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Introduction & Course Overview. Lesson 1. Teacher. Martin Hjorth Stender Room: 426 [email protected] Course Overview. Generel communication in Protocol stacks Peer-to-peer communication Upper and lower layer Syntaxes for describing PDU (messages exchanged between peer layers)

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introduction course overview

Introduction & Course Overview

Lesson 1

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teacher
Teacher

Martin Hjorth Stender

Room: 426

[email protected]

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course overview
Course Overview
  • Generel communication in Protocol stacks
    • Peer-to-peer communication
    • Upper and lower layer
  • Syntaxes for describing PDU (messages exchanged between peer layers)
  • Protocol Design (Patterns)
  • Testing protocols

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outline for today
Outline for today
  • Fundamentals of Computer Networks (Rep.)
    • Circuit Switching vs. Packet Switching
    • Connection-Oriented vs. Connectionless
    • Communication Protocol Stacks in Action
  • Standard Organizations
    • 3GPP
    • IETF
    • BlueTooth
    • Zigbee

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outline for today1
Outline for today
  • Fundamentals of protocols in a multi-service network
    • Layers of Communication
    • Horizontal Communication
    • Vertical Communication
  • Protocols in Real
    • 3GPP Long Term Evolution
    • ZigBee
    • ETSI Digital Enhanced Cordless Telecommunications
    • TCP

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fundamentals of computer networks1
Fundamentals of Computer Networks

Two fundamental types of Network Switching:

Circuit Switching

Packet Switching

*TDM/FDM

*Time-Division Multiplexing

Frequency-Division Multiplexing

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network core circuit switching
Network core – Circuit switching

Circuit Switching

  • Requires a Setup/release phase
    • for ressource reservation
  • Quaranteed end-to-end connection
  • Quaranteed constant rate (bandwidth)

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fundamentals of computer networks2

10 Mb/s

Ethernet

C

A

statistical multiplexing

1.5 Mb/s

B

queue of packets

waiting for output

link

D

E

Fundamentals of Computer Networks

Packet Switching

  • data stream divided into packets
  • packets share network resources
  • packets uses full link bandwidth and as needed
  • packets are stored & forwarded and queued.

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packet and circuit switched
Packet- and Circuit switched

Packet switching allows more users to use network!

  • 1 Mb/s link
  • each user:
    • 100 kb/s when “active”
    • active 10% of time
  • circuit-switching:
    • 10 users
  • packet switching:
    • with 35 users, probability > 10 active less than .0004 = 0.04%

N users

1 Mbps link

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connection oriented service
Connection-Oriented Service
  • Before two computers can communicate, they:
    • Establish a ’connection’ through the network, by
      • One computer requests a connection
      • Second computer accepts the connection
      • Data is transferred (full duplex…)
      • Connection is terminated

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connectionless service
Connectionless Service
  • When computer wants to send data, it:
    • Place data in an appropriate frame format
    • Attach the address of the destination computer
    • Pass the frame to the network for delivery

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communication protocol stacks in action
Communication Protocol Stacks in Action

GSM

GPRS

HTTP

TCP/IP

EDGE

SIP

RTP/RTCP

HSPA

UMTS

UDP/IP

FTP

LTE

DECT

LTE-A

SDP

TETRA

BlueTooth

Zigbee

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standard organizations
Standard Organizations
  • 3GPP
    • Specifies mobile communication protocols
      • GSM, GPRS, EDGE, UMTS, HSPA, LTE, LTE-A

The 3rd Generation Partnership Project (3GPP) is a collaboration between groups of telecommunications associations, to make a globally applicable third generation (3G) mobile phone system specification within the scope of the International Mobile Telecommunications-2000 project of the International Telecommunication Union (ITU).

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standard organizations1
Standard Organizations
  • IETF
    • Specifies all Internet related protocols
      • TCP, UDP, IP, HTTP, FTP, SIP, SDP……

The Internet Engineering Task Force (IETF) develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standard bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite

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standard organizations2
Standard Organizations
  • BlueTooth
    • Specifies (surprise surprise) BlueTooth (core + profiles)

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standard organizations3
Standard Organizations
  • Zigbee Alliance
    • Specifies (surprise) Zigbee (core + profiles)

ZigBee is a specification for a suite of high level communication protocols using small, low-power digital radios based on the IEEE 802.15.4-2003standard for wireless personal area networks (WPANs), such as wireless headphones connecting with cell phones via short-range radio.

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layered communication
Layered Communication

Computer Networks & Communication Systems

- a need for structure?

Ressource

Management

Integrity protection

Modulation

Channel coding

Flow control

Interleaving

Error concealment

Authentication

Encryption

Connection

Management

Addressing

Error correction

Re-transmission

Identification

Assembly

Link adaptation

Segmentation

File transfer

Location

Tracking

Web browsing

Error detection

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layered communication1
Layered Communication

Conclusion:

- Computer Networks & Communication Systems are complicated processes.

- To cope with this complexity we organize the systems into:

LAYERS

  • A layer performs some of the functions necessary to achive communication
  • between systems
  • Each layer built upon the layer below (except for the lowest layer)
  • The layers provide levels of abstraction

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layered communication2
Layered Communication

The OSI Reference Model

Intermediate Systems

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layered communication3
Layered Communication

OSI Reference Model – Lower layers

The physical layer

Provides the mechanical, electrical and procedural means for transmitting bits over a communication medium.

