Module 3 wlan,bluetooth vlan

MODULE 3 MCA-402 Computer Networks ADMN 2012-‘15
Dept. of Computer Science And Applications, SJCET, Palai Page 1
WIRELESS LAN
 Is a wireless local area network that uses radio waves as its carrier
 Advantages
 very flexible within the reception area
 Ad-hoc networks without previous planning possible
 (almost) no wiring difficulties
 More robust against disasters like, e.g., earthquakes, fire - or users pulling a plug...
 Disadvantages
 typically very low bandwidth (1-10 Mbit/s)
 products have to follow many national restrictions
A wireless LAN is based on a cellular architecture where the system is subdivided into cells, where each
cell (called Base Service Set or BSS*) is controlled by a Base station (called Access point or AP).
 key application areas:
i. LAN extension
ii. cross-building interconnect
iii. nomadic access
iv. ad hoc networking
i. LAN Extension
 Wireless LAN will be linked into a wired LAN on the same premises.
Fig 3.1 Single cell LAN extension

In a single-cell wireless LAN all of the wireless end systems are within range of a single control
module.
Fig 3.2 Multi cell LAN extension
In a multiple-cell wireless LAN, there are multiple control modules interconnected by a wired
LAN. Each control module supports a number of wireless end systems within its transmission range. For
example, with an infrared LAN, transmission is limited to a single room; therefore, one cell is needed for
each room in an office building that requires wireless support.
ii. Cross-Building Interconnect
 connect LANs in nearby buildings
 point-to-point wireless link
 Devices connected are typically bridges or routers.
 Used where cable connection not possible (e.g. across a street)
iii. Nomadic Access
 Wireless link between LAN hub and mobile data terminal equipped with antenna
 also useful in extended environment such as campus or cluster of buildings
 users move around with portable computers
iv. Ad Hoc Networking
 Temporary peer-to-peer network set up to meet immediate need

Fig 3.3 Ad-hoc network
WIRELESS LAN REQUIREMENTS
 throughput - efficient use wireless medium
 no of nodes - hundreds of nodes across multiple cells
 connection to backbone LAN - using control modules
 service area - 100 to 300 m
 low power consumption - for long battery life on mobiles
 transmission robustness and security
 license-free operation
 handoff/roaming
 dynamic configuration - aaddition, deletion, and relocation of end systems without disruption to
users
WIRELESS LAN TECHNOLOGY
 Generally categorized according to the transmission technique that is used. They are:
i. Infrared (IR) LANs
ii. Spread spectrum LANs
iii. Narrowband microwave
i. Infrared LANs
 constructed using infrared portion of spectrum
 strengths
 spectrum virtually unlimited hence high rates possible
 unregulated spectrum
 infrared shares some properties of visible light

i. reflection covers room, walls isolate networks
 inexpensive and simple
 weaknesses
 background radiation, e.g. ssunlight, indoor lighting
 power limited by concerns for eye safety and power consumption
 Transmission Techniques
 directed-beam IR
 point-to-point links
 range depends on power and focusing
 for indoor use can set up token ring LAN
 omnidirectional
 single base station with line of sight to other stations
 acts as a multiport repeater
 other stations use directional beam to it
 diffused configuration
 stations focused / aimed at diffusely reflecting ceiling
ii. Spread Spectrum LAN Configuration
 usually use multiple-cell arrangement
 Adjacent cells use different center frequencies.
 configurations:
 hub
i. connected to wired LAN
ii. connect to stations on wired LAN and in other cells
iii. may do automatic handoff
 peer-to-peer
i. no hub
ii. MAC algorithm such as CSMA used to control access
iii. for ad hoc LANs
Transmission Issue
 Three microwave bands have been set aside by FCC which doesn’t need a license if the
equipment’s operates under 1W power
They are:
 902-928 MHz (915 MHz band)-Industrial Band
 2.4-2.4835 GHz (2.4 GHz band)-Scientific Band

