocol modelling techniques
Protocol Modelling Techniques
  • High-level Programming Languages
    • Convenient tool – Communication party represented as a program
    • Can represent data, variables, counters, etc…
    • Cannot represent complex structures – general metrics
    • Do not serve the purpose of calculating traffic
  • Finite State Machines
    • Use in the early stages of Protocol definition
    • Single-machine model vs. Multi-machine approach
    • The model is applicable to any protocol having a finite number parties involved in communication
  • Petri Nets
    • Petri Nets can model a protocol that has an infinite number of states
    • We can develop a model that allows messages to have size using the so called Coloured Petri Nets extension
    • The size of the graph can become a problem
      • Even in the case of simple protocols this can result in growing to complexities that are not easy to manage
finite state machine model
Finite State Machine Model

Process 2

(server)

Process 1

(user)

IDLE

Not Logged-in

+ LOGIN

- LOGIN

+ ACK_LOGOUT

- ACK_LOGOUT

+ ACK_LOGIN

+ LOGOUT

Service_Request

Authenticated

Wait

Logged-in

- ACK_LOGIN

- LOGOUT

petri nets model
Petri Nets Model

Client

Network

Server

Login

Idle

Msg1

Send Login

Login Received

Wait1

Service Login Request

Logged-in

Ack1

Login Ack

Authenticated

Ack Login Received

Msg2

Send Logout

Logout Received

Logout

Wait2

Service Logout Request

Ack2

Logged Out

Logout Ack

Ack Logout Received

Logged Out

slide27
Surf the MSc Thesis
    • Background, Problems and Methods
    • (Mobile) Internet Communications
    • Packet Data Access in Mobile Networks
    • Layered Network Architectures
    • Protocol Modelling
    • Protocol Modelling for Performance Measurements
    • Conclusions
  • Personal Experience (How I wrote my MSc. Thesis)
protocol measurement system

Context

The System

Entity A

Entity B

Network

Measure the traffic flowing through the network

Protocol Measurement System
handling an external event in the measuring environment
Handling an external event in the measuring environment

The System

Entity A

Entity B

Network

External Event

(data)

The protocol implementation transforms the external event in a protocol primitive / message packing the data carried by the event

Message 1

Relay Message 1

Entity B Processes the Message and creates response

Response Message 1

Relay Response Message 1

External Response

(data)

External Event

(data)

a user client server model
A User – Client – Server Model

Access to information

User

The System

Entity A

(client)

Entity B

(server)

Network

Use client

Application

Measure the traffic flowing through the network

connect subscribe notify disconnect
Connect / Subscribe / Notify / Disconnect

Connect

User

The System

Entity A

(client)

Entity B

(server)

Network

Notify

Use client

Application

Disconnect

use case execution
Use Case Execution

The System

Entity A

(client)

Entity B

(server)

(1) Start

use case

User

stable state 0

stable state 0

(2) message 1

(3)

(3)

server state x

client state x

(4) message 2

(5)

(5)

server state y

client state y

(6) message 3

(7)

(7)

server state z

(8) message 4

client state z

(9)

(9)

stable state 1

stable state 1

a graphical representation of fsp

Process 1

(server)

Process 1

(user)

Time

Not Logged-in

IDLE

- LOGIN

+ LOGIN

Wait

Service_Request

- ACK_LOGIN

+ ACK_LOGIN

Logged-in

Authenticated

- LOGOUT

+ LOGOUT

Wait

Service_Request

+ ACK_LOGOUT

- ACK_LOGOUT

Not Logged-in

IDLE

A Graphical Representation of FSP
abstract time line mode for presence

Presence Server

Presence Client

IDLE

IDLE

Time

Connect to Service

State 1

State 1

Publish Presence Information

State 2

State 2

Subscribe for Presence Information

State 3

State 3

State 1 – Connected

State 2 – Connected & Published

State 3 - Connected & Published & Subscribed

Abstract Time-line Mode for Presence
simple connection to presence service

Presence Server

Presence Client

Connect to Service

IDLE

IDLE

SIP Register

Time

SIP 401 Unauthorized

SIP Register

SIP 200 OK

State 1

State 1

State 1 – Connected

State 2 – Connected & Published

State 3 - Connected & Published & Subscribed

SIMPLE Connection to Presence Service
simple presence publication

Presence Server

Presence Client

IDLE

IDLE

Time

Publish Presence Information

State 1

State 1

SIP Publish

SIP Publish

SIP 200 OK

SIP 200 OK

Publication expires or

user changes the Information

State 1 – Connected

State 2 – Connected & Published

State 3 - Connected & Published & Subscribed

SIMPLE Presence Publication
simple presence subscription

Presence Server

Presence Client

IDLE

IDLE

Time

State 1

State 1

Publish Presence Information

State 1

State 1

SIP Subscribe

SIP 200 OK

SIP Notify

SIP 200 OK

Subscription expires or

Connection is lost the Information

State 1 – Connected

State 2 – Connected & Published

State 3 - Connected & Published & Subscribed

SIMPLE Presence Subscription
slide40
Surf the MSc Thesis
    • Background, Problems and Methods
    • (Mobile) Internet Communications
    • Packet Data Access in Mobile Networks
    • Layered Network Architectures
    • Protocol Modelling
    • Protocol Modelling for Performance Measurements
    • Conclusions
  • Personal Experience (How I wrote my MSc. Thesis)
conclusions general
ConclusionsGeneral
  • New directions in Mobile Communications are shaped by the business requirements optimization needs for profitable investments
  • Increase complexity – introduce fixed-Internet technologies to the Mobile Domain
  • IETF protocols and especially the level-5 ones are becoming the de facto protocols for mobile services
  • Solve the performance or efficiency evaluation
  • Need to understand how a certain technology works
    • Improves the performance
    • Quality of the Services
    • Impact on the operational costs
conclusions protocol modelling
ConclusionsProtocol Modelling
  • Finite State Machines and Petri Nets - in their original form - did not suite all our needs
    • Good for validation and verification
    • Not good for measurements due to lack of metric
  • Colored Petri Nets
    • Good for measurements
    • Hard to use
    • Potentially will alienate some of the stakeholders
  • Improvement of the Finite State Machines - METRICS
future work
Future Work
  • The performance measurements need to address two aspects
    • Number of messages sent over the network
    • Amount of data exchanged in the communication
  • FSP model proposed by this work is able to handle well the first aspect
  • The amount of data aspect is not handled in an elegant way
  • An improved model to deal with this aspect is needed
    • Coloured Petri Nets are a good candidate for this particular aspect
  • Extended versions of the general automata, such as X-machines, provide computability and therefore direct implementability and testing.
slide44
Surf the MSc Thesis
    • Background, Problems and Methods
    • (Mobile) Internet Communications
    • Packet Data Access in Mobile Networks
    • Layered Network Architectures
    • Protocol Modelling
    • Protocol Modelling for Performance Measurements
  • Personal Experience (How I wrote my MSc. Thesis)
the subject
The Subject
  • Choose the subject early enough
  • Stick with it – do not give up when things get tough
  • Get your references well in advance
  • Read all your references and the some
  • Attend the Scientific Writing in Human-Computer Interaction (Kari-Jouko Räihä OR Howell Istance)
work and study
Work and Study
  • A real problem
  • How to get the work done and how to get the work done 
  • Difficulties
    • Share time in the office / time at the University / time at home / travelling
    • Confidentiality management
    • Relationship with the management
  • Time management
    • How many hours do you allocate per week to your studies
    • Try to find a day when you spend most of those hours – preferably a working day
    • Save your evening for reading
  • The feeling after    