UNESCO PROJECT

Advanced Course on Networking Professor Khalid Al-Begain

UNESCO/CISM SECOND ADVANCED SCHOOL OF INFORMATICS

University of Damascus, Syria, 06 - 15 April 2004

I am Khalid Al-Begain

School of Computing, University of Glamorgan, Wales, UK

Professor in Mobile Networking Head of the Mobile Computing and

Networking Research Group– Performance evaluation Modelling, simulation

and analysis– QoS Routing and Multicast Routing– Resource Management and Call admission Control– Traffic Engineering– Mobile Services for next generation mobile and

wireless networks

Course Content Four Lectures A combination of essential and advanced

topics New compared with last year : WIRELESS The Course covers

LANs and WLAN standards TCP/IP Theory : Protocols and Applications Wireless and Cellular Networks: Channel

Allocation Schemes

LAN versus WAN -RevisitedLocal Area Networks Wide Area Networks

Geographical Coverage Limited (room, building, campus) Widespread (country, worldwide)

Data Rates High - typically 1M to 1Gbps Historically low <= 64Kbps.Now much higher up to 2.4G

Transmission Media

Private (coax, twisted-pairs, optic fibres, radio)

Use of “Common Carriers” (BT, Mercury)

(Fibres, microwaves, satellite…)

Error Rates Low Better than 1 in 1010

Historically hightypically worse than 1 in 106.Now comparable with LANs

Types Ethernet (IEEE 802.3)Token Ring (IEEE 802.5)Token Bus (IEEE 802.4)Wireless (IEEE 802.11), Bluetooth

Packet Switching (ITU X.25)Cell Switching (ATM)Circuit Switching (ITU ISDN)

Access Multiple Access Individual Access Links

LANs: Major medium access techniques

Access methods

Carrier sense multipleaccess (CSMA)

Token passing

p-persistentCSMA

Tokenring

Tokenbus

Slottedring

CSMA/CD CSMA/CA

Dedicated lines

Demandpriority

Switching

Access methods

Carrier sense multipleaccess (CSMA)

Token passing

p-persistentCSMA

Tokenring

Tokenbus

Slottedring

CSMA/CD CSMA/CA

Dedicated lines

Demandpriority

Switching

LANs: Major medium access techniques

Access methods

Carrier sense multipleaccess (CSMA)

Token passing

p-persistentCSMA

Tokenring

Tokenbus

Slottedring

CSMA/CD CSMA/CA

Dedicated lines

Demandpriority

Switching

Access methods

Carrier sense multipleaccess (CSMA)

Token passing

p-persistentCSMA

Tokenring

Tokenbus

Slottedring

CSMA/CD CSMA/CA

Dedicated lines

Demandpriority

Switching

CD: Collision Detection

Ethernet, Fast Ethernet

LANs: Major medium access techniques

Access methods

Carrier sense multipleaccess (CSMA)

Token passing

p-persistentCSMA

Tokenring

Tokenbus

Slottedring

CSMA/CD CSMA/CA

Dedicated lines

Demandpriority

Switching

Access methods

Carrier sense multipleaccess (CSMA)

Token passing

p-persistentCSMA

Tokenring

Tokenbus

Slottedring

CSMA/CD CSMA/CA

Dedicated lines

Demandpriority

Switching

CA: Collision Avoidance

WLAN, Bluetooth

IEEE 802 :LANs

The Data Link Layer

Logical Link Control Sublayer

Medium Access Sublayer

IEEE 802

Important

The future will tell!

IEEE 802.3

Classic Ethernet (10 Mbps) (First Founded by Xerox in 1976)

Fast Ethernet (100Mbps) (IEEE 802.3u)

Gigabit Ethernet (1Gbps) (IEEE 802.3z)

Classical Ethernet

The most common cabling methods

Classical Ethernet

The most common cabling methods

Manchester Encoding

Used in Classical Ethernet

Ethernet : Frame Formats

Two versions exist: (a) DIX (Digital, Intel, Xerox)(b) IEEE 802.3

Ethernet Medium Access CSMA All stations are connected to the cable When a station wishes to transmit, it “listens” to

the cable - if there is no signal it starts to transmit, otherwise it tries again later.

(Non-Persistent, 1-Persistent, p-Persistent) Whilst a station is transmitting it compares the

signal on the coax with the signal it is transmitting - if they are different it stops and tries again later

CD: Collision Detection means when detects collision then stop transmission wait random time try again

The time to wait is calculated using the Binary Exponential Backoff algorithm.

Collision Detection

Cause: Signals need time to propagate!