 5.725-5.825 GHz (5.8 GHz band)- Medical Band
 Commonly known as ISM band ,it is used by Wireless LAN with spread spectrum technology
iii. Narrowband Microwave LANs
 Use of a microwave radio frequency band for signal transmission
i. Licensed
ii. Unlicensed
1. Licensed Narrowband RF
 Microwave radio frequencies are licensed within specific geographic areas to avoid potential
interference.
 Each geographic area has a radius of 28 km and can contain five licenses, with each license
covering two frequencies.
 Uses cell configuration(18GHz)
 One advantage of the licensed narrowband LAN is that it guarantees interference-free
communication
2. Unlicensed Narrowband RF
 Radio LAN introduced narrowband wireless LAN in 1995 which uses the unlicensed ISM
spectrum
 Used at low power (0.5 watts or less)
 Operates at 10 Mbps in the 5.8-GHz band
 Range = 50 m to 100 m
 The RadioLAN product makes use of a peer-to-peer configuration.
 RadioLAN product automatically elects one node as the Dynamic Master.
IEEE 802.11
 IEEE has defined the specifications for a wireless LAN, called IEEE 802.11, which covers the
physical and data link layers.
 Defines standard for WLANs using the following four technologies
 Frequency Hopping Spread Spectrum (FHSS)
 Direct Sequence Spread Spectrum (DSSS)
 Infrared (IR)
 Orthogonal Frequency Division Multiplexing (OFDM)
 Versions: 802.11a, 802.11b, 802.11g, 802.11e, 802.11f, 802.11i

802.11 - ARCHITECTURE
Fig 3.4 a. Ad-hoc network b. Infrastructure network
 Station (STA)
 terminal with access mechanisms to the wireless medium and radio contact to the access
point
 Basic Service Set (BSS)
 group of stations using the same radio frequency
 Access Point
 station integrated into the wireless LAN and the distribution system
 Portal
 bridge to other (wired) networks
 Distribution System
 interconnection network to form one logical network
802.11 Services
a) Distribution of Messages
 Distribution service (DS):Used to exchange MAC frames from station in one BSS to station in
another BSS
 Integration service: Transfer of data between station on IEEE 802.11 LAN and station on
integrated IEEE 802.x LAN
b) Association Related Services
 Association: Establishes initial association between station and AP.
 Re-association: Enables transfer of association from one AP to another, allowing station to move
from one BSS to another.

 Disassociation: Association termination notice from station or AP
c) Access and Privacy Services
 Authentication: Establishes identity of stations to each other.
 De-authentication: Invoked when existing authentication is terminated
 Privacy: Prevents message contents from being read by unintended recipient
802.11 PROTOCOL STACK
Fig 3.5 802.11 protocol stack
Medium Access Control
The Medium Access Control sub layer of wireless local area network is more complex than MAC sub
layer of wired local area networks.
 MAC layer covers three functional areas
 reliable data delivery
 access control
 Security
i. Reliable Data Delivery
 Loss of frames due to noise, interference, and propagation effects.
 To ensure reliable data delivery IEEE 802.11 includes a frame exchange protocol.
 Two frame exchange

 Source station transmits data
 Destination responds with acknowledgment (ACK)
 If source doesn’t receive ACK, it retransmits frame
 Four frame exchange for enhanced reliability
 Source issues request to send (RTS)
 Destination responds with clear to send (CTS)
 Source transmits data
 Destination responds with ACK
 The RTS alerts all stations that are within reception range of the source that an exchange is under
way
 Similarly, the CTS alerts all stations that are within reception range of the destination that an
exchange is under way
ii. Access Control
 Medium access control is based on distributed control and centralized control.
 Uses a MAC algorithm called DFWMAC (distributed foundation wireless MAC).
 It provides a distributed access control mechanism with an optional centralized control.
 IEEE 802.11 defines two MAC sub layers: the distributed coordination function (DCF) & Point
coordination Function (PCF).
1. Distributed Coordination Function(DCF)
 The lower sub layer of the MAC layer.
 DCF sub layer uses CSMA /CA
 if station has frame to send it listens to medium
 if medium idle, station may transmit
 else waits until current transmission complete
 To ensure the smooth and fair functioning of CSMA, the MAC frame transmissions are separated
by a time gap called IFS.
2. Point Coordination Function (PCF)
 polling by centralized polling master (point coordinator)
 uses PIFS when issuing polls
 point coordinator polls in round-robin to stations configured for polling
 when poll issued, polled station may respond using SIFS
 if point coordinator receives response, it issues another poll using PIFS
 if no response during expected turnaround time, coordinator issues poll