The data link layer

Provides services for the transmission of data between directly connected systems in a communication network.

The network layer

Handles the routing of data through communication networks.

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layered communication4
Layered Communication

OSI Reference Model – Upper layers

The transport layer

Provides reliable end-to-end services without being concerned about the route through communication networks.

The Session layer

provides facilities to organise and synchronise dialogues, i.e. communications that consist of several strands such as audio and video components.

The Presentation layer

deals with issues about how data is represented and ensures that the systems agree on how the information is transferred.

The Application layer

provides the means for application programs to access the communication system represented by the OSI reference model. For instance, the application layer can provide services for supporting file transfer and email.

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layered communication5
Layered Communication

OSI Reference Model – Reflections

  • There should not be more layers than is necessary.
  • Boundaries should be located where they have proved successful in the past.
  • Boundaries should be located to minimise the interactions between layers.
  • Boundaries should be located where a standardised interface may be useful.
  • Separate layers should be created to perform functions that are associated with different technologies or levels of abstraction.
  • Functions associated with similar technology should be collected together in the same layers.

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layered communication6
Layered Communication

Example – 4 layered protocol stack

peer-to-peer communication

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layered communication7
Layered Communication

Definition:

- The rules for sending blocks of data (each known as a Protocol Data Unit (PDU)) from one node in a network to another node.

  • A protocol specification defines the operation of the protocol and may also suggest how the protocol should be implemented. It consists of three parts:
  • Definition of Protocol Control Information (PCI) format which forms the PDU header
  • Definition of procedures for transmitting and receiving PDUs
  • Definition of services provided by the protocol layers

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layered communication8
Layered Communication

Protocol Data Unit

  • Header (PCI - Protocol Control Information
  • Payload (SDU - Service Data Unit)
  • The protocol does not define or constrain the data carried in the payload part.
  • It does specify the format of the PCI, defining the fields which are present and the way in which the patterns of bits are to be interpreted

Packet

Payload

Packet

Header

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layered communication9
Layered Communication
  • A protocol also defines the procedures which determine how the PDU will be processed at the transmit and receive nodes. The procedures specify the valid values for the PCI fields, and the action be taken upon reception of each PCI value (usually based on stored control information). Examples of procedures which are implemented in protocols include :
  • error recovery (e.g. the go-back-n procedure)
  • flow control
  • segmentation
  • service access point selection
  • connection management

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horizontal communication
Horizontal Communication

PDU

PCI

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vertical communication
Vertical Communication

Protocol Header Processing for Transmission by Layer N

Layer N+1

Protocol Data Unit

becomes a Layer N

Service Data Unit

PDU

PCI

+

SDU

PCI

SDU

Layer N PDU

PCI

+

SDU

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vertical communication1
Vertical Communication

Protocol Header Processing on Reception by Layer N

Layer N+1

Protocol Data Unit

is formed from

the Layer N

Service Data Unit

PDU

PCI

+

SDU

PCI

SDU

Layer N PDU

PCI

+

SDU

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vertical communication2
Vertical Communication

Summary:

  • A layer encapsulates the SDU by adding a protocol header (PCI)
  • The combined PCI and SDU are known as a PDU
  • The PDU of Layer N forms the SDU of the layer below (N-1)

Reflections:

- Layer N does NOT know anything about the content of the PDU received

How do we cope with a layer below that is providing multi-services?

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vertical communication3
Vertical Communication

How do communication takes place between two adjacent layers in the same system?

  • OSI view of adjacent layer communication
  • Service Access Points (SAP)
  • Processes that communicates across the interface are called entities

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vertical communication4
Vertical Communication

The interaction between adjacent layers is expressed in terms of issuing and receiving primitives

  • For each primitive up to four basic types are available
  • request – an entity invokes a service
  • indication – an entity is informed of an event
  • response – an entity reacts to an event
  • confirm – an entity is infromed of the result of an earlier request

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vertical communication5
Vertical Communication

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vertical communication6
Vertical Communication
  • Example: DECT Call Control (NWK Layer) services:
  • Setup
    • Setup a phone call to remote (called party)
  • Alert service
    • Alert to the caller that the call is received (but not answered)
  • Connect
    • Connect to an incoming call
  • Release
    • Release (terminate) a call

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vertical communication7
Vertical Communication
  • Example: DECT Call Control (NWK Layer) services:
  • Setup service
    • Setup.req, Setup.ind, Setup.res, Setup.cfm primitives
  • Alerting service
    • Alert.req, Alert.ind
  • Connect service
    • Connect.req, Connect.ind, Connect.res, Connect.cfm
  • Release service
    • Release.req, Release.ind, Release.res, Release.cfm

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vertical communication8
Vertical Communication

Example: DECT Call Control (NWK Layer) services:

PDUs

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vertical communication9
Vertical Communication

Most primitives carries data

  • Example DECT Setup.req:
  • Called party number
  • Calling party number
  • Transaction Identifier
  • Presentation Indication (may my number be displayed?)

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vertical communication10
Vertical Communication

Most primitives carries data

  • Example DECT Setup.req:
  • Called party number
  • Calling party number
  • Transaction Identifier
  • Presentation Indication (may my number be displayed?)

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