Binary Exponential BackoffTime slot = 51.2μs

Binary Exponential Backoff:

• After 1st collision each participating station waits randomly 0 or 1 slot

• After 2nd collision each participating station waits 0,1,2, or 3 slots

• After n-th collision each participating station waits between 0 .. 2n-1 slots

• Maximum Backoff = 1023 slots

Beyond the 10Mbps The early1980s luxury:

8 MHz PC 256 KByte RAM 10 MByte Hard Disk Connected to the Dream 10Mbps LAN

But Parkinson’s Law is valid here too:“Work Expands to fill the time available for its

Completion”

In other words:“Data expands to fill the bandwidth available for their

transmission”

The 100Mbps LAN Many proposals came to have faster LANs or

MANs FDDI : Fibre Distributed Data Interface DQDB : Dual Queue Dual Bus Fibre Channel

Common Feature : Very complexHigh Cost

However for a technology to work, it must be follow the KISS Law:

“Keep It Simple, Stupid”

Fast Ethernet

1992 : the IEEE 802.3 committee again.

Task: make faster LAN. Results:

Fast Ethernet (IEEE 802.3u) which is in principle identical to Ethernet except that bit time is 10ns instead of 100ns.

Fast Ethernet Cabling

• Fast Ethernet uses either HUBs or Switches

• No Manchester Encoding

Gigabit Ethernet

1995: the same idea: make Ethernet 10 time faster.

The Ethernet real Competitor: Let us Go Wireless

Who is interested?

Desktop and laptop systems Handheld devices

PCs, scanners, data collection devices PDAs Palmtops etc

WLAN implications

Multiple propagation pathways Signal interference Lifetime of battery Security Path loss Installation and connectivity Health

IEEE 802.11

1997 standard 2.4GHz 1Mbit/s and 2Mbit/s FHSS and DSSS

1999 standard 802.11a

5 GHz - Orthogonal FDM up to 54 Mbit/s

802.11b 2.4 GHz - DSSS up to 11 Mbit/s

Logical Link

Control (LLC)

Media Access

Control (MAC)

Frequency

Hopping

Direct

Sequence

Infrared

light

PhysicalLayer

Data Link layer

IEEE 802.11a,b Pros & Cons! IEEE 802.11a

+ Very high data rates- 5 GHz licensing problem- Competition with ETSI HiperLAN 2 - Illegal in Europe- Higher cost

IEEE 802.11b+ Works in the Unlicensed band of 2.4 GHz~ Data rates comparable with LANs- Interference with Cordless phones and Microwave

ovens+ Cheaper devices

WLAN

Two modes of operation(a) Centralised(b) Ad hoc

A multicel 802.11 network

IEEE 802.11 MAC

The hidden Station problem:

Distributed Coordination Function (DCF)

To solve the problem of Hidden stationUse DCF: Uses CSMA/CA (Collision Avoidance) It is based on virtual channel sensing

All WLANs must support DCF.For centralised WLANs, there is also

PCF (Point Coordination Function)

Virtual Channel Sensing using CSMA/CA

Example: A, B, C, and D stations (D out of the range of A)

Request To Send Clear To Send

Network Allocation Vector

Due to unreliable medium

Frame Fragmentation

Because the radio link is unreliable short frames are needed long frames has to be fragmented.

Interframe Spacing in 802.11

IEEE802.11 Frame Structure

IEEE802.11 MAC Services

Distribution system services Association Disassociation Re-association Distribution Integration

Station services Authentication De-authentication Privacy Data Delivery

What else in Wireless

Bluetooth (IEEE 802.15) Broadband Wireless (IEEE 802.16)

And the Cellular Wireless Technologies GSM, GPRS, and UMTS

What else in Wireless

Bluetooth (IEEE 802.15) Broadband Wireless (IEEE 802.16)

(will follow but very briefly)

And the Cellular Wireless Technologies GSM, GPRS, and UMTS

Bluetooth

1994: Ericsson SIG started(with IBM, Intel, Nokia and Toshiba)

Named after Viking King Harald Blaatand (Bluetooth) who unified Denmark and Norway without wires!!

Goal: Short-range, inexpensive (<$5) method to connect devices without wires (E.g., mobile-PDA)

July 1999, PAN (Personal Area Network) standard IEEE 802.15

Bluetooth Characteristics Works in the 2.4 GHz band (together

with WLANs and microwave ovens) Low range (< 10m) 79 channels each with 1MHz 1Mbps Organised into pico-cells (1 Master and

7 slaves) Uses FHSS (Frequency Hopping)

controlled by Master (1600 hops/sec) Uses same Frequency band and hoping

as WLAN (problem!!!)

Bluetooth Architecture

Scatternet, 255 parked slaves, Ad hoc

Bluetooth Services

Broadband Wireless IEEE802.16

Wireless MAN or Wireless Local Loop High data rates to Buildings Can be seen as Wireless Cable TV

network. Uses bandwidth between 10-66 GHz Uses sophisticated modulation to

achieve high rates

IEEE 802.16 Transmission Environment

For example: with 25MHz spectrum rates are : 150, 100, 50 Mbps