3. SIFS (short IFS)
The shortest IFS, used for all immediate response actions, like Acknowledgment, and Clear to send
(CTS) Frames
Fig 3.6 Access control
Following illustrates the use of these time values. Consider first the SIFS. Any station using SIFS
to determine transmission opportunity has, in effect, the highest priority, because it will always gain
access in preference to a station waiting an amount of time equal to PIFS or DIFS.
Fig 3.7 basic access method

802.11 MAC Frame Format
Fig 3.7 IEEE 802.3 MAC frame
Control Frames
 Power Save-Poll (PS-Poll)
 Request to Send (RTS)
 Clear to Send (CTS)
 Acknowledgment (ACK)
 Contention-Free (CF)-end
 CF-End + CF-Ack
Management Frames
 used to manage communications between stations and Aps
 such as management of associations
 requests, response, reassociation, dissociation, and authentication
Data Frames
 eight data frame subtypes, in two groups
1. Data Carrying
 carry upper-level data
2. Not Data Carrying
 do not carry user data
 Null Function
 carries no data, polls, or acknowledgments
 carries power mgmt. bit in frame control field to AP
 indicates station is changing to low-power state

802.11 Addressing
 There are four address fields, each 6 bytes long.
 The IEEE 802.11 addressing mechanism specifies four cases, defined by the value of the two flags
in the FC field, To DS and From DS.
 The interpretation of the four addresses (address 1 to address 4) in the MAC frame depends on the
value of these flags
Fig 3.8 addressing in 802.11 MAC
802.11 Physical Layer
 The PHY is the interface between the MAC and wireless media, which transmits and receives data
frames over a shared wireless medium.
 The physical layer is further subdivided into sub layers:
Physical Layer Convergence Procedure (PLCP) sub layer:
 Reformats data received from MAC layer into frame that PMD sub layer can transmit
Physical Medium Dependent (PMD) Sub layer:
 Takes the binary bits of information from PLCP-PDU (PPDU) and transform them into RF signals
 defines method for transmitting and receiving data
Three physical media are defined in the original 802.11 standard:
 Direct sequence spread spectrum (DSSS)
 Frequency-hopping spread spectrum (FHSS)
 Infrared
802.11 DSSS
 Operating in the 2.4-GHz ISM band, at data rates of 1 Mbps and 2 Mbps.
 Up to three non-overlapping channels, each with a data rate of 1 Mbps or 2 Mbps, can be used in
the DSSS scheme.
 Each channel has a bandwidth of 5 MHz
 The encoding scheme that is used is DBPSK (differential binary phase shift keying) for the 1 Mbps
rate and DQPSK(differential Quadrature phase shift keying )for the 2 Mbps rate.

802.11 FHSS
 FHSS system makes use of multiple channels,
 Data transmission over the media is controlled by the FHSS PMD sub layer as directed by the
FHSS PLCP sub layer.
 PMD takes the binary bits of and transforms them into RF signals for the wireless media by using
carrier modulation and FHSS technique
802.11b HR-DSSS
 The IEEE 802.11b PHY is one of the PHY layer extensions of IEEE 802.11 and is referred to as
high rate direct sequence spread spectrum (HR/DSSS).
 Providing data rates of 5.5 and 11 Mbps.
 IEEE 802.11b defines two physical-layer frame formats, which differ only in the length of the
preamble
802.11a OFDM
 Makes use of the frequency band called the Universal Networking Information Infrastructure
(UNII), which is divided into three parts.
 UNII-1 band is intended for indoor use
 UNII-2 band be used either indoor or outdoor,
 UNII-3 band is for outdoor use.
 The IEEE 802.11a PHY adopts orthogonal frequency division multiplexing (OFDM) instead of
spread spectrum techniques
 OFDM splits a single high-speed digital signal into several slower signals running in parallel.
 Provides rates of 6, 9 , 12, 18, 24, 36, 48, 54 Mbps
802.11g OFDM
 Extends data rates above 20 Mbps, up to 54 Mbps.
 Operates in the 2.4-GHz.
 Offers a wider array of data rate and modulation schemes.
 Provides compatibility with 802.11 by specifying the same modulation and framing schemes as
these standards for 1, 2, 5.5, and 11 Mbps.
BLUE TOOTH
 IEEE 802.15
 Is a wireless LAN technology using short-range radio links, intended to replace the cable(s)
connecting portable and/or fixed electronic devices.

 Is an ad hoc network where devices can automatically find each other, establish connections, and
discover what they can do for each other.
 Range 10-100 metres.
 Features are robustness, low complexity, low power and low cost.
 uses a 2.4-GHz ISM band divided into 79 channels of 1 MHz each
 A Bluetooth device has a built-in short-range radio transmitter.
 It uses Frequency Hop Spread Spectrum (FHSS) to avoid any interference.
Applications
 Automatic synchronization between mobile and stationary devices
 Connecting mobile users to the internet using Bluetooth-enabled wire-bound connection ports
 Dynamic creation of private networks
Types of Bluetooth Wireless Technology
 Depending on the power consumption and range of the device, there are 3 Bluetooth Classes as:
1. Class 1: Max Power – 100mW ; Range – 100 m
2. Class 2: Max Power – 2.5mW ; Range – 10 m
3. Class 3: Max Power – 1mW ; Range – 1 m
Protocol Architecture
 Bluetooth is a layered protocol architecture
 Core protocols
 Cable replacement and telephony control protocols
 Adopted protocols
 Core protocols
 Radio
 Baseband
 Link manager protocol (LMP)
 Logical link control and adaptation protocol (L2CAP)
 Service discovery protocol (SDP)
 Cable replacement protocol
 RFCOMM
 Telephony control protocol
 Telephony control specification – binary (TCS BIN)
 Adopted protocols
 TCP/UDP/IP
 OBEX

 WAE/WAP
Fig 3.9 Bluetooth protocol architecture
Radio Layer
 The bottom layer in protocol stack, equivalent to the physical layer of the Internet model.
 It deals with radio transmission and modulation.
 The Radio layer defines the requirements for a Bluetooth transceiver operating in the 2.4 GHz ISM
band.
 Divided into 79 channels of 1 MHz each.
 Support data rate: 1Mbps (Basic Rate) / 3 Mbps (Enhanced Data Rate).
 Uses a technique called frequency hopping, for establishing radio links with other Bluetooth
devices
Baseband layer
 Is roughly equivalent to the MAC sub layer in LANs.
 It is responsible for constructing, encoding and decoding packets, and managing error correction,
encrypting and decrypting for secure communication etc..
 The primary and secondary communicate with each other using time slots.
 Two types of links can be established between primary and secondary:
 Synchronous connection-oriented (SCO) links:
 Used when avoiding latency (delay in data delivery) is more important than

integrity (error- free delivery).
 Used for voice transmission.
 Asynchronous connectionless (ACL) links:
 Used when data integrity is more important than avoiding latency.
 Used for data transmission.
L2CAP
 The Logical Link Control and Adaptation Protocol, is roughly equivalent to the LLC sub layer in
LANs.
 Used for data exchange on an ACL link; SCO channels do not use L2CAP.
 This layer has four major functions:
• First, it accepts packets of up to 64 KB from the upper layers and breaks them into frames for
transmission.
• Second, it handles the multiplexing and de-multiplexing of multiple packet sources.
• Third, L2CAP handles Segmentation and reassembly
• Finally, L2CAP enforces quality of service requirements between multiple links.
Audio: interfaces directly with the baseband. Each voice connection is over a 64Kbps.uses PCM
encoding.
Host Controller Interface: provides a uniform method of access to the baseband, control registers, etc
through USB, PCI, or UART.
Service Discover Protocol (SDP): protocol of locating services provided by a Bluetooth device.
Telephony Control Specification (TCS): defines the call control signaling for the establishment of
speech and data calls between Bluetooth devices.
RFCOMM: provides emulation of serial links (RS232). Up to 60 connections
Bluetooth Topology
 Bluetooth defines two types of network topology:
 Piconet
 Scatternet
PICONET
 Known as small net, have up to eight stations.
 One primary, the rest are secondary.
 Communication can be one-to-one or one-to-many.
 Each of the active slaves has an assigned 3-bit Active Member address.
 An additional eight secondary's can be in the “parked state.

 A secondary in a “parked state” is synchronised with the primary but cannot take part in
communication until it is moved from the “parked state”
Fig 3.10 Piconet
Scatternet
 Formed by the combinations of piconet.
 A secondary station in one piconet can be the primary in another piconet.
 This station can receive messages from the primary in the first piconet (as a secondary) and acting
as a primary, deliver them to secondary’s in the second piconet .
Fig 3.11 scatternet

States of a Bluetooth Device
 ACTIVE (connected/transmit): the device is uniquely identified by a 3bits AM_ADDR and is fully
participating.
 SNIFF state: participates in the piconet only within the SNIFF interval.
 HOLD state: no data transfer, master can put slaves on HOLD state.
 PARK state (low-power): releases AM_ADDR but stays synchronized with master
Fig 3.12 Bluetooth device states
Bluetooth Link Security
 Elements:
 Authentication – verify claimed identity
 Encryption – privacy
 Key management and usage
 Security algorithm parameters:
 Unit address
 Secret authentication key (128 bits key)
 Secret privacy key (4-128 bits secret key)
 Random number
VIRTUAL LAN
 A virtual local area network (VLAN) is a logical group of workstations, servers and network
devices that appear to be on the same LAN despite their geographical distribution.
 All workstations and servers used by a particular workgroup share the same VLAN, regardless of
the physical connection or location.
 The group membership in VLANs is defined by software, not hardware.
 A VLAN is a broadcast domain created by one or more switches.
 802.1Q

Fig 3.13 network without VLAN and with VLAN
VLAN Membership
 Each switch port could be assigned to a different VLAN.
 Ports assigned to the same VLAN share broadcasts.
 Ports that do not belong to that VLAN do not share these broadcasts.
VLAN operation
1. VLANs are assigned on the switch port. There is no “VLAN” assignment done on the host
(usually).
2. In order for a host to be a part of that VLAN, it must be assigned an IP address that belongs to the
proper subnet. Remember: VLAN = Subnet.
3. Assigning a host to the correct VLAN is a 2-step process:
1. Connect the host to the correct port on the switch.
2. Assign to the host the correct IP address depending on the VLAN membership
1. Static VLAN
 Are called port-based and port-centric membership VLANs.
 Ports on a switch are manually assigned to a VLAN.
 This is the most common method of assigning ports to VLANs.
 As a device enters the network, it automatically assumes the VLAN membership of the port to
which it is attached.
2. Dynamic VLAN
 Allow membership based on the MAC address of the device connected to the switch port.
 As a device enters the network, it queries a database within the switch for a VLAN membership.
 Membership is configured using a special server called a VLAN Membership Policy Server
(VMPS).

Configuration
 Network administrators are responsible for configuring VLANs both manually and statically
Fig 3.14 VLAN configuration
Communication
 Each switch must know about which station belongs to which VLAN and the membership of
stations connected to other switches.
 Three methods have been devised for this purpose:
i. Table maintenance
ii. Frame tagging
iii. Time-division multiplexing.
i. Table Maintenance
 When a station sends a broadcast frame to its group members, the switch creates an entry in a table
and records station membership.
 The switches send their tables to one another periodically for updating.
ii. Frame Tagging
 When a frame is traveling between switches, an extra header is added to the MAC frame to
define the destination VLAN.
 The frame tag is used by the receiving switches to determine the VLANs to be receiving the
broadcast message.
iii. Time-Division Multiplexing (TDM)
 the connection (trunk) between switches is divided into timeshared channels

IEEE 802.1Q: Features
 Allows up to 4095 VLANs
 Allows port based and MAC address based,
 Upward compatible with existing VLAN-unware hubs and bridges
 Supports both shared-media and switched LANs.
 Retains plug and play mode of current LAN bridges.
 Allows priority associated with each VLAN.
 Supports static and dynamic configurations for each VLAN
Advantages & Disadvantage
Disadvantage:
 Costly
 Software based
 Human labor to program
 Depending on variety switches
 Management complexity
Advantages:
 More Security
 Ease of administration
 Broadcast control
 Reduction in network traffic

Module 3 wlan,bluetooth vlan